Bridging Antenna Coax

I am setting up my RV-6 for IFR. My plan for a second Comm is a handheld. I have wired this into the intercom so that I can switch to it, when necessary, and still use my headset and PTT.

I would like to be able to have this handheld use the aircraft Comm antenna in the event of a primary Comm failure. One option is to add a male and female connector in the coax run and loop it to the front of the panel for emergency access. Wasn't sure if this would create any loss issues.

The other option is to bridge the connection and bring the bridged coax to the front of the panel. The plan would be to only connect the bridged coax to the handheld when the primary comm was Off.

Looking for input on the feasibility of these options and any special splitters that I may need to accomplish it.

Thanks for your support on this decision.

Larry

There will be a negligible loss in the splice and its usually specified in db by the connector manufacturer. It will be minor so having a loop of wire where you can get to it with your handheld is a good way to do it.

Plan A is okay, as Bob says, at these frequencies connector and coax losses are small. But it sounds awkward to do, especially if ifr.
What do you mean by 'bridge'? Inserting splitters? That will not work.
You could insert a good coaxial switch, but they cost as much as a second antenna.

You could tee off the coax and install a bulkhead BNC fitting on your panel or somewhere convenient. Then just put a rubber cap on it until you need to use it.
Make a length of coax with male fittings on each end to connect from your hand held antenna fitting to the bulkhead fitting you installed.
It's a couple more BNC fittings but much cleaner and the signal loss won't be noticed for your application
Good luck

No you can't have splitter on a transmission line because the impedance gets screwed up.

No you can't have splitter on a transmission line because the impedance gets screwed up.

Click to expand...

Yep, an open ended quarter wavelength piece of coax looks like a dead short at the tee.
And, you would be transmitting into the other radio.

PaigeHoffart said:

Yep, an open ended quarter wavelength piece of coax looks like a dead short at the tee.
And, you would be transmitting into the other radio.

Click to expand...

And if you did that...poof.

Actually both transmitters would go poof.

The XCom radios I servce have varactor diodes in the output section to isolate the receiver any time the transmitter is keyed up.

Yeah, that's right
Another option would be to mount the bulkhead fitting in an inconspicuous place that could be reached in flight (under the panel?) that is a direct run to the antenna. The radio coax wold connect to this fitting. If the radio dies, just disconnect the main radio coax and connect the coax from the hand held
Probably a lot easier/better to just install a second antenna and run a coax to an emergency use spot.

How about a box made specifically for this function?

http://www.skygeek.com/icom-icant-s...aign=froogle&gclid=CP2vjPnkysACFRSEfgodo4cAMA

Floor hatch?.....

My comm antenna is mounted right under the pilots legs just ahead of the spar - I have a carpet "hatch" in the floorboard that allows me to disconnect the panel radio right at the the antenna and hookup a handheld with a coax pigtail.

I have only tried it once, but it worked great.

Gill,

Have you found any specs on that box? Insertion loss? SWR?

1/8" phone plugs aren't exactly designed for VHF. I also have to wonder how often people have tried to plug a MP3 player into that thing.

Paige

sf3543 said:

Yeah, that's right
Another option would be to mount the bulkhead fitting in an inconspicuous place that could be reached in flight (under the panel?) that is a direct run to the antenna. The radio coax wold connect to this fitting. If the radio dies, just disconnect the main radio coax and connect the coax from the hand held
Probably a lot easier/better to just install a second antenna and run a coax to an emergency use spot.

Click to expand...

I was thinking of this instead of the loop of coax. A 90* connector should make it work without being noticeable.

Thanks for all the advice here guys, I really appreciate it. I was afraid the tee idea might have issues, but I am not much of "radio guy" and wasn't sure. I'll put in some type of connector that I can reach. Should be able to manage a swap in IFR with the autopilot. good to have it there for the possibility.

Larry

How about a coaxial relay or switch?

Perform an eBay search for "coaxial relay" or "coaxial switch". Connect the common port to your antenna and each of the radios to the switched ports. Should be pretty easy and clean to install and give you a quick and easy way to select the radio you want online. I would suggest that you may want to make sure that your radios have isolators on the outputs to protect them if they are trying to transmit into open or shorted feeds.

Larosta