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"Howard" wrote in message ... On Thu, 2 Dec 2004 14:08:25 -0600, "Dave" wrote: "Michael Lawson" wrote in message . .. "Dave" wrote in message ... "Dale Parfitt" wrote in message news:25Krd.8148$1z5.1438@trnddc06... " Thanks for the quick response, Mike! 65 feet of coax between the radio (DX-402/ATS-505) and the antenna (200 feet of 300 ohm twin-lead hidden along the ridge on the roof of the house.) And I don't think I would call it "severely" degraded, only slightly so. Only a little less than the old "temporary" antenna (60 feet of four strand copper wire thrown over the house.) Also, the new antenna is oriented primarily E/W while the "temporary" antenna was oriented primarily N/S, if that matters. The orientation does matter if you're not using a vertical, but the first thing that popped into my mind was overloading the ATS-505 with 200 feet of antenna wire. The longest I've ever run into my old DX-440/ATS-803A was about 40-50 feet, and while I never overloaded it, I've never tried anything close to 200 feet into it. But yeah, the E/W orientation will work well for stations that are north or south of you (like tropical band stuff), but not so good for hearing things east or west of you (like from Europe or Africa or -depending on where you're at- relays like Sackville). Unless the antenna is a approx. 1/2 wavelength up or higher ( at tropical band= 150' or so) the end nulls fill in making even horizontal antennas near omni. Guess my question is, how are you connecting the twin lead- if simply connecting it to the balun, you have little more than a 300 Ohm transmission line, not an antenna. In fact, if the baluns were perfectly balanced, and the twin lead clear of metallic objects ( which would unbalance it) you would theoretically get zero signal. Dale W4OP Hey Dale, thanks for jumping in. Well, get the calculator out. The two freqs of interest to me are 9335 KHz and 11710 KHz, so I am going to work with something between those two numbers (10 MHz). If I am correct, 10 Mhz has a wavelength of 30 meters, which works out to about 98 feet. And I am working with 200 feet. (Maybe I should call this a long-wire antenna?) Question for you: what is an end null? And yes, I simply connected the 300-ohm to the baluns to the coax, to another balun, and then a third that plugs into my external antenna socket. And I a definetly getting a signal. Whatcha think? Are you using the 300 ohm balanced as a twin lead folded dipole or as an equivalent of a longwire?? If you're using it as a longwire and have hooked up a 300/75 balun to it, Dale's right and it's effectively a long transmission line. I'm with Ace on this, I don't understand the 2nd and 3rd baluns. --Mike L. I am using it as a longwire. What is a "transmission line" and how does it differ from a recieving antenna? The second and third baluns are to allow me to plug it into my external antenna connector. The first (attached to he coax) makes it possible to carry the received signal to the second (with the mini-plug on it.) I am using this with a small portable radio. Dave Dave, Two too many baluns and the 300 ohm cable is not being used to it's best advantage. Suggest the following: 1) use the 30 ohm cable to make a folded dipole, at each end connect the two wire, then in the middle of the length cut the bottom wire and strip some insulation from each lead. 2) Connect the balun to the two leads of the folded dipole. 3) Connect the 75 ohm coax to the balun, hook the shield to ground and route into the house. 4) Get an "F" to 1/8 phone plug adapter, Radio Shack carries them. Attach the 75 ohm cable to the adapter & plug into your radio. 5) Turn radio on and expect better performance than you now have. You may wish to consider that a dipole is a resonant antenna and a 200 foot dipole is going to be resonant at a little over 2 MHz. Though to be realistic, you should be more concerned about signal overload than resonance. A consideration is to whack about 50 feet from each end of the cable to give a 100 ft folded dipole. I suspect you are using a stock 300/75 ohm balun as used for TV antennas: these do not function as well at HF as they do at higher frequencies and that could well be stealing some signal from you. Suggest you read the following article http://www.anarc.org/naswa/badx/ante...e_antenna.html which describes how to wind a balun using stock 300/75 ohm transformer - the wind ratio of 30/10 is for a 9:1 balun so you could use a ratio of 10/5 which would give a 4:1 balun. Good Luck! Howard Thanks for the input Howard. And thank you very much for that link. Yes, I am using standard television 300/75 baluns, which I expected to steal some signal, but wasn't worried about it at first. My first experiment with 50-60 feet of four strand copper wire gave me signal to waste, but not this rig. Will definetly check out winding some more efficient baluns. I didn't initially go with a folded dipole because I understood it to be highly directional. No? Oh, and I didn't know anybody made an F connector to 1/8" miniplug adapter. Will definetly look for that. Would be much better. Thanks again, Dave |
"Howard" wrote in message ... On Thu, 2 Dec 2004 14:08:25 -0600, "Dave" wrote: "Michael Lawson" wrote in message . .. "Dave" wrote in message ... "Dale Parfitt" wrote in message news:25Krd.8148$1z5.1438@trnddc06... " Thanks for the quick response, Mike! 65 feet of coax between the radio (DX-402/ATS-505) and the antenna (200 feet of 300 ohm twin-lead hidden along the ridge on the roof of the house.) And I don't think I would call it "severely" degraded, only slightly so. Only a little less than the old "temporary" antenna (60 feet of four strand copper wire thrown over the house.) Also, the new antenna is oriented primarily E/W while the "temporary" antenna was oriented primarily N/S, if that matters. The orientation does matter if you're not using a vertical, but the first thing that popped into my mind was overloading the ATS-505 with 200 feet of antenna wire. The longest I've ever run into my old DX-440/ATS-803A was about 40-50 feet, and while I never overloaded it, I've never tried anything close to 200 feet into it. But yeah, the E/W orientation will work well for stations that are north or south of you (like tropical band stuff), but not so good for hearing things east or west of you (like from Europe or Africa or -depending on where you're at- relays like Sackville). Unless the antenna is a approx. 1/2 wavelength up or higher ( at tropical band= 150' or so) the end nulls fill in making even horizontal antennas near omni. Guess my question is, how are you connecting the twin lead- if simply connecting it to the balun, you have little more than a 300 Ohm transmission line, not an antenna. In fact, if the baluns were perfectly balanced, and the twin lead clear of metallic objects ( which would unbalance it) you would theoretically get zero signal. Dale W4OP Hey Dale, thanks for jumping in. Well, get the calculator out. The two freqs of interest to me are 9335 KHz and 11710 KHz, so I am going to work with something between those two numbers (10 MHz). If I am correct, 10 Mhz has a wavelength of 30 meters, which works out to about 98 feet. And I am working with 200 feet. (Maybe I should call this a long-wire antenna?) Question for you: what is an end null? And yes, I simply connected the 300-ohm to the baluns to the coax, to another balun, and then a third that plugs into my external antenna socket. And I a definetly getting a signal. Whatcha think? Are you using the 300 ohm balanced as a twin lead folded dipole or as an equivalent of a longwire?? If you're using it as a longwire and have hooked up a 300/75 balun to it, Dale's right and it's effectively a long transmission line. I'm with Ace on this, I don't understand the 2nd and 3rd baluns. --Mike L. I am using it as a longwire. What is a "transmission line" and how does it differ from a recieving antenna? The second and third baluns are to allow me to plug it into my external antenna connector. The first (attached to he coax) makes it possible to carry the received signal to the second (with the mini-plug on it.) I am using this with a small portable radio. Dave Dave, Two too many baluns and the 300 ohm cable is not being used to it's best advantage. Suggest the following: 1) use the 30 ohm cable to make a folded dipole, at each end connect the two wire, then in the middle of the length cut the bottom wire and strip some insulation from each lead. 2) Connect the balun to the two leads of the folded dipole. 3) Connect the 75 ohm coax to the balun, hook the shield to ground and route into the house. 4) Get an "F" to 1/8 phone plug adapter, Radio Shack carries them. Attach the 75 ohm cable to the adapter & plug into your radio. 5) Turn radio on and expect better performance than you now have. You may wish to consider that a dipole is a resonant antenna and a 200 foot dipole is going to be resonant at a little over 2 MHz. Though to be realistic, you should be more concerned about signal overload than resonance. A consideration is to whack about 50 feet from each end of the cable to give a 100 ft folded dipole. I suspect you are using a stock 300/75 ohm balun as used for TV antennas: these do not function as well at HF as they do at higher frequencies and that could well be stealing some signal from you. Suggest you read the following article http://www.anarc.org/naswa/badx/ante...e_antenna.html which describes how to wind a balun using stock 300/75 ohm transformer - the wind ratio of 30/10 is for a 9:1 balun so you could use a ratio of 10/5 which would give a 4:1 balun. Good Luck! Howard Thanks for the input, Howard. Yes, I am using standard 300/75 ohm TV baluns, which I expected to steal some signal, but I thought I would have signal to spare. My first experiment with 50-60 feet four-strand copper wire gave me signal to waste, but not this rig. Thanks for the link. I will definetly look into that. Oh, and I didn't know anyone made a F-connector to 1/8" mini-plug adapter. Will look for that, too. Thanks again, Dave |
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