[TenTec] Century 21 audio hum

Josh Gibbs gibbsjj at gmail.com
Tue May 30 17:09:11 EDT 2017

Thanks Carl. I think you are right about the headphones - the 'swamping
resistor' is achieving the same thing, but I might look for a higher
impedance set. Only other set I have are 32 Ohm, and that sounded the same
as the 8 Ohm set.

What kind of .01 caps, and where should I put them?


On Tue, May 30, 2017 at 1:57 PM, Carl Moreschi <n4py3 at earthlink.net> wrote:

> I don't think 8 ohm headphones were correct.  I think much higher
> impedance phones forces you to turn the volume up and drown out the hum.
> Direct conversion receivers are susceptible to a hum because the VFO is
> running at the operating frequency and can mix externally with 60 hertz.
> This is then detected in the receiver as a hum.  I used to put .01 caps
> across my HW8 power supply to kill this RF and remove a lot of the hum.
> Electrolytic caps don't work at RF.

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