Topband: control voltage noise in K9AY loop

Paul Baldock pbaldock at
Wed Oct 10 21:33:14 EDT 2007

At 02:39 PM 10/10/2007, you wrote:
>The problem is that I have serious hum modulation in each of the powered
>positions of the direction switch (+/- 24 DC and 24 AC).

I had the same problem, but only with +/-12V but not with 12V AC. I 
solved it by using an isolation style 9:1 transformer rather than the 
auto-transformer. I let the input side of the transformer and relays 
float from ground out at the antenna.

Also I put .022uF on the output the halfwave rectified signals back 
at the shack, because those signals can have pretty fast edges at 
zero crossing.

That should fix it.

- Paul

More information about the Topband mailing list