Good job. I considered that but it is so unusual to have a strong enough
field to produce noticable change in the permiability of a powdered core.
An interesting experiment would be to rotate the receiver carefully and see
if the earth's field shifts the frequency. It should have the same effect
on receive as transmit in this case. Just tune in a strong carrier and
rotate the radio carefully.
73
Bill wa4lav
At 12:13 PM 12/18/2003 -0700, you wrote:
I want to thank everyone who replied to my message for help with hum on my
Argonaut 505. In retrospect I feel a good bit like Click and Clack, those
well known NPR Auto Mechanics, with their Weekly Puzzler. As you can see
from my original plea below, the real clue was the speculation that it
might be FM on the local oscillator.
Dave, K8BBM, had the right answer when he wrote, "move power supply away
from rig some, some TT rigs subject to hum is PS too close to one end of
rig." Indeed, if I position the 210 power supply so that the power
transformer is over the front, center of the rig and thus on top of the
vfo box, the hum as judged by the audio output of my R4B monitor receiver
becomes extreme. At the same time there is absolutely no ripple present
on the RF wave envelope. So I presume that the AC field from the
transformer is interacting with the permiability of the tuning slugs in
the oscillator coils and creating FM. I also see the same effect when I
run the rig from a battery supply and I either position the turned-on but
disconnected 210 AC supply above the vfo or even when I position a
turned-on Autek audio filter with an internal AC power supply above the vfo.
Further, when I move the 210 away from the transceiver and use it as the
power source, the hum disappears.
So I have my answer. Thanks again to all and especially to Dave.
73 and Merry Christmas,
Jim, W8KGI
----- Original Message -----
From: JAMES T HANLON
To: tentec@contesting.com
Sent: Wednesday, December 17, 2003 9:49 AM
Subject: [TenTec] Argonaut 505
Y'all,
I just became a new owner of an Argonaut 505, the very first Argonaut
and my first Ten Tec rig. It came with the model 210 power supply. I am
noticing a 120 Hz hum on the transmitter note on CW and a corresponding
hum on the SSB signal when I run the rig from the 210. When I power it
from a battery there is no hum. It is most noticable on 40 meters which
is where the local oscillator is tripling, and I don't see a hum on the
wave-envelope with my HP1740A 100 mHz oscilloscope. So it may be FM on
the local oscillator.
I would appreciate first of all a circuit diagram for the 210 power
supply, and then of course any suggestions about what to do. It is a
really fun little rig when I run it from the battery.
Thanks,
Jim Hanlon, W8KGI
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