[Fourlanders] Radio problem

[Jim Worsham]

I think as scientist (as an engineer I consider myself to be a bit of a
scientist) we all know what needs to be done.  Experiment.  We need to set
the 6 meter station up BEFORE the contest as close as we possibly can to how
it will be setup on the mountain and see if we can reproduce and
troubleshoot these problems.  We can set the tower trailer up with the
antenna on it.  We can even run it off of the generator to see if it might
be power related.  We could even use the trailer to set the station up in if
we wanted to be really fanatical about it.  Bob, your place is probably the
best place to do this since you have the room to set everything up.  I don't
see any point in doing this now.  Lets look at doing it next year as soon as
it warms back up some.

73
Jim W4KXY

----- Original Message ----- 
From: "Bob Lear" <k4sz at alltel.net>
To: <fourlanders at contesting.com>; "Fred Runkle K4KAZ" <runkle at charter.net>
Sent: Wednesday, October 08, 2003 5:17 PM
Subject: [Fourlanders] Radio problem


> Gentlemen, I've finally gotten around to testing my FT 920 that gave us
> a problem at the beginning of the contest on 6m.  As you may remember,
> it was producing garbled SSB output, so bad it was hard for our friends
> to copy.  I disconnected it from the amp, computer and everything I
> could on the mountain to no avail.  It had the problem at high and low
> power, with different mikes, etc.
>
> When I got around to testing it, I hooked everything up, computer,
> radio, PS, etc. and found no problems with it here!!!!!!!
> Even with the same Samlex switching supply I was using on the mountain
> and I even tried it with a variac on the input to simulate low line
> voltage as suggested by Fred K4KAZ, it wouldn't even start to sound
> funny until I got down to 50% input voltage, and then the PS was
> groaning, not a problem that we saw on the mountain.
>
> I sure thought we had this figured out, but I'm at a loss as to what
> happened.  We did the remainder of the contest with a borrowed FT897,
> same PS, amp, computer, Headset, connections, etc, pretty much without a
> hitch and certainly no distortion like I experienced there at the
> beginning of the contest with the 920.
>
> Any thoughts on what the problem might have been from anyone out
> there!!  I'm glad my FT920 is OK, but I sure wish we knew what was going
> on.  Neal is also going to test his 990 (with internal switching supply)
> on a variac, but I'm not holding my breath for that to be a problem
> either.
>
> It's looking like RF feedback, but why only with certain radios?  Are
> switching supplies more susceptible to RF than linear supplies?
>
> Maybe we can set up the antenna out in the yard on the trailer sometime
> and set one of the problem stations up again to see if we can duplicate
> the problem at home and figure out a solution.  Not a lot of fun to try
> to fix right after the contest has started.  BTW, my system was fine on
> Friday night and Saturday morning.  It wasn't until we got the linear on
> at the beginning of the contest that we had a problem.  And of course we
> shut the linear down and took it completely out of line and still had
> the distortion problem, and then it was OK with the 897 and same PS.
>
> I'm tired of this 'VooDoo curse' we seem to find up on the mountain!!!
>
> Any comments or suggestions are welcome.
>
> 73 Bob
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