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indigoonlatigo(at)msn.com
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 Posted: Tue Jul 27, 2010 8:12 pm Post subject: Transponder antenna location |
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Has anyone placed the transponder antenna on the cowl right in front of the louvers. If I follow the antenna mounting on my fiberglass sailplane, I can easily make a ground plane for the antenna and ground it to the firewall, but what I am most concerned about is the prop creating a blind spot directly in front of the antenna. The further back on the fuselage the antenna placement, the shallower the angle will be of the blind spot(smaller blind spot). Of course, the wings will also create a blind spot when in a turn also if mounted at or behind the wings.
I would put an easy to reach disconnect on the cable so the lower cowl can be removed.
Thoughts.
Thanks,
JOhn #409
Next plane>>>
  
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coop85(at)verizon.net
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| Posted: Wed Jul 28, 2010 6:04 am Post subject: Transponder antenna location |
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John,
My antenna is aft of the firewall about a foot and I have not had any issues ever in 450 hours with the transponder being seen. Just a thought about the cowl location, you mentioned having a quick disconnect which is a good idea, but you’ll have to have a fair amount of extra cable to allow access and securing it from the exhaust might be an issue. Also, it gets REALLY hot right around there which may cause a number of long term issues.
With all the extra effort with creating a ground plane and such it doesn’t really seem to be an added benefit and worth the work, but that is just my opinion.
Marcus
Do not archive
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Gonzalez
Sent: Wednesday, July 28, 2010 12:12 AM
To: RV 10 group
Subject: Transponder antenna location
Has anyone placed the transponder antenna on the cowl right in front of the louvers. If I follow the antenna mounting on my fiberglass sailplane, I can easily make a ground plane for the antenna and ground it to the firewall, but what I am most concerned about is the prop creating a blind spot directly in front of the antenna. The further back on the fuselage the antenna placement, the shallower the angle will be of the blind spot(smaller blind spot). Of course, the wings will also create a blind spot when in a turn also if mounted at or behind the wings.
I would put an easy to reach disconnect on the cable so the lower cowl can be removed.
Thoughts.
Thanks,
JOhn #409
Next plane>>>
- The RV10-List Email Forum utilities such as List Photoshare, and much much --> http://www.matronic=================[/b][/quote] - MATRONICS WEB FORUMS via the Web --> http://forums.matronics.comstyle='mso-spacerun:yes'> - List Contribution Web Site style='mso-spacerun:yes'> Thank you for your generous style='mso-spacerun:yes'> -Matt style='mso-spacerun:yes'> --> http://www.matronics.com/c=[/b] [b]
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rene(at)felker.com
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| Posted: Wed Jul 28, 2010 7:13 am Post subject: Transponder antenna location |
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I have mine about 8 inches behind the firewall. The only time I have had controllers say they cannot see my transponder is when I fly west of Ogden Utah, 6000 feet about a mile south of the nexrad site……it has happened more than once…….but I think the interrogator is up on Francis Peak at close to 9000 feet. So who knows what causes the problem.
If I am getting this right, you would be placing the antenna pretty close to the nose wheel strut. You may want to look at that. I know that Vans has theirs relatively close to the main gear?
Rene' Felker
N423CF
801-721-6080
From: owner-rv10-list-server(at)matronics.com [mailto:owner-rv10-list-server(at)matronics.com] On Behalf Of John Gonzalez
Sent: Tuesday, July 27, 2010 10:12 PM
To: RV 10 group
Subject: Transponder antenna location
Has anyone placed the transponder antenna on the cowl right in front of the louvers. If I follow the antenna mounting on my fiberglass sailplane, I can easily make a ground plane for the antenna and ground it to the firewall, but what I am most concerned about is the prop creating a blind spot directly in front of the antenna. The further back on the fuselage the antenna placement, the shallower the angle will be of the blind spot(smaller blind spot). Of course, the wings will also create a blind spot when in a turn also if mounted at or behind the wings.
I would put an easy to reach disconnect on the cable so the lower cowl can be removed.
Thoughts.
Thanks,
JOhn #409
Next plane>>>
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jeff(at)westcottpress.com
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| Posted: Wed Jul 28, 2010 8:38 am Post subject: Transponder antenna location |
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Hi John,
I believe there is a specific range of distance (at least for the transponder I'm planning to use) that the antenna can be from the transponder... no more than x, no less than y... that really narrows your location options. Mine wound up in the tunnel, aft of the fuel selector, below the bellcrank. I used a 90 degree BNC connector to eliminate any chances of things getting tangled up in there.
Jeff Carpenter
40304
On Jul 27, 2010, at 9:11 PM, John Gonzalez wrote:
| Quote: | Has anyone placed the transponder antenna on the cowl right in front of the louvers. If I follow the antenna mounting on my fiberglass sailplane, I can easily make a ground plane for the antenna and ground it to the firewall, but what I am most concerned about is the prop creating a blind spot directly in front of the antenna. The further back on the fuselage the antenna placement, the shallower the angle will be of the blind spot(smaller blind spot). Of course, the wings will also create a blind spot when in a turn also if mounted at or behind the wings.
I would put an easy to reach disconnect on the cable so the lower cowl can be removed.
Thoughts.
Thanks,
JOhn #409
Next plane>>>
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Bob Turner
Joined: 03 Jan 2009
Posts: 885
Location: Castro Valley, CA
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| Posted: Wed Jul 28, 2010 9:45 am Post subject: Re: Transponder antenna location |
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I wouldn't be at all concerned about the prop - it turns very slowly compared to the pulse transmitted by the transponder. It might block the signal once in a great while, but that's all.
I would be concerned about the heat. Coax doesn't really like it, extra heat can cause the center conductor to slowly move toward the shield at bends. Also all connectors are somewhat lossy at 1 GHz. Generally best to minimize them. Rather than a "quick disconnect" it would be better if you could reach the coax to antenna connection and disconnect it there.
Finally, there will be a tiny bit more drag, due to the high speed air coming off the prop.
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Bob Turner
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rv10builder(at)verizon.ne
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| Posted: Wed Jul 28, 2010 10:47 am Post subject: Transponder antenna location |
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I have a 22 inch separation and mine is in the tunnel fore of the selector, which was basically the best I could find to keep the antenna separation and best angle away from the exhaust port. I was told to move the antenna back by both my TC and RAMI due to the exhaust stack sitting lower than the antenna was. I was than told to move it as far back as possible while keeping the Coax as short as possible and having the 2 foot separation between antenna and transponder.
From: Jeff Carpenter (jeff(at)westcottpress.com)
Sent: Wednesday, July 28, 2010 9:38 AM
To: rv10-list(at)matronics.com (rv10-list(at)matronics.com)
Subject: Re: Transponder antenna location
Hi John,
I believe there is a specific range of distance (at least for the transponder I'm planning to use) that the antenna can be from the transponder... no more than x, no less than y... that really narrows your location options. Mine wound up in the tunnel, aft of the fuel selector, below the bellcrank. I used a 90 degree BNC connector to eliminate any chances of things getting tangled up in there.
Jeff Carpenter
40304
On Jul 27, 2010, at 9:11 PM, John Gonzalez wrote:
[quote] Has anyone placed the transponder antenna on the cowl right in front of the louvers. If I follow the antenna mounting on my fiberglass sailplane, I can easily make a ground plane for the antenna and ground it to the firewall, but what I am most concerned about is the prop creating a blind spot directly in front of the antenna. The further back on the fuselage the antenna placement, the shallower the angle will be of the blind spot(smaller blind spot). Of course, the wings will also create a blind spot when in a turn also if mounted at or behind the wings.
I would put an easy to reach disconnect on the cable so the lower cowl can be removed.
Thoughts.
Thanks,
JOhn #409
Next plane>>>
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