Hatfields and the McCoys?
Mon, 29 Mar 1999 10:45:32 -0600
Yes, I think we are in agreement here. The military blazed the trail with their approach to
communications and their set of priorities. The one-way underwater submarine communications
at 21.4 kHz(?) with Cesium clocks and encoding come to mind. Some of our members back in
the early 90's followed suit with signal processing techniques applied to differential BPSK,
and synthesizers locked to WWVB, in order to achieve major improvements in S/N and range. I
have been playing with Bill de Carle's "AFRICA" software for decoding BPSK on the LowFER
band. It is incredible! If you get the chance, look in next month's LOWDOWN (April `99)
for an article on vehicular reception of differential BPSK: I had solid copy for 330 miles,
real-time decoding, for a 5 milliwatt ERP signal. The distance would have been farther, but
I ran out of highway once I got to the Gulf of Mexico. Bill de Carle's software is
available for free at:
73 de Bill
Andre' Kesteloot wrote:
> Hello, Bill,
> I basically agree with almost everything you have written. One point though:
> William Cantrell wrote:
> > Granted, we aren't doing anything that hasn't already been done
> > by the military to enhance LF communications,
> No quite.
> a) The military (and the broadcasters) are interested in _100% reliability, 24 hours a
> day_. Hence their devotion to vertical polarization and ground wave coverage. We
> Hams/Experimenters/Lowfers are interested in making contacts, and we will gladly work
> with a system that only allows for QSOs 30 minutes a day, by using sky-waves for
> instance. (I believe most QSOs on 136 kHz, between OH1TN and the British Hams to have
> been of the sky-wave variety)
> b) Also the military have a tendency to think that "more is better", i.e., larger
> antennas, bigger transmitters. We, on the other hand, with our limited financial
> resources, have to rely more on ingenuity.
> c) Finally many things were tried by the military twenty or thirty years ago that
> needed, literally, racks and racks of equipment to achieve. Nowadays, many of these
> solutions can be replaced by a sound-card, or a 56002 Motorola DSP board. This is where
> we can shine. Many of us know how to write software.
> Hence there are literally _lots_ of things we can experiment with that the military
> would discount as being "not quite reliable enough".
> And that's where the fun begins, IMHO :-)
> Andre' N4ICK