[Heathkit] GR-78 modulation hum
W2HX
w2hx at w2hx.com
Thu Dec 17 21:21:53 EST 2009
Maybe it just doesn't know the words? (sorry, couldn't resist). Happy
holidays
73 Eugene W2HX
-----Original Message-----
From: heathkit-bounces at mailman.qth.net
[mailto:heathkit-bounces at mailman.qth.net] On Behalf Of SX-25
Sent: Thursday, December 17, 2009 10:48 AM
To: heathkit at mailman.qth.net
Subject: [Heathkit] GR-78 modulation hum
Hello all,
Has anyone any experience dealing with modulation hum on the mid-70s vintage
Heathkit GR-78 portable shortwave receiver? As with most modulation hum it
is prevalent on stronger stations and the greater the signal strength, the
greater the hum. I have checked out the usual things, bonding of the tuning
capacitor to ground...voltage being supplied to the front end and removal of
AC charging and allowing it to run just from batteries. In my tube type
radios modulation hum is often cured by arrangements of filament to grid
bypassing, but obviously such is not the case here. Of course, my wire
bundle may be the culprit, although it is tightly dressed and routed
precisely as Heath described in their assembly manual.
Anyone have any other ideas?
Thanks and hope all on this reflector have a safe, healthy and happy
Christmas in peace.
WPE9GHF
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