20dB Coupler with 3rd port disconnected

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darrenrainer
Posts: 15
Joined: Thu Aug 09, 2018 12:40 pm

20dB Coupler with 3rd port disconnected

Post by darrenrainer » Fri Aug 16, 2019 3:31 pm

Stupid question time. I have a 20dB 200W 3 port coupler. If I unplug the power meter from the coupler sampling port will it affect the matching of the straight thru ports ? I am thinking it will not but just want to make sure. Just wondering if I can leave a coupler in line when used in conjunction with a high power PA at 2.4GHz.

AdrianH
Posts: 20
Joined: Thu Jul 18, 2019 2:46 pm

Re: 20dB Coupler with 3rd port disconnected

Post by AdrianH » Fri Aug 16, 2019 6:38 pm

I would suggest that any loading or mismatch would be down at -20 dB to an open port and -20 dB back so around 40 dB down, so not really having much of an effect, but, If you have any concerns about it then just connect a small dummy load to the port and give it 50 Ohms.

Adrian
G8UGD

darrenrainer
Posts: 15
Joined: Thu Aug 09, 2018 12:40 pm

Re: 20dB Coupler with 3rd port disconnected

Post by darrenrainer » Sat Aug 17, 2019 9:29 pm

Thanks for the advice Adrian. It puts my mind at rest. Didnt want to destroy the amp.
73s Darren G4VTQ

AdrianH
Posts: 20
Joined: Thu Jul 18, 2019 2:46 pm

Re: 20dB Coupler with 3rd port disconnected

Post by AdrianH » Sat Aug 17, 2019 9:37 pm

Hello Darren, it is my assumption anyway, it will probably be slightly worse then -40 dB down as that should be the case when terminated with 50 OHms so when not terminated it will probably be higher.

I would find a 1 to 5 watt load and stick it on the 3rd port.

Adrian
G8UGD

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