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Balcony Antenna for Shortwave Listening
Hello,
I am a complete newbie in SWL. At fourth floor (last one) of a building, I get a balcony where I could put an antenna for ham and broadcast reception (SWL). Well the balcony is quite small, but quite comfortable too :) Now, I get a poor wire from my flat to the ground (near the ground). It gives me some night reception for broadcast from 500 KHz to 1500 MHz (it is quite interesting, but quite limited too...). Except that, I get nothing. Frustrating. I planned to build some loop antennas, but first of all, I wanted to focus on long wire antennas. Please, give me your thoughts: I am about to build a long wire antenna, but something quite different... Like hand-held receivers antennas, I want to wrap 100 meters of standard wire around on a 4cm (diameter) plastic tube (like a slinky antenna). I get three different ways to do that: - like the standard long wire, feeder on one side with a 9:1 balun - like a dipole (feeder at the center) - like a 1/4 wave (vertical one) with the steel fence for the ground and to hang up the plastic tube. The fence itself is grounded. What do you think about this type of antenna? What about the reception efficiency of each kind of solution for all bands between 500 KHz to 30 MHz? Tell me if it is interesting to test that or I should not lose my time and begin building a loop antenna? Thanks. Sebastien. In French : Hello, Ma situation est la suivante. Au 4ème et dernier étage d'un immeuble, je dispose d'un balcon sur lequel disposer une antenne pour recevoir les émission broadcast et les émissions radio-amateur en HF. Evidemment, c'est assez petit quoiqu'assez confortable. Pour le moment, un vague fil pendouillait par le balcon, ce dernier m'offrant un peu de réception, de nuit entre 500 Hz et 1500 MHz (c'est pas inintéressant, mais c'est limité....). Sorti de ça, je n'ai rien. Fort sentiment de frustration. J'ai en projet la réalisation d'une antenne loop, mais dans un premier temps, je voudrais me concentrer sur le long fil. J'aurais voulu avoir votre avis. Je suis sur le point de construire une antenne de réception de type long fil, mais modifiée... A l'image des antennes de réception des récepteurs portables, je pensais bobiner une bonne longueur de fil (une centaine de mètres) sur du tuyau PVC de diamètre 4cm (fil électrique de base, bobinage Ã* spires jointives). Trois possibilités s'offrent Ã* moi : - Alimentation par une extrémité, le long fil classique, mais bobiné - Alimentation au milieu en doublet 1/2 ondes, évidemment toujours bobiné - Alimentation en quart d'onde, verticale (encore bobiné), en utilisant la rambarde métallique comme terre (et comme support pour mon tube), la rambarde faisant la longueur de l'immeuble (la rambarde étant elle-même raccordée Ã* la terre). Que pensez-vous du principe ? Et que pensez-vous du rendement de chacune des solutions en HF toutes bandes ? Avec mes remerciements, Sébastien. |
Balcony Antenna for Shortwave Listening
On 07 Dec 2010 23:11:16 GMT, Sébastien MEDARD wrote:
Now, I get a poor wire from my flat to the ground (near the ground). It gives me some night reception for broadcast from 500 KHz to 1500 MHz (it is quite interesting, but quite limited too...). Except that, I get nothing. Frustrating. Hi Sebastien, Use an antenna tuner (same thing Amateurs use, but without the meters). You probably need this because of the Broadcast transmitters. Those transmitters can force your radio to create an AGC voltage even when you are not tuned to the Broadcast frequency. This AGC voltage causes your radio to lose sensitivity. To put it another way, suppose: you have a strong Broadcast station nearby on 1 MHz; you connect your radio to a long antenna for SWL; you tune to the 31M band; the Broadcast signal creates a very strong AGC; you (naturally) do not hear the Broadcast signal; you (un-naturally) do not hear many 31M band signals. To solve this: Add a tuner; you adjust it for the 31M band; it removes the Broadcast signal; your AGC voltage is now based on 31M band signals; your radio becomes very sensitive; you hear more 31M band signals. This will also work for weak Broadcast signals. 73's Richard Clark, KB7QHC |
Balcony Antenna for Shortwave Listening
Hello,
On Tue, 07 Dec 2010 16:21:41 -0800, Richard Clark wrote: On 07 Dec 2010 23:11:16 GMT, Sébastien MEDARD wrote: To solve this: Add a tuner; You cut corners :) I was thinking about adding a Tuner or maybe something that is called preselector/tuner... But, before that I just wanted to know what would be a good antenna, or good antennas for where I live. Thus, I was thinking about adapting the basics (long wire, dipole) to my situation. What do you think about shorting a long wire to a big self? Would this self work better adapted on one side, like a dipole or a quarter of a wave? By the way...... What would be a good antenna tuner for a SWL? Any advice for a brand? Any advice for a good DIY kit? :) Thanks. Sebastien. |
Balcony Antenna for Shortwave Listening
S?bastien MEDARD wrote:
By the way...... What would be a good antenna tuner for a SWL? Any advice for a brand? Any advice for a good DIY kit? :) Here's my suggestion. It's a combination pre-selector and amplifer: http://rffun.com/catalog/preamps/2158.html If you are handy with a soldering iron you can easily add a second receiver output. Geoff. -- Geoffrey S. Mendelson N3OWJ/4X1GM Those who cannot remember the past are condemned to misquote it. |
Balcony Antenna for Shortwave Listening
On 08 Dec 2010 00:45:41 GMT, Sébastien MEDARD wrote:
But, before that I just wanted to know what would be a good antenna, or good antennas for where I live. Hi Sebastien, The best is the one that will be as high as possible. Length should be 5 to 10 meters. Orientation should be broadside to the stations you want to listen to. You should have a choke (W2DU style BalUn) connected at the feedpoint. One example shown at: http://www.n0ss.net/qrp_1-1_w2du_coaxial_balun.pdf You should think of more than one antenna (maybe one vertical, one horizontal). Paying attention to your ground is important, but if you live upstairs in an apartment, then think dipole (even if one side is vertical - where the horizontal wire would be called a "long-wire"). By the way...... What would be a good antenna tuner for a SWL? Any advice for a brand? Any advice for a good DIY kit? :) The price you could pay is not a predictor of performance. Look at the schematic on the last page of: http://www.mfjenterprises.com/man/pdf/MFJ-902.pdf It can be built from parts for less than $100. It basically represents the most flexible design, but there are other useful designs. Even there, with a good switching design you could use the same components to build them too. (I am thinking of PI configuration, L, and so on). Old AM (tube) radio parts are perfect for building your own tuner. 73's Richard Clark, KB7QHC |
Balcony Antenna for Shortwave Listening
Hello,
On Tue, 07 Dec 2010 21:58:17 -0800, Richard Clark wrote: On 08 Dec 2010 00:45:41 GMT, Sébastien MEDARD wrote: But, before that I just wanted to know what would be a good antenna, or good antennas for where I live. want to listen to. You should have a choke (W2DU style BalUn) connected at the feedpoint. One example shown at: http://www.n0ss.net/qrp_1-1_w2du_coaxial_balun.pdf That's the first thing I will do. Ferrite ordered :) Paying attention to your ground is important, but if you live upstairs in an apartment, then think dipole (even if one side is vertical - where the horizontal wire would be called a "long-wire"). OK. By the way...... What would be a good antenna tuner for a SWL? Any advice for a brand? Any advice for a good DIY kit? :) The price you could pay is not a predictor of performance. Look at the schematic on the last page of: http://www.mfjenterprises.com/man/pdf/MFJ-902.pdf Seems not so simple for me. I see two things on the schematic : - 2 variable capcitor and an inductance on the center - A balun for balanced line (ie dipole????) As I already get a balun for dipole could you confirm that I just need the center part of the schematic? If the answer is yes, if I understand the schematic well, both of variable capacitors are put one after the other inserted into the line. The big question is how to make the variable inductance? Some wire wired on a ferrite rod? (L ----------- A????) with a selector? Are the number of half-loops means the number of turns? Even there, with a good switching design you could use the same components to build them too. (I am thinking of PI configuration, L, and so on). What is the influence of these different configurations? Old AM (tube) radio parts are perfect for building your own tuner. It seems I need to find some :) Thank you for your patience, Sebastien. |
Balcony Antenna for Shortwave Listening
On 09 Dec 2010 17:11:54 GMT, Sébastien MEDARD wrote:
http://www.n0ss.net/qrp_1-1_w2du_coaxial_balun.pdf That's the first thing I will do. Ferrite ordered :) Hi Sébastien, Good first step. http://www.mfjenterprises.com/man/pdf/MFJ-902.pdf Seems not so simple for me. I see two things on the schematic : - 2 variable capcitor and an inductance on the center Good. - A balun for balanced line (ie dipole????) Yes. As I already get a balun for dipole could you confirm that I just need the center part of the schematic? Confirmed, yes. If the answer is yes, if I understand the schematic well, both of variable capacitors are put one after the other inserted into the line. The big question is how to make the variable inductance? Some wire wired on a ferrite rod? (L ----------- A????) with a selector? Are the number of half-loops means the number of turns? Making the coil is easy. It is just bare wire. You connect leads between various turns in the coil and a switch. A three to five position switch will work. You can even wind separate coils and put them on the switch so they add up in series as you turn the switch. Even there, with a good switching design you could use the same components to build them too. (I am thinking of PI configuration, L, and so on). What is the influence of these different configurations? Some antennas (I am speaking of their wavelength, not style like horizontal, vertical, end-fed, or other) are easier to tune with these other styles, but the style offered in the link is fairly general purpose. Old AM (tube) radio parts are perfect for building your own tuner. It seems I need to find some :) It may not be easy, but if you can find the right shop, you will find many. Tell the shop owner you want this for experimentation and you might get something that isn't in the shop display. The only thing you really need is the variable capacitor from two radios. This technology was very common and found in nearly every home in the 1950s and 60s, but now would be rare unless you find that shop. Thank you for your patience, Feel free to ask more questions when it comes time to put this together. 73's Richard Clark, KB7QHC |
Balcony Antenna for Shortwave Listening
On 8 dic, 00:11, Sébastien MEDARD wrote:
Hello, I am a complete newbie in SWL. At fourth floor (last one) of a building, I get a balcony where I could put an antenna for ham and broadcast reception (SWL). Well the balcony is quite small, but quite comfortable too :) Now, I get a poor wire from my flat to the ground (near the ground). It gives me some night reception for broadcast from 500 KHz to 1500 MHz (it is quite interesting, but quite limited too...). Except that, I get nothing. Frustrating. I planned to build some loop antennas, but first of all, I wanted to focus on long wire antennas. Please, give me your thoughts: I am about to build a long wire antenna, but something quite different... Like hand-held receivers antennas, I want to wrap 100 meters of standard wire around on a 4cm (diameter) plastic tube (like a slinky antenna). I get three different ways to do that: - like the standard long wire, feeder on one side with a 9:1 balun - like a dipole (feeder at the center) - like a 1/4 wave (vertical one) with the steel fence for the ground and to hang up the plastic tube. The fence itself is grounded. What do you think about this type of antenna? What about the reception efficiency of each kind of solution for all bands between 500 KHz to 30 MHz? Tell me if it is interesting to test that or I should not lose my time and begin building a loop antenna? Thanks. Sebastien. In French : Hello, Ma situation est la suivante. Au 4ème et dernier étage d'un immeuble, je dispose d'un balcon sur lequel disposer une antenne pour recevoir les émission broadcast et les émissions radio-amateur en HF. Evidemment, c'est assez petit quoiqu'assez confortable. Pour le moment, un vague fil pendouillait par le balcon, ce dernier m'offrant un peu de réception, de nuit entre 500 Hz et 1500 MHz (c'est pas inintéressant, mais c'est limité....). Sorti de ça, je n'ai rien. |
Balcony Antenna for Shortwave Listening
On Thu, 09 Dec 2010 11:33:27 -0800, Richard Clark wrote:
If the answer is yes, if I understand the schematic well, both of variable capacitors are put one after the other inserted into the line. The big question is how to make the variable inductance? Some wire wired on a ferrite rod? (L ----------- A????) with a selector? Are the number of half-loops means the number of turns? Making the coil is easy. It is just bare wire. You connect leads between various turns in the coil and a switch. A three to five position switch will work. You can even wind separate coils and put them on the switch so they add up in series as you turn the switch. OK. Even there, with a good switching design you could use the same components to build them too. (I am thinking of PI configuration, L, and so on). What is the influence of these different configurations? Some antennas (I am speaking of their wavelength, not style like horizontal, vertical, end-fed, or other) are easier to tune with these other styles, but the style offered in the link is fairly general purpose. I found a PI network tuner shematic. Many thanks for the first steps help! Sébastien. |
Balcony Antenna for Shortwave Listening
Hello,
On Fri, 10 Dec 2010 06:15:51 -0800, Wimpie wrote: it may result in worse reception because of overloading electronic circuits in your receiver. OK for that. If your balcony has a metal fence (that may be connected to rebar also), you can use this as a ground provision for a wire antenna of about 5… 10m. I didn't test that until now. I will. Adding a 9:1 transformer (outside, directly below the antenna) will increase antenna output at the lower bands. This does not automatically mean that your S/N ratio increases also. Portable receivers may experience overload. A preselector may help. www.tetech.nl/divers/SimplePreselector2.jpg shows an (old) example. I better see what could be a home made tuner. Seems quite easy to build :)) This one tunes from 3.3 to 26 MHz. By changing the crocodile clips, you can perform some matching to get more output from the antenna, and change the bandwidth of the preselection. The crocodile clips can be replaced by a selector. Am I OK on that? For the lower bands (AM broadcast) a loop may have advantage. Figure 2(a) in http://www.compliance-club.com/archi...ive/030718.htm shows the construction of a loop out of coaxial cable. These types of loops have built-in balanced to coaxial transition. A square or circle of about 1m (diameter) is a good start for the AM BC band. It is called a shielded loop. Am I wrong? Be careful with (expensive) loop antennas. If you can't get reception with a simple well-constructed (tuned) loop because of local interference (noise), the most expensive loop will not change that. For now, I tried a lot of different things... The best result were on loops. A big loop (1.6mx4 = 6.4 meters), one turn, with an air variable capacitor + an inside loop connected to the coaxial cable seems to give better ways to give something to eat to my receiver. Sometimes my air capacitor was not powerful enough, in the lower bands if I remember well... To improve that I will have to add a fixed capacitor (lets say 300pF) in parallel (to be bypassed) or more depending on the band I am listening to. For now I am just experimenting (with some simple wire), but I think I will build a more solid one... A big loop (1.6mx4 = 6.4 meters), one turn, with the the universal balun from Wellbrook. Don't know why, but, it gives very good results, far better than a long wire in my flat, or a short wire on my balcony... At this time it seems there is a Ham Contest in Italia... I can get them fully on 80m :) LSB/CW/RTTY... Well I live in South of France, so it is easier for me :))) But the first solution seems more efficient. Need to do further investigations.... Sebastien. |
Balcony Antenna for Shortwave Listening
On 11 Dec 2010 23:28:18 GMT, Sébastien MEDARD wrote:
For now, I tried a lot of different things... The best result were on loops. Hi Sebastien, This is a good lesson. A big loop (1.6mx4 = 6.4 meters), one turn, with an air variable capacitor + an inside loop connected to the coaxial cable seems to give better ways to give something to eat to my receiver. This is an excellent antenna for BCB and Tropical Bands. Sometimes my air capacitor was not powerful enough, in the lower bands if I remember well... To improve that I will have to add a fixed capacitor (lets say 300pF) in parallel (to be bypassed) or more depending on the band I am listening to. This is a great solution. For now I am just experimenting (with some simple wire), but I think I will build a more solid one... A big loop (1.6mx4 = 6.4 meters), one turn, with the the universal balun from Wellbrook. Don't know why, but, it gives very good results, far better than a long wire in my flat, or a short wire on my balcony... At this time it seems there is a Ham Contest in Italia... I can get them fully on 80m :) LSB/CW/RTTY... Well I live in South of France, so it is easier for me :))) The reason why this antenna performs so well is that it incorporates the tuning function in the large loop - the smaller loop does the matching. In other words, the large loop wire and the capacitor will reject signals that could overpower your radio and create AGC that reduces its sensitivity. It is, in effect, a tuner as we have already discussed. It also happens to be your antenna too. But the first solution seems more efficient. Need to do further investigations.... One point to consider, this large loop will not perform the same when its diameter is large when compared to the wavelength you are tuning to. Your longwire with tuner will probably be better in the 50M band and higher. However, experimentation may prove different, especially if you can tip the loop over (or change its angle to earth). 73's Richard Clark, KB7QHC |
Balcony Antenna for Shortwave Listening
On 12 dic, 00:28, Sébastien MEDARD wrote:
Hello, On Fri, 10 Dec 2010 06:15:51 -0800, Wimpie wrote: it may result in worse reception because of overloading electronic circuits in your receiver. OK for that. If your balcony has a metal fence (that may be connected to rebar also), you can use this as a ground provision for a wire antenna of about 5… 10m. I didn't test that until now. I will. Adding a 9:1 transformer (outside, directly below the antenna) will increase antenna output at the lower bands. This does not automatically mean that your S/N ratio increases also. Portable receivers may experience overload. A preselector may help. http://www.tetech.nl/divers/SimplePr...tor2.jpg*shows an (old) example. I better see what could be a home made tuner. Seems quite easy to build :)) This one tunes from 3.3 to 26 MHz. By changing the crocodile clips, you can perform some matching to get more output from the antenna, and change the bandwidth of the preselection. The crocodile clips can be replaced by a selector. Am I OK on that? Correct, you can use two selectors instead of the clips. For the lower bands (AM broadcast) a loop may have advantage. Figure 2(a) in http://www.compliance-club.com/archi...30718.htmshows the construction of a loop out of coaxial cable. These types of loops have built-in balanced to coaxial transition. *A square or circle of about 1m (diameter) is a good start for the AM BC band. It is called a shielded loop. Am I wrong? Correct. To have the balun function, the cut in the shield must be opposite to the position where the feeder leaves the loop. Be careful with (expensive) loop antennas. If you can't get reception with a simple well-constructed (tuned) loop because of local interference (noise), the most expensive loop will not change that. For now, I tried a lot of different things... The best result were on loops. A big loop (1.6mx4 = *6.4 meters), one turn, with an air variable capacitor + an inside loop connected to the coaxial cable seems to give better ways to give something to eat to my receiver. Sometimes my air capacitor was not powerful enough, in the lower bands if I remember well... To improve that I will have to add a fixed capacitor (lets say 300pF) in parallel (to be bypassed) or more depending on the band I am listening to. For now I am just experimenting (with some simple wire), but I think I will build a more solid one... A big loop (1.6mx4 = *6.4 meters), one turn, with the the universal balun from Wellbrook. Don't know why, but, it gives very good results, far better than a long wire in my flat, or a short wire on my balcony... At this time it seems there is a Ham Contest in Italia... I can get them fully on 80m :) LSB/CW/RTTY... Well I live in South of France, so it is easier for me :))) My experience is that at the lower bands (AM BC up to 3.6 MHz), loops show better S/N ratio. However for the higher bands, performance becomes similar to dipoles or monopoles. For reception I like the small loops, as you can rotate them easily. They give less output, but here tuning (even tuning inside close to the receiver) will improve output (and noise….). Regarding the large resonant loop with inside coupling loop, yes that works well. I have a small one (0.6*0.4m) that tunes on the ham bands from 3.6 to 30 MHz, it uses additional fixed capacitance for the lower bands. Unless you live in a very quiet environment, you can reduce the size without sacrificing S/N ratio. But the first solution seems more efficient. Need to do further investigations.... Sebastien. Best regards, Wim PA3DJS www.tetech.nl |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Sat, 11 Dec 2010 16:21:29 -0800, Richard Clark wrote:
On 11 Dec 2010 23:28:18 GMT, Sébastien MEDARD wrote: For now, I tried a lot of different things... The best result were on loops. Hi Sebastien, This is a good lesson. Thanks. I think I will try long wire again... I don't like to give up without fighting a little bit. But perhaps I will try it outdoor putting my receiver in the car outside any city or in a place where I get some place. So everything about antenna tuners need more investigation. A big loop (1.6mx4 = 6.4 meters), one turn, with an air variable capacitor + an inside loop connected to the coaxial cable seems to give better ways to give something to eat to my receiver. This is an excellent antenna for BCB and Tropical Bands. The problem seems to be related to wave propagation... I need to test that a little bit more but... It is easier to receive radio broadcast during the night. I need to know what are the differences between night/ day for wave propagation. What should I listen during the night and what I should better listen during daylight... I need to know a little bit more about digital transmission modes... To be able to recognize digital patterns (on the waterfall display) to be able apply the good settings for decoding... Easy for CW... Easy for RTTY used by HAM... But what is the pattern for Meteo Faxes for example...? By the way... I searched for good free software to decode meteo faxes... But it seems not easy to find something free and easy to use... Do you know shere I could find something interesting? Sometimes my air capacitor was not powerful enough, in the lower bands if I remember well... To improve that I will have to add a fixed capacitor (lets say 300pF) in parallel (to be bypassed) or more depending on the band I am listening to. This is a great solution. This is something I found on a website.... When you don't know anything about electronics... Your learning curve is quite flat :))) For now I am just experimenting (with some simple wire), but I think I will build a more solid one... A big loop (1.6mx4 = 6.4 meters), one turn, with the the universal balun from Wellbrook. Don't know why, but, it gives very good results, far better than a long wire in my flat, or a short wire on my balcony... At this time it seems there is a Ham Contest in Italia... I can get them fully on 80m :) LSB/CW/RTTY... Well I live in South of France, so it is easier for me :))) One point to consider, this large loop will not perform the same when its diameter is large when compared to the wavelength you are tuning to. Your longwire with tuner will probably be better in the 50M band and higher. I need to make a tuner first... Then I will tell you about it. However, experimentation may prove different, especially if you can tip the loop over (or change its angle to earth). Well.... not so easy for now... My "experimentation board" is a big wood shelf with a lot of books on it... Not so easy to flip, rotate or.... But it is well oriented (east-west) :) My next tries will be on a multiple turns loops. With or without matching loop inside. I will try with simple wire but connection ribbon cables could be a good alternative... (like old hard drive ribbon cable) I was wondering... It seems loop antennas are a never ending story. As far as I know, it seems there is no book that makes a good overview of the different loop designs, with accessible schematics for preamp or tuning stuff, how to avoid QRMs... There could be a very interesting area both for SWL and HAM... Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but it is quite expensive and an Amazon reviewer says it is not so interesting... What about the "Joe Carr's Receiving Antenna Handbook" ? Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 12 Dec 2010 13:59:06 GMT, Sébastien MEDARD wrote:
The problem seems to be related to wave propagation... I need to test that a little bit more but... It is easier to receive radio broadcast during the night. I need to know what are the differences between night/ day for wave propagation. What should I listen during the night and what I should better listen during daylight... Hi Sébastien, What you are talking about is common to DXing. Get yourself a globe of the world. Light it up with an artificial "sun." The edge of the dark/light should be half way between you and the transmitter you want to hear. So, during the late day, your best signals are probably from Eastern Europe, Turkey, and Asia. During the early-to-late night, your best signals are probably from the Americas. During the late afternoon to early evening you best signals are from the south or the north. I need to know a little bit more about digital transmission modes... To be able to recognize digital patterns (on the waterfall display) to be able apply the good settings for decoding... Easy for CW... Easy for RTTY used by HAM... But what is the pattern for Meteo Faxes for example...? When I used to teach RTTY there were only two tones. If modem technology is any indication, that number has been raised and phase is important. By the way... I searched for good free software to decode meteo faxes... But it seems not easy to find something free and easy to use... Do you know shere I could find something interesting? Nope. My next tries will be on a multiple turns loops. With or without matching loop inside. I will try with simple wire but connection ribbon cables could be a good alternative... (like old hard drive ribbon cable) This will reveal the "Law of Diminishing Returns" (the more you add, the less you get back). I was wondering... It seems loop antennas are a never ending story. As far as I know, it seems there is no book that makes a good overview of the different loop designs, with accessible schematics for preamp or tuning stuff, how to avoid QRMs... There could be a very interesting area both for SWL and HAM... Oh, I am sure there are many such books gathering dust on shelves. Loops have been around for more than a century, and if they were such a good idea, then everyone would be using them. Well, at one time they were a good idea, and EVERYONE used them - when we had transistor pocket radios with analog tuning. The ferrite antenna was the king of antennas for the vast majority of radio owners. Before the transistor radio and ferrites, every table radio had a flat pancake loop antenna in the back of the radio behind all the glowing tubes. Oddly enough, no radios in this age have either of these antennas anymore, and they still seem to pick up stations. So, there you have a century of technical perspective on the topic. Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but it is quite expensive and an Amazon reviewer says it is not so interesting... What about the "Joe Carr's Receiving Antenna Handbook" ? He is a respected author. I always look at the bad Amazon reviews to see if something is terribly wrong with the product or terribly wrong with the customer. Quite often the customer is disappointed because that customer is stupid. If I encounter a smart customer that is disappointed, I can well imagine all the good comments are not very reliable. The thing about all these -um- books is that many of them serve up old wives' tales about low noise and other magical characteristics. Remember the lessons of a century worth of experience with loop antennas within an inch of the guts of any radio. That worked fine for a billion radios and radios were not bought if they were "noisy." The real science of low noise is found in the distance to the source. Quite often it is your neighbor's aquarium heater that is noisy (the most often complained of source of noise reported here). Your loop sits in your shack and that aquarium is 10 Meters away. You switch to your longwire that runs to the fence and the aquarium is 1 meter away. Do I have to work out the math on that? Is the loop quieter because of its magic design - or simply because it is 10 times further away (20dB) from the noise? We get writers here who pound the table because their magic loop in the shack is noisy and their long wire 10M away in the back yard is quiet. They have to be told to turn off the flourescent light in the shack if they want their magic loop to work. (Their magic loop low score on Amazon) = (stupid.) 73's Richard Clark, KB7QHC |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Sun, 12 Dec 2010 12:25:59 -0800, Richard Clark wrote:
On 12 Dec 2010 13:59:06 GMT, Sébastien MEDARD wrote: What you are talking about is common to DXing. Get yourself a globe of the world. Light it up with an artificial "sun." The edge of the dark/light should be half way between you and the transmitter you want to hear. So, during the late day, your best signals are probably from Eastern Europe, Turkey, and Asia. During the early-to-late night, your best signals are probably from the Americas. During the late afternoon to early evening you best signals are from the south or the north. I understand better what is the purpose of this kind of map (on SDR- Radio.com software for example). Where you can see an OM, you are pretty sure to see this kind of map. I need to know a little bit more about digital transmission modes... To be able to recognize digital patterns (on the waterfall display) to be able apply the good settings for decoding... Easy for CW... Easy for RTTY used by HAM... But what is the pattern for Meteo Faxes for example...? When I used to teach RTTY there were only two tones. The reason why they call you OM ? :)) By the way... I searched for good free software to decode meteo faxes... But it seems not easy to find something free and easy to use... Do you know shere I could find something interesting? Nope. OK. I will try that later... For now I get some problems to use Linrad with the SDR-IQ... Painful to boot on windows every time I want to listen to shortwaves... And using a virtual system is not very efficient on my old computer... My next tries will be on a multiple turns loops. With or without matching loop inside. I will try with simple wire but connection ribbon cables could be a good alternative... (like old hard drive ribbon cable) This will reveal the "Law of Diminishing Returns" (the more you add, the less you get back). Interesting. What would be the best ratio? I was wondering... It seems loop antennas are a never ending story. So, there you have a century of technical perspective on the topic. :)) Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but it is quite expensive and an Amazon reviewer says it is not so interesting... What about the "Joe Carr's Receiving Antenna Handbook" ? He is a respected author. I always look at the bad Amazon reviews to see if something is terribly wrong with the product or terribly wrong with the customer. Quite often the customer is disappointed because that customer is stupid. If I encounter a smart customer that is disappointed, I can well imagine all the good comments are not very reliable. I will try to find one when they are cheaper. The thing about all these -um- books is that many of them serve up old wives' tales about low noise and other magical characteristics. Remember the lessons of a century worth of experience with loop antennas within an inch of the guts of any radio. That worked fine for a billion radios and radios were not bought if they were "noisy." OK. But today we probably ask more to radios than yesterday, no? The real science of low noise is found in the distance to the source. Lapalisse would have said exactly the same thing. He would have said that the real science of good reception is found in the distance to the source too :)) Is the loop quieter because of its magic design - or simply because it is 10 times further away (20dB) from the noise? OK for that. We get writers here who pound the table because their magic loop in the shack is noisy and their long wire 10M away in the back yard is quiet. They have to be told to turn off the flourescent light in the shack if they want their magic loop to work. (Their magic loop low score on Amazon) = (stupid.) Lesson one = learned. Thanks. Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Dec 13, 3:01*pm, Sébastien MEDARD wrote:
We get writers here who pound the table because their magic loop in the shack is noisy and their long wire 10M away in the back yard is quiet. They have to be told to turn off the flourescent light in the shack if they want their magic loop to work. * *(Their magic loop low score on Amazon) = (stupid.) Lesson one = learned. Thanks. Sebastien. One thing handy about a small loop is you can turn it to null out the offending noise. Like Richard says, there is no magical quality which provides lower noise vs any other antenna. The real benefit is being about to turn it, usually while in the listening position. If the loop is well balanced, the nulls are quite sharp and deep and in many cases you could make that nasty noise source vanish. You can also turn it to receive multiple stations that are on the same frequency. You null the one you want to get rid of. But these type of loops are best suited for the low bands. LW, MW are where they are best suited. You get much better nulls off a ground wave signal, than you do one that is propagated via skywave. So they tend to work better at nulls in the daytime vs at night. At night, you get a mix of ground and sky wave, and the nulls are not as deep. In the day, I can make most ground wave signals totally vanish by nulling them out. These can be used in the SW bands, but don't expect the deep nulls, being as most all SW will come via sky wave. For general SWL, you are usually better off with the various wire antennas. Random wires, dipoles, etc.. But I recommend a small loop for MW if you want the ability to null noise or undesired stations. Most of mine, I build from PVC tubing for the frames. I have one in this room that is a diamond, 42 inches per side. It's on a stand which allows it to rotate, and it stands almost as tall as the ceiling. But they don't have to be that big. I've got another round one that is about 16 inches across, and it works very well too. Just a tad less signal than the big one. But the s/n ratio is much the same for the majority of the stations listened to. http://home.comcast.net/~nm5k/loop5.jpg This is my usual favored method for building a low cost MW loop. The hardest part to come by these days is the variable cap. I dig them out of old radios, and old analog tuning stereo receivers. Those are some of the best ones to use, as they often have several gangs which can be wired in parallel for more capacitance, or deleted for less. For the upper tuning ranges of the loop, it's best to delete most of the gangs, and use one of the very small ones by itself. That way you get a smaller value, and will increase the upper tuning range, vs just turning all the gangs in parallel to the minimum setting. So I use switches to do this quickly. But if you can't find any old radios to acquire the variable caps, you can buy them online from a few places. I wouldn't use one any less than a dual 365pf BC cap. You can wire the two gangs together for 730 pf. With careful loop turn design, you can usually cover the whole MW BC band with one of those. But I prefer the ones out of old stereo receivers. They are even better, and can give a wider tuning range. I think the one on my big loop has four or five gangs, some being small and useful for upper end tuning, if the other larger gangs are switched out. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 13 Dec 2010 21:01:30 GMT, Sébastien MEDARD wrote:
I understand better what is the purpose of this kind of map (on SDR- Radio.com software for example). Where you can see an OM, you are pretty sure to see this kind of map. Hi Sébastien, If you mean the "gray line" map - yes. When I used to teach RTTY there were only two tones. The reason why they call you OM ? :)) Touché This will reveal the "Law of Diminishing Returns" (the more you add, the less you get back). Interesting. What would be the best ratio? You mean the best number of turns? Depending upon band, maybe as many as 6 to 10. One is good enough. There are many options to balance. One correspondent here, years ago (silent key), wrote extensively on this subject - google this group (or the internet) for Reg Edwards, G4FGQ. For instance, google the keywords in: RJELOOP1 * Performance of Transceiving, single-turn, magloop antennas of various regular shapes. RJELOOP2 * Performance of Transceiving, single-turn, magloop antennas of rectangular shape. RJELOOP3 * Analysis of receiving, multi-turn, square, loop (or frame) antennas, ELF to HF. I will try to find one when they are cheaper. Try: http://www.bookfinder.com/search/?au...ic&st=sr&ac=qr OK. But today we probably ask more to radios than yesterday, no? No, probably less. Being an OM, (40 years ago) I also taught classes for repair and maintenance of Collins' famous receiver, the R-390. EVEN NOW (40 years later), this is probably the best receiver for its price (and even two to three times its price). The real science of low noise is found in the distance to the source. Lapalisse would have said exactly the same thing. He would have said that the real science of good reception is found in the distance to the source too :)) So, my comment was a lapalissade? Certainly. 73's Richard Clark, KB7QHC |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 13 dic, 22:01, Sébastien MEDARD wrote:
On Sun, 12 Dec 2010 12:25:59 -0800, Richard Clark wrote: On 12 Dec 2010 13:59:06 GMT, Sébastien MEDARD wrote: What you are talking about is common to DXing. *Get yourself a globe of the world. *Light it up with an artificial "sun." *The edge of the dark/light should be half way between you and the transmitter you want to hear. *So, during the late day, your best signals are probably from Eastern Europe, Turkey, and Asia. *During the early-to-late night, your best signals are probably from the Americas. *During the late afternoon to early evening you best signals are from the south or the north. I understand better what is the purpose of this kind of map (on SDR- Radio.com software for example). Where you can see an OM, you are pretty sure to see this kind of map. I need to know a little bit more about digital transmission modes... To be able to recognize digital patterns (on the waterfall display) to be able apply the good settings for decoding... Easy for CW... Easy for RTTY used by HAM... But what is the pattern for Meteo Faxes for example...? When I used to teach RTTY there were only two tones. The reason why they call you OM ? :)) By the way... I searched for good free software to decode meteo faxes.... But it seems not easy to find something free and easy to use... Do you know shere I could find something interesting? Nope. OK. I will try that later... For now I get some problems to use Linrad with the SDR-IQ... Painful to boot on windows every time I want to listen to shortwaves... And using a virtual system is not very efficient on my old computer... My next tries will be on a multiple turns loops. With or without matching loop inside. I will try with simple wire but connection ribbon cables could be a good alternative... (like old hard drive ribbon cable) This will reveal the "Law of Diminishing Returns" (the more you add, the less you get back). Interesting. What would be the best ratio? I was wondering... It seems loop antennas are a never ending story. So, there you have a century of technical perspective on the topic. :)) Perhaps the "Joe Carr's Loop Antenna Handbook" may be interesting, but it is quite expensive and an Amazon reviewer says it is not so interesting... What about the "Joe Carr's Receiving Antenna Handbook" ? He is a respected author. *I always look at the bad Amazon reviews to see if something is terribly wrong with the product or terribly wrong with the customer. *Quite often the customer is disappointed because that customer is stupid. *If I encounter a smart customer that is disappointed, I can well imagine all the good comments are not very reliable. I will try to find one when they are cheaper. The thing about all these -um- books is that many of them serve up old wives' tales about low noise and other magical characteristics. Remember the lessons of a century worth of experience with loop antennas within an inch of the guts of any radio. *That worked fine for a billion radios and radios were not bought if they were "noisy." OK. But today we probably ask more to radios than yesterday, no? The real science of low noise is found in the distance to the source. Lapalisse would have said exactly the same thing. He would have said that the real science of good reception is found in the distance to the source too :)) Is the loop quieter because of its magic design - or simply because it is 10 times further away (20dB) from the noise? OK for that. We get writers here who pound the table because their magic loop in the shack is noisy and their long wire 10M away in the back yard is quiet. They have to be told to turn off the flourescent light in the shack if they want their magic loop to work. * *(Their magic loop low score on Amazon) = (stupid.) Lesson one = learned. Thanks. Sebastien. Hello Sébastien, Regarding tuning, loops and (long) wires. You probably locate your antenna far away from noise sources. Mostly this is not where your receiver is. In case of tuned loops, you have to go outside for each significant frequency change. This is one of the reasons that I want my preselection / tuning adjacent to the receiver. Loops aren't magic things. A wire from your balcony to a tree or other tie point may give better S/N ratio then the best (expensive) loop on your balcony. Best matching isn't required for reception at HF, just sufficient signal. In case of a PI tuning / preselector device, you need to adjust two capacitors in case of major frequency change. In my opinion a single capacitor device is more pleasant to use. (deep) Nulls in the radiation pattern at low frequency (AM BC and below) are the main benefit of the loop if you are willing to change the orientation frequently when tuning across the bands. At increasing frequency, the nulls are less pronounced because of propagation issues. Off course a small horizontally oriented dipole has also figure-of-eight radiation pattern, but polarization isn't good for AM BC and lower. For experimentation / comparison, I used a 1m diameter non-tuned loop in the attic with preselection / tuning adjacent to the receiver. In most cases a 5 m outdoor wire with same preselector and receiver gives similar or better S/N ratio. This may be because of the attic has mains wiring and I didn't want to go to the attic for reorientation of the loop. If you want to experiment with some long wire (unbalanced) antennas, make sure to have a ground (counterpoise) provision outside; otherwise your coaxial cable will be part of the antenna. This may result in more interference from indoor sources. Whether or not you have sufficient signal from your antenna is easy to check. Listen to a known station. Tune your preselector to maximum signal. Now tune to a free frequency close to your station's frequency so that you hear noise. Remove the antenna, the audio noise should be less now. If you use a tapped coil preselector (like the one in my link), and have sufficient noise from the antenna, you may even change the taps. The preselector will give more insertion loss, but it will be more selective also. This can be of use when you have strong signals in your neighborhood. Because of portability, I frequently use an AOR AR8200. Without preselection, such a wide band receiver is useless with an external antenna. Best regards, Wim PA3DJS www.tetech.nl without abc, PM will reach me very likely |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Mon, 13 Dec 2010 15:38:20 -0800, nm5k wrote:
On Dec 13, 3:01Â*pm, Sébastien MEDARD wrote: One thing handy about a small loop is you can turn it to null out the offending noise. I should try small loops too. You get much better nulls off a ground wave signal, than you do one that is propagated via skywave. So they tend to work better at nulls in the daytime vs at night. At night, you get a mix of ground and sky wave, and the nulls are not as deep. In the day, I can make most ground wave signals totally vanish by nulling them out. That's an interesting concept. The difference between ground and sky waves and the way to use loops. And small loops are easier to make... Most of mine, I build from PVC tubing for the frames. A simple, but good idea. PVC tubing is inexpensive and quite rigid... I have one in this room that is a diamond, 42 inches per side. One meter... It is approximatively what I wanted to do at the beginning. It's on a stand which allows it to rotate, and it stands almost as tall as the ceiling. Do you tune it, or not? Is there a small loop inside or not? But they don't have to be that big. I've got another round one that is about 16 inches across, and it works very well too. Just a tad less signal than the big one. But the s/n ratio is much the same for the majority of the stations listened to. I definitively need to test them. http://home.comcast.net/~nm5k/loop5.jpg This is my usual favored method for building a low cost MW loop. The hardest part to come by these days is the variable cap. I got one and I am searching for others. It seems that variable caps are one of the center of a lot of things in radio reception :)) I can see on the loop5.jpg image that you connected one wire to the ground and one wire to both other connections (double gang capacitor) so that you add the result of both capacitors. Is that correct? That way you get a smaller value, and will increase the upper tuning range, vs just turning all the gangs in parallel to the minimum setting. So I use switches to do this quickly. Exact. That sounds good. But if you can't find any old radios to acquire the variable caps, you can buy them online from a few places. I wouldn't use one any less than a dual 365pf BC cap. You can wire the two gangs together for 730 pf. That's the kind I get. With careful loop turn design, you can usually cover the whole MW BC band with one of those. But I prefer the ones out of old stereo receivers. They are even better, and can give a wider tuning range. I think the one on my big loop has four or five gangs, some being small and useful for upper end tuning, if the other larger gangs are switched out. I found a 500pF + 500pF one too, with a slow motion drive. Another way to drive them slowly is to get a 20cm (10 inches) piece of wood, perforate it on one side to put the capacitor axis into the hole (put some glue, but a smaller hole is better, and push it hard so that the axis enters inside the hole), and you get something that can be tune very precisely with one finger... About the piece of wood, the longer, the higher in precision tuning. Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Mon, 13 Dec 2010 16:06:51 -0800, Richard Clark wrote:
On 13 Dec 2010 21:01:30 GMT, Sébastien MEDARD wrote: I understand better what is the purpose of this kind of map (on SDR- Radio.com software for example). Where you can see an OM, you are pretty sure to see this kind of map. Hi Sébastien, If you mean the "gray line" map - yes. There should free software displaying this gray line with UTC time, no? This will reveal the "Law of Diminishing Returns" (the more you add, the less you get back). Interesting. What would be the best ratio? You mean the best number of turns? Economics is interesting too :) RJELOOP3 * Analysis of receiving, multi-turn, square, loop (or frame) antennas, ELF to HF. Can be find here : http://www.zerobeat.net/G4FGQ/page3.html#S301 I will try to find one when they are cheaper. Try: http://www.bookfinder.com/search/?au...%27s+Receiving +Antenna+Handbook&lang=en&isbn=&submit=Begin +search&new_used=*&destination=us¤cy=USD&mod e=basic&st=sr&ac=qr I found the "Receiving Antenna Handbook" quite cheap, but the "Loop Antenna Handbook" is still expensive. Between $60 to $257... I will try the cheapest. OK. But today we probably ask more to radios than yesterday, no? No, probably less. Being an OM, (40 years ago) I also taught classes for repair and maintenance of Collins' famous receiver, the R-390. EVEN NOW (40 years later), this is probably the best receiver for its price (and even two to three times its price). Do you calculate that in constant dollar from the 50's? :) I can imagine the teaching class. Everybody with a Collin's in front of him/her... A one year project to restore completely one of this legendary radio. I would like that! With a good DSP outside (Audio DSP only), can beat every other ones? It seems not easy to get one, especially in Europe... The real science of low noise is found in the distance to the source. Lapalisse would have said exactly the same thing. He would have said that the real science of good reception is found in the distance to the source too :)) So, my comment was a lapalissade? Certainly. You got the picture :) Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Tue, 14 Dec 2010 09:17:40 -0800, Wimpie wrote:
Regarding tuning, loops and (long) wires. You probably locate your antenna far away from noise sources. Mostly this is not where your receiver is. That's a problem, indeed. In case of tuned loops, you have to go outside for each significant frequency change. This is one of the reasons that I want my preselection / tuning adjacent to the receiver. It seems there is another solution. The varactor diodes seem to act as a variable capacitor driven by their voltage (the capacitance of this kind of diode decreases as the potential is increased). It seems there are some loop designs with varactor diodes as tuners. But I don't know what could be the price of a such solution. Loops aren't magic things. A wire from your balcony to a tree or other tie point may give better S/N ratio then the best (expensive) loop on your balcony. I think so, but there is nothing I can change for that today. Best matching isn't required for reception at HF, just sufficient signal. In case of a PI tuning / preselector device, you need to adjust two capacitors in case of major frequency change. In my opinion a single capacitor device is more pleasant to use. I will try different configurations when I get them. If you want to experiment with some long wire (unbalanced) antennas, make sure to have a ground (counterpoise) provision outside; otherwise your coaxial cable will be part of the antenna. This may result in more interference from indoor sources. Yes, but the place I plan to experiment should be far away from this kind of trouble... I won't be able to get a good ground there. If you use a tapped coil preselector (like the one in my link), Sorry, where is it in your web site? and have sufficient noise from the antenna, you may even change the taps. The preselector will give more insertion loss, but it will be more selective also. How is called this design? This can be of use when you have strong signals in your neighborhood. Because of portability, I frequently use an AOR AR8200. Without preselection, such a wide band receiver is useless with an external antenna. I don't like these receivers... Or they should be used with optoelectronics frequency counters to drive the receiver... But more than that, the screen of these receivers is too small, too few information... I prefer being at home (or in a car) with a laptop computer displaying a beautiful waterfall picture :)) That's the reason why I owned a SDR-IQ. And on upper frequencies, it will keep being useful with an appropriate scanner (if I see a cheap one on the second hand market). For the moment, I prefer exploring the bands than picking up a frequency in a database (it may change...) Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 15 Dec 2010 20:52:22 GMT, Sébastien MEDARD wrote:
There should free software displaying this gray line with UTC time, no? Hi Sébastien, I'm sure there is - somewhere. GoogleEarth would be an elaborate tool to accomplish this. I found the "Receiving Antenna Handbook" quite cheap, but the "Loop Antenna Handbook" is still expensive. Between $60 to $257... I will try the cheapest. Myself, I would not advise spending more than $20. Professional antenna books barely give more than one section of the first chapter to its discussion. OK. But today we probably ask more to radios than yesterday, no? No, probably less. Being an OM, (40 years ago) I also taught classes for repair and maintenance of Collins' famous receiver, the R-390. EVEN NOW (40 years later), this is probably the best receiver for its price (and even two to three times its price). Do you calculate that in constant dollar from the 50's? :) Today's cost matched with the price of equivalent performance from an available vendor. I can imagine the teaching class. Everybody with a Collin's in front of him/her... A one year project to restore completely one of this legendary radio. I would like that! There were two to a radio. 40 to 30 hours learning the schematic theory of operation; and troubleshooting and tuning procedures and 30 to 40 hours in front of the radio. The class was 2 weeks long. Complete restore unnessecary, of course, as the last class had fixed any problem. No, we had a data bank of known problems, known solutions, and the time to debug them averaged over at least 100 students for each problem. With a good DSP outside (Audio DSP only), can beat every other ones? Good for filtering, probably tighter than the mechanical filters (theoretically), but there are many, many other considerations. It seems not easy to get one, especially in Europe... That seems like a very real impediment. And with it weighing in at 85 pounds (40 kilograms), the cost to deliver would add considerably. So, my comment was a lapalissade? Certainly. You got the picture :) In technicolor and 3D. 73's Richard Clark, KB7QHC |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 15 dic, 22:32, Sébastien MEDARD wrote:
On Tue, 14 Dec 2010 09:17:40 -0800, Wimpie wrote: Regarding tuning, loops and (long) wires. You probably locate your antenna far away from noise sources. *Mostly this is not where your receiver is. That's a problem, indeed. In case of tuned loops, you have to go outside for each significant frequency change. *This is one of the reasons that I want my preselection / tuning adjacent to the receiver. It seems there is another solution. The varactor diodes seem to act as a variable capacitor driven by their voltage (the capacitance of this kind of diode decreases as the potential is increased). It seems there are some loop designs with varactor diodes as tuners. But I don't know what could be the price of a such solution. That is an option, as they are frequently used in VHF/UHF systems. The varactor is a non-linear device, so you may get intermodulation in a large signal environment. You may use the varactor as fine tuning in combination with fixed capacitors. Loops aren't magic things. A wire from your balcony to a tree or other tie point may give better S/N ratio then the best (expensive) loop on your balcony. I think so, but there is nothing I can change for that today. Best matching isn't required for reception at HF, just sufficient signal. *In case of a PI tuning / preselector device, you need to adjust two capacitors in case of major frequency change. *In my opinion a single capacitor device is more pleasant to use. I will try different configurations when I get them. If you want to experiment with some long wire (unbalanced) antennas, make sure to have a ground (counterpoise) provision outside; otherwise your coaxial cable will be part of the antenna. This may result in more interference from indoor sources. Yes, but the place I plan to experiment should be far away from this kind of trouble... I won't be able to get a good ground there. Did you try the balcony fence or other large metallic structure as floating ground (counterpoise)? If you use a tapped coil preselector (like the one in my link), Sorry, where is it in your web site? It is the simple thing I referenced earlier www.tetech.nl/divers/SimplePreselector2.jpg and have sufficient noise from the antenna, you may even change the taps. The preselector will give more insertion loss, but it will be more selective also. How is called this design? I don't know the name for it, it is just a parallel resonant LC circuit where the input and output goes via an inductive tap. Moving the tap changes the coupling between the source/load and the resonant circuit, hance changing the loaded Q-factor. This can be of use when you have strong signals in your neighborhood. * Because of portability, I frequently use an AOR AR8200. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Dec 15, 2:17*pm, Sébastien MEDARD wrote:
Do you tune it, or not? Is there a small loop inside or not? Yes for both. The cap is down at the bottom corner, and I use a separate coupling loop because I'm feeding coax to the radio. The 42 inch per side loop uses 5 turns on the main loop. The coupling loop is on the inside, and maybe 36 or so inches out from center. Sounds like you are in good shape for caps. That 500-500 would be good. I'd put a small mini switch between the two gangs to be able to cut or add the second gang. That's what I do on mine anyway. I solder the switches right to the tabs on the cap. I also have a handful of fixed caps to add if I want to drop further down into longwave. I don't use them that often so I just clip them on if needed. I think my 16 inch round loop has about 12 turns if I remember right.. It also uses a inner coupling loop. For me, those loops are mainly for AM-BC, but I do wander down and listen to the air beacons from time to time. And the big one covers 160 meters, so I use it for that sometimes. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On Thu, 16 Dec 2010 03:34:56 -0800, Wimpie wrote:
It seems there are some loop designs with varactor diodes as tuners. But I don't know what could be the price of a such solution. That is an option, as they are frequently used in VHF/UHF systems. The varactor is a non-linear device, so you may get intermodulation in a large signal environment. You may use the varactor as fine tuning in combination with fixed capacitors. OK. If you want to experiment with some long wire (unbalanced) antennas, make sure to have a ground (counterpoise) provision outside; otherwise your coaxial cable will be part of the antenna. This may result in more interference from indoor sources. Yes, but the place I plan to experiment should be far away from this kind of trouble... I won't be able to get a good ground there. Then I shall use a dipole... Did you try the balcony fence or other large metallic structure as floating ground (counterpoise)? Not at this time. This is planned. If you use a tapped coil preselector (like the one in my link), Sorry, where is it in your web site? It is the simple thing I referenced earlier www.tetech.nl/divers/SimplePreselector2.jpg Sorry... Yes, your design seems quite simple. But as a beginer, I think i get some problems to understand how things are connected to the variable capacitor, I mean I think the way the variable capacitor works is missing in my information pool... Based on your photo let say we get : On the upper side : two connectors On the lower side : two other connectors But the upper side connectors are connected to the lower side connectors... via the capacitor itself. Am I right? The tap coil preselectors seem quite easy to carry out. You use different connectors on the tap to select the band you want to use. You get a switch on the upper side that seems to avoid using one gang of the capacitor... But I cannot see of it is connected to the ground or not. The air capacitor ground is connected to the ground. On the right side, the tap coil preselectors are connected to the ground too. There is a tiny capacitor that connects one gang to the ground again. The central board should be used to avoid both tapped coil preselectors to get an inductive action on the other? Is this correct? Would it be possible to get the schematic so that I could try to carry it out? How did you compute the place to put the connectors (number of turns) for the tapped coil connectors? and have sufficient noise from the antenna, you may even change the taps. The preselector will give more insertion loss, but it will be more selective also. How is called this design? I don't know the name for it, it is just a parallel resonant LC circuit where the input and output goes via an inductive tap. Moving the tap changes the coupling between the source/load and the resonant circuit, hance changing the loaded Q-factor. How do you use it? Quite a blind test, no? This can be of use when you have strong signals in your neighborhood. Â* Because of portability, I frequently use an AOR AR8200. Without preselection, such a wide band receiver is useless with an external antenna. I have a big QRM (well, I don't know what it is) at 1500 MHz and other smaller ones elsewhere that I cannot switch off :)) Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
Hello,
On Wed, 15 Dec 2010 15:40:31 -0800, Richard Clark wrote: On 15 Dec 2010 20:52:22 GMT, Sébastien MEDARD wrote: There should free software displaying this gray line with UTC time, no? I'm sure there is - somewhere. GoogleEarth would be an elaborate tool to accomplish this. Well... In French we say that it is like using backhoes to move a bucket of sand... I found some software here : http://www.ac6v.com/software.htm#GEO Need to be tested... I found the "Receiving Antenna Handbook" quite cheap, but the "Loop Antenna Handbook" is still expensive. Between $60 to $257... I will try the cheapest. Myself, I would not advise spending more than $20. Professional antenna books barely give more than one section of the first chapter to its discussion. I totally agree, I will see what the seller proposes. I can imagine the teaching class. Everybody with a Collin's in front of him/her... A one year project to restore completely one of this legendary radio. I would like that! There were two to a radio. 40 to 30 hours learning the schematic theory of operation; and troubleshooting and tuning procedures and 30 to 40 hours in front of the radio. The class was 2 weeks long. Complete restore unnecessary, of course, as the last class had fixed any problem. No, we had a data bank of known problems, known solutions, and the time to debug them averaged over at least 100 students for each problem. :) With a good DSP outside (Audio DSP only), can beat every other ones? Good for filtering, probably tighter than the mechanical filters (theoretically), but there are many, many other considerations. I should try to see if there are any OM near the place I live. Could be interesting to see those old boxes. Well, many thanks for the basic information you gave me. Now, I need to use it. Sébastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
Hello Sébastien,
This: http://www.tetech.nl/divers/Simple_HF_Preselector1.png will help you. It shows the basic idea of a simple single variable capacitor preselector. You can use one coil and put two selectors on it, but with two seperate coils the attenuation for out-of-band signals is much better. This is because the individual turns of each coil have low mutual coupling (they don't act as a transformer). As I have sufficient antenna noise, the selectors (in my case clips) are mostly on the lowest position (I don't need matching to get more signal and noise). For AM BC operation you need more turns (w.r.t. the coils on the photo). Wim PA3DJS www.tetech.nl without abc, PM will reach me in most cases. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
Hello,
On Thu, 16 Dec 2010 09:40:15 -0800, Wimpie wrote: Hello Sébastien, This: http://www.tetech.nl/divers/Simple_HF_Preselector1.png will help you. It shows the basic idea of a simple single variable capacitor preselector. Many thanks. I will try it as soon as possible. You can use one coil and put two selectors on it, but with two seperate coils the attenuation for out-of-band signals is much better. This is because the individual turns of each coil have low mutual coupling (they don't act as a transformer). As I have sufficient antenna noise, the selectors (in my case clips) are mostly on the lowest position (I don't need matching to get more signal and noise). OK. For AM BC operation you need more turns (w.r.t. the coils on the photo). As I want to use it from 0.5 to 30MHz, what would be size of both coils? How many turns? What diameter? What would be the value of the C1 capacitor? A lot of questions.... Thanks again. Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
Hello,
On Thu, 16 Dec 2010 05:33:58 -0800, nm5k wrote: Yes for both. The cap is down at the bottom corner, and I use a separate coupling loop because I'm feeding coax to the radio. I saw a lot of photos where I saw the cap on the top and the coax feeded to the coupling loop on the bottom. Is doing the other way OK? The 42 inch per side loop uses 5 turns on the main loop. The coupling loop is on the inside, and maybe 36 or so inches out from center. Sounds like you are in good shape for caps. That 500-500 would be good. Great. I'd put a small mini switch between the two gangs to be able to cut or add the second gang. Definitively a good idea. That's what I do on mine anyway. I solder the switches right to the tabs on the cap. Good advice. I also have a handful of fixed caps to add if I want to drop further down into longwave. I don't use them that often so I just clip them on if needed. Planned. The thing that can be done is to use the same base board on the different loops to be used. Tell me your thoughts.... I was planning to put everything on a wood board... I think my 16 inch round loop has about 12 turns if I remember right.. It also uses a inner coupling loop. For me, those loops are mainly for AM-BC, It seems the size of the loop (I didn't play with loop software yet) is not critical, but is it possible to say that the lower band you want to listen, the taller loop you should use? but I do wander down and listen to the air beacons from time to time. And the big one covers 160 meters, so I use it for that sometimes. Well... Sorry for the newbie question.... But what do you mean by beacons? Sebastien. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 17 Dec 2010 15:28:08 GMT, Sébastien MEDARD wrote:
As I want to use it from 0.5 to 30MHz, what would be size of both coils? How many turns? What diameter? What would be the value of the C1 capacitor? A lot of questions.... Hi Sebastien, Reg Edward's software, that you already have access to, will answer that far faster than asking here. Reason for that is because of all the variables that come into play. You can judge for yourself when you enter them into the program and observe what results are returned. 73's Richard Clark, KB7QHC |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 17 dic, 16:28, Sébastien MEDARD wrote:
Hello, On Thu, 16 Dec 2010 09:40:15 -0800, Wimpie wrote: Hello Sébastien, This: *http://www.tetech.nl/divers/Simple_H...ctor1.png*will help you. It shows the basic idea of a simple single variable capacitor preselector. Many thanks. I will try it as soon as possible. You can use one coil and put two selectors on it, but with two seperate coils the attenuation for out-of-band signals is much better. This is because the individual turns of each coil have low mutual coupling (they don't act as a transformer). * As I have sufficient antenna noise, the selectors (in my case clips) are mostly on the lowest position (I don't need matching to get more signal and noise). OK. For AM BC operation you need more turns (w.r.t. the coils on the photo).. As I want to use it from 0.5 to 30MHz, what would be size of both coils? How many turns? What diameter? What would be the value of the C1 capacitor? A lot of questions.... Thanks again. Sebastien. Hello, Do you have some background in electronics and/or AC circuits (concept of reactance, impedance, resonance, etc)? Wim PA3DJS |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
Hello,
On Sat, 18 Dec 2010 08:09:52 -0800, Wimpie wrote: Do you have some background in electronics and/or AC circuits (concept of reactance, impedance, resonance, etc)? I should.... But I was better in chemistry :) I should have studied RLC circuits but at this time it was boring... If I had some interest in shortwave listening, I would have been a better student in physics :) But I should be able to understand :) I think I am going to see if there is any radio club near the place I live. Because I have a lot of questions and English is, as you understood it, not my main spoken language :) Seb. |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 19 dic, 23:10, Sébastien MEDARD wrote:
Hello, On Sat, 18 Dec 2010 08:09:52 -0800, Wimpie wrote: Do you have some background in electronics and/or AC circuits (concept of reactance, impedance, resonance, etc)? I should.... But I was better in chemistry :) I should have studied RLC circuits but at this time it was boring... If I had some interest in shortwave listening, I would have been a better student in physics :) But I should be able to understand :) I think I am going to see if there is any radio club near the place I live. Because I have a lot of questions and English is, as you understood it, not my main spoken language :) Seb. Hello Sébastien, I think it is a good thing to contact some people locally. Besides support with the calculation for the inductors and capacitors, small "construction errors" can degrade performance of a basically good design significantly. Be prepared to get many different answers to the same question! Yesterday evening I experienced strong increase in mains supply synchronized interference. After some elimination tests, the "offender" was a new tiny switching plug-in adapter. I had to use several ferrite cores to reduce the interference from 3.3 MHz to 15 MHz to an acceptable level. The volume and weight of the ferrite cores I used exceeds that of the adapter. Best regards, Wim PA3DJS www.tetech.nl without abc, PM will reach me |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
Hello,
On Tue, 21 Dec 2010 08:07:03 -0800, Wimpie wrote: I think it is a good thing to contact some people locally. I think I am prepared to do that :) I had to use several ferrite cores to reduce the interference from 3.3 MHz to 15 MHz to an acceptable level. The volume and weight of the ferrite cores I used exceeds that of the adapter. About ferrite cores and tapped coils.... I was wondering about something... Imagine a tapped coil from a inductance value, let's say "i". what is the effect of progressively introducing a ferrite core (wand) inside the tapped coil? Reducing, or increasing "i"? We were speaking about a Collins receiver. If I read well, it seems to use this kind of feature. Could be better for experimentation, no? Sebastien. p.s. I need to buy something to measure capacitance and inductance (RLC bridge...). |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
On 21 dic, 17:42, Sébastien MEDARD wrote:
Hello, On Tue, 21 Dec 2010 08:07:03 -0800, Wimpie wrote: I think it is a good thing to contact some people locally. I think I am prepared to do that :) I had to use several ferrite cores to reduce the interference from 3.3 MHz to 15 MHz to an acceptable level. * The volume and weight of the ferrite cores I used exceeds that of the adapter. About ferrite cores and tapped coils.... I was wondering about something... Imagine a tapped coil from a inductance value, let's say "i". what is the effect of progressively introducing a ferrite core (wand) inside the tapped coil? Reducing, or increasing "i"? We were speaking about a Collins receiver. If I read well, it seems to use this kind of feature. Could be better for experimentation, no? Sebastien. p.s. I need to buy something to measure capacitance and inductance (RLC bridge...). Hello Sébastien, When you put in a ferrite bar of suitable material, the total inductance will increase. The longer and thicker, the more will be the increase of inductance. The actual increase depends on several factors (length/diameter ratio of coil, and to a lesser extend, ferrite magnetic permeability). When I put 10*150mm^2 ferrite rods (from old vacuum tube AM/FM radios I believe) into my simple single capacitor preselector, the lowest frequency goes down from 3.4 MHz to 1.1 MHz. The 5 m wire outside wire performs equal w.r.t. my small portable indoor loop on AM BC 1476, 1485 kHz (Spanish stations). Of course, loop positioned and oriented for best reception. When you look into the technical documentation of ferrite producers/ vendors (Ferroxcube, Fairrite, Amidon, TDK, Epcos, Kitagawa, etc), they will show you a graph that relates inductance change ratio versus coil dimensions and ferrite permeability. Wrong choice of ferrite material will reduce Q-factor significantly. The effect on a tapped coil in a circuit depends also on where you start pushing the bar into the coil, as the part of the coil closest to the ferrite bar changes inductance first. Regarding LCR meter, There are some very nice kits around that measures small inductors and capacitors very well: http://electronics-diy.com/lc_meter.php gives an example. Best regards, Wim PA3DJS www.tetech.nl without abc, PM will reach me |
SWL for Newbies (was: Balcony Antenna for Shortwave Listening)
Hello,
On Fri, 17 Dec 2010 09:20:48 -0800, Richard Clark wrote: Reg Edward's software, that you already have access to, will answer that far faster than asking here. Reason for that is because of all the variables that come into play. You can judge for yourself when you enter them into the program and observe what results are returned. Tonight and yesterday night I played with my experimentation board (loop...s on my shelves). I have a 4 loops (square) web : 1 - 8 turns - 1.5 m /side 2 - 3 turns - 1.0m /side 3 - 1 turn - 0.8m /side 4 - 1 turn- 0.65m /side Each one is inside the other one. I used the second to be the matching one from the previous, the firts. The third, to be the mathcing one of the second, etc. The resonant one gets a variable air capacitor (I change it every time I need to go higher....). Very interesting, indeed. If I understand well, the loop gets the role of inductance and the capacitor the role of the capacitance... (Lapalisse...). Matching both gets the best result for a given frequency. I succeed in making apparent signals that I was not aware of... With this antenna I can tune in the frequency from 300 KHz to near 7300 KHz... Completely amazing. That's the first time I can exactly see (thanks to the waterfall information display) how it does increase, not only the signal, but what's more important, the signal/noise ratio. I understand now how this is very important... What I can see, is that depending on the size of the loop and the frequency I am monitoring, the variable capacitor may or may not be very difficult to use, and the bandwidth lack of noise, narrow or wide... Interesting to see that it is possible to increase the signal without increasing a lot the signal/noise ratio (better than nothing :). But you can't play when the signal is too weak.... :) I am quite happy. It does not tell anything about the antenna efficiency, but it helps me understand how it works. I get somebody in my family who is a physics teacher... I need to ask her information about "RLC oscillators for newbies" to be able to put some rational things upon my experimentations :) To do next : - Try to carry out the tiny preselector from Wim (need to find some coper wire... And need to try to recover some old radio parts to play with.... (get some ferrite rods, low value variable capacitors, etc.) - Try to get some time, and some place, to play with long wires, dipoles and their related matching systems... Sebastien. |
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