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Old June 23rd 08, 12:04 AM posted to rec.antiques.radio+phono,rec.radio.amateur.boatanchors
[email protected] w4pqw@cox.net is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 69
Default Tunable hum in Heathkit SB-401 RF output

On Jun 22, 3:37*pm, wrote:
On Jun 22, 4:07*pm, "Kim Herron" wrote:

Hi Dave.


* * Over the years I too have run into the same situation and what the
fellows here are telling you is most likely correct. *I can also tell
you the you don't need any antenna to pick up that transmitter when it's
that close. *In fact you'll do better if you don't use an antenna or
something very short to get a better picture of what your xmtr sounds
like. *This is one time where an RF envelope monitor scope comes in REAL
handy. *If you have hum on the transmitted envelope you'll see it on the
scope.
Kim *W8ZV


Thanks, Kim. *As recommended by another poster, I think the best
course of action is to use an external antenna and make a few contacts
to get signal reports.

You’re right about the monitor scope. *There’s a companion Heakthkit
SB-610 Monitor Scope that I don’t have, but could use right now.

-Dave Drumheller, K3WQ


You mentioned that when you plug in the mic it changes the hum
level,,This may sound too simple,, BUT,,Always bond all items together
(Rec,xmtr,spkr,etc)and to a good earth ground.They used to call it
GROUND LOOPS, I never figured exactly what a groundloop is ,,I do
understand grounding and I hope you have done that first..OK W4PQW
PS (I think a groundloop is when you deliberately wreck your
airplane at the end of the runway just before you kill yourself..)