On Jun 20, 2010, at 11:42 AM, Bill VanAlstyne W5WVO wrote (in part):
> Same with the de facto CW sub-band (50080 to 50100). CW takes up almost zero
> bandwidth, if you have a decent down-conversion receiver with narrow 1st IF
> filters, like a K3.
>
> If and when we get to the point where 6 meter activity doubles or triples
> from where it is today (wouldn't that be great!), or if we actually get F2
> this solar cycle (looks doubtful based on current predictions), maybe the
> world as a whole ought to revisit the 6m band plan in a more formal way. But
> for now, even with this very good Es season now under way, I just don't see a
> problem here.
Bill - More than any other band, the perceptions of 6M operating are very
colored by geographical location. Although I have seldom (never) heard the .080
to .100 portion full of CW signals, I am sure that it occurs on the east coast.
And it is difficult to get through that curtain of east coast signals to Europe
when it is in here. Many Northeast corridor VHF contesters complain about too
much calling activity on the callign frequency, but we have the opposite
problem here,
A few posts after yours, Jordan, VE6ZT posted this:
Here are some of the signals that worked their way over the 'North-West
Passage' into DO21xb the last 2 mornings.
50078 IK0FTA
50076 IK5MEJ
50078 I0JX
50088 S57RR
50087 SV1DH
50087 HA5JA
50086 I4EAT
50087 UR5FAV
50088 DL2DX
50082 SP3RNZ
50084 HA8CE
50095 YU7EF (Possible image SDR 2x IF = 18khz so poss. 50073)
50070 LZ2HN
50070 L2CC
50079 YT1AA
50085 EA3AKY
50074 S57A
50076 ON4GG
50071 G4IGO
50074 G4FUF
50064 ON7GB
50097 SP4MPB
50085 9A8A
50084 EA7RM
Now if all these are active at the same time, and each has a dozen or more US
callers, that is a lot of stations in a small bandwidth.
CW with good shaping and rise and fall times takes up about 200 Hz to be 20 dB
down from the peak signal. Whether or not that is zero bandwidth depends on
your viewpoint I suppose. Louder stations will be heard in a wider bandwidth,
and those that have poor key clicks will be heard even further away. It is the
transmitted signal that sets the bandwidth, not the receiver. At 200 Hz
bandwidth, that is 5 signals per kHz, or 100 signals in the de facto CW 6M
band. We can't channelize CW signals, so there is an efficiency problem and 3
or 4 per kHz is probably the best one can do. There certainly isn't an infinite
bandwidth available for a CW band as zero bandwidth would imply.
The band could be better utilized, particularly the CW part of it, and as more
CW operators migrate to 6M from HF, this will become an increasingly bigger
problem. It is better to deal with it now, instead of when F skip makes it even
a bigger problem in a few years.
On another note, that has nothing to do with this discussion, I always cringe
when I hear rigs such as the K3 referred to as "down-conversion IF" when the
proper term (at least to me) is a rig with a single conversion HF IF. I realize
that the downconversion term is in common usage, even by Elecraft designers and
will not go away. But how exactly does one down-convert 160M, 80M, 60M, and 40M
to an IF of 8.125 MHz? Just a nit I realize, but it bothers me. I am not
Elecraft bashing, I have a K1 and K2, and will probably get a K3 when
circumstances warrant it. But I would like people to stop using down-conversion
when they really mean a single conversion receiver with an HF IF. :^)= They
aren't the same thing. - Duffey
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