High noise level until transmit

Mark_WS7M · October 2020

Hi all,

A friend of mine has a nice SteppIR beam next to his home. I've brought my Flex 6300 over for test and also he has an Icom 7300. We've noticed something rather interesting:

On 20m yesterday we were looking at an S9 noise level pretty much across the band. This was with his SteppIR beam tuned to about 1:1.

He transmitted on USB voice briefly giving his call and the noise level AFTER transmit dropped to like S4.

Then over a period of 5 minutes it began to creep back up to S9.

We put the flex inline and saw the same behavior.

We have tried different pre-amp settings and he has a good station ground. We are scratching our heads on what is causing the high noise level.

I have 20m in my car and tuned it up in the driveway and saw roughly the S4-5 noise level I would expect.

I suspect some kind of a ground loop perhaps but the disappearance of the noise after transmit is puzzling.

Anyone have any ideas?

KD0RC · October 2020

Hi Mark, I would suspect a bad connection somewhere. Once a little (or a lot...) of current flows through it, the connection "corrects" itself for a bit. I would unplug/plug in all connectors and loosen and retighten all ground connections. If that is not it, take a look inside the SteppIR to see if there is a loose or corroded connection in there.

To verify that it is the SteppIR (or one of the connections to it), try a different feedline and antenna, even if it is just a temporary wire.

73,

Len, KD0RC

Tim - W4TME · October 2020

It's a problem in the antenna system

High noise level until transmit

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