[R-390] update: HP8640B RF Sig Gen Leakage

Fri, 18 Apr 2003 15:28:40 -0400

Hi,

Any time you are working on a sensitive radio it's a good idea to check for
stray pickup. The R-390 isn't as well shielded as it might be and as this
thread has demonstrated there are problems with signal generators as well.

A simple quick check is to pop the coax off of the generator and then touch
the shield of the cable to the chassis of the generator. That way you have
the same ground loops set up when you do the check as when you do the test.
If all is going well you should be able to crank the generator output up
fairly high before you hear anything in the radio. You should not be able to
hear a difference when you power cycle the generator.

If you fail the test then a quick solution is often an attenuator at the
input to the radio. This obviously will only work if the signal is getting
in through the antenna and not if it's coming in through the power cord. If
it's still a problem then simple separation of the generator and the radio
often helps. Filtering type rfi/surge suppressors also can come in handy.

None of this is specific to any one R-390 (A or not an A) or  HP-8640. All
are usually good pieces of gear. Any of them can have problems and it's a
good thing to check when you are doing work. It can save a *lot* of time
....

    Take Care!

        Bob Camp
        KB8TQ

----- Original Message -----
From: "mikea" <[email protected]>
To: <[email protected]>
Sent: Wednesday, April 16, 2003 9:00 PM
Subject: Re: [R-390] update: HP8640B RF Sig Gen Leakage

> On Wed, Apr 16, 2003 at 06:35:11PM -0400, Bob Camp wrote:
> > Hi,
> >
> > Hey, good job!!!
> >
> > This is the same sort of thing they used to have to do back at Motorola
on
> > the same gear fresh from HP. The bottom line seems to be that most
people
> > don't check really low levels with this kind of gear.
>
> Maybe this (leakage) is why I keep running out of attenuator when I
> try to do sensitivity measurements on my R-390.
>
> --
> Mike Andrews
> [email protected]
> Tired old sysadmin since 1964
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