[Elecraft] PX3 Problem?

[Dave Sublette]

Using just one of 20 “extra” spurs, I measuredthe spur peak at -90 with the preamp on. Base line is -125 with it on.

Turning off the preamp, the peak is -75, base line -112.

The s/n remains basically with preamp on and off.  The main thing is, Those spurs were not there previously. 

I just took the PX3 out to the shop and hooked it to another supply.  The spurs are still there.

Dave
> On Jul 16, 2017, at 10:22 PM, Don Wilhelm <donwilh at embarqmail.com> wrote:
> 
> Dave,
> 
> The KX3 is designed to be operated with the preamp on most of the time. The only reason to turn it off is when extremely strong signals are encountered.
> 
> The preamp eliminates many spurious signals that are actually out of band due to its signal rejection "filtering".  That has nothing to do with the sensitivity, and it can kill extraneous results such as you are seeing.
> 
> If it makes those responses substantial with the preamp on, then there may be a problem to be addressed.
> 
> 73,
> Don W3FPR
> 
> On 7/16/2017 10:07 PM, Dave Sublette wrote:
>> Good point.  However I am on 20 meters, which really doesn’t need the preamp.  Besides, the spikes are 40 dB high or so.  No, this behavior is definitely looking like a failure.  I have one more thing to try.  I will carry it out to the shop in my garage and plug it in.  If it is the same there as in here, it’s not any external influence.  Thanks for hanging in there with me.
>> 73,
>> Dave
>>> On Jul 16, 2017, at 9:56 PM, Dale Boresz <dmboresz at gmail.com> wrote:
>>> 
>>> Dave, make sure that the preamp is engaged on your KX3. If the preamp is off and you are receiving on a quiet band, you'll see "stuff" that would normally be covered by the band noise. Turn on the preamp, and the artifacts that you're seeing should be pushed below the noise floor of just about any band.