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Author Topic: 2 Radio AB Switch  (Read 2030 times)
N4DXI
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Posts: 3




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« on: January 17, 2007, 04:59:17 PM »

I have two transceivers and want to switch either one to my main antenna via an A/B Switch which grounds the unused position.  I am doing this primarily to compare reception with the two rigs.  However, even grounded, I noticed the unused transceiver's S Meter gets pinned when I transmit on the other transceiver.

I know there is a chance that if I forget to switch and key the transmitter, I may be transmitting to ground.

I am more concerned about RF jumping the A/B switch and burning out the front end of my unused transceiver.  I am running a 200 watt FT 1000 D and an Orion II.  

Any suggestions?  Can I damage my unused transceiver's front end this way?

73...John, n4dxi
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KB9CRY
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« Reply #1 on: January 20, 2007, 10:54:13 AM »

Yes, there is not enough isolation in those switches.  Turn off the unused rig.

Phil
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N0UY
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Posts: 167




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« Reply #2 on: January 20, 2007, 03:55:14 PM »

John,
I agree with Phil.  However, I bet your S meter will continue to peg even if you disconnect the coax from the unused rig while transmitting with the other one.  There is enough stray RF in the shack to this.  It doesn't take much.

If the object is to compare receivers, don't transmit with the other one in the circuit.  Isolated or not.

Good Luck with the comparison.

ray
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K9KJM
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Posts: 2415




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« Reply #3 on: January 29, 2007, 12:35:51 AM »

I recently bought a Daiwa CS-201GH 2Ghz coax switch
(Claimed 50db isolation @ 1Ghz) for just such a radio comparison. (I am comparing a TS-2000 vs IC 756PRO)
I started out with very low transmit power levels until I was satisfied that the unswitched radio was not being overdriven with RF.
(I would never trust an older coax switch like the B&W ceramic jobs I usually use for HF for such a comparison. Just not enough isolation)
AND I would never use such a lash up for normal operations.....  This is for temporary testing only!
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KO4NX
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Posts: 179




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« Reply #4 on: December 10, 2008, 07:44:50 PM »

I know this is a little late, but I recently designed a 2x2 RF Switch Matrix which does exactly what you describe. My Design uses four Vacuum Relays, and provides plenty of isolation for my QRO SO2R station.

If you would like a schematic I can see about scanning one over to you. I can be emailed at ko4nx@arrl.net.

73


Rich, AJ3G
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