[RTTY] Decoder performance on crowded bands

[Tim Shoppa]

Wow, thanks for all the responses! Most especially to Lee VE7CC himself,
who helped me figure out how to reset a filter I had apparently applied
over a year ago (probably by clicking on the "NE ONLY" button in N1MM). The
density of good CW skimmers in NE USA meant that I had never noticed this
filter until the RTTY contest, where most of the USA RTTY Skimmers were in
7-land.

AA5AU and GU0SUP raised an issue, about how sometimes S&P stations are
spotted as CQ'ing by skimmers. It is my observation is that this is
repeated often for the same run station, or repeated for the same S&P
station - I think there must be some detail in their TU message or their CQ
message or their timing that causes S&P calls to be mistaken for running
calls. I personally prefer to have little filtering on the skimmers, I do
not expect a spot (be it CW or phone or RTTY) to be 100% reliable, and
after I work all the strong guys I want even questionable spots to appear
on my screen for me to apply some human judgement.

Now, there were a couple folks in the contest with very very odd macros and
call/response patterns. There were a couple sending their exchange in their
CQ. There were folks who would reply to my CQ, with their call and their
exchange. Then I would send my exchange, then they would send TU and their
call as if they owned my run frequency. These odd patterns confuse the heck
out of me and they must also confuse the skimmer. I think at least part of
it is, they are using the same message set for running as they are for S&P.
They remind me a lot of what I saw when I did PSK31 on Field Day - complete
confusion at the end of each QSO as to who owned the run frequency.

There were some stations out there who were consistently misspotted with
extra characters at beginning or end of their call. During the contest I
looked at their detailed messages and noted that these guys did not send a
leading space/CR, or did not send a trailing space/CR.

David G3YYD, you specifically asked which decoder I was using in 2Tone. I
only had a single 2Tone running and mostly kept it at "selective" but would
sometimes switch it to "flutter". I did not try much with "flat" or
"spread".

One thing that only occurred to me at the end of the 48-hour contest - If I
set the N1MM DI window to show multiple decoders as "SINGLE OVER EACH
OTHER", I could have more reasonably added a 3rd and 4th decoder window
without my eyes having to dart all over the screen to cross-correlate and
pick out calls.

I have an old crufty low-performance PC (bought as an $80 refurb about 2
years ago) and was a little worried about CPU usage with multiple decoders
running simultaneously would be too much, but it seems I can run 4 decoders
with only 20% CPU usage.

As to what NR4M wrote - I want to add "me too!". The huge level of
participation in this past weekend's CQ WW RTTY was a joy.

Tim N3QE

Tim N3QE