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A Single com antenna used for dual com radios?

DennisRhodes

DennisRhodes

Well Known Member
Is there a splitter that can be installed into the antenna Coax such that either of two com transceivers can operate off one antenna( but not at the same time) and not damage either radio? I know about the dividers for getting two NAvs to work off a single antenna but receiving s is a bit different than transmitting energy into the antenna ( or other com) .?
Any suggestions would be appreciated, Not interested in adding another com antenna to the belly. It already has a TXPDR, ADSB, COM, ELT , OAT and two GPS pucks on it now. Thanks .
 
No.

You can get a *switch* (actually an RF relay) that'll do it, but they ain't cheap, and you'd then have a failure point that could take out both radios' ability to transmit or receive. I'd choose a rubber ducky sticking out of the glare shield, first.
 
If it's for #2 radio you could try an Archer Comm antenna in a wingtip. They get mixed reviews for comm.

But to my knowledge Comm should not be split like the Nav can.
 
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The short answer is that it can be done.
The longer answer is that, by the time you've purchased a good-quality coaxial relay, you've spent more than buying a good antenna.

As others have pointed out, that coaxial relay becomes a single point of failure. What hasn't been pointed out is that one of the failure modes can result in the transmitter output of one comm radio blasting straight into your other comm radio, making for a very expensive repair.

In the long run, just install a second antenna and coax run. There's a reason why nobody runs one antenna on two radios. In fact there are a truck load of reasons. It's just a bad idea. I've seen it done and seen the coaxial relay fail spectacularly. Just don't go there.
 
That's kinda where I got to on that single antenna idea also. Know if anyone has ever had any luck with a vertical rod antenna down the inside of the main gear leg fairing?. Looks like ther may be room but you have that steel tube there blocking. A piece of nylon tube could insulate the radiator off the gear.Ground plane could be a 90 deg turn and mounted on the firewall on a tailwheel plane. ???
 
Sorry; you can't 'insulate' the RF from the gear leg.

My 1st choice would be an Archer in the wingtip. 2nd would be another whip. 3rd, if it's just a backup radio, would be in-flight access to the coax so I could move it from one radio to the other.
 
Thinking toward rubber duckie in the baggage vertical up in the plexy. May not be best but after all my handheld works fairly decent just from the cabin. I thing someone suggested duckie in the windscreen. Thanks for all the comments, VAF comments are the best.
 
DennisRhodes said:
Thinking toward rubber duckie in the baggage vertical up in the plexy. May not be best but after all my handheld works fairly decent just from the cabin. .
Click to expand...

Really? How far can you transmit with that?
The Archer, properly installed (you need to get as much vertical component as you can in the leading edge) will not be as good as an external whip, but a whole lot better than a rubber duckie.
 
Ive use the handheld in airport traffic areas on occasion ie 5 to 6 miles maybe a couple less. Usually get an answer, but I'm sure it not that great. But never depended on it in positive control areas. The receive is usually very clear. That's with a set of headset adapters hard coupled of course.

Thanks Carl for the link wasn't aware of that option for a handheld as much as I have looked at AS. Notice it for Icom A6, A xx , Ayy

That's kinda comical in that if the Icom panel mount A210 would WORK! most of the time I wouldn't need that box! But thanks anyway for the heads up.
 
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RV8JD said:
Antenna Switch Box. Something like this?

https://www.aircraftspruce.com/catalog/avpages/icomswitchbox.php?clickkey=32257
Click to expand...
Suggest doing a deep dive into what that box actually does, and how it does it. I think you'll find that it works the same way as the headphone jack on an old stereo works, with the insertion of the mini phone plug breaking the connection from the panel radio and connecting the antenna to the patch cable. If I'm right, you can duplicate it for about $15 & an hour of work, and either way, it's a failure point. IIRC, there are plans for one on the Aeroelectric Connection website.

FWIW, a relatively common location for old style ELT antennas (middle of the comm band) in RVs is in the baggage compartment, arcing up following a rear window. Compare an old ELT antenna to a Comm whip.

Charlie
 
DennisRhodes said:
Ive use the handheld in airport traffic areas on occasion ie 5 to 6 miles maybe a couple less. Usually get an answer, but I'm sure it not that great. But never depended on it in positive control areas. The receive is usually very clear. That's with a set of headset adapters hard coupled of course.
Click to expand...

Receivers work great even with lousy antennas, because it's relative easy to make an incredibly sensitive one, with huge gains and low internal noise. As I said, an Archer will not equal an external whip, but will get you heard a whole lot further out than 5 to 6 miles.
 
Bob looks like that Archer 01A Com antenna has a 11 inch leg requirement in the vertical, If you need to stand it up completely vertical. I don't believe there's more that 7 to 8 inches vertical in an RV9 wingtip. might be wrong Guess that why it says get as much vertical as possible in that installation

Just for conversation but no applicable here , I used a vertical dipole ( no ground plane) alum tape mounted within the e glass plies within the vertical fin of a LongEZ that worked quite well.
 
ELT antenna for com 2

DennisRhodes said:
Thinking toward rubber duckie in the baggage vertical up in the plexy. May not be best but after all my handheld works fairly decent just from the cabin. I thing someone suggested duckie in the windscreen. Thanks for all the comments, VAF comments are the best.
Click to expand...

I added a second com and just used an ELT antenna in the baggage compartment. I have never had any complaints during radio checks with ATC. The reception is about 80% of the external antenna. It serves just fine for what com 2 is used for:

Monitoring Unicom while talking to ATC
Copying ATIS
Monitoring guard 121.5
Backup if com 1 fails

I am totally happy with it.
 
Mconner7 said:
I added a second com and just used an ELT antenna in the baggage compartment. I have never had any complaints during radio checks with ATC. The reception is about 80% of the external antenna. It serves just fine for what com 2 is used for:

Monitoring Unicom while talking to ATC
Copying ATIS
Monitoring guard 121.5
Backup if com 1 fails

I am totally happy with it.
Click to expand...

Thanks Mc7 I like that idea. I got one already there in the baggage complete with BNC .
 
BobTurner said:
Really? How far can you transmit with that?
The Archer, properly installed (you need to get as much vertical component as you can in the leading edge) will not be as good as an external whip, but a whole lot better than a rubber duckie.
Click to expand...

My home-made Archers in the wingtips receive and transmit out past 50 miles. How much more is needed?
 
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