Ron D'Eau Claire wrote:
Note that there are *NO* FCC rules about the bandwidth of an SSB (or other)
signal that say a certain bandwidth is "illegal".
I would certainly agree with others that 6kHz SSB would be a
contravention of the UK licence, although it might only be a SHOULD
violation, rather than a MUST one. It would also violate the voluntary
band plans.
More importantly, it would seem to me a case of playing the marketing
numbers game (bigger is better, in this case more bandwidth is better).
It does not represent pushing the limits of technology in any way.
It's always been possible, but it has not been done (except possibly for
broadcast and the transmission of broadcast quality signals over
telephone carrier systems) because it is bad engineering for a speech
communications system. Whilst amateur radio users may think they are in
the forefront by using this, they are far from it.
Incidentally, a not much larger bandwidth is the basis of both analogue
and PCM telephony, and pre-PCM telephone carrier systems used SSB on the
wire. The nominal maximum frequency for analogue telephony is 3.4kHz.
That allows a respectable guard band when channelised into 4kHz
channels. PCM telephony is based on a sample rate of 8 kHz, which gives
the same channel width of 4kHz, reducing to the typical 3.4kHz maximum
when you apply realistic anti-aliasing filters.
ESSB, properly done as the K3 does it, uses no more spectrum than AM phone,
which is perfectly within the normal amateur practice on the phone bands.
(Actually, the last I heard, the K3 ESSB mode occupies *less* than the 6 kHz
of a normal AM phone signal).
Generally, double sideband full carrier transmissions are permitted
because of grandfathering (i.e. the process by which regulations permit
the continued use of obsolete standards, even though they don't comply
with the current technical requirements). There is also, probably a
certain element of the self training aspect of amateur radio as well, in
that it permits someone to self construct a very simple transmitter
(although I think the expectation would be that such transmitters would
never be used with more than a few watts of output, these days).
Incidentally, historically amateur DSB full carrier transmissions
haven't had tight bandwidth control, so the 6kHz is more a statement
about where most of the power is in the speech spectrum. I suspect that
broadcast transmissions, these days, are tightly filtered, although
that leaves one with the interesting position that the channelisation of
shortwave broadcasts means that the equivalent SSB bandwidth is actually
less than 2.7kHz!
One of the important activities we Hams participate in is experimenting with
various signal formats (or "modes" if you prefer). Fortunately, our licenses
I really don't see that there is anything to experiment about here. If
you want to experiment, look for ways of improving speech communication
in the current or lower bandwidths, and specifically in the context of
high noise, interference and frequency selective fading; if the signal
cannot tolerate these, it should be experimented with over wired
connections. I would use the word "play", instead.
PS Don, I think you meant troll, not phish. Phishing is attempting to
find finance related access control credentials by pretending to be the
organisation with which you would legitimately use them.
--
David Woolley
Emails are not formal business letters, whatever businesses may want.
RFC1855 says there should be an address here, but, in a world of spam,
that is no longer good advice, as archive address hiding may not work.
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