[Skimmertalk] I/Q Balance and CQWW Skimmer observations

[Dean R. Madsen]

Pete & the group:

I have tried the transmitting in the dummy load, but it did not solve 
the problem.  The signal from the clock of another soft rock was 
probably stronger than the signal from the dummy load.  Thus the idea 
of editing the data.

I did run the skimmers in the CQ WW contest.

I live on an older 50ft wide city lot in Des Moines, IA.  I am 
fortunate to have a 40 ft tower with tri-bander, GAP Titan DX 
vertical, 80/40 dipole and Alpha Delta DX-LB Plus dipole for 160.

Unfortunately, this means that all my antennas are all very close to 
each other.  I can't really operate the contest and have the skimmers 
running at the same time.

I did briefly provide skimmer spots for a multi-op effort..  This 
caused a black blur on the band map (probably need to turn "show 
unworkable spots" to "off").  The rate at which the skimmer spots 
came in far exceeded regular packet cluster.  Unfortunately, many 
spots were flipped on the wrong side of the soft rock center 
frequency adding to the deluge.  There was also a big difference in 
antennas between that station and my station that most of my skimmer 
spots (especially on 40-160) were zero pointers.

It was decided that it was more useful to be able to watch the DX 
cluster spots as they come in than have the influx of mostly useless 
skimmer spots.  The skimmers were disconnected from the logging 
software only a few hours into the contest (but remained reporting to 
skimmer.dxwatch.com).

I found the contest to be a good test of the skimmer computer.

I am using a quad core 2.83GHz Intel processor over clocked to 
2.91GHz with 4 GB (3.5 GB) RAM under Windows XP Pro.  Three M-Audio 
Delta 44 sound cards, Softrock Lite 6.1 for 15m, 20m, 40m, 80m and 
160m, a Soft  Rock Lite-Xtall (dip switch version) for 10m.  The five 
Softrock Lite 6.1 receivers are mounted in a small Radio Shack 
aluminum project box (this seemed like a good idea at the time and 
was a nice compact package, but it appears the receiver clocks 
interfere with other receivers).  The Lite-Xtall is hanging outside 
the box as it was just built.  10m, 15m and 20m share the tri-band 
beam.  40m has the vertical and 80 & 160 have the appropriate dipole. 
CW Skimmer is installed in six sub-directories, one for each band.

Normally Windows task manager CPU utilization is about 40% on a week 
night with all 6 copies of CW Skimmer and the aggregators running.  I 
expected the increased activity during the contest would bring the 
computer to a crawl.
I was surprised to see CPU utilization was only around 60% during the 
contest.  Summing the CPU % reported by the individual instances of 
CW Skimmer would have been greater than 100%.

All copies were set for aggressive callsign validation and from what 
I could tell seemed to reasonably keep up (new stations spottable 
about the same time) with other skimmers on dxwatch.com.

Next time I integrate skimmer into a logging program I will make sure 
"show unworkable spots" is turned off and then band map is zoomed 
appropriately.  For a DX contest it would be worth trying to filter 
the skimmer spots through something like VE7CC's ARUSER program to 
eliminate the spots that aren't worth points and to slow the cluster 
window scroll rate.

I have noticed that this release of CW Skimmer is very stable.  I 
have not had any crashes.

I would find the option to start skimming upon program startup helpful.


73,
Dean - N0XR


>From: Pete Smith <n4zr at contesting.com>
>Subject: Re: [Skimmertalk] CW Skimmer I/Q balance calibration
>To: "Dean R. Madsen" <dean at acsnet.com>,skimmertalk at contesting.com
>Message-ID: <6.2.0.14.2.20081201074815.05191c30 at mail.comcast.net>
>Content-Type: text/plain; charset="us-ascii"; format=flowed
>
>Hi Dean - there is no balance editor, per se.  However, you can add
>additional data points in the same part of the spectrum where the bad data
>points are, and the calibrator will eventually let the majority win.  One
>way I have done this is to run my radio into a dummy load, and arrange the
>antenna on the softrock so that it gets enough signal to calibrate, but not
>so much that it goes into clipping.  It looks as if about a 25 dB SNR is
>needed.  Then you can tune the radio up and down the band, sending dits,
>and it'll calibrate quickly.
>
>I discovered in the course of trying to bandswitch my softrock lite 8.3
>all-band version that the I/Q gain and phase corrections apparently are
>limited to about 20 degrees of phase difference - above that nothing
>works.  I wonder if a variation on that might explain your issue with the
>Delta 44?
>
>Sounds like you are running multiple softrocks with Skimmer - I'd be
>interested in hearing more, for my upcoming NCJ article.  Have you used it
>in a contest?  How did it work for you?
>
>73, Pete N4ZR
>
>At 01:20 AM 12/1/2008, Dean R. Madsen wrote:
> >Has anyone else noticed that when CW Skimmer runs using channels 3 &
> >4 (the second of two input "ports") of a Delta 44 sound card, the I/Q
> >balance function does not work (function is enabled, but no pixels or
> >lines are plotted)?
> >
> >I had to change skimmer configuration and softrock to sound card
> >connections to swap sound card input ports so the half of CW Skimmer
> >copies that never calibrated would calibrate.
> >
> >Now that I have all receivers "calibrated", is there an I/Q balance
> >editor to delete the errant pixel that throws the adjustment line
> >into a parabola instead of a line matching most of the data points?
> >
> >Thanks,
> >
> >Dean Madsen - N0XR
> >
> >Dean R Madsen
> >dean at acsnet.com          ICQ:5510840
> >
> >_______________________________________________
> >Skimmertalk mailing list
> >Skimmertalk at contesting.com
> >http://dayton.contesting.com/mailman/listinfo/skimmertalk
>
>
>
>------------------------------

Dean R Madsen
dean at acsnet.com          ICQ:5510840