What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

RV-8 Antenna Suggestions please

H

humptybump

Well Known Member
What COMM antennas are pilots using on the belly of the RV-8.



Background:

I am having a "weak reception" issue with my Garmin radio (GTR20) in my RV-8.

I've had the radio and antenna checked for power output, frequency accuracy, and SWR. All are good.

My COMM antennas are mounted in the usual location - under the pilot, just aft of the main spar.

My radio calls are being heard by other airplane's and by the ground stations - eg Aproach / Departure control. However, I do not hear the ground stations unless I am within at least 20nm and sometimes closer. It varies but in general, i need to be closer than I would expect.

If I open the squelch, I do hear the response from the ground stations and it is faint.
 
Last edited:
I have similar reception problems in my RV-8. I've been planning to check the BNC connectors and try another antennae or 2.
I seem to remember much better radio reception in the past, so I'm thinking something has deteriorated. I might slide in another radio also (Terra, I have a few take outs from other planes)
 
Mine is working perfectly. Location is the same as you describe, behind the spar on centerline under seat. I'm using a basic bent whip comm antenna from DeltaPop aviation. It's a semi ridged white style. I'm hooked up with a run of RG400 going to a Garmin GTR200 radio. I just have a single comm, and then ADSB & Xpndr blade style antennas are located further back on the same centerline with about 24" between each of the 3 antennas.
 
look elsewhere

Antennas work 'in' and 'out', that is, if it's a good transmitter it will also be a good receiver. I'd look at your receiver, or maybe the signal is being masked by a noise source your receiver is picking up.
 
On a flight today I tortured myself by flying around with the squelch open. I hear several radios exchanges between aircraft and Approach control. They were not what would be described as "loud" but they were more than sufficiently understandable. With the squelch enabled I would not hear the ground station.

I'm interesting in the antennas others are using on the RV-8. I'll also investigate the radio receiver suggestion.
 
Due to the 'automatic gain control (AGC)' found in virtually all radios, the signals will only be about as loud as the noise you hear when there is no signal. When you did hear a signal, was the background noise suppressed (not noticeable)? If the answer is 'yes' then you need to go into a 'hidden' menu and adjust the squelch level.
 
I'd say "yes" - the noise level did "fall to the background" when I was hearing the ground station. It wasn't 100 gone but I was not having a problem understanding Approach Control.

What is this "hidden menu" of which you speak?
 
jdearborn said:
Another option may be the impedance of your headset or a corroded connection.
Click to expand...

I would think a headset issue would affect all communications. My experience is with approach/departure stations which are more than 15-20nm away. It might also apply to airports but I don't tend to radio direct to a tower when I'm 20nm out.

I cycle the headset connection every few flights or couple of weeks, which ever is sooner. I tend to "spin" the connections as a ground operation on every flight.
 
BobTurner said:
I'm not familiar with your particular radio, but it's in the installation manual. Usually you need to hold down some button while booting up. There will be a place to adjust the squelch.
Click to expand...

From the G3X Touch installation manual, there is a configuration page for COMM. It has an RF Squelch setting:

RF Squelch - Used to set the received signal level required to break squelch. Increasing this setting increases the signal level required to break squelch. Receiver squelch can be set from 0-10, a setting of 0 (default) represents the factory calibration.​

My unit was initially set to "0". I changed it to "1" and have not experienced any improvement.
 
What type of coax is used, RG-58 or RG-400 or what? A higher quality coax might help. There is not much to go wrong with an antenna. But mounting location or grounding of the base could affect performance. The majority of electrical problems are caused by poor connections.
 
humptybump said:
From the G3X Touch installation manual, there is a configuration page for COMM. It has an RF Squelch setting:

RF Squelch - Used to set the received signal level required to break squelch. Increasing this setting increases the signal level required to break squelch. Receiver squelch can be set from 0-10, a setting of 0 (default) represents the factory calibration.​

My unit was initially set to "0". I changed it to "1" and have not experienced any improvement.
Click to expand...

This doesn't sound good to me. If the box is still under warantee call Garmin. If not, can you borrow a similar, known good, radio, and swap it in? Then you'll know for sure if it's the radio or antenna/coax. For a test you could even plug your antenna/coax into a hand-held, see how well it receives.
 
Not the antenna; it was the TX interlock

Chock up another win for the g3xperts!

Based on a bunch of answers via email, the great and powerful g3xpert Steve consulting with the engineers ...

Pin 5 on the rear connector is the TX INTERLOCK IN pin, which when grounded de-senses the receiver about 30 dB to protect the COM receiver when another radio in the aircraft is transmitting. Any chance this input is grounded?​

Grounded? No. But it did measure 5K for some reason (blame the installer).

I made sure the pin was OPEN and completed a test flight.

WOW! The GTR20 sure is a great radio when it's not hamstrung by a 30dB de-sensing :eek:
 
You must log in or register to reply here.
Back
Top