Transponder Ant. was Re: REFLECTOR:anntenas

[Laurence Coen]

Scott,

The ground plane needs to be a circle at least of a radius equal to the
length of the antenna.  It can be larger for purposes of shielding but will
not improve antenna performance.  One thing that will improve performance is
not using RG 58 U coax.  RG 8 mini is a low loss coax of the correct
impendence (50 ohm).  In fact it may fix your transponder problem at its
current location. Something to think about the next time your wing falls off
;-).

Larry Coen
SE-RG/Franklin

----- Original Message -----
From: "Scott Derrick" <scott@tnstaafl.net>
To: <reflector@tvbf.org>
Sent: Friday, April 11, 2003 8:12 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
> >
> >
>
>
> _______________________________________________
> To change your email address, visit
http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  tvbf:jamaicangoose
>