How much isolation is necessary?

[w1jsParticipant]

I am new to SDR, but not ham radio, and recently purchased an SDRplay RSP1A. I successfully launched the SDRuno program and have been having fun playing with the numerous buttons/options. I use a 4 position AlphaDelta antenna coax switch to switch among 4 radios prior to my linear amplifier, the RSP1A antenna lead using one of those positions. To date, due to the stern warnings in the documentation, I have also unplugged the antenna lead at the SDR when using another rig to protect it from RF. Is this really necessary or is the isolation of the antenna switch sufficient? Thanks in advance for all replies.

Jack
W1JS

[RogerParticipant]

The Alpha Delta 4 position coax switch is specified as >60 dB isolation.
Switch specs

Your switch is before your linear so the drive will be less than 100 watts or 50 dBm. With 60 dB of isolation the RSP should see -10 dBm or less which is a safe level. I would test it by turning your transceiver power as low as it will go – lets say 1 W or 30 dBm and put out out a CW signal at this level. Then measure in SDRuno the power level you are seeing leaking through the switch. With 60 dB isolation it should be -30 dBm or less in SDRuno. If that is the case you are OK at 100W.

[w1jsParticipant]

Thank you! 🙂

[Author]

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