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help...Multiple radios, one antenna?

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Old 07-30-2008, 01:56 PM
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Default help...Multiple radios, one antenna?


Does anyone know of a way (on vhf/uhf or even hf) to have more than one radio on one transmission line / antenna and not use an antenna switch? I don't need to transmit at the same time, but i would like to be able to have one rig that is able to monitor on an antenna while another radio is actively using it on the same band. Is this even possible?


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Old 07-30-2008, 04:15 PM
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You want to use one antenna to transmit on, and to receive on at the same time?

Unless you're talking about REALLY high frequencies (radar comes to mind), I'd guess not.

With radar, the transmitted signal is pulsed briefly (microseconds of time) and then the transmitter shuts off while the receiver listens for the returned signal on the same antenna. While the transmitter is on, the receiver is muted.

Don't use an expensive receiver if you're experimenting with this arrangement.
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Old 07-30-2008, 04:33 PM
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That's basically how VHF/UHF repeaters work, which use a duplexer for simultaneous receive and transmit on the same band but not the same frequency. There are several "buts" when doing that, and not exactly cheap/simple to do. Same thing is possible with HF, but extremely 'not cheap' or 'simple'.
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Old 07-30-2008, 05:41 PM
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Three words come to mind. "Tunable bandpass filters." This approach is however neither simple nor cheap.

Three more words come to mind. "I see smoke."

Unless you have deep pockets and lots of know-how I do not recommend proceeding with this application.

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Old 07-30-2008, 09:22 PM
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Well I can envision the smoke possibilities as I was thinking about this. I also understand how repeaters work, which is why I was trying to figure out how this might be possible. I really don't want to rx on the same frequency I'm transmitting on, just possibly within the same band. You guys understand the problem right? House in the city...limited antenna space, etc. Oh well, if it's too difficult or expensive to accomplish I guess I'll have to think up something else.

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Old 07-30-2008, 09:26 PM
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That's why I said tunable bandpass filters. They would allow what you want but they would have to be of extremely good quality (expensive) to have the filtering required to attenuate the TX freq enough to prevent desensing the RX.Differant bands would not be the problem but a TX and an RX on the same band gets dicey.

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Old 08-25-2008, 08:54 PM
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Default 1 antenna multiple radios

Diamond sells a triplexer. HF/VHF/UHF or VHF/UHF/1.2 Ghz. this allows you to use 1 antenna with 1 feed line x 3 inputs. I use the 1.2Ghz version on my Ts 2000X, works very well with almost no loss. The cost depending on where you buy it is between $69.00-$89.00. I have seen them on E-Bay for 59 bucks. And yes you can receive on the other bands as you transmit on another, no switching involved. Did I just start a sentence with "and"?

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Old 08-25-2008, 09:00 PM
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Ahh, but the question wasn't about TX/RX on different bands...it was about doing so on the SAME band. The triplexer/duplexer won't work for that.

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