[Elecraft] K3 Amplifier Drive Inconsistency

[Jim Rhodes]

Thanks for the suggestion. The antenna is less than 25 feet from the rig.
The RF getting into the audio could be coming from the coax or the antenna,
no way to say which. There is 5-6 turns of coax, 6 inches in diameter, a
couple of feet from the rig where it comes into the apartment.  Beads on
the coax might do the trick, but I am not near my parts boxes, they are
about a 12 hour each way drive away. And I am in very rural North Dakota,
would have to order something mail order and wait till pony express gets it
here. So I will stick with what works. I am in a tiny apartment with just a
little patch of weeds with a little grass on it and can't get the antenna
any further away. I had the same problem when I tried a short dipole with a
fair balun (elecraft of course) at the feed point. And, as I said, I now
have zero problems. Well, other than a crappy antenna setup.

On Mon, Aug 5, 2019 at 8:45 PM Don Wilhelm <donwilh at embarqmail.com> wrote:

> Jim,
>
> That sounds like RF getting into the audio.  Try moving the ferrites to
> the antenna feedpoint to choke off the RF on the coax shield.  Yes, the
> coax from a vertical needs a current choke.  In fact, you may need a 2nd
> choke at the shack entry point as well.  The coax will try to be an
> additional radial and that means it will have RF current on it - if not
> from the antenna itself, the radiation from the radiator may couple with
> the coax shield and cause RF on the shield (that is why the additional
> choke at the shack entry).
>
> The KX3 has one characteristic that may cause confusion.  If the signal
> to the mic input is too large, the KX3 will shut down the audio gain
> giving the impression that there is not enough audio when in fact there
> is too much signal at the input.
>
> 73,
> Don W3FPR
>
>
> On 8/5/2019 9:23 PM, Jim Rhodes wrote:
> > Last night I noticed I had little to no output from my KX3/KXPA100 combo
> > especially on 40. I did a little experimenting and discovered that 3
> turns
> > of the transmit audio line through an unknown mix clamp on ferrite fixed
> > the problem. Without it I was mildly affected on 20 and not at all on 15.
> > With that choke in place I was stable on 40 and all other bands I tried.
> I
> > am currently portable for work (in North Dakota) and am using a mobile
> > antenna clamped to the top of a 6 ft tall wooden fence. Without the choke
> > the ALC would go up when keyed, then drop off to near nothing. I know
> AFSK
> > is becoming a more preferred method of generating RTTY, but I have never
> > had this issue with FSK. So I learned a lesson about the little USB
> > soundcard I use for portable ops.
>