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#1
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OK, I've got it.
ftp://users.aol.com/DGoncz/Antenna/ 08/22/2004 05:43AM 161,463 BoomClip.JPG 08/19/2004 07:45AM 112,318 CeilingSpacer.JPG 08/22/2004 05:43AM 180,516 ConnectionDetail.JPG 08/22/2004 05:43AM 190,270 ConnectorDetail.JPG 08/19/2004 07:45AM 111,110 HangerAndLead.JPG 08/22/2004 05:43AM 192,334 HangerDetail.JPG 08/22/2004 05:44AM 126,769 HangerOverall.JPG 08/19/2004 07:45AM 137,884 LeadCloseup.JPG 08/22/2004 05:43AM 157,620 OverallConnection.JPG 08/22/2004 05:43AM 129,931 OverallView.JPG 08/22/2004 05:43AM 128,858 OverallView2.JPG 08/22/2004 05:43AM 133,346 PlugCovered.JPG 08/22/2004 05:43AM 100,341 PlugFilled.JPG 08/22/2004 05:43AM 96,303 PlugSoldered.JPG 08/22/2004 05:43AM 102,568 PlugTaped.JPG 08/22/2004 05:43AM 146,279 PlugWhipped.JPG 08/22/2004 05:43AM 172,030 ShieldClip.JPG 08/22/2004 05:43AM 199,604 StrainRelief.JPG WHFS in stereo at 3 AM. I note the plug has to be in just more than half way, not all the way for best results. Maybe I should be using a balun, coax, and a phone jack adapter as suggested. But the original antenna was a dipole. So what did they do, ground one leg? I have checked and the sleeve/barrel at the computer is grounded. I'll pull the board and have another look at the traces. I'm sure tip and ring are balanced but we'll just have a look under the hood.... The flat chisel tip did a much better job of transferring heat to the connector lug and hardly any plastic melted this time. The lug heated quickly and the tip drew a film of solder over it. My apprenticeship ended in 1986. I filled the space with hot melt, and applied a little over the connection, then taped it, drew over the braid, and whipped the braid down over the end, with the ends of the braid falling neatly into the groove between the threads and the flange. Then I lacquered the whipping with nail polish. I'll heat shrink over it some day. The boom and therefore the reflector elements are grounded, as they normally would be. I don't know if this does anything. They are grounded from the sheild through a clip lead to a bracket supporting a reflector element. No active amplification is used. It works just great. No rabbit ears, no aluminum foil, and it picks up pointed due east as it should. All 10 FM stations on my dial read the same on the VU meter, all are in stereo, and there is very little noise or interference. Just one thing. There's a cable dangling from the middle of the ceiling. For now, primary Teri can live with this. We will be sharing this whole space soon. Right now I am renting 26 square feet of office space and paying towards the cable modem and fax line. Yours, Doug Goncz ( ftp://users.aol.com/DGoncz/incoming ) Student member SAE for one year. I love: Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically. I drive: A double-step Thunderbolt with 657% range. |
#3
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Richard Clark wrote in message . ..
On 22 Aug 2004 10:01:17 GMT, ( Doug Goncz ) wrote: OK, I've got it. ftp://users.aol.com/DGoncz/Antenna/ WHFS in stereo at 3 AM. I note the plug has to be in just more than half way, not all the way for best results. Maybe I should be using a balun, coax, and a phone jack adapter as suggested. Yes, very much if things are this touchy. You are trying to feed a high Z antenna into a low Z cable. Radio Shack has a very common BalUn product designed to take care of this very simply (and using common coaxial products they sell too). No active amplification is used. That's fine, but by all of your accounts, you are on the thin edge. For now, primary Teri can live with this. Hi Doug, Teri may be able to get along with it much more, if you realized you have two antennas in one and simply remove one of them. Simple, is easier said than simple. By all appearances you have a combination FM-TV antenna as I see at least 5 elements (you don't show the entire antenna by the way) and you are only using 3 of them. Your connection should be at the end that is pointing (east) at the station you want to hear. If it is not, you have it pointed backwards and this may explain why things are so hinky. Another clue that you can verify. There should be another set of antenna connections (like wing nuts that presently you connect to) at the OPPOSITE end of the boom - n'est pas? They should be on the next to last elements before the end of the boom. 73's Richard Clark, KB7QHC Dear Richard, You (Richard Clark ) wrote in message . .. On 22 Aug 2004 10:01:17 GMT, ( Doug Goncz ) wrote: OK, I've got it. ftp://users.aol.com/DGoncz/Antenna/ WHFS in stereo at 3 AM. I note the plug has to be in just more than half way, not all the way for best results. Maybe I should be using a balun, coax, and a phone jack adapter as suggested. Yes, very much if things are this touchy. You are trying to feed a high Z antenna into a low Z cable. Radio Shack has a very common BalUn product designed to take care of this very simply (and using common coaxial products they sell too). No active amplification is used. That's fine, but by all of your accounts, you are on the thin edge. For now, primary Teri can live with this. Hi Doug, Teri may be able to get along with it much more, if you realized you have two antennas in one and simply remove one of them. Simple, is easier said than simple. By all appearances you have a combination FM-TV antenna as I see at least 5 elements (you don't show the entire antenna by the way) and you are only using 3 of them. Your connection should be at the end that is pointing (east) at the station you want to hear. If it is not, you have it pointed backwards and this may explain why things are so hinky. Another clue that you can verify. There should be another set of antenna connections (like wing nuts that presently you connect to) at the OPPOSITE end of the boom - n'est pas? They should be on the next to last elements before the end of the boom. 73's Richard Clark, KB7QHC Oh, dear. I opened ftp://users.aol.com/DGoncz/Antenna/ to add to my post, closed the window, and lost the post. Rewrite: The antenna, a Radio Shack 15-2163 6-Element Triple Drive Outdoor FM Antenna, is an open dipole having a characterstic impedance near that of the twinaxial cable. That's how I selected the cable. I matched the inner conductors and insulation to those of the flexible open dipole supplied by the OEM. The twinaxial cable has slightly thicker conductors, but the insulation on both is polyethylene, not PVC, and the spacing is similar. The connection is indeed at the east end. The lead hangs straight down now, and is lashed to a coat hanger wire narrow V that steadies the antenna side to side, preventing contact with the ceiling. The weight of the cable steadies the antenna. I propose a length of chain to lower the antenna to above head height to get it below the upper sill, and weights to level and balance it. That way it will rotate left and right a total of 360 degrees for testing, although it will only have one stable position. The cup hook in the ceiling appear secure. I have a plastic screw shield to improve the cup hook mount. It's in there with wooden splints now. Not bad, but not a hard mount. The cable is under the rug now, avoiding another trip, which damaged the phone plug. A 5C collet and closer will straighten the plug. A cat toy house protects the cable at the transition to the floor. Tasha likes to curl up in there. They both bat the cable once in a while. Yours, Doug Goncz Replikon Research Seven Corners, VA |
#4
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On 25 Aug 2004 02:54:24 -0700, (Doug Goncz) wrote:
The antenna, a Radio Shack 15-2163 6-Element Triple Drive Outdoor FM Antenna Hi Doug, I see nothing of twinax at all. consult: http://www.radioshack.com/images/Pro...OME15-2163.pdf However, you seem to have come to a working arrangement, twinax doesn't make all that much difference, and it is pointed in the right direction. I'm sure you are enjoying the music. 73's Richard Clark, KB7QHC |
#5
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Dear Richard,
The Radio Shack manual linked below, which I have, and came with the antenna, doesn't mention twiaxial cable because no twinaxial cable with an impedance of 75 ohms is available at a reasonable price, so people use 75 ohm cable because it's cheaper. If I could get 75 ohm twinaxial cable I'd use it. The impedance of this and every open dipole antenna is around 75 ohms, one quarter of the impedance of a 300 ohm folded dipole, just about ten percent from the impedance of empty space. We are in an atmosphere.... However, the OEM antenna is a flexible _open_ dipole with a characterstic impedance of 75 ohms. I think 100 ohm twinax is a good choice. Can any readers source 75 ohm twinax? Doug Richard Clark wrote in message . .. On 25 Aug 2004 02:54:24 -0700, (Doug Goncz) wrote: The antenna, a Radio Shack 15-2163 6-Element Triple Drive Outdoor FM Antenna Hi Doug, I see nothing of twinax at all. consult: http://www.radioshack.com/images/Pro...OME15-2163.pdf However, you seem to have come to a working arrangement, twinax doesn't make all that much difference, and it is pointed in the right direction. I'm sure you are enjoying the music. 73's Richard Clark, KB7QHC |
#6
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(Doug Goncz) wrote in message . com...
Dear Richard, The Radio Shack manual linked below, which I have, and came with the antenna, doesn't mention twiaxial cable because no twinaxial cable with an impedance of 75 ohms is available at a reasonable price, so people use 75 ohm cable because it's cheaper. If I could get 75 ohm twinaxial cable I'd use it. The impedance of this and every open dipole antenna is around 75 ohms, one quarter of the impedance of a 300 ohm folded dipole, just about ten percent from the impedance of empty space. We are in an atmosphere.... However, the OEM antenna is a flexible _open_ dipole with a characterstic impedance of 75 ohms. I think 100 ohm twinax is a good choice. Can any readers source 75 ohm twinax? Doug http://www.electronicsurplus.com/com...=1093701353153 I have ordered 16 feet of Belden "Blue Hose" 78 ohm twinaxial cable. Doug |
#7
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From: (Doug Goncz)
I have ordered 16 feet of Belden "Blue Hose" 78 ohm twinaxial cable. And the impedance of an open dipole in air is about 75 ohms. Product: 78-OHM TWINAX SOLID COAX CABLE FOIL+BRAID SHIELD 2 CONDUCTOR 20AWG 100FT/REEL NEW BLUE JACKET Unit Price: $0.40 Quantity: 16 Items Total: $6.40 Order Subtotal: $6.40 Shipping Cost: $10.80 Tax: $0.00 Order Total: $17.20 Yours, Doug Goncz ( ftp://users.aol.com/DGoncz/incoming ) Student member SAE for one year. I love: Dona, Jeff, Kim, Mom, Neelix, Tasha, and Teri, alphabetically. I drive: A double-step Thunderbolt with 657% range. |
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