Tom,

 

The Marker Beacon antenna can be very short (10" foil, center tapped) and does not need a ground plane.  Remember that one is very close to the marker beacon transmitter when you receive such a signal - if it is too good you can get markers from every nearby ILS approach.  Another alternative is to use a splitter on a NAV antenna line for the marker.  That will work. 

 

Be very careful about the xpdr antenna as the ADS-B Out from a transponder with extended squitter or ES requires a specific level (TSO) for the antenna (i.e. the hi speed Comant blade does not meet the spec whilst the shorter deeper blade does).  Your transponder should now be at least mode-S with an upgrade path to ES (i.e. Garmin GTX 330).  The ground plane should be excellent for this antenna (14"?) and perhaps you could consider someplace on the bottom of a wing (i.e. Aileron bellcrank access door if one exists).

 

Scott Krueger

 

Hi Tom,

my conclusion on the Bob Archer in the tail is that under the very best conditions it will work sort of okay to the left and right and not work straight ahead.    Long as you aren't talking to anyone at your destination this should not be a problem. ;->

The very best location on a IV for a com antenna is indeed just ahead of the gear.   I don't know why you are disqualifying that area because of the fuel tank.  You can use copper tape in the shape of an asterisk, applied to the outside, as the ground plane.   If you have to run on the coax on the outside til you get to the back of the tank you could fair it well enough.      Next best place is a little back from the front of the gear wells.

I don't have any direct experience with the marker beacon but I've heard of a lot of people doing that.

What was your plan for nav antennas?

Colyn

On Mar 2, 2013, at 2:51 PM, Tom & Beth Sullivan wrote:

 

   I did a search on the LML archives and found a pot pouri of questions, problems and tips, but much of the info had to do with glass planes (not carbon fiber), and I have some unique challenges as well.

 

   I have already installed the Bob Archer com antenna in the vert/stab and a nav antenna in the winglet (think just one).  My unique challenge is the fact that most of my belly between the gear and forward to the firewall is fuel tank, so this area is unusable for antennas.  I think, based on complaints, that I want at least one more com antenna.  As shown in the attached picture, of the aft fuselage area with my A/C, there is no way I can get a large ground plane in there.  With carbon, do they usually install it in the fuselage (wondering if the ground plane does any good behind the carbon)?  I may be able to get a "segmented" one in there, with part of the ground plane inside the A/C condenser box, and run a ground strap or strip between the segments at each end of the "pie slice" cut out for the A/C.  Otherwise I am limited to a smaller ground plane, or installing one on the outside of the skin (already body worked and in primer). 

 

  Also, for the transponder and Marker beacon antennas, wondering if I could place one at the rear of each wing fairing, as I think the ground plane (G/P) on those would be smaller, and the G/P could be "seen"  easily through the fiberglass of those fairings.  My understanding is the gound plane need only be as large in radius as the length of the actual antenna it is connected to?

 

Thanks in advance for any advice.

 

Tom Sullivan

 

 

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