Can Primer affect antennas
 

I have all my antennas..com, nav, and 2 gps antennas under fiberglass. The GPS antennas are just forward of the wind screen, theNav antenna is in the belly and the com in the leading edge of the vert stabilizer.

The only difference between my plane and the prototype is the primer and my control surfaces (elevator, rudder, ailerons, and flaps) are carbon fiber not fiberglass. Everything in the prototype works just fine.

The Prototype used PPG K36 with K201 hardener, I used Dupont Nason 421-19 with 483-87 hardener.

The MDSS lists aluminum, iron sulfate and carbon black in unknown quantities in the DuPont product. These are not listed in th MDSS for the PPG product.

I find I transmit and recieve normally on frequencies below 125.00 but TX and RX is very weak above this. My Nav reception is exceedingly weak across the board and both GPSs take up to 10 minutyes to lock and then only see 4 sats.

The com nav bench checks fine and when I recieved the BMA Efiss and tested them in the car they locked on in seconds.

Can the stuff in the primer cause this? If so how large an area around the antennas do I need to sand.

yes
 

when i was in the army we could not paint the antennas on helicopters because the paint affected the signals . they were painted with a special paint. or maybe it's not special any more but just polyurethane.
but if iirc the fuse paint was IR dispersing or something like that and the antenna's were different

Just because they're not specifically listed doesn't mean they're not there. If they're not inherently hazardous, they don't need to be listed. Everybody does in differently!

Paint pigments and fillers tend to be somewhat universal, and are based on color or intent (primer, surfacer, final coat, etc) rather than manufacturer.

Poor performance in a certain frequency range could be antenna mismatch; i.e- High SWR's at the higher frequency. You would expect this to be a transition type thing, with things worsening some what gradually, but a sharply tuned antenna for a lower frequency could have this effect. I would find it hard to believe that paint/primer would cause this. If anything, you would expect the opposite (but probably not even measureable) since higher frequencies tend to penetrate better.

Where is your NAV antenna located, and how is it mounted? NAV signals are horizontally polarized, and require the antenna to be horizontal rather than vertical. This can have a TREMENDOUS negative effect on your reception.

Are you sure you don't have the NAV and COMM antennas reversed? That could display your kind of problems also.

GPS signals are notoriously weak to begin with, so any obstruction whatsoever can have a significant effect. Sometimes an active antenna (preamp) can be used to boost the signal.

Any metallic substance can attenuate the signal. As to how much to clear, it depends on the specific antenna and placement. The GPS antennal needs a clear look at the whols sky.

1/4 wave whips radiate along their whole length, whereas 5/8 wave whips tend to concentrate the signal nearer the tip.

NAV antennas just need a clear window with the right polarization.

Hope this helps!

I was afraid that was the case.

It is flat horizontal in the belly pan.

Thats next on the list to check. Boy if that turns out to be the problem I'll never admit it and I'll blame it on the paint.

The prototype has it's GPS antenna laying on top of their raddio stack 6" below the fuselage surface and works great.

Sanded the primer down in the region of the GPS antennas and it seemed to cure one but not the other. Sanded the vert stab and belly pan and it helped but did not cure the com. Didn't do squat for the nav.

Tomorrow I'll swap GPS antennas and track the ant cables back to the com nav.

Thanks for the input. If you think of anything else please speak up.