In article <telecom24.118.13@telecom-digest.org>, bonomi@host122.r-
bonomi.com says:
> In article <telecom24.117.9@telecom-digest.org>, Michael Quinn
> <quinnm@bah.com> wrote:
>> Along this line, and at the risk of perhaps being slightly OT, if anyone
>> knows why television uses channels while radio uses frequencies (for the
>> most part, that is, the 88 channel) FM Marine Band in the 156 MHz range
>> being an exception), I would be interested in hearing about it.
> There's no intrinsic reason for using one form of naming over another.
> However, note that _if_ you assign "channel numbers" to specific
> frequency allocations, you are *permanently* fixing the utilization of
> that chunk of RF spectrum. e.g. in going from 15khz deviation to 5khz
> deviation on FM, you'd have to either completely 're-number'
> everything, or you have non- consecutive "channel numbers" as you go
> up the band.
> When you (the regulatory authority) "haven't decided" what the minimum
> allowable spacing between frequency assignments is, or even _if_ the
> spacing between assignments will always be a multiple of that minimum
> -- it is *really* difficult to come up with a channel 'number'.
> [TELECOM Digest Editor's Note: This is an example of how someone
> screwed up when the Citizens Band radio channels were numbered. CB is
> allocated the space between 26.965 kc and (originally) 27.255 kc. The
> 'channels' were 10 kc apart, and there were (originally) 23 channels.
> (Well, not originally, when there were 8 channels, but in later
> years.) If you look at the difference between 27.255 and 26.965 as
> divided in 10 kc increments you get more than 23. That's because the
> FCC took three spaces in the middle and reserved them for use on
> garage door openers. So we had channel 22 as 27.225 and channel 23
> a full 30 kc later, on 27.255. Then the FCC said they would expand the
> CB area all the way up to 27.405, or 40 channels, although common
> sense would imply actually 43 channels if you take 27.405 minus 26.965
> at 10 kc increments. What the FCC did, in an effort to 'tidy up' that
> discrepany was run the channels slightly out of order. After channel
> 22 (27.225) they created channel _24_ at 27.235, channel _25_ at 27.245,
> then they had the (already existing) channel _23_ at 27.255 where it
> had always been, and then by 10 kc up to channel 40 at 27.405. Having
> those two channels out of order in the frequency allocations did make
> for some tricky programming of the 'gang switches' (revolving knobs
> which select the channels). PAT]
LOL - and then there were those who had the Siltronics sets. They used
to be on 27.415 or Channel 41 as we called it. This was in the days
before I got my amateur license.
Tony P. (kd1s@nospamplease.cox.reallynospam.net)