Transponder Ant. was Re: REFLECTOR:anntenas
Chris Martin
reflector@tvbf.org
Fri, 11 Apr 2003 17:12:30 -0700
Scott,
I also had a transponder mounted inside of the outside strake. Poor
reception by ATC. I moved it to the floor of the fuselage underneath the
retract gear and offset to the co-pilot side. I used a small 3" Transponder
antenna mounted on a 8" square aluminum plate. The antenna pokes through a
hole in the floor of the fuselage and the backing plate is attached to the
floor with 2 pop rivets. The cable attaches with a B & C connector. This is
the only antenna I have that is visible outside the plane. Only 2" actually
is visible. The ATC has no problem seeing this antenna transmission, really
excellent results. I recentally added the Garmen GTX 330 Mode S Transponder
with TIS (Traffic Information Service). This displays traffic on my Garmin
430 moving map. I can recieve the TIS information within 500 feet of the
ground. So, this new antenna is not only transmitting well but is receiving
well.
For those of you that live in a high traffic area, (I live in one of the
busyest, Los Angeles). This TIS information is a wonderful aid. I strongly
recomend it.
Chris Martin
Velocity XL RG
> [Original Message]
> From: Scott Derrick <scott@tnstaafl.net>
> To: <reflector@tvbf.org>
> Date: 4/11/2003 5:36:05 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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