Check the bias switch (relay, transistor, ?). If cutoff is
not being applied in receive, the tube will generate wideband
noise ("shot" noise).
73,
... Joe, W4TV
> -----Original Message-----
> From: amps-bounces@contesting.com
> [mailto:amps-bounces@contesting.com] On Behalf Of Paul Kraemer
> Sent: Saturday, December 06, 2008 12:57 PM
> To: n8de@thepoint.net; K1TTT
> Cc: Amps
> Subject: Re: [Amps] rx noise?
>
>
> How about from a zener diode in a bias supply.
> They make dandy noise generators and were the source of
> widband rf for the
> old Omega noise bridge. The current to make noise is
> critical, line voltage
> upset could put it at that point?
> Just fuel for thought.
> Paul K0UYA
> ----- Original Message -----
> From: <n8de@thepoint.net>
> To: "K1TTT" <K1TTT@ARRL.NET>
> Cc: "Amps" <amps@contesting.com>
> Sent: Saturday, December 06, 2008 11:24 AM
> Subject: Re: [Amps] rx noise?
>
>
> > Dave,
> > Sounds like a leaky power supply capacitor. Might be a cold solder
> > joint in the capacitor chain. Good luck
> > Don
> > N8DE
> >
> > Quoting K1TTT <K1TTT@ARRL.NET>:
> >
> >> I have a commander hf-2500 (pair of 3cx800a7's, no qsk)
> that seems to
> >> be working fine. However, during cqww cw last week I had
> to pull it
> >> off the 20m station because it was making a broadband
> noise while on
> >> receive. I put it back on the station today and it isn't doing it
> >> now. I tried warming it
> >> up a bit and it still didn't do it....though its obviously
> not as warmed
> >> through as after 40 or so hours of cqww. The only other
> thing I noticed
> >> is
> >> when it was doing it the plate voltage dropped a bit,
> maybe 50-100v, but
> >> I'm
> >> not sure if that was a cause or effect since the line
> voltage sag from
> >> the
> >> other stations can make the hv sag a bit here. Any ideas
> where to start
> >> looking??
> >>
> >>
> >> David Robbins K1TTT
> >> e-mail: mailto:k1ttt@arrl.net
> >> web: http://www.k1ttt.net
> >> AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
> >>
> >>
> >>
> >>
> >> _______________________________________________
> >> Amps mailing list
> >> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
> >>
> >
> >
> >
> > _______________________________________________
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>
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