Transponder Ant. was Re: REFLECTOR:anntenas

jack davis reflector@tvbf.org
Fri, 11 Apr 2003 22:44:25 -0400


I had my transponder antenna mounted in the outboard strake as the manual
suggested and use to get the same complaints from ATC about intermittent
response.  I relocated the antenna to the center of the fuselage near the
gear bulkhead (mounted externally) and have never had a problem with
reception since.

Jack
----- Original Message -----
From: "Scott Derrick" <scott@tnstaafl.net>
To: <reflector@tvbf.org>
Sent: Friday, April 11, 2003 9:12 AM
Subject: Transponder Ant. was Re: REFLECTOR:anntenas


> 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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