[AMRadio] Re: [Boatanchors] AM bandwidth

Phil Galasso k2pg at worldnet.att.net
Thu Feb 2 22:21:11 EST 2006

----- Original Message -----

> AOR and Ten-tec have already demonstrated on the air that 3 KHz digital
> phone can work and sound very good. AOR claims "as good as FM quality" in
> 1/5 the bandwidth. Technically minded AM'ers should look into this type
> of technology as forward going work within the AM community. Boatanchors
> still could be the "power-driving" force and the reception tool but each
> piece of hardware would require some type of encoder and decoder.

Broadcasters have been doing that for years when using ordinary telco lines
for remote broadcasts. The encoder/decoder package is called a Comrex Hot
Line, Blue Box (no relation to the device used by "phone phreaks" to bypass
billing equipment on telephone lines), or any of a number of products made
by Musicam in Holmdel, NJ. All of these sound great, but they are horribly
expensive. Likewise, the new commercially made amateur gear is very
expensive. I will not plunk down $3,000 or more for a glorified ricebox,
analog or digital...especially when I can take equipment cast off by
stations in other radio services and convert it to suit my needs.

To get decent fidelity in a narrow bandwidth, the bitstream has to be
severely compressed and there would be a lot of latency. In the broadcast
equipment that I mentioned in the previous paragraph, the latency can be as
much as several seconds! During remote broadcasts using such equipment, the
air talent cannot monitor the on-air signal, as the delay is too
distracting. The talent has to monitor him/herself locally on headphones.
Working with that delay would be a strange experience in amateur radio. If
you want cell phone quality, the delay would be reduced, but it would still
be about a second. In the AM version of the so-called "HD Radio", now used
by several broadcasters in the New York area (WOR, WADO, and WGSM), the
delay is 7 seconds, although the digital stream decodes into stereophonic
audio with very good fidelity. The bandwidth for that is much more than 3
kHz, however...it is more like 30 kHz and it totally trashes reception of
stations on first and second adjacent channels.

It's fine to be progressive and on the cutting edge of technology. But
amateur radio is also a hobby. Many of us use it for relaxation. Did it ever
occur to you that, maybe, some of us just enjoy restoring vintage gear and
using it on the air in the good, old fashioned analog modes, just as some
people like to go horseback riding on Sunday afternoons, even though
technology has made that mode of transportation obsolete. Dump the damn
restrictions in 97.307 and 97.309 and let us enjoy our hobby! If the unused
and underused CW/data segments can be opened up for all modes of emission,
there should be room for everybody, from the most progressive digital
experimenter to us vintage radio buffs.

Phil G.

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