Re: qrp digital?


Date: Mon Jul 31 1995 - 23:10:49 EDT

To answer some of the questions on QRP digital:

I have inadvertently worked QRP digital. I ran a packet gateway between
18.105 Mhz and a local 2M packet channel. (This was a friendly gateway, a
KAM, anyone could go through it... not a traffic pump). Anyway, I had the
power on the rig turned down for QRP-CW and forgot about it for several
weeks. The 17-2 meter gateway continued though only one user reported
problems prior to my discovering the power at the 3 watt setting. No
complaints from the other users. It is possible to operate QRP digital.

Modes- listen on any band and you'll hear RTTY, Amtor, Pactor, GTOR and
packet. You can tell the sounds apart. I think at low (QRP) power the
modes with little or no error correction (RTTY, Amtor) will not do as well as
the newer modes (Pactor, GTOR, Packet) but this is often true at high power
as well.

Using a KAM and IC735 on each end, I ran a few experiments with QRP data
modes on 1990 kHz (160 m!). The fixed station used a B&W AC 1.8-30 allband
wire antenna. The mobile used a Mobile-Mark helical antenna cut for 1990
kHz. Both radios were at 3 watts. A laptop was used in the mobile. While
driving regular routes within 12 miles of the fixed station, I compared
Amtor, Pactor, Packet and GTOR. Generally speaking, GTOR held up the best,
then Pactor followed by packet... Amtor fell behind the rest. Though maybe
more fun than scientific, the mobile 160 experiment shows that 160 can also
be used for data and which modes worked best in noisy daytime conditions on
an MF band. Mileage may vary.

TNCs.. I once had a PK-232 in my City EOC and replaced it as soon as the
budget allowed with a KAM. True dual ports, node, gateway and so on. I hear
that AEAs TNC products have evolved a lot and some now boast a node and real
gateway. The (extra?) filtering in the AEA multimode TNC may be a good idea
for pulling weak signals out of the noise. With narrow filters it will
become more improtant to have stable VFOs, correct modulation tones and/or
shift freqs. A few hertz drift and the signal will be retry city because it
fell out of the filter passband!

Bands. You may not wish to work 160 from a laptop in a mobile on an LA
freeway. I have heard digital modes on all nine bands. 14 Mhz seems to be a
place for the herd, the unimaginative, or those with older (non-WARC) radios.
 You can also find digital of all kinds on the other bands. 10 and 18 Mhz
are great coverage compromises for brave souls who are tired of the
congestion on 14 Mhz.

73, Jay
WB6AAM Extra (low) Class
WB6AAM allmode (QRO) TOR station 1990 kHz LSB (dial freq) Arcadia, CA.

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