[Skimmertalk] Skimmer in SSCW - lots of lessons learned

[Pete Smith]

As you can see, I wasn't awake - that's 2 *GB* of RAM.

73, Pete N4ZR

At 07:27 AM 11/3/2008, I wrote:
>This year I decided to go Unlimited for the first time in over 50 years of
>Sweepstakes, in order to be able to try out CW Skimmer under full-up,
>high-activity SO2R conditions.
>
>For those who will ask - my computer is an oldish Dell 2.66 GHz Celeron
>(single core) with 2 GHz of RAM.  I ran N1MM Logger 8.10.7, and used an
>SDR-IQ receiver for Skimmer.  CW was via Winkey, so there were no problems
>with producing CW via the LPT or serial port.  SO2R control was via a
>MicroHam MK2R+, using the Microham SO2R protocol to handle all band data
>and switching.  Antenna and bandpass filter selection was automated using
>the MK2R+ to control two W9XT band decoders.  WintelnetX was used to mix
>spots from Skimmer and one Telnet cluster.
>
>I wish that I had done this sort of test in one of the earlier contests
>that I don't care about so much, because then I would have had time to fix
>some things, and could have learned to optimize others.  I guess I'm not
>very good at constructing test scenarios in the absence of real
>conditions.  Items:
>
>1.  With this computer, CWSkimmer's demands on the CPU are just too large
>for effective computer-controlled SO2R.  There were small, variable, subtle
>delays in logging program operation that manifested themselves in several
>ways.  For example, if I wanted to interrupt a CQ on the run radio to call
>a station on the S&P radio, normally I rely on the computer to switch focus
>and start transmitting immediately.
>
>With Skimmer running there was a small but perceptible delay in both the
>focus switch and the beginning of CW.  My timing is normally pretty good,
>but with Skimmer running I was consistently late.  Worse yet, focus changes
>in general were often delayed and sometimes out of synch.  N1MM would send
>a command to the MK2R+, so that the audio in the headphones changed, but
>the entry focus would "hang" for a variable period before it followed
>suit.  This led, all too often, to my entering part of a callsign in the
>wrong entry window, which led to as lot of frenzied keyboarding to try to
>get things back where they should be.
>
>There's no question in my mind that CPU loading was the culprit, because as
>soon as I stopped the Skimmer waterfall there was a noticeable return to
>normal behavior.
>
>The solution seems fairly straightforward.  Skimmer should run on a
>separate actual or virtual CPU.  The easiest way might be to network a
>second older computer to the main logging machine, eliminating any sharing
>at all.  Band-changing can be easily managed by sending commands to the
>Skimmer from the Telnet window of the logging software - commands such as
>"skimmer/qsy 14000" can be stored in a single button.
>
>Users of modern computers which have two or more virtual CPUs may be able
>to solve this problem by assigning their logging software to one CPU and
>Skimmer to another.  I have not tried this, but hope that someone will.
>
>What I did, as a work-around for this contest, was to stop the waterfall
>after Skimmer had run for a minute or two, and work my way through the band
>using the S&P radio, making QSOs interleaved with my QSOs on the Run
>radio.  That seemed to work reasonably well.
>
>2.  Other than the computer issue, Skimmer worked very well.  2-3 minutes
>of Skimmer on a given band would post 150-200 calls to the bandmap for the
>band in question.  N1MM Logger would color-code these as new or dupe, and
>would note which ones, based on the call history file, would be new
>multipliers.  The potential advantage on Sunday in a contest like
>Sweepstakes is huge - instead of tuning the band listening to CQers, 95
>percent of whom are dupes, you can jump right to the new multiplier or the
>"fresh meat."
>
>Since no Skimmer spot is more than 10 minutes old, and all represent
>stations that were being heard at my QTH, I found that I was getting a much
>higher percentage of "hits" with Skimmer spots than with "normal" ones.  In
>fact, the next time I use Skimmer in SS, I think I will turn off the Telnet
>spots altogether.
>
>I found that concerns about the run radio interfering with Skimmer's
>ability to copy signals on the S&P radio were largely unfounded, because of
>the bandpass filters I use for SO2R, which also protect the Skimmer
>RX.  Often, I would watch the S&P radio bandmap while the run radio was
>CQing, and see new spots flowing in at a rate of better than 1 a
>second.  Pretty impressive
>
>I will be pulling together an article for NCJ early in the new year,
>dealing with Skimmer experiences in this fall's contests.  If you used
>Skimmer, please drop me a note and let me know how it worked (or didn't),
>as well as what you liked and what you didn't.
>
>73, Pete N4ZR
>
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