Two Antennas for receive and transmit on 6400?

Mike-N1VE · October 2020

I have two antennas (20-meter dipole and Cushcraft R7) and would like to operate them for both transmit and receive on my 6400 with the Maestro.

When I use an antenna switch and change from one antenna to the other on ANT1, the Flex has difficulty tuning the second antenna, though both antennas are quite resonant on the frequency. I wonder if this is the purpose of having a second antenna input/output on the Flex? I have read the manual and haven't found anything specific about this situation.

Using the antenna switch to select one antenna or the other when connected to my FT-990 poses no tuning or operating problems. Why is there a difference with the Flex 6400?

George KF2T · October 2020

I'm guessing that you don't mean you want to run them simultaneously, right?

If the antennas are close enough to resonance, then don't use the built-in tuner. Switching back and forth between the two is pretty easy from SmartSDR.

As for "why there is a difference" - probably because the Flex internal tuner is just sensitive enough to the change in reactances that it senses the need to retune. You can have the same SWR but very different reactance values. That's be my guess.

73!

KD0RC · October 2020

Hi Mike, one other possibility is that there is a little reactance in the external switch or cabling that the Flex tuner reacts to. If you have an antenna analyzer, check the antenna with and without the external switch. You may find a bad or marginal switch or piece of coax. Since the Flex 6400 has two antenna ports, you could eliminate the external switch all together, and as George suggested, use SmartSDR to do the switching. You will need to continue using the external switch if you are using an amplifier, or external noise canceller.

73,

Len, KD0RC

Two Antennas for receive and transmit on 6400?

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