[VHFcontesting] [VHF] Beacon Subbands and CW

[James Duffey]

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