[Skimmertalk] My experience with my skimmer system

[David Robbins K1TTT]

What os are you running where you saw the floating point errors??  Is that
with the sdr-iq or some other radio?? I ran 1.1, 1.2, and now 1.3 almost
continuously with an sdr-iq on vista ultimate and have never seen a floating
point error.


David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
web: http://www.k1ttt.net
AR-Cluster node: 145.69MHz or telnet://dxc.k1ttt.net
 

> -----Original Message-----
> From: Rick Walker [mailto:rnwalker at bellsouth.net]
> Sent: Thursday, November 27, 2008 12:52
> To: skimmertalk at contesting.com
> Subject: [Skimmertalk] My experience with my skimmer system
> 
> All,
> 
> Just a few notes on my experience with my skimmer system.
> 
> First, skimmer version 1.3 is extremely stable.  In version 1.2 I had
> constant problems with the application hanging and also with it producing
> huge volumes of floating point errors.  My version 1.2 skimmer
> applications
> would produce hundreds of megabytes of error files (some of which I zipped
> and sent to Alex).  However, since switching to version 1.3 I have
> experienced only one floating point error to date.  That's "one" version
> 1.3
> error in 24 days versus hundreds of version 1.2 errors per week.  The
> version 1.3 skimmer applications sit quietly and perform their mission
> day-after-day with little to no attention required.  I would give Alex a
> major gold star for stability improvement.
> 
> Second, the decoding seems to be much more snappy in version 1.3.  I have
> not done any sort of formal study to ascertain actual performance metrics
> between the two versions, but my general impression is that the latest
> version produces much more timely spots.  As to spot accuracy, I have not
> been able to test the new version under any sort of significant load, but
> users of my skimmer telnet cluster report that the skimmer spots are of
> excellent quality.  The addition of the SNR parameter in the remarks field
> does allow one to develop a certain amount of initial confidence in the
> spot
> even prior to visiting the spot frequency to apply the "grey matter"
> decoder
> to it.  Another gold star to Alex on this front as well.
> 
> I recently switched over to the Wintelnetx application, developed by
> K1TTT,
> to perform the fusion and aggregation function for my six skimmer
> applications.  Dave, all I have say about this application is "WOW!!!"  It
> is extremely easy to set up and maintain.  The application has the
> capability to create and store different .ini files that enable me to
> reconfigure it to accomadate changes within my station IT infrastructure.
> The auto-reconnect functions work as advertised and quickly restore lost
> connections making my system much more robust and "self-healing" than the
> application I was using previously.  I highly recommend this application
> and
> give K1TTT a major gold star on it as well.
> 
> I have found that skimmer performance is directly correlated to processor
> performance.  This obviously comes as no shock, but the take-away point is
> that one's enjoyment and utility of the application is marginalized when
> running it on machines that aren't equipped to handle the load.  I have
> found that my main skimmer server (using Intel Xenon 2.5 GHz dual quad-
> core
> processors) will easily handle six concurrent skimmer applications at 96
> kHz
> bandwidths.  The system runs at around 25 to 30 percent CPU utilization
> during normal days and at 70 to 80 percent utilization on peak loads.
> (Note:  At peak loads the system is producing between 1950 and 2000 spots
> per hour on average).  During the initial setup and checkout of my server,
> I
> experimented with manually setting the affinity of the six individual
> skimmer applications to specific virtual CPUs.  I noticed that in this
> configuration the CPU utilization actually went down enough to be
> significant (a drop of approximately 5 percent overall), most of which was
> associated with less OS time spent in kernel space rather than in
> application space.  I tried setting the affinities of version 1.2
> executables using the "imagecfg.exe" utility (enabling persistent affinity
> on application start-up) but found this wouldn't work.  I was told that
> this
> might be due to the way the skimmer application was compiled so I mention
> it
> in the hopes that future skimmer versions would be compiled to support
> this
> capability.  I have found that a computer using a 2.4 GHz Intel core(tm)2
> quad processor will easily handle the load of two SDR-IQ receivers (again
> at
> 96 kHz bandwidths) as well as running my main SO2R station configuration.
> With the help of George (NW4G) at Gigaparts, I have recently finished
> upgrading the computers at my station operating positions to this hardware
> baseline.  Another interesting and recent improvement to my station's IT
> infrastructure is the addition of a Windows Home Server.  This machine
> (sufficiently equipped to handle the data throughput requirements) has
> proved to be an excellent addition.  It gives me the capability to access
> skimmer replay files from any computer on my network.  I expect this to
> significantly improve my ability to store and retrieve data for both
> real-time and after-action analysis of station performance.
> 
> Speaking of storage and retrieval, one of the most disappointing aspects
> of
> the current skimmer application, in my opinion, is its recording and
> replay
> function.  I have not found a way to break the recordings into smaller
> increments than one hour.  At the receiver bandwidths I use, it means that
> each replay file is about 2 GB in size.  This makes them impractical to
> share and/or move except within the station on the GB LAN.  It would be
> beneficial to be able to "tune" the size of the replay files by selection
> of
> smaller recording intervals.  In addition, the replay function would be
> more
> usable if it were to allow me to jump to a specific time via some form of
> direct input instead of the "hunt and peck" method I employ with the
> current
> slider bar.  It would be helpful to be able to store the output of the
> native skimmer telnet server along side its associated recording file.
> This
> could serve as a basic "index" of the recording.  Another beneficial
> capability would be to enable the placement of "markers" within the replay
> files that could be used to highlight items of interest for off-line
> review
> or analysis.  I realize most of this is still "over the horizon," but
> hopefully not too far over...
> 
> Finally, I, for one, do not utilize the skimmer GUI to any great extent.
> In
> fact, the only time the skimmer windows ever get expanded is when I am
> engaged in some form of diagnostic effort.  I know there has been a great
> deal of positive comment regarding the use of a "blind mode" skimmer as a
> visual bandmap aid.  Since I use SDR-IQ receivers, I prefer to use the
> SpectraVue application to perform visual inspection of a "band."  The SDR-
> IQ
> receiver comes with a software server application that enables remote
> access
> by SpectraVue via a TCP/IP connection.  I am using a gigabit LAN in my
> station so this sort of architecture works well and puts an additional
> receiver on any desktop in my station.  So I would be interested in some
> sort of "reverse blind mode" skimmer that has little in the way of GUI and
> devotes more of it's processing time to signal detection and decoding.
> 
> I hope each of you who are planning to experiment with skimmer during the
> CQWW this weekend have an enjoyable experience.  I am looking forward to
> reading comments on the various experiences and "lessons learned" that we
> will certainly gather.
> 
> 73,
> 
> Rick
> K4TD
> 
> 
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