Re: LF: WSPR problems

[Chris Osborn <g3xizchris@gmail.com>]

Hi Stefan,

Many thanks for the prompt reply.

I shall do as you suggest and hopefully cure the problem.

73

Chris

On Sat, Jun 17, 2017 at 12:57 PM, DK7FC <selberdenken@posteo.de> wrote:

Hi Chris,

Try a 1:1 RF ferrite decoupling trasformer, right behind the PA. Maybe also on the PA input. Try to use a battery for the PA, just for one WSPR sequence, to see if that solves the problem. If it does, then use common mode chokes in the PA supply cable. Avoid ground loops. Use shielded circuits only.

73, Stefan

Am 17.06.2017 13:20, schrieb Chris Osborn:

GA LF,

I have a recurring problem with my home made LF WSPR TX  :-

As the PC's audio signal shuts down (after the nominal 2 minute  transmission time) it picks up RF  -  this is fed back to the TX input causing several seconds of instability.

Has anyone else had this trouble and/or knows of a simple solution?

I've tried putting ferrite rings around the PC's input and output cables which solved the problem for a while.

In desperation I'm considering adding a monostable to ground the TX input for a few seconds after the PC's AF shuts down, but this will be a last resort.

Any useful advice or comments would be most welcome.

73
Chris (G3XIZ)