REFLECTOR: Transponder woes

[David Scharfenberg]

I started with my XPDR antenna mounted at the end of the wing strake 
with RG-142 coax.  I forgot the name of the antenna, but I bought it 
from Bill Butters in MO.  ATC received my XPDR fine from one side, but 
not the other, so I think there was definitely "shadowing" going on.  
My next try was a post with ball type of antenna with about a 7" ground 
plane placed below the rear seat.  That seemed to be very weak, ATC 
very rarely received it at all.  Then I drilled a hole through the 
fuselage, below the rear seat and extended the pole through it.  No 
better.  Finally, I replaced that antenna with a "fin" type under the 
back seat.  That has been working pretty well so far.  I agree that 
many times it is ATC's equipment problem, so don't worry too much if 
you have an occasional loss of reception.  Nothing seems to tick 
controllers off quicker than transponder problems.

Dave Scharfenberg

N424DS
std.rg







On Mar 15, 2005, at 10:24 AM, Scott Derrick wrote:

> I mounted an aluminum plate to the underside of my battery box.  I'm 
> using an Odyssey battery which is smaller in size than a standard wet 
> cell.  There is ample room to mount a standard "Ted's" transponder 
> antenna with the connector end sticking up next to the battery.  The 
> tip(ball) of the  antenna just touches the inside of the fuselage.  
> The antenna is slightly offset from the center of the aluminum.
>
> No problems with ATC seeing me.  Very short, less than 3 ft, cable run 
> from the radio.
>
> Scott
>
> Andy Millin wrote:
>
>> Gary,
>>
>> John has provided some good data and some positive things to look for.
>>
>> Wayne Lanza had is Velocity at OSH last year.  He had the "hood" off 
>> so we
>> could see in the nose.  I noticed that he had basically the same 
>> setup that
>> you are talking about.  There was a fabricated fiberglass bracket on 
>> the
>> right side with transponder antenna mounted on it.
>>
>> Since Wayne does this for a living, I would believe he has it worked 
>> out.  I
>> didn't speak with him about the installation or the performance.  
>> Wayne
>> hasn't been seen on the list since the last hurricane.  Just a 
>> suggestion,
>> but you might want to consult with him as well.
>>
>> Best,
>>
>> Andy
>>
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