Transponder Ant. was Re: REFLECTOR:anntenas

Jim Agnew reflector@tvbf.org
Fri, 11 Apr 2003 06:34:15 -0700 (PDT)


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