[R-390] Re: Line filter issues?

[bw]

I don't have much help for you here, but I had a similar problem a while
back. I have a nice 6' rack that had my R-390A in it near the top. There was
a SP 600 beneath that, and a tube amplifier below the amp. A variac sat on
the base of the rack below all of the gear with a lot of metal between it
and the top of the rack. I had bought the Quantum QX Pro loop which is
incredibly sensitive on MW/LW. Well, the rack made a great reflector in the
shack with the loop located on a lower shelf unit so I put the loop on top
of the rack. I have a swivel chair that sits kind of high up and I could
rotate the loop well enough for the time being. I was getting terrible
buzzing everywhere and the loop was just about unusable in this setup. I
finally moved the loop and my LF receiver to the other end of the house
where it is very quiet there. A few months later I brought the QX Pro back
to do some testing with the R-390A again. The buzzing was gone. The only
thing that I know of changing was the variac location. I had moved it to the
side of the rack, sitting on the floor. Anyway, the buzzing is gone now. My
guess was that the variac was causing the problems but I never checked into
it.


Barry non-Hauser


> Here's more on the issue. A couple of weeks ago, when testing a small
> homebrew amplifier/speaker combination to use with the diode load input, I
> noticed 
> some buzzing coming from the speaker. At this point, the hum was not audible
> from the set's audio on any band, with much of it unnoticable if there was a
> good 
> signal from the receiver, or if the speaker was moved away from the set; it
> would go away completely when unplugging the variac setup I always use to
> power 
> up my radio, and was still present when using no variac whatsoever. However,
> during a recording session of a local BC oldies station, the hum began coming
> through over the BC station with force. At first, I attributed it to the fact
> that I had taken off the Utah plate for display purposes, but putting it back
> on made no difference whatsoever. Earlier today, I decided to see if the noise
> was still coming through, and it was still present, so I began turning off
> various appliances in the house (none of the other line-powered BC sets I've
> tried have exhibited this interference), but this had no effect on the
> buzzing. I 
> then tried using a small transistor radio tuned to the same station to trace
> the source of the buzzing. I got clear reception until I got within a few feet
> of the receiver. I thought that it was perhaps the homebrew variac setup
> which was causing the interference, but trying a commercial variac instead had
> no 
> effect, and unplugging the R-390A from either variac got rid of the buzzing
> altogether. I can live with the problem for now, since it doesn't appear to be
> affecting most of the SW bands, but I would like to find a solution which
> wouldn't affect the look of the set too much (i.e. I'd rather not have a IEC
> connector present in the back of the set, but if there's no way around it, so
> be it; 
> I'll just have to replace the molded plug on the new IEC cord with the
> military-style three-prong plug from the old one!). How hard is it to access
> the old 
> line filter without displacing the rest of the radio? TIA.
> -Adam
> (BTW: I tried sending this twice from AOL Web Mail, as suggested in the
> NoMIME FAQ, and it was rejected as spam by qth.net's filters both times.
> Strange...)
> 
> Adam Vaughn