Transponder Ant. was Re: REFLECTOR:anntenas

Scott Derrick reflector@tvbf.org
Fri, 11 Apr 2003 07:55:28 -0600


I wonder which would be more difficult, pulling new coax through the 
very full conduit or mounting a new antenna.

I'd prefer leaving it where it is.  I think I'll price out the 142 stuff.

I've also found two connectors in the transponders coax line, I have no 
idea why. Each of these contributes a bit to the loss.

Scott


Jim Agnew wrote:
> Your antenna placement is fine, it is the loss in the coax.
>  The standard coax is good for 8-9 feet, for distances up
> to about 17 feet use RG-142 coax.  It is much lower in loss
> but you might get sticker shock on cost.  It is a special
> Mil Spec coax.
> 
> Jim
> --- Scott Derrick <scott@tnstaafl.net> wrote:
> 
>>I'll second Wayne's "DO NOT" for the transponder. Mine is
>>in the strake 
>>in the outside wing bolt hole space.  I get periodic
>>complaints from ATC 
>>about intermittent transponder.  I think I'll purchase
>>another antenna 
>>and try mounting one closer to the transmitter.
>>
>>I don't want it out side though, don't have any external
>>antennas now, 
>>and don't want any.
>>
>>Where's a good spot in a standard RG?  I was thinking
>>about mounting it 
>>to the bottom of the rear seat?
>>
>>How big does the ground plane need to be?
>>
>>My GPS antenna is mounted to the inside of the nose
>>access door, 4 feet 
>>of cable and works great.
>>
>>Scott
>>
>>Wayne Lanza wrote:
>>
>>>
>>>Regarding the antennas, our experience at the builders
>>
>>center points to 
>>
>>>the following:
>>> > Transponder ANT = between the firewall and gear bulk
>>
>>head, on center 
>>
>>>line. DO NOT
>>>put this ANT out in the strake, many transponders don't
>>
>>like to drive 
>>
>>>this much wire!
>>> > GPS = on top of the landing light or on top of the
>>
>>canard, keep this 
>>
>>>wire under 8' long.
>>> > Marker Beacon = Inside or outside of the keel, or on
>>
>>the floor near 
>>
>>>the keel. Locate
>>>the foil such that you don't tear it up when
>>
>>upholstering or mounting 
>>
>>>the seats...
>>> > Glide Slope = On the floor under the copilot front
>>
>>seat area.
>>
>>> > AM/FM = Not too critical, string a 23" piece of the
>>
>>ANT wire (center 
>>
>>>conductor only)
>>>across the under side of the structure in front of the
>>
>>canopy. Make sure 
>>
>>>that the pitch
>>>trim spring doesn't interfere.
>>> > ELT = Mount the ELT to the floor between the gear
>>
>>bulk head and the 
>>
>>>keel bulk head
>>>on the copilot side. Run two 23" foils on a diagonal
>>
>>centered at the 
>>
>>>fuselage joint, the
>>>angle of the foils is such that they are fairly
>>
>>straight (they might 
>>
>>>wrap onto the ceiling).
>>>This is not super critical, but this antenna should be
>>
>>vertically 
>>
>>>mounted not horizontal!
>>>Use the torroids and connect the coax braid to the
>>
>>lower foil. Secure 
>>
>>>foils, torroids and
>>>the end of the lead in coax with 1 ply of bid. This
>>
>>needs to be 
>>
>>>shock/impact secured.
>>> > ADF = I've heard of them :-)
>>>
>>>In general, use the correct type of coax (not TV wire
>>
>>or solid center 
>>
>>>conductor), use the
>>>proper BNC terminals and appropriate tools. Keep the
>>
>>coax runs short and 
>>
>>>secure.
>>>
>>>Fly Safe,
>>>Wayne Lanza
>>>Composite Design, Inc.
>>>(electrical weenie at the Velocity Builder's Center)
>>>
>>
> ____________________________________________________________________
> 
>>>On Friday, April 11, 2003, at 06:37 AM, Lynn Gallup
>>
>>wrote:
>>
>>>    Noel,
>>>    As near as possible, I followed the suggestions in
>>
>>the Velocity
>>
>>>    manual. After 185 hours flying my airplane in a
>>
>>wide variety of
>>
>>>    circumstances I can pronounce perfect operation of
>>
>>my nav & com
>>
>>>    radios, localizer & glideslope, marker beacon
>>
>>receiver and
>>
>>>    transponder. Even the ADF works acceptably although
>>
>>its range is a
>>
>>>    little short. The GPS would benefit from shielding
>>
>>or a slight
>>
>>>    relocation as it will blank out if one of the nav
>>
>>receivers is tuned
>>
>>>    to a particular VOR frequency. (Leakage of nav's IF
>>
>>frequency signal
>>
>>>    out of the localizer antenna overcomes the
>>
>>satellite signals.)
>>
>>>    Mine is a hatch door, long wing, RG. The antenna
>>
>>locations are:
>>
>>>    Com antennas - In the tip sails.
>>>    Nav antenna - One shared antenna on top of fuselage
>>
>>about four
>>
>>>    inches forward of engine bulkhead.
>>>    Marker beacon antenna - Along right side about two
>>
>>inches below
>>
>>>    windows.
>>>    Transponder antenna - Bottom of fuselage below
>>
>>right rear seat.
>>
>>>    ADF antennna - Bottom of fuselage below left rear
>>
>>seat.
>>
>>>    Localizer antenna - On canard top surface,
>>
>>center-line of fuselage.
>>
>>>    GPS antenna - Front of canard top, centered.
>>
>>Forward of localizer
>>
>>>    antenna. It should be remounted under the top of
>>
>>the fuselage above
>>
>>>    the localizer antenna.
>>>
>>>    Regards,
>>>    Lynn
>>>    =====================
>>>    At 11:46 PM 4/10/2003 Thursday, you wrote:
>>>
>>>     
>>>    Now that it's finally starting to warm up, I'm
>>
>>doing the planning
>>
>>>    for my summer project... The wings / canard.
>>>    I realize that antenna placement is variable,
>>
>>But...
>>
>>>    What do I really need? Do I need a Com and Nav in
>>
>>each wing?
>>
>>>    Where's the best place for a glideslope antenna.
>>
>>The keel was
>>
>>>    already down when I got the kit.
>>>    I assume the transponder would be best on the
>>
>>floor, and the gps on
>>
>>>    the ceiling.
>>>    What about something for the am/fm?
>>>    I've seen Don's elt antenna on the main wingspar
>>
>>shearweb, and it
>>
>>>    looked pretty survivable.
>>>     
>>>    What's popular / what's practical
>>>     
>>>    Noel 3suv103
>>>
>>>
>>
>>
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> 
> 
> 
> =====
> James F. Agnew
> Jim_Agnew_2@Yahoo.Com
> Tampa, FL
> Velocity 173 Elite Aircraft Completed
> _______________________________________________
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> 
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>