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Make your own T2FD
Hello fellow shortwave listeners !
More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees |
Kees wrote:
Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees http://members.home.nl/rita.kees/t2fd1.gif I found that my garage is WAY to far away to use this setup. Following the formula, I took an average frequency of 10 Megahertz. I divided into 100, as per the formula. I got an antenna length of (100ft/10,000,000) = 1 X 10^-5 feet, or 0.00012 inches. I then thought that this just couldn't be right. I redid it using Meters instead of feet and arrived at 0.00001 meters length. MUCH BETTER! The problem now is that the store only sells full length rolls of wire. Where can I mail order a smaller chunk? Can they just wrap the postage stamp around it to save shipping costs? Being ever on the watch for cheap alternatives, what is a cheap way of relocating the far end antenna support? I don't want to pay to have the garage moved. Any insights appreciated. mike -- __ __ __ __ __ __ __ __ / /\ / /\ / /\ / /\ / /\ / /\ / /\ / / / /\ \/ /\ \/ /\ \/ / /_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/ \/_/ ..let the cat out to reply.. ©Densa International 'Think tanks cleaned cheap' |
"Kees" wrote in message
... Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees The Tilted Terminated Folded Dipole ("T2FD") is a broadband folded dipole antenna design that provides a relatively stable feed point impedance over about a five to one frequency range. The antenna length in meters is approximately 100 divided by the lowest desired operating frequency in megahertz. The upper element of the folded dipole is opened in the center and a non-inductive terminating resistor of around 350-400 ohms is inserted. The bottom element is fed in the center through a 6-to-1 balun for a good match to 50 ohm feed line. The antenna is not as efficient as a matched half wave dipole at any specific frequency, but it also does not require an antenna tuner for operation, making it easy to use. The loss of receiving efficiency is not generally noticeable in the high frequency range (2-30 MHz), amounting to less than 6 db (one standard S-unit) during extensive on-the-air testing. Here is additional information on the T2FD antenna. Barker & Williamson actually applied for a US patent (US Patent #4423423) for their specific T2FD antenna design. http://www.fact-index.com/t/t2/t2fd_antenna.html While this may be acceptable for SWL operation, the resistor does not have sufficient wattage for any station attempting to use this for a transmitting antenna. http://www.tuberadio.com/tfd.html http://www.universal-radio.com/catalog/sw_ant/0562.html w9gb |
m II wrote:
Kees wrote: Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees http://members.home.nl/rita.kees/t2fd1.gif I found that my garage is WAY to far away to use this setup. Following the formula, I took an average frequency of 10 Megahertz. I divided into 100, as per the formula. I got an antenna length of (100ft/10,000,000) = 1 X 10^-5 feet, or 0.00012 inches. I then thought that this just couldn't be right. I redid it using Meters instead of feet and arrived at 0.00001 meters length. MUCH BETTER! The problem now is that the store only sells full length rolls of wire. Where can I mail order a smaller chunk? Can they just wrap the postage stamp around it to save shipping costs? Being ever on the watch for cheap alternatives, what is a cheap way of relocating the far end antenna support? I don't want to pay to have the garage moved. Any insights appreciated. mike In physics always use meters, kilograms, joules and not inches, pounds or horsepower Hans |
Hans wrote:
In physics always use meters, kilograms, joules and not inches, pounds or horsepower Of course. Sorry about my retrograde calculations, however, the numbers provided on the site need to be clarified, as they don't work either in either method. An example at the bottom of the page using the proper units would be in order. The confusion is what caused me to post to begin with. 100 anything divided by millions of other units is bound to cause very small numbers and in this case very small numbers give birds no place to perch. mike |
= = = "G.Beat" wrote in message
= = = news:UdtBc.152030$Ly.30888@attbi_s01... "Kees" wrote in message ... Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees The Tilted Terminated Folded Dipole ("T2FD") is a broadband folded dipole antenna design that provides a relatively stable feed point impedance over about a five to one frequency range. The antenna length in meters is approximately 100 divided by the lowest desired operating frequency in megahertz. The upper element of the folded dipole is opened in the center and a non-inductive terminating resistor of around 350-400 ohms is inserted. The bottom element is fed in the center through a 6-to-1 balun for a good match to 50 ohm feed line. The antenna is not as efficient as a matched half wave dipole at any specific frequency, but it also does not require an antenna tuner for operation, making it easy to use. The loss of receiving efficiency is not generally noticeable in the high frequency range (2-30 MHz), amounting to less than 6 db (one standard S-unit) during extensive on-the-air testing. Here is additional information on the T2FD antenna. Barker & Williamson actually applied for a US patent (US Patent #4423423) for their specific T2FD antenna design. http://www.fact-index.com/t/t2/t2fd_antenna.html W9GB, B&W makes two general statements about the T2FD: * For example, an {T2FD} Antenna for the lower portion of Shortwave (3 - 18 MHz) will be roughly 33m (110 feet) long, with conductors spaced 1m (3.3 feet). [With a Top End mounted about 60 Feet High at 30 Degrees.] * In order to cover the higher portion of Shortwave (5 - 30 MHz), this {T2FD} Antenna will be roughly 20m (66 feet) long, with a spacing of 60 cm (24 inches). [With a Top End mounted about 40 Feet High at 30 Degrees.] Build one size or the other = No Formula Required. Read: T2FD Antenna - WOW ! ! ! {One SWL's Experiance} http://groups.yahoo.com/group/Shortw...na/message/293 iane ~ RHF .. .. While this may be acceptable for SWL operation, the resistor does not have sufficient wattage for any station attempting to use this for a transmitting antenna. http://www.tuberadio.com/tfd.html http://www.universal-radio.com/catalog/sw_ant/0562.html w9gb .. |
The fact that we get widely varying reports about the performance of the
T2FD antenna suggests that an equally-long dipole would give good results across the frequency spectrum if used with an antenna tuner. What the T2FD really buys you is the ability to avoid an antenna tuner. There is an amateur antenna out there consisting of an 80-meter dipole (I mean one that is a half wave at 80 meters, not one physically 80 meters long) fed with about 100 feet of 450 ohm ladder line. It turns out that 100 feet of line is within about 10% of the idea length to match the antenna to 50 ohms on all amateur bands. One design of this antenna uses a tuner to correct for the mismatch, while another uses various lengths of 450 ohm line added to the feedline to achieve a match. -- jhhaynes at earthlink dot net |
"Kees" wrote in message ... Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees I have no idea how well the antenna works, but the method of connecting the reisistor is very complicated. May I suggest: Connect the two wires to a normal dog-bone insulator, and solder the resistor across the insulator to the two wires. Insulate if you wish. For receive only, a 1/2 W resistor is as good, or better. Tam/WB2TT |
I have no idea how well the antenna works, but the method of connecting the
reisistor is very complicated. May I suggest: Hi Tam, For receive only, a doublet antenna, as high as possible, with 50 ohm,or 75, or 300 ohm feedline will work well. I have no idea why people want to complicate receive antennas with resistors. Do you? 73 Gary N4AST |
"JGBOYLES" wrote in message ... I have no idea how well the antenna works, but the method of connecting the reisistor is very complicated. May I suggest: Hi Tam, For receive only, a doublet antenna, as high as possible, with 50 ohm,or 75, or 300 ohm feedline will work well. I have no idea why people want to complicate receive antennas with resistors. Do you? 73 Gary N4AST Hi Gary, I use my 75 m antenna, which tops out at 70 feet for SWL listening. For 99% of SWL listeners the limiting things are the poor IF filtering and overload prone front ends. Also, I dont think you see a noise blanker in a sub $300 radio. Tam |
The T2FD (Terminated Tilted Folded Dipole) was developed by the US Navy
after carrying out experiments using terminating resistors. Numerous variations have appeared over the years, usually accompanied by warnings that as a transmitting aperiodic multiband antenna, its performance may leave something to be desired. This is because the transmitting power may be wasted in the terminating resistor. As mentioned previously the antenna developed from US Naval experiments to broaden the bandwidth of a folded dipole to a reasonable degree. The was first described publicly in 1949, after Navy Captain C.L. Countryman tested it for long periods in California during WWII. The T2FD (also known as a tilted, centre fed, terminated, folded dipole) can offer claimed gains of 4-6dB over a dipole, depending on the frequency, although 1-3dB is nearer the mark with some frequencies exhibiting 1dB, as the resistor absorbs the RF power in transmission. The main attraction of the T2FD is not its gain however; it's its broadbandedness. It was, and still is, being publicized in journals as a broadband aerial suitable for use between 3.5 and 28 Mhz. In addition the T2FD has some attractive properties in terms of noise reduction, which some long wires / dipoles and ATU combinations are susceptible too. In addition the T2FD can be used at higher frequencies than its design frequency. Some sources claim that it can be used over a range of 5 or even 6:1, although my own observations indicate 4:1. None the less a 40-meter version will cover 7Mhz to 25 Mhz, with some useful performance up into the 27 Mhz CB band. See http://www.gb4iom.co.uk/new_page_4.htm for more information. 73 Adrian M1LCR "Kees" wrote in message ... Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees |
= = = "Tam/WB2TT" wrote in message
= = = ... "Kees" wrote in message ... Hello fellow shortwave listeners ! More info to make a T2FD yourself, like I did mine, please have a look at: http://members.home.nl/rita.kees/t2fdmake.html I hope you can appreciate it and use it for your practice. I will be glad to answer your questions. 73/cheers Kees I have no idea how well the antenna works, but the method of connecting the reisistor is very complicated. May I suggest: Connect the two wires to a normal dog-bone insulator, and solder the resistor across the insulator to the two wires. Insulate if you wish. For receive only, a 1/2 W resistor is as good, or better. Tam/WB2TT WB2TT - Simplier is better ~ RHF .. |
On Tue, 22 Jun 2004 00:56:48 +0000, M1LCR wrote:
between 3.5 and 28 Mhz. In addition the T2FD has some attractive properties in terms of noise reduction, which some long wires / dipoles and ATU combinations are susceptible too. I live in a suburb. My dipoles and long wires had so much noise that I hardly ever would listen to HF. Once I read about the noise immunity provided by a T2FD antenna, I constructed one to try. It was the best thing I could have done! It made HF livable in my high noise urban environment. I almost don't notice the noise I had before. I am able to pick up signals that my neighbor with a tri-band 3 element yagi is unable to hear due to his noise. I would recommend this design to anyone combating local QRM. |
On Tue, 22 Jun 2004 05:45:27 GMT, yea right wrote:
On Tue, 22 Jun 2004 00:56:48 +0000, M1LCR wrote: between 3.5 and 28 Mhz. In addition the T2FD has some attractive properties in terms of noise reduction, which some long wires / dipoles and ATU combinations are susceptible too. I live in a suburb. My dipoles and long wires had so much noise that I hardly ever would listen to HF. Once I read about the noise immunity provided by a T2FD antenna, I constructed one to try. It was the best thing I could have done! It made HF livable in my high noise urban environment. I almost don't notice the noise I had before. I am able to pick up signals that my neighbor with a tri-band 3 element yagi is unable to hear due to his noise. I would recommend this design to anyone combating local QRM. That's indeed what it is: a very low-noise antenna. Look at : http://members.home.nl/rita.kees/t2fdmake.html for my "version ". |
On Tue, 22 Jun 2004 05:45:27 GMT, yea right wrote:
On Tue, 22 Jun 2004 00:56:48 +0000, M1LCR wrote: between 3.5 and 28 Mhz. In addition the T2FD has some attractive properties in terms of noise reduction, which some long wires / dipoles and ATU combinations are susceptible too. I live in a suburb. My dipoles and long wires had so much noise that I hardly ever would listen to HF. Once I read about the noise immunity provided by a T2FD antenna, I constructed one to try. It was the best thing I could have done! It made HF livable in my high noise urban environment. I almost don't notice the noise I had before. I am able to pick up signals that my neighbor with a tri-band 3 element yagi is unable to hear due to his noise. I would recommend this design to anyone combating local QRM. That's indeed what it is: a very low-noise antenna. Look at : http://members.home.nl/rita.kees/t2fdmake.html for my "version ". |
Yes, that is an advantage. Everytime someone asks a question about a receive
only antenna on this newsgroup, there are always many responses saying to just put up a piece of wire and run it strait to your radio. That will work, assuming that you live out in the middle of nowhere, have no neighbors and have no electrical appliances. For the rest of us, noise is a consideration and more thought needs to be put into an antenna system. "Kees" wrote in message ... That's indeed what it is: a very low-noise antenna. Look at : http://members.home.nl/rita.kees/t2fdmake.html for my "version ". |
Yes, that is an advantage. Everytime someone asks a question about a receive
only antenna on this newsgroup, there are always many responses saying to just put up a piece of wire and run it strait to your radio. That will work, assuming that you live out in the middle of nowhere, have no neighbors and have no electrical appliances. For the rest of us, noise is a consideration and more thought needs to be put into an antenna system. "Kees" wrote in message ... That's indeed what it is: a very low-noise antenna. Look at : http://members.home.nl/rita.kees/t2fdmake.html for my "version ". |
"CW" no adddress@spam free.com wrote in message ... Yes, that is an advantage. Everytime someone asks a question about a receive only antenna on this newsgroup, there are always many responses saying to just put up a piece of wire and run it strait to your radio. That will work, assuming that you live out in the middle of nowhere, have no neighbors and have no electrical appliances. For the rest of us, noise is a consideration and more thought needs to be put into an antenna system. How does the antenna differentiate between "noise" and a valid signal? (Perhaps these are going to be the solution to BPL.) Pete |
"CW" no adddress@spam free.com wrote in message ... Yes, that is an advantage. Everytime someone asks a question about a receive only antenna on this newsgroup, there are always many responses saying to just put up a piece of wire and run it strait to your radio. That will work, assuming that you live out in the middle of nowhere, have no neighbors and have no electrical appliances. For the rest of us, noise is a consideration and more thought needs to be put into an antenna system. How does the antenna differentiate between "noise" and a valid signal? (Perhaps these are going to be the solution to BPL.) Pete |
In article sBEDc.1168$Rr2.4@lakeread03,
" Uncle Peter" wrote: "CW" no adddress@spam free.com wrote in message ... Yes, that is an advantage. Everytime someone asks a question about a receive only antenna on this newsgroup, there are always many responses saying to just put up a piece of wire and run it strait to your radio. That will work, assuming that you live out in the middle of nowhere, have no neighbors and have no electrical appliances. For the rest of us, noise is a consideration and more thought needs to be put into an antenna system. How does the antenna differentiate between "noise" and a valid signal? Antennas are not intelligent agents able to differentiate between noise and a broadcast signal. If the noise signal is generated a long distance from the antenna it will be received right along with broadcast signals. The only advantage some antennas would have here is its reception pattern where the antenna could be orientated to be relatively insensitive in the direction of the noise signal. This generally is not helpful for short wave signals though because they are generally too spread out directionally instead of looking like a point source to take advantage of antenna nulls. Another problem for most people is the fact that they cannot get the antenna up high enough for it to exhibit its directional characteristics to a great degree. A local noise is another matter greatly affecting many peoples reception of short wave signals since many electronic devices around the home and neighbor¹s homes generate noise. Here the type of antenna, how it is connected to the receiver, and where it is located on the user¹s property makes a huge difference on what may be heard. Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. -- Telamon Ventura, California |
In article sBEDc.1168$Rr2.4@lakeread03,
" Uncle Peter" wrote: "CW" no adddress@spam free.com wrote in message ... Yes, that is an advantage. Everytime someone asks a question about a receive only antenna on this newsgroup, there are always many responses saying to just put up a piece of wire and run it strait to your radio. That will work, assuming that you live out in the middle of nowhere, have no neighbors and have no electrical appliances. For the rest of us, noise is a consideration and more thought needs to be put into an antenna system. How does the antenna differentiate between "noise" and a valid signal? Antennas are not intelligent agents able to differentiate between noise and a broadcast signal. If the noise signal is generated a long distance from the antenna it will be received right along with broadcast signals. The only advantage some antennas would have here is its reception pattern where the antenna could be orientated to be relatively insensitive in the direction of the noise signal. This generally is not helpful for short wave signals though because they are generally too spread out directionally instead of looking like a point source to take advantage of antenna nulls. Another problem for most people is the fact that they cannot get the antenna up high enough for it to exhibit its directional characteristics to a great degree. A local noise is another matter greatly affecting many peoples reception of short wave signals since many electronic devices around the home and neighbor¹s homes generate noise. Here the type of antenna, how it is connected to the receiver, and where it is located on the user¹s property makes a huge difference on what may be heard. Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. -- Telamon Ventura, California |
"Telamon" wrote in message ... In article sBEDc.1168$Rr2.4@lakeread03, " Uncle Peter" wrote: How does the antenna differentiate between "noise" and a valid signal? SNIP Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. -- Telamon Ventura, California You'd also have to decouple the coax shield from the antenna to prevent signals or noise from carried on the outside of the shield common-mode fashion from being coupled back into your remotely located antenna. Pete |
"Telamon" wrote in message ... In article sBEDc.1168$Rr2.4@lakeread03, " Uncle Peter" wrote: How does the antenna differentiate between "noise" and a valid signal? SNIP Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. -- Telamon Ventura, California You'd also have to decouple the coax shield from the antenna to prevent signals or noise from carried on the outside of the shield common-mode fashion from being coupled back into your remotely located antenna. Pete |
Telamon wrote:
A local noise is another matter greatly affecting many peoples reception of short wave signals since many electronic devices around the home and neighbor¹s homes generate noise. Here the type of antenna, how it is connected to the receiver, and where it is located on the user¹s property makes a huge difference on what may be heard. Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. Yes! You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). With an unbalanced antenna you must take more care to keep common mode out of the feed system. It is not terribly hard, however, to reduce common mode coupling to negligible levels, even with an unbalanced antenna (see http://www.anarc.org/naswa/badx/ante...e_antenna.html). One may want an unbalanced system for other reasons. A balanced dipole close to the ground generally has a poor vertical radiation pattern, while an inverted-L is much better. You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. This claim is widely made in the hobbyist literature, but I've never seen any measurements to back it up. I've tried to check it myself, and found the opposite: close to modern sources of EMI, the field tends to be predominantly magnetic. You have to be very close the source to see any effect at all: beyond ~0.1 wavelength induction balances the field pretty effectively. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. Yes! -jpd |
Telamon wrote:
A local noise is another matter greatly affecting many peoples reception of short wave signals since many electronic devices around the home and neighbor¹s homes generate noise. Here the type of antenna, how it is connected to the receiver, and where it is located on the user¹s property makes a huge difference on what may be heard. Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. Yes! You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). With an unbalanced antenna you must take more care to keep common mode out of the feed system. It is not terribly hard, however, to reduce common mode coupling to negligible levels, even with an unbalanced antenna (see http://www.anarc.org/naswa/badx/ante...e_antenna.html). One may want an unbalanced system for other reasons. A balanced dipole close to the ground generally has a poor vertical radiation pattern, while an inverted-L is much better. You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. This claim is widely made in the hobbyist literature, but I've never seen any measurements to back it up. I've tried to check it myself, and found the opposite: close to modern sources of EMI, the field tends to be predominantly magnetic. You have to be very close the source to see any effect at all: beyond ~0.1 wavelength induction balances the field pretty effectively. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. Yes! -jpd |
They don't but if you go by the advice you generally get on the antenna
group, you run an unshielded lead in (part of the antenna) right into the shack (big noise source). When I made my prior comments about the lack of consideration given to receive antenna, I was referring to the antenna group. I didn't realize that the message was cross posted. It just amazes me that they will debate a transmitting antenna to minute detail but receiving antennas deserve no consideration other than a random piece of wire thrown into a tree. Despite their often one sidedness I have learned a great deal from them and mean no disrespect. " Uncle Peter" wrote in message news:sBEDc.1168$Rr2.4@lakeread03... How does the antenna differentiate between "noise" and a valid signal? |
They don't but if you go by the advice you generally get on the antenna
group, you run an unshielded lead in (part of the antenna) right into the shack (big noise source). When I made my prior comments about the lack of consideration given to receive antenna, I was referring to the antenna group. I didn't realize that the message was cross posted. It just amazes me that they will debate a transmitting antenna to minute detail but receiving antennas deserve no consideration other than a random piece of wire thrown into a tree. Despite their often one sidedness I have learned a great deal from them and mean no disrespect. " Uncle Peter" wrote in message news:sBEDc.1168$Rr2.4@lakeread03... How does the antenna differentiate between "noise" and a valid signal? |
" Uncle Peter" wrote in message news:HVKDc.1192$Rr2.241@lakeread03... "Telamon" wrote in message ... In article sBEDc.1168$Rr2.4@lakeread03, " Uncle Peter" wrote: How does the antenna differentiate between "noise" and a valid signal? SNIP Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. -- Telamon Ventura, California You'd also have to decouple the coax shield from the antenna to prevent signals or noise from carried on the outside of the shield common-mode fashion from being coupled back into your remotely located antenna. Pete Quite true. |
" Uncle Peter" wrote in message news:HVKDc.1192$Rr2.241@lakeread03... "Telamon" wrote in message ... In article sBEDc.1168$Rr2.4@lakeread03, " Uncle Peter" wrote: How does the antenna differentiate between "noise" and a valid signal? SNIP Fundamentally, you want the entire antenna system to reject common mode noise since to a local antenna this is the mode in which, the local noise will couple to the antenna. You will want to use an antenna that is balanced (Hertzian) instead of unbalanced (Marconi). You might also want to consider using an antenna type that responds more to the magnetic field component of the radio wave instead of the electric. These two suggestions encompass the fact that most of the local noise energy reaching and coupling to the antenna is a common mode electric field and since the far field broadcast signals you want to receive is composed of both electric and magnetic the later will be enhanced at the expense of the former. The connection from radio to antenna is best shielded so you would use coax. You could use a balance line but they are harder to acquire, use, and still will not work as well as coax shielding against local noise. The antenna would be located as far from the majority of local noise sources as possible on the property. Distance reduces the coupling to local noise sources. -- Telamon Ventura, California You'd also have to decouple the coax shield from the antenna to prevent signals or noise from carried on the outside of the shield common-mode fashion from being coupled back into your remotely located antenna. Pete Quite true. |
On Sun, 27 Jun 2004 19:55:58 -0700, "CW" no adddress@spam free.com
wrote: When I made my prior comments about the lack of consideration given to receive antenna, I was referring to the antenna group. I didn't realize that the message was cross posted. It just amazes me that they will debate a transmitting antenna to minute detail but receiving antennas deserve no consideration other than a random piece of wire thrown into a tree. Hi OM, As generalizations go, this one falls short with them all. We here at rec.radio.amateur.antenna often recite the credo that "reciprocity rules." This means that all considerations given to a transmitting antenna are equally applied to receiving antennas. However, I am sure you are responding to the disparity in coverage between receiving and transmitting antennas - and this is for good reason. Reception and Transmission are NOT reciprocal operations. A receiver has far more latitude to accomplish its goal than does a transmitter. Unless you have an abysmal receiver poorly connected to an inadequate whip, the stock receiver with a simple length of wire is often very close to doing a good job. If the receiver suffers from any of a multitude of issues, there is generally a solution that answers the problem specifically. About the only thing you can do for the transmitter is to turn up the power, or lower the transmission loss. It stands to reason that our focus is on optimizing the loss side of the balance ledger. Returning to the credo of "reciprocity rules," any gain to the advantage of a transmitter is enjoyed by the receiver and the SWLer stands the same advantage. But if that advantage is measured at 3dB, this has the significance of 50W in 100W compared to the SWL S-Meter change from S5 to S6 (BFD). Even though it is the same 3dB, there is the illusion of perspective (my 50W compared to your 5µV). If the SW station is buried in S9 noise, then this is not an antenna problem (unless you can null the noise out through careful lobe positioning). Filtering and/or DSP stand to answer the problem, but these are obviously not remedies to transmission issues. There is another thread discussing the goal of constructing a small loop for 80M reception (and how well 5 turns might achieve some benefit). The same issues of loss prevail for the comparison of Radiation Resistance to Ohmic Resistance for a 1 Meter loop. The loop Rr is in the thousandths of an Ohm and about on par for a small wire's Ohmic loss. There's that 3dB again and what concerns the transmission efficiency is far easier to tolerate with the receiver and its surplus of gain. If the SWLer pays attention to this issue as it concerns the transmission problems, then that SWLer stands to gain in the efficiency returned. However, this is not to suggest that there is an actual need to obtain this efficiency; but if the SWLer mismanages the construction, the topic is discussed to the necessary depth to correct it. A simple basis of comparison will illustrate. Many SW radios have a ferrite stick antenna that will work with at least some stations (VOA, WWV, BBC and a host of others). Try transmitting through that same ferrite stick and it will be like trying to shout through a straw. Our only alternative is to add an amp, but the big KW is only going to render smoke. 73's Richard Clark, KB7QHC |
On Sun, 27 Jun 2004 19:55:58 -0700, "CW" no adddress@spam free.com
wrote: When I made my prior comments about the lack of consideration given to receive antenna, I was referring to the antenna group. I didn't realize that the message was cross posted. It just amazes me that they will debate a transmitting antenna to minute detail but receiving antennas deserve no consideration other than a random piece of wire thrown into a tree. Hi OM, As generalizations go, this one falls short with them all. We here at rec.radio.amateur.antenna often recite the credo that "reciprocity rules." This means that all considerations given to a transmitting antenna are equally applied to receiving antennas. However, I am sure you are responding to the disparity in coverage between receiving and transmitting antennas - and this is for good reason. Reception and Transmission are NOT reciprocal operations. A receiver has far more latitude to accomplish its goal than does a transmitter. Unless you have an abysmal receiver poorly connected to an inadequate whip, the stock receiver with a simple length of wire is often very close to doing a good job. If the receiver suffers from any of a multitude of issues, there is generally a solution that answers the problem specifically. About the only thing you can do for the transmitter is to turn up the power, or lower the transmission loss. It stands to reason that our focus is on optimizing the loss side of the balance ledger. Returning to the credo of "reciprocity rules," any gain to the advantage of a transmitter is enjoyed by the receiver and the SWLer stands the same advantage. But if that advantage is measured at 3dB, this has the significance of 50W in 100W compared to the SWL S-Meter change from S5 to S6 (BFD). Even though it is the same 3dB, there is the illusion of perspective (my 50W compared to your 5µV). If the SW station is buried in S9 noise, then this is not an antenna problem (unless you can null the noise out through careful lobe positioning). Filtering and/or DSP stand to answer the problem, but these are obviously not remedies to transmission issues. There is another thread discussing the goal of constructing a small loop for 80M reception (and how well 5 turns might achieve some benefit). The same issues of loss prevail for the comparison of Radiation Resistance to Ohmic Resistance for a 1 Meter loop. The loop Rr is in the thousandths of an Ohm and about on par for a small wire's Ohmic loss. There's that 3dB again and what concerns the transmission efficiency is far easier to tolerate with the receiver and its surplus of gain. If the SWLer pays attention to this issue as it concerns the transmission problems, then that SWLer stands to gain in the efficiency returned. However, this is not to suggest that there is an actual need to obtain this efficiency; but if the SWLer mismanages the construction, the topic is discussed to the necessary depth to correct it. A simple basis of comparison will illustrate. Many SW radios have a ferrite stick antenna that will work with at least some stations (VOA, WWV, BBC and a host of others). Try transmitting through that same ferrite stick and it will be like trying to shout through a straw. Our only alternative is to add an amp, but the big KW is only going to render smoke. 73's Richard Clark, KB7QHC |
In article ,
John Doty wrote: Telamon wrote: Snip This claim is widely made in the hobbyist literature, but I've never seen any measurements to back it up. I've tried to check it myself, and found the opposite: close to modern sources of EMI, the field tends to be predominantly magnetic. You have to be very close the source to see any effect at all: beyond ~0.1 wavelength induction balances the field pretty effectively. First off I did not realize this was cross posted so this is my last post to this thread. I'm not not regurgitating hobbyist claims but my experience in this matter. Although 0.1 wavelength is more than enough to cover a urban lot and your neighbor at short wave frequencies theory does not do justice to a non homogenous environment we all live in. Most electronic noise generators do not have efficient antennas attached to them where the environment easily distorts the electric fields. I have repeatedly experienced predominantly voltage common mode coupling of local noise sources. Without exception mitigation methods against voltage common mode noise were always successful and current mode antennas always picked up less local noise. -- Telamon Ventura, California |
In article ,
John Doty wrote: Telamon wrote: Snip This claim is widely made in the hobbyist literature, but I've never seen any measurements to back it up. I've tried to check it myself, and found the opposite: close to modern sources of EMI, the field tends to be predominantly magnetic. You have to be very close the source to see any effect at all: beyond ~0.1 wavelength induction balances the field pretty effectively. First off I did not realize this was cross posted so this is my last post to this thread. I'm not not regurgitating hobbyist claims but my experience in this matter. Although 0.1 wavelength is more than enough to cover a urban lot and your neighbor at short wave frequencies theory does not do justice to a non homogenous environment we all live in. Most electronic noise generators do not have efficient antennas attached to them where the environment easily distorts the electric fields. I have repeatedly experienced predominantly voltage common mode coupling of local noise sources. Without exception mitigation methods against voltage common mode noise were always successful and current mode antennas always picked up less local noise. -- Telamon Ventura, California |
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For your information:
You are posting this hole trhead on two dutch newsgroups! Telamon a écrit In article , John Doty wrote: Telamon wrote: Snip This claim is widely made in the hobbyist literature, but I've never seen any measurements to back it up. I've tried to check it myself, and found the opposite: close to modern sources of EMI, the field tends to be predominantly magnetic. You have to be very close the source to see any effect at all: beyond ~0.1 wavelength induction balances the field pretty effectively. First off I did not realize this was cross posted so this is my last post to this thread. I'm not not regurgitating hobbyist claims but my experience in this matter. Although 0.1 wavelength is more than enough to cover a urban lot and your neighbor at short wave frequencies theory does not do justice to a non homogenous environment we all live in. Most electronic noise generators do not have efficient antennas attached to them where the environment easily distorts the electric fields. I have repeatedly experienced predominantly voltage common mode coupling of local noise sources. Without exception mitigation methods against voltage common mode noise were always successful and current mode antennas always picked up less local noise. |
For your information:
You are posting this hole trhead on two dutch newsgroups! Telamon a écrit In article , John Doty wrote: Telamon wrote: Snip This claim is widely made in the hobbyist literature, but I've never seen any measurements to back it up. I've tried to check it myself, and found the opposite: close to modern sources of EMI, the field tends to be predominantly magnetic. You have to be very close the source to see any effect at all: beyond ~0.1 wavelength induction balances the field pretty effectively. First off I did not realize this was cross posted so this is my last post to this thread. I'm not not regurgitating hobbyist claims but my experience in this matter. Although 0.1 wavelength is more than enough to cover a urban lot and your neighbor at short wave frequencies theory does not do justice to a non homogenous environment we all live in. Most electronic noise generators do not have efficient antennas attached to them where the environment easily distorts the electric fields. I have repeatedly experienced predominantly voltage common mode coupling of local noise sources. Without exception mitigation methods against voltage common mode noise were always successful and current mode antennas always picked up less local noise. |
"CW" no adddress@spam free.com wrote in message ...
They don't but if you go by the advice you generally get on the antenna group, you run an unshielded lead in (part of the antenna) right into the shack (big noise source). When I made my prior comments about the lack of consideration given to receive antenna, I was referring to the antenna group. I didn't realize that the message was cross posted. It just amazes me that they will debate a transmitting antenna to minute detail but receiving antennas deserve no consideration other than a random piece of wire thrown into a tree. Despite their often one sidedness I have learned a great deal from them and mean no disrespect. CW, That is 'why' I set-up the "Shortwave Listeners (SWL) AM/FM Antennas" eGroup on YAHOO ! SWL-ANT= http://groups.yahoo.com/group/Shortwave-SWL-Antenna/ Most HAM are concerned about getting the most power transfer into the Antenna and the greatest Signal Output from the Antenna. This may not result in the best receiving antenna. A better SWL Receive ONLY Antenna is usually a result of a Clean 'outside' Signal with a "Low Noise" factor. Yes the topic is SWL Receive ONLY Antennas. SWL-ANT= http://groups.yahoo.com/group/Shortwave-SWL-Antenna/ iane ~ RHF .. |
"CW" no adddress@spam free.com wrote in message ...
They don't but if you go by the advice you generally get on the antenna group, you run an unshielded lead in (part of the antenna) right into the shack (big noise source). When I made my prior comments about the lack of consideration given to receive antenna, I was referring to the antenna group. I didn't realize that the message was cross posted. It just amazes me that they will debate a transmitting antenna to minute detail but receiving antennas deserve no consideration other than a random piece of wire thrown into a tree. Despite their often one sidedness I have learned a great deal from them and mean no disrespect. CW, That is 'why' I set-up the "Shortwave Listeners (SWL) AM/FM Antennas" eGroup on YAHOO ! SWL-ANT= http://groups.yahoo.com/group/Shortwave-SWL-Antenna/ Most HAM are concerned about getting the most power transfer into the Antenna and the greatest Signal Output from the Antenna. This may not result in the best receiving antenna. A better SWL Receive ONLY Antenna is usually a result of a Clean 'outside' Signal with a "Low Noise" factor. Yes the topic is SWL Receive ONLY Antennas. SWL-ANT= http://groups.yahoo.com/group/Shortwave-SWL-Antenna/ iane ~ RHF .. |
= = = Richard Clark wrote in message
= = = . .. On Sun, 27 Jun 2004 19:55:58 -0700, "CW" no adddress@spam free.com wrote: When I made my prior comments about the lack of consideration given to receive antenna, I was referring to the antenna group. I didn't realize that the message was cross posted. It just amazes me that they will debate a transmitting antenna to minute detail but receiving antennas deserve no consideration other than a random piece of wire thrown into a tree. Hi OM, As generalizations go, this one falls short with them all. We here at rec.radio.amateur.antenna often recite the credo that "reciprocity rules." This means that all considerations given to a transmitting antenna are equally applied to receiving antennas. However, I am sure you are responding to the disparity in coverage between receiving and transmitting antennas - and this is for good reason. Reception and Transmission are NOT reciprocal operations. A receiver has far more latitude to accomplish its goal than does a transmitter. Unless you have an abysmal receiver poorly connected to an inadequate whip, the stock receiver with a simple length of wire is often very close to doing a good job. If the receiver suffers from any of a multitude of issues, there is generally a solution that answers the problem specifically. About the only thing you can do for the transmitter is to turn up the power, or lower the transmission loss. It stands to reason that our focus is on optimizing the loss side of the balance ledger. Returning to the credo of "reciprocity rules," any gain to the advantage of a transmitter is enjoyed by the receiver and the SWLer stands the same advantage. But if that advantage is measured at 3dB, this has the significance of 50W in 100W compared to the SWL S-Meter change from S5 to S6 (BFD). Even though it is the same 3dB, there is the illusion of perspective (my 50W compared to your 5µV). If the SW station is buried in S9 noise, then this is not an antenna problem (unless you can null the noise out through careful lobe positioning). Filtering and/or DSP stand to answer the problem, but these are obviously not remedies to transmission issues. There is another thread discussing the goal of constructing a small loop for 80M reception (and how well 5 turns might achieve some benefit). The same issues of loss prevail for the comparison of Radiation Resistance to Ohmic Resistance for a 1 Meter loop. The loop Rr is in the thousandths of an Ohm and about on par for a small wire's Ohmic loss. There's that 3dB again and what concerns the transmission efficiency is far easier to tolerate with the receiver and its surplus of gain. If the SWLer pays attention to this issue as it concerns the transmission problems, then that SWLer stands to gain in the efficiency returned. However, this is not to suggest that there is an actual need to obtain this efficiency; but if the SWLer mismanages the construction, the topic is discussed to the necessary depth to correct it. A simple basis of comparison will illustrate. Many SW radios have a ferrite stick antenna that will work with at least some stations (VOA, WWV, BBC and a host of others). Try transmitting through that same ferrite stick and it will be like trying to shout through a straw. Our only alternative is to add an amp, but the big KW is only going to render smoke. 73's Richard Clark, KB7QHC RC, In the same location using the same Antenna: 100uV of background noise being re-radiated by a Transmitting Antenna that is being powered at 50W or 100W is simply not an issue for the Amateur/HAM. - Background Noise is NOT an Issue when thinking of Transmitting Antennas that are Radiating Power in the Tens and Hundreds of Watts. - For the HAM Signal-to-Noise is NOT a Transmission Antenna Parameter. 100uV of background noise being received by a Receiving Antenna that is seeking a 25uV Signal is unacceptable for a SWLer. - Background Noise IS an Issue when thinking of Receiving Antennas that are 'acquiring' Radiated Power in the Milliwatts or micro-watts. - For the SWLer Signal-to-Noise IS a key Receiving Antenna Parameter. iane ~ RHF .. Shortwave Listeners (SWL) AM/FM Antennas eGroup on YAHOO ! SWL-ANTENNA= http://groups.yahoo.com/group/Shortwave-SWL-Antenna/ .. |
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