New KX1 low power and 20m oscillation

[Stan Gibbs, KR7C]

Ian,

IanMW wrote

Just to recap my earlier thoughts, I think your Q7 is fine, the negative voltage is a red herring. It's due to the RF that is being grounded via Q7 (its task).
...
In the mean time, I'd get up a hill!

Thanks for taking the time to check out your rig for comparison.  Good idea to email Elecraft support.  Gary's numbers were very similar to ours, so I guess the negative voltage is, as you say, a red herring (is there any other color?).

If you get a chance to scope Q7's terminals, I would be very interested in the results.

I finished the ATU this morning and everything seems to be working well, though the low 40m power still knaws at me.  I think I'll put the sideband issue on the back burner as long as nobody reports a crappy signal.

And, I'll definitely get up a hill soon!  After all, the KX1 is really a sweet little rig designed just for such a purpose.  Kudos to Elecraft once again!

[Don Wilhelm-4]

Stan,

Another thing to check carefully is the 20 meter low pass filter
following the DDS - L4, L5, C50, C51 and C52.  Check for good soldering
and proper values.  Since L4 and L5 now being supplied do not fit the
holes, be certain the bent under leads are not touching another solder
pad or via hole.

73,
Don W3FPR

On 5/8/2012 10:25 PM, Stan Gibbs wrote:
> Don, I tried your experiment but it had no effect. I just grounded point A
> because it is damn hard to jumper Q7.  R28 measures good and is well
> soldered.  It has -0.25V or so on the base side and 5.5V on the other during
> transmit.
>
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[Stan Gibbs, KR7C]

Don,

I took a look at all those components, their values and installation, and everything looks normal.  It may be that one of those components is bad, or that the DDS is exceeding its spec harmonic output for some reason.

I'm not certain that these harmonics are not somehow an artifact of my using the K3/P3 as a spectrum analyzer.  And, I'm also not certain how to determine the answer, short of picking up a spectrum analyzer.

Thanks for your support and time on this.