Thread: Tunable hum in Heathkit SB-401 RF output
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Old June 23rd 08, 07:47 PM posted to rec.antiques.radio+phono,rec.radio.amateur.boatanchors
Fred McKenzie Fred McKenzie is offline
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First recorded activity by RadioBanter: Jul 2006
Posts: 317
Default Tunable hum in Heathkit SB-401 RF output
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,
wrote:

Išve finished refurbishing a Heathkit SB-401 transmitter, but have one
last problem to fix: 60 Hz tunable hum audible on the output. (Hum
modulates the audio.)

David-

When I saw the word, "tunable", the first thing that popped into my mind
was "parasitic oscillation"!

You might recheck neutralization of the rig's finals. The manual
probably covers it. One thing to check, is to see if the plate current
dip corresponds to peak power output.

Fred
K4DII
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