[aprssig] Alinco or ???
Stephen H. Smith
wa8lmf2 at aol.com
Thu Nov 10 03:01:34 CST 2005
scott at opentrac.org wrote:
>Did some more tweaking on my board and copy is much better now, at least
>with the test source. Real-world performance is still lacking. Hey,
>WA8LMF, are you still out there? Did you ever get that test CD of APRS
>traffic made? Would be nice for performance testing.
I'm currently in my home town of East Lansing, MI visiting my mother
and sister who still live here. I've got two of the three tracks
completed. The third one (A half-hour recording of my D700 mobile
alone, beaconing every 10 seconds, on a non-144.39 channel as I drive
about a 10-mile loop that should take me from hard quieting to fringe
flutter and multipath) will be finished as soon as I get back to L.A.
around the 21st of this month.
The project got delayed because of an unexpected change of cars. I had
to strip my entire mobile shack (FT-100, TM-742, D700, mobile SSTV
LiveCam, laptop, etc) out of my old Passat TDI turbodiesel. I just
finished relocating everything into my new Prius two days before
departing on this trip. [I hadn't expected to get the Prius for another
2 or 3 months...]
The first two cuts of the TNC Test CD are resting on this very laptop I
am writing on right now.
One is a clean strong signal recording of a single packet from my D700
beaconing taken directly off the low-distortion discriminator of my
IFR-1500 and then duplicated 100 times in the CoolEdit audio editor.
The intent is to use this recording to modulate an RF signal generator
while varying the RF output level to characterize TNCs as the RF level
becomes less than fully quieted. Since I have exactly 100 identical
Mic-E bursts on this track, it will be easy to compute the failure rate
in percent by counting the number of decoded packets through a given TNC
at a given RF level.
The second is a recording off-the-air, from the discriminator of an
FT-1500, of the "carnage" on 144.39 during the peak of the afternoon
commuter rush in L.A. . It includes a wild variety of under and
over-deviated signals, collisions with signals on top of each other,
digipeaters clobbering each other, etc. I have edited out nearly all
the quiet spots so the longest period of non-activity is less than one
second in order to challenge buffers in TNCs and programs. By removing
most of the dead spots, I was able to fit over half an hour of real-time
activity into only 15 minutes of recording. My assumption is that this
one would be played back as audio directly directly from a CD player or
CD-ROM's audio jack, into a TNC - not via modulated RF. )
The third one will also be recorded from the FT-1500's discriminator as
I make the test run around midnight to minimize the chance of other
signals on the channel during the test.
#2 and #3 are recorded open-squelch so there is unquieted discriminator
white noise between bursts to test software DCD if desired. All are
recorded "flat" directly off the discriminator. If you want to simulate
audio taken from the speaker (i.e. de-emphasized) you can cobble in your
own RC de-empasis network at the output of the CD player.
I will be putting this stuff up in standard audio CD [not as MP3s or
WAVs on a CD-ROM] so the samples will be in full lossless 44.1K CD
audio. Another advantage of using CD audio rather than WAVs on a
CD-ROM is that you can play it back on an old junker CD-ROM drive
stand-alone, via the earphone jack, without needing a computer.
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: 14400 [Think bottom of the 2M band]
Home Page: http://wa8lmf.com
"APRS 101" Explanation of APRS Path Selection & Digipeating
Updated APRS Symbol Chart
New/Updated "Rev G" APRS http://webs.lanset.com/wa8lmf/aprs
Symbols Set for UI-View,
UIpoint and APRSplus:
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