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Author Topic: Antenna switch  (Read 497 times)

K8BHS

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Antenna switch
« on: December 05, 2019, 07:49:35 AM »

I have 2 hf transceivers and 1 vertical antenna and was wondering if I could use an antenna switch in reverse configuration to  allow me to switch from one transceiver to the other without doing any damage to the other radio. My main concern would be RF getting from one radio to the other. any thoughts?
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WJ4VA

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Re: Antenna switch
« Reply #1 on: December 05, 2019, 08:03:53 AM »

It would depend on how much isolation is provided between the two ports by the switch.  MFJ makes a specific switch for this purpose with 6 antenna and 6 radio ports. 
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K1VSK

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Re: Antenna switch
« Reply #2 on: December 05, 2019, 08:05:08 AM »

Most of us with multiple rigs have been doing just that for years/decades. Isolation figures for all contemporary switches are published. Many also ground unused ports.
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K7JQ

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Re: Antenna switch
« Reply #3 on: December 05, 2019, 08:19:09 AM »

I have 2 hf transceivers and 1 vertical antenna and was wondering if I could use an antenna switch in reverse configuration to  allow me to switch from one transceiver to the other without doing any damage to the other radio. My main concern would be RF getting from one radio to the other. any thoughts?

No problem if you get a switch with ample isolation between ports, such as I have used for many years in such a situation..Alpha Delta. It grounds unused ports. But only run just the typical xcvr 100W through it. If you use an amp, insert it after the switch into your vertical. Also, common practice is to only have one radio at a time powered on.

73, Bob K7JQ
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KL7CW

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Re: Antenna switch
« Reply #4 on: December 05, 2019, 11:57:24 AM »

Check the maximum signal spec on your transceivers.  Usually something up to +10 dBm is considered a safe level.  So if your TX power is say + 50 dBm this would imply that switch isolation of at least 40 dB would be required, so you could look for something like 50 dBm isolation just to be extra safe.  Please check out my math yourself.  I think ARRL uses the figure of +10 dBm as the maximum level they put into a transceiver when they do their testing.  Some folks with multiple transceivers and antennas use patch panels which have good isolation, and make accidental mishaps nearly impossible.  In commercial installations patch panels are often utilized.   Rick  KL7CW
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WJ4VA

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Re: Antenna switch
« Reply #5 on: December 05, 2019, 04:53:03 PM »

I made the "Patch Panel" below to be able to accomplish the same thing.  The bottom half of the SO-239s have jumpers going to the outputs of the various radios, then I can connect any antenna to any radio by simply connecting whatever antenna I want to whatever radio I want....and as a bonus when not in use the antennas are completely disconnected.
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K0UA

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Re: Antenna switch
« Reply #6 on: January 02, 2020, 01:19:37 PM »

I made the "Patch Panel" below to be able to accomplish the same thing.  The bottom half of the SO-239s have jumpers going to the outputs of the various radios, then I can connect any antenna to any radio by simply connecting whatever antenna I want to whatever radio I want....and as a bonus when not in use the antennas are completely disconnected.

That is what I do.   There is no way possible to "mess up" and feed a transmitter into another. And the isolation is better than the best antenna switch. I built my panel on a piece of thick sheet brass.  But if you don't want to build your own panel MFJ makes one.  Of course I would want to check it out pretty good before using it.  :)
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73  James K0UA
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