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<p><font face="Arial">The test run announced last week was a
complete fiasco with numerous hardware and software problems. </font></p>
<p><font face="Arial">
</font></p>
<p><font face="Arial">For example, I discovered the FLdigi program's
audio detector on receive is so sensitive that transmitting on
one mode would cause the other instance of FLdigi (on receive)
to hear the RSID code and auto-switch to to the same mode! So
I would beacon on MFSK16 -- then the next beacon (from the other
copy of FLdigi) would also beacon on MFKS16 instead of OFDM. <br>
</font></p>
<p><font face="Arial">I think some sort of sneak audio path in the
hardware of the computer or interface, or perhaps possibly stray
detection of transmitted RF. <br>
</font></p>
<p><font face="Arial">I did days of testing in my carport before
heading out on the trip. For the at-home tests, I had a 10dB
50-watt attenuator in the line between the transceiver and the
mobile antenna. Partly to keep the nearby base station receiver
from overloading so badly, and partly to hide the severe
de-tuning of the mobile whip when parked under the carport
canopy, from the transceiver. (In the interest of keeping the
transceiver PA as linear as possible.) Under these conditions
there were no problems. On the road, without out the attenuator
with the antenna matched and radiating full power, the problems
began. <br>
</font></p>
<p><font face="Arial">Also, my experiment to have VSPE (Virtual
Serial Ports Emulator) allow three applications to share the
same serial port for PTT keying worked fine on the desktop
pre-test, but came unglued in the real world. It would work for
a while, then randomly lockup and stop doing PTT. I suspect
this had something to do with the DigiRig interface I used
having NO isolation between the computer side and the radio
side; i.e. common ground connections, aggravated by automotive
electrical noise circulation on the vehicle ground systems.
(Again, the home desktop pre-test worked perfectly for days when
the the transceiver (Yaesu FT-891) and computer were being
powered by clean DC power from a 12 VDC 100AH battery bank being
float-charged by a good 20A DC power supply. <br>
</font></p>
<p><font face="Arial">At the same times,. a second VSPE serial
splitter setup sharing a single GPS receiver with 5 destinations
(MS MapPoint for navigation, the main two-meters APRS instance
of UIview, and three copies of UIview being used for the
experiment on 60 meters) would also quit. The normal setup
(MapPoint, two UIviews, a GPS monitoring tool "GPS View" and
sometimes Delorme Topo NA) has been absolutely bullet-proof
with this setup in the past for over 100,000 miles of mobile
operating. <br>
</font></p>
<p><font face="Arial">I lost a lot of tine stopping at highway rest
areas rebooting the Toughbook and restarting applications in a
precise sequence. On the return trip from the hamfest, I began
to suspect the interface and noise/ground loops as the problem.
<br>
</font></p>
<p><font face="Arial">I stopped by the side of route Michigan 115
and switched the interface to my own homebrew totally passive
tone-activated self-powered and TOTALLY ISOLATED interface
(that I had been demoing at the hamfest). I lost an hour
re-configuring and tweaking multiple applications on the
Toughbook; then resumed the drive. The GPS splitting and PTT
was now bulletproof! <br>
</font></p>
<p><font face="Arial">But I hadn't noticed that in the meantime the
audio tone freqs in both copies of FLdigi had shifted downward
100 Hz, ruining the remainder of the test! <br>
</font></p>
<p><font face="Arial">I plan to run a proof-of-concept test on a
short drive from East Lansing to Grand Rapids (about 70 mi away)
sometime next week. Before running a "real" test farther afield
enroute to a ham fest in a month or two. <br>
</font></p>
<p><br>
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<p><font face="Arial">All this comes with the territory of mobile
radio systems engineering which I have been doing for decades!
<br>
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<hr width="100%" size="2"><font face="Arial">Stephen H. Smith
wa8lmf (at) aol.com <br>
Skype: WA8LMF<br>
EchoLink: Node # 14400 [Think bottom of the 2-meter band]<br>
Home Page: <a class="moz-txt-link-freetext" href="http://wa8lmf.net">http://wa8lmf.net</a><br>
<br>
-- APRS over FLdigi Modes --<br>
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60-Meter APRS! HF NVIS APRS Igate Now Operating<br>
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