Fuse mounted Comm Antennas...A grounding plane really works

[C5Engineer 1170]

I have a comm antenna about halfway between my turtle deck and vertical stab. When I got the plane it had some gold tin foil stuff stuck to the covering inside the fuse for the most of the way around the antenna. Over time it's sort of peeled off and was hanging down in my fuse. Recently one piece fell off and was laying in the fuse. I've noticed that lately I was getting a lot more noise thru my radio and I had to keep the squeltch up a lot higher than I used to. Today I busted out the 3M spray adhesive and restuck all the Gold tin foil "stuff" that was on there and I went for a flight and I couldn't believe how much clearer the radio was. I also got rid of almost all the noise I was getting when I actuated my Ivo IFA prop. Sooo some cheezy gold foil stuck to the bottom of your fabric around your comm antenna might be the ticket if your having Comm issues.

[EDMO 1078]

the plastic plane guys use a copper or gold tape or film to give them a groundplane for their antennas.

A thin sheet of aluminum or stainless will do the same - I think it needs to be about 1/4 radius of the length of the antenna, but surely someone on here knows more about that than I know.

EdMo

Edited 26 Oct 2014 by Ed In Missouri

[C150L 6]

Do do believe the horizontal radials (ground plane) is nearly the same length as the vertical length of the antenna for a given frequency. Actually, about 5% longer than the vertical/radiating element.

 

That ground plane should also be electrically connected to the shield of the feed line (coax) from the radio and is to be connect at the base of the vertical element. I'm not exactly sure how this works out with some sort of metallized plastic film. The gorund plane is actully the second half of the antenna system. With out a properly connected ground plane, in a sense, you only have 1/2 an antenna, which might not be good for the transmitter in the radio.

 

I added 4 radial wires under the antenna inside my FP202 Koala when a good friend of mine told me I had "a nice 1/2 an antenna" in it. (old ham radio guy from way back, I mean way back. He just turned 101 2 weeks ago.) I didn't have it when I had my Koala FP202, but It would have been nice to test that home brew antenna with my antenna analyzer. This analyzer checks impedance, resonance frequency, SWR, % of match and a whole lot more.

 

I was later using a "no ground plane required antenna" in my Koala which I made during a training session with Paul. (That old friend of mine.) With that antenna, I was talking with someone in the pattern at an airport 100nm away. That radio check was done with my old STS handheld radio using it's attached battery, not the12 volt battery in the plane. Not bad, huh?

 

FYI: Transmission is a totally different animal than receiving. If only receiving others transmissions, that ground plane makes little difference. In transmission, the antenna system is everything. If your SWR, % of match, etc is not at or close to that which it should be, much of that energy your radio is putting out will be radiated back into the radio and can cause damage to the transmitter/outputs of the radio. My friend Paul told me I was lucky I didn't burn out my handhelds transmitter, not having the ground plane radials under that antenna.

 

Again, I'm not sure how the metalized poly is electrically connected to the antenna/coax. As for reducing engine or IFA prop system interference, I know this. RF interference travels in mostly straight lines. I'm picturing this metalized film ground plane material mentioned by OP or what ever it is, might be large enough and of size adequate to block RF emissions (noise) radiating off the engine ingition, charging system or off the motor(?) of the IFA prop system. Another form of noise a radio might pick up on is noise from wires/electrical system itself. That's often reduced or eliminated with filters and such across wires, components, etc.

 

Now, perhaps I've confused the topic enough. If I can clarify or answer anything, please ask. D

[marshawk 82]

Thanks for posting this, I'm having problems with radio noise,it seems to be worse at high rpms and my antenna is bolted on the turtle deck which is all aluminum ,so Im  thinking the  grounding shouldn't be a problem, is there a noise suppressor I should try or any other ideas , I seperated the antenna wire as far away from the electrical wires a s possible but hasn't fixed the noise,the radio model is a  FL760

[C150L 6]

Thanks for posting this, I'm having problems with radio noise,it seems to be worse at high rpms and my antenna is bolted on the turtle deck which is all aluminum ,so Im  thinking the  grounding shouldn't be a problem, is there a noise suppressor I should try or any other ideas , I seperated the antenna wire as far away from the electrical wires a s possible but hasn't fixed the noise,the radio model is a  FL760

 

Wished I had some great suggestion, but if not installed, find a recommended inline filter on the DC supply to the radio. Radio user manual might have a recommendation. Also, there might be some filter/suppressor suggested by your engine mfg to instal across the charging system, etc. Noise or other interference can be a pain to get rid of.

[EDMO 1078]

If your noise is a whine from the alternator, then a Capacitor, often called a filter, should take care of it - ask someone with more knowledge than me as to the size and location for your system - I think it is on the ground side? Rarely do these go bad, but it has happened, and a replacement fixes it.

EdMO

Edited 27 Oct 2014 by Ed In Missouri

[marksires 484]

I had the engine/alternator noise problem in mine. I got a noise suppressor at radio shack and put it in the power line to the radio. Seems to have fixed it.

[C5Engineer 1170]

If it's an ICOM they sell a DC power supply with it built in. Kind of spendy but works well.

[akflyer 1427]

I used an inline filter I got from napa aircraft section do you have a ground wire from the turtle deck to the air frame? I has to put one on my brothers kitfox to make the antenna work good with it on the turtle deck.

[marshawk 82]

thanks for the ideas everyone, I have no ground wire bonded to the frame just the 7 camlocs that hold it onto the airframe but maybe its not grounding properlty ,worth a try

[wolves200 31]

additional to all this, I know somebody had an annoying sound on the radio and after tons of investments on filters and all sorts of things, he couldn´t get rid of a cracking sound on the radio, he later find out by accident that one loose ground contact somewhere was vibrating against a metal plate and creating the noise, it was worst at high RPM and start or stop ramdomly.

 

spend money and even worst "LOT OF TIME" and all what he need it to do is just tight a screw......

 

) ) ) I love electrical problems

 

Regards

Dimi3