I just turned on the radio at 1800Z, and saw the following spots from WZ7I-#:
1800Z W1AW/7 21080.9 My K3/mmtty reports 21081.13
1802Z EA1HNP 14087.5 My K3 reports 14087.66
At 1805Z, WQ1H spotted W1AW/7 at 21081.1, agreeing with my K3.
In the last few minutes WZ7I-# also reports AG3V, WB4GLI, KI0KB, W6SFK, IK2RPE
cq’ing on 21080.9. These are actually stations working W1AW/7.
I guess I don’t understand what’s going on. W1AW/7 is still there with a good
pileup, so here is a chance for others to report some measurements also.
Thanks.
Dave Hachadorian, K6LL
Yuma, AZ
From: Wes Cosand
Sent: Friday, January 10, 2014 8:32 AM
To: rckskimmer@yahoogroups.com
Subject: [rckskimmer] Frequency accuracy of WZ7I RCKskimmer spots
Hi Folk:
I have received several emails suggesting that the spots from the WZ7I RTTY
skimmer may be significantly off. While it is not my aspiration to be a
fiduciary frequency reference, I want to be accurate enough for the reported
signal to fall within your RTTY passband filters. That is not the case for
some users.
During RTTY Roundup I used QS1R units for 40, 20, and 15 meters. Each of the
QS1R SDR units send RF to 16 instances of HDSDR. Each instance of HDSDR is
calibrated using the built in exalted carrier single sideband calibration
facility against WWV. Audio then goes from HDSDR to RCKskimmer. Some users
suggested that RCKskimmer must be introducing some systematic frequency error
since spots from all RCKskimmer spotter stations seemed off.
This week I used both RCKskimmer and MMTTY to monitor the W1AW bulletin Baudot
transmissions on 80, 40, and 20 meters. The frequencies reported by RCKskimmer
were well within 100hz of the published frequency, Using LSB fed to MMTTY and
observing the crossed ellipse display, the VFO dial frequency was quite close
to the 2125hz difference from the published Mark frequency one would have
predicted.
During Roundup I was using a 25 year old Ten Tec on 10 and 80 meters so there
is greater opportunity for inaccuracy on these bands. Also RCKskimmer
generates a low number of spurious spots by some mechanism I do not understand
but they are usually out of band. For any given 2.4 khz band segment there is
some low but significant probability of making an error when I type the
reference frequency into RCKskimmer or into HDSDR while setting up the
receivers.
The W1AW digital bulletins are transmitted at 6 and 9 PM EST during weekday
evenings. The frequencies can be found at
http://www.arrl.org/w1aw-operating-schedule
If anyone has suggestions for how the skimmer spots can be improved I would
certainly welcome an email. I am aware of the issue of spots that are
generated by stations in S&P mode. Hopefully we can improve our skimming tools
over the next few months but I, at least, am having fun with the present
software. Hope some of you are as well. ... chuckle....
Wes, WZ7I
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