Two radios on one antenna.

[airboss1634]

I am a ham and should already know the answer to this stupid question, however it got me thinking. A ham friend of mine says that there is a device out there that would allow you to use two UHF radios in the same bandsplit on one UHF antenna (not a selector switch). Anyone seen this product? If not, don't feel bad, I don't expect an answer. Commence laughing.

 

[bagmouse7]

If you are talking about receive only, the device is called an antenna multicoupler. There are solutions for transmit as well, but they are more complicated.

 

[zz0468]

...There are solutions for transmit as well, but they are more complicated.

And MUCH more expensive.

It's a device called a control station combiner. They're intended for dispatch centers, etc. where there are a number of control stations used for repeater access, and a requirement exists to minimize the number of antennas used. They allow frequency agile radios (like trunking) to transmit and receive on a single antenna.

As I mentioned, they are expensive. They are also lossy, so there is a substantial performance hit that probably makes them a bad idea for amateur use.

A more affordable approach would be to use several RF rated relays, a sequencer, and a passive multicoupler. A multicoupler would feed the the receivers until either one is keyed to transmit, then the RF relays close the path from the transmitter direct to the antenna. The sequencer prevents the transmitter from actually being keyed until all the relays have been switched. Sounds a bit complicated, but it really isn't.

 

[jackj]

There's nothing to laugh at airboss1634, it's just a question. Bagmouse7 has given you an answer for receiver-only. A splitter could also be used but a splitter has lousy port-to-port isolation. A diplexer might work for 2 transmitters on one antenna if their frequencies are far enough apart. If you are talking about transmitting on frequencies that are close together then I don't know how you could do that. A diplexer is a tuned device, each port is tuned to pass it's frequency and reject the other port's frequency. So it wouldn't work very well with scanners.

 

[wv8mat]

what about if you have a 2m radio and a 70cm radio and you want to run 1 antenna. Like for me, i have a pick up truck with a dual band antenna 2m/70cm, what if i had 2 sep radios and still wanted 1 antenna

 

[KT4HX]

what about if you have a 2m radio and a 70cm radio and you want to run 1 antenna. Like for me, i have a pick up truck with a dual band antenna 2m/70cm, what if i had 2 sep radios and still wanted 1 antenna

I would use a VHF/UHF duplexer. Connect the antenna to the side with one connector and then the jumpers from the VHF and UHF ports to the appropriate radio. An example would be the Comet CF-416A on this page:

Comet Duplexers and Triplexers

There are different models and manufacturers, but the principle is the same. Hope that helps.

 

[wv8mat]

well that helps me out, thanks

 

[W2NJS]

Here is the page from the HRO catalog that has the thingies you all are talking about, with prices, too.

http://www.hamradio.com/web/newcat/hrocat8.pdf

 

[mjthomas59]

what about if you have a 2m radio and a 70cm radio and you want to run 1 antenna. Like for me, i have a pick up truck with a dual band antenna 2m/70cm, what if i had 2 sep radios and still wanted 1 antenna

Easiest way would be to sell the 2 sep radios and buy 1 dual-band radio. The yaesu dual-banders, i.e. ft-7800, ft8800, etc have the duplexer built in. Thus you can use 1 antenna, you save mounting space by having 1 antenna, and you dont have the expense of some of these $100 dollar duplexers that may or may not be tuned for what you are trying to do.

 

[K8TEK]

Those are technically called diplexers, not duplexers. A duplexer is used to transmit/recieve through the same antenna on the same band.