Why does changing Xmit antenna affect Receive.

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  • Updated 3 years ago

Why does changing Xmit antenna affect Receive.  6700.


I am in a location at 7000 ft on the continental divide in Montana.  It is so quite here that on 20m I can add 30db of pre-amp and noise and noise floor doest not increase but a weak signal will go to arm chair copy.  


Open Two pan adapters

Set both to Rec ant 1  and Xmit ant 1

Set Ant preamp to +30

Notice that the noise floor is at around -130


Change one pan to rec ant2

Signals ago away preamp goes to 0 and noise floor stays the same as expected.



On one Pan change to Xmit Ant2

The noise floor on both goes shifts to -160 on both Pans



Now put the top pan to rec ant1  xmit ant 1

The noise floor goes back to -130 and preamp is turned off  

Doesnt seem to me that changing the xmit antenna should change rec antenna settings.



Photo of roger na4rr

roger na4rr

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Posted 3 years ago

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Photo of km9r.mike


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OK I re created your scenario but came up with different results. I do not know why the difference but they are not the same. In addition, I used attenuation in my run vice preamp, however, I just did the same with +30 preamp on20m   and received the same results. Please note , I made the ant changes to the lower pan but this should not matter. In addition, I have no antenna connected to ant 2 on my 6700 but that too should not matter since the radio is not smart enough to know this. See below for results

First two pans same band both tx ant1 and rec ant1

Two pans same band upper pan tx ant1 rec ant1 lower tx ant1 rec ant2

Two pans same band upper pan tx ant1 rec ant1 lower tx ant2 rec ant2

Finally two pans same band upper pan tx ant1 rec ant1 lower tx ant1 rec ant1

Again I do not know why you are seeing what you are but as you can see I did not get the changes that you did. There has to be an explanation.

Sorry that this does not solve much but at least you have another data point.