[CQ-Contest] How close is too close?

Dick Green WC1M wc1m73 at gmail.com
Mon Feb 20 13:20:53 PST 2012


Several of the Super Multis that hang out at the bottom of the band use a
certain brand of radio that, IMHO, doesn't deal with interference as well as
other radios.

As for relative loudness, the antennas at these stations are so big that
everyone from every direction seems loud, even when you're not pointing
their way. When operating at the 20m band edge at such a station, I've heard
you between me and the band edge. You're definitely loud enough to be
distracting or sometimes cover my callers.

The general rule of thumb we follow is to park at XX.000.500, i.e., 500 Hz
above the band edge. I believe K1DG originated the rule. He showed that when
you operate upper sideband with a modern radio, your signal does not extend
below the suppressed carrier frequency. As I recall, he recommended 500 Hz
as a safety factor in case the radio isn't properly aligned. I've noticed
that more and more stations are parking right in the band edge these days,
perhaps because they haven't seen K1DG's recommendation. I think if the big
stations believed that they could park right at the band edge, they would do
so and there wouldn't be any room for you below them.

I agree that "frequency defense" is probably part of it, too. Ops at the big
gun stations are conditioned to grab the band edge and hold on to it for
dear life, the theory being that you won't get any interference from below.
Two problems with that theory: ops like you that are willing to squeeze into
the 500 Hz space, and loud stations from other countries that can operate
below our band edge. Another reason the big guns try to run you off is that
any interfering signal, no matter how weak, is worrisome because over time
people tend to move closer to you as they get interference from the other
side of the passband.

Hanging out at the bottom of the band with less than a super station is a
two-edged sword. For most of my serious contesting efforts, I've always
tried to run as low as possible, usually just above the big US multis, say
from XX.0005 to XX.0015. I rarely run higher than XX.025. I've been able to
do so, possibly thanks to high power and good filtering, but I've wondered
if squeezing in between really big stations actually hurts my rate. I
checked the RBN results for me, K1DG and K5ZD in last fall's CQ WW CW, and
noticed that even though my relative signal strength was comparable to
theirs, I got spotted by Skimmer significantly less on the first day. I got
spotted more than they did on the second day. I think the reason may be that
they operated higher in the band on the first day, where there was less
interference from big stations. The lack of Skimmer spots on the first day
probably hurt my rate by itself, but I wonder if humans with
less-than-optimal filtering and/or a fast hand on the VFO knob passed me by
because there were much louder stations close to me on either side. By the
second day, things had thinned out enough that I had a clearer frequency low
in the band.

Another issue is that if you're close enough, you can get that effect where
you're not exactly sure which station an off-frequency caller is answering,
resulting in lots of NILs and dupes. I tend to run a fairly high rate of
dupes (75-100 for 3,000+ QSOs), and I think this may be the reason.

73, Dick WC1M

> -----Original Message-----
> From: Edward Sawyer [mailto:SawyerEd at earthlink.net]
> Sent: Monday, February 20, 2012 6:56 AM
> To: cq-contest at contesting.com
> Subject: [CQ-Contest] How close is too close?
> It is interesting that I hear all these great reports of how wonderful
> the (plug in your favorite radio here) receiver is for close channel
> separation and brick wall blah blah blah.  Usually the venerable
> FT1000MP is used as a comparison dummy in the statement.  I run 2 of
> them here.  And low power (which for this past weekend was 150W).
> Numerous times this weekend I am being asked to QSY when "firing up"
> about
> 350 to 500hz away from a BIG GUN Multi.  One of them was 10 over to me
> on 40M and I had zero problem hearing the noise floor where I was
> sitting and was actually running at 100 rate.  Yet this clearly bothered
> the other op.
> What's with this?
> Why would the FT1000MP Low Power guy be bothering the full power guy
> with much newer and clearly better gear?  Is it that they are expecting
> 700 - 1000hz of quiet breathing room in one of the biggest CW contests
> of the year on an open band?  I certainly hope not.
> So what is the opinion from the group?  With the great rated receivers
> out there, how close can someone get on CW and not really bother your
> run?  For me its 350hz.  Inside that and it causes problems.  If I hear
> 2 guys 700 - 900hz apart, I am slipping in between.
> Maybe I should buy an amp and really push the impact out there.  With
> low power, I shouldn't be your worst problem.
> Ed  N1UR

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