[Elecraft] K3 spurious radiation?

[VR2BrettGraham]

M0TRN replied to K8AZT:

> I had this happen to me a few days ago where I was calling CQ on 7.015 and
> was spotted on 14.0614 by Tim KQ8M's skimmer. I emailed KQ8M to ask him if
> there was a problem with his skimmer. He replied that he wouldn't rule out
> that the problem was in his Rx setup, but it was tuned to 20m.
>
> Now I was running through the linear and an ATU, and I can't see any
> logical relationship between the two frequencies, so I'm leaning to the
> theory that his receiver was the culprit, although I did find it very
> strange.
>
> I think a lot of RBN skimmers use SoftRock receivers, and I'm guessing 
> that
> if his VFO was tuned to 14.050 using the 2nd harmonic of a 7.025
> fundamental, it would kind of fit, but I'm still surprised that my 300W
> signal to an inverted V was 6dB over the noise on the wrong band in Ohio,
> 3800 miles away on the other side of the Atlantic... I'm not sure exactly
> because I don't know what receiver he was using, but it did have me 
> puzzled
> and when I saw John's post I thought I'd mention it.
>
> Here's the spot in question:
>
> de dx freq cq/dx snr speed time
> M0TRN 14061.4 CQ [LoTW] 6 dB 22 wpm 1952z 22 Jan KQ8M
> M0TRN 7015.0 CQ [LoTW] 14 dB 21 wpm 1952z 22 Jan S50ARX
> M0TRN 7015.0 CQ [LoTW] 14 dB 19 wpm 1952z 22 Jan W3LPL
> M0TRN 7015.0 CQ [LoTW] 14 dB 19 wpm 1952z 22 Jan W3LPL

This from only a very quick look at RBN spots from the day I believe 
K8AZT's wrong-band RBN spot happened on - but all of the 14 wrong-band 
RBN spots from that skimmer had a relationship between the wrong-band 
spotted & the actual frequencies the stations were on (based on where 
all the other skimmers were spotting those 14 stations at the time).

In the course of looking those up, I noticed another wrong-band RBN spot 
from KQ8M's skimmer that wrong-band spotted M0TRN above.

Also found in the course of looking at not quite all of the 13 calls 
spotted on 10m by the skimmer that wrong-band spotted K8AZT 
(coincidentally another K3 owner), were three wrong-band RBN spots from 
yet another skimmer.

Not sure, but I think all three skimmers concerned use Softrock SDRs 
(standalone, not IF).

Well spotted, gentlemen.  No worries about your K3s, but anyone into RBN 
might bear in mind I see about at least 3% of what was RBN spotted on 
one day by one of these three skimmers (together roughly 2.5% of 
skimmers QRV in the past 7 days) was spotted on 10, 15 or 20 when the 
station was actually on 40m.  I even found two of these skimmers saying 
one station's CQ was on both 28031 & 14043 at the same time (not a 
multi-multi contest station & it was a GMT Monday).  A more thorough 
look into all the possible Softrock spurious response RBN spots might be 
interesting, but beyond me.  I'm rather surprised at how many of these 
apparently LO harmonic related ones I found in such short order.

73/HLNY, ex-VR2BG/p.

> On 24 January 2012 13:08, John/K8AZT <k8azt-k3 at sbcglobal.net> wrote:
>
>> > I have not been monitoring this mail list much recently so I 
>> apologize if
>> > this
>> > subject has been discussed previously.
>> >
>> > I like to monitor the reversebeacon.net website while calling cq or just
>> > monitoring looking for a qso. Recently I have discovered a situation
>> > which has
>> > me puzzled and I am hoping someone here might be able to give me some
>> > insight
>> > what might be happening.
>> >
>> > When calling cq (CW) on 7.0 MHz cw, I see several hits on the reverse
>> > beacon
>> > website on 7.0 MHz, however I have also seen a couple stations allegedly
>> > hearing
>> > me on 10.1 MHz (2 occurrences) and a station hearing me on 28 MHz 
>> bands (1
>> > occurrence). I am hoping this is a problem with the skimmers, but 
>> want to
>> > check
>> > out if there is anything which might not be right with my K3 and/or 
>> antenna
>> > which might be generating unwanted radiations. At the moment I do 
>> not have
>> > exact frequencies where I was being monitored. I just thought someone
>> > might
>> > have a suggestion where do I proceed.
>> >
>> > At the moment I do not have access to a frequency analyzer, but hope 
>> I can
>> > find
>> > one to borrow locally.
>> >
>> > Thank you for any suggestions/comments anyone in the reflector might 
>> have.
>> >
>> > 73,
>> > John/K8AZT