[CQ-Contest] Skimmer

[Bill Tippett]

W4ZV:
 >This may present an interesting dilemma for contest
 >sponsors.  Skimmer is pure hardware...no external help from other
 >ops.  How could you disallow Skimmer (effectively gleaning spots
 >like Packet) and yet allow SO2R?  Both are purely hardware, so
 >why allow one and not the other?

W4PA:
You can't legislate it effectively, I think.  And my gut reaction is if you're
using a piece of computer software to decode CW signals on radios that you are
sitting in front of, with no outside assistance, that's just one more tool for
SO2R if you can manage some way to use it effectively.  How is it much
different from decoding multiple digital mode signals at the same time?

         I agree with you Scott.  It will become a tool that everyone
who wants to compete effectively must have.  Just as some have chosen
not to use SO2R, SO1R folks today find themselves at a significant
competitive disadvantage to those who use SO2R.  The grey area will be
how to distinguish between Assisted and Unassisted.  Skimmer may be the
ingredient that triggers a change to only "Single Op".  If I had to
choose between Packet and Skimmer, I might choose the latter because it
will only report signals that are actually readable on my antenna...and
it would probably report some before Packet, but there is no reason one
could not use both (if Packet were allowed).

 >I'd be interested to see how well in a major contest with a band full of
signals the software works.  I don't see (unless I missed it) a dynamic range
specification for the software.  What is it?

         IMD should be very good...on the order of 95 dB at close spacings
based on the SDR-1000 and SDR-5000.  Where most wideband SDR rigs
fall apart is BDR.  The SDR-5000 is the best at ~120 dB compared to
~140 dB for rigs like Orion or the K3.  This means the decoder may not
work as well while transmitting on teh same band but bandpass filters
should relieve that problem on other bands.  Computers are very patient
and would have no problem persevering until they get a call, even if
they had to wait for you to stop transmitting on the primary run band.

 >If you decide to use a top-shelf HF rig for decoding CW signals, 
likely you're
going to need more bandwidth than 3 kHz for watching signals up and down the
band -- goodbye narrow roofing filter -- sayonara receiver performance -- now
you're looking at a band full of big signals with a compromised receiver
front-end.  Is that practical?

         Again the correct analogy is the Flex SDR...or a classical
rig like a K3 using SDR on it's wideband IF output.  SDRs can see
192 kHz of spectrum and still maintain extremely good performance.
Trying to use SDR on the same band will run into BDR limitations,
but using one behind a set of bandpass filters should work fine.
The K3 and SDR of course have these built in, so you still need 2
real radios.  The Softrock40 wouldn't work very well unless you
added BPFs ahead of it.

                                         73,  Bill  W4ZV