Things go round and around ....
Back 70 years ago the FCC band SPARK GAP because it was wide
and interfered with other stations. CLEAN NARROW signals became the standard.
With bands like 220 MHz sitting there dead one would think wide band on 20
meters
would be the last thing we see. .....
--- On Thu, 3/26/09, kh6ty <kh...@comcast.net> wrote:
From: kh6ty <kh...@comcast.net>
Subject: Re: [digitalradio] No FCC data bandwidth limit on HF Re: USA ham rules
To: digitalradio@yahoogroups.com
Date: Thursday, March 26, 2009, 6:00 AM
The short answer, as Steve Ford likes to say, based on the Cohen paper, is
that the "necessary bandwidth" appears to be "roughly" twice the frequency
shift, although an exact calculation is obviously very complicated.
More importantly, with regards to the amateur radio service is the summary
statement, "The necessary bandwidth is the minimum emission bandwidth
required for an acceptable quality of service."
It has already been concluded, after many months (even years!) of debate,
that radio amateurs are "amateurs" and not "professionals" and do not have
either the ability or the means to measure "necessary bandwidth" of their
signals. Their communications are casual "amateur"communicat ions and not
"professional" communications.
If the "necessary bandwidth is the minimum emission bandwidth required for
an acceptable quality of service" were to be codified into the radio amateur
service regulations, it would also be necessary to also define what
"acceptable" quality is, in particular for the radio amateur service. That
definition will obviously be different for casual conversation, DX
exchanges, and contest exchanges, than it is for commercial or
quasi-commercial "messaging" services. It will probably fall somewhere
between PSK31 and MFSK16 or WSJT bandwidths, which provide "casual"
communications quality in exchange for the higher bit rates needed for
sending long messages. Even narrow bandwith modes, like PSK31, can be
utilized to reduce the error rate to zero through the use of ARQ. It is just
that the throughput is half that of the non-ARQ use of the mode, but that is
generally "acceptable" for casual communications. What would NOT be
acceptable is using a 150 KHz-wide signal on a band that is only 350 KHz
wide merely in order to achieve faster throughput for two dominating
stations at the expense of hundreds of others. Should 150 KHz-wide signals
start being used on 20m, for example, it would not take very long for the
FCC regulations to be changed (or re-interpreted) to protect the "casual"
communications use of the 20m band. To infer that using "low power" would
make that acceptable ignores the fact that "low power" to someone distant is
"high power" to someone close by. The BPL debacle should have made that
clear by now.
The regulations already require that the minimum power necessary for
communicatons be used, and if a similar requirement were made for emitted
bandwidth, it could easily stifle innovation (at least with regard to using
wider, or spread-spectrum modes), and not promote it. We might all then wind
up having to be content with PSK31 plus ARQ for our casual communications!
Better not ask for something you may not want!
I agree that the regulations do not "specifically" limit bandwidth on the HF
bands, but that does not mean this could not easily happen if there are
enough abuses to justify it. It is true that the regulations have not kept
up with technology, but the intent to protect casual communications is still
there, and that intent could be codified if it becomes necessary. However,
we may not be happy with the end result, especially considering the
extremely minor interest in digital messaging or using digital modes other
than PSK31, CW, and RTTY.
With the advent of satphones, cell phones, and the Internet, the relevance
of amateur radio as anything more than a hobby activity is rapidly
diminishing and we can expect future regulatory changes to further support
the hobby interests rather than quasi-commercial interests in amateur radio.
73, Skip KH6TY
