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Alinco $88 HT @ 9600 Baud

Regarding using the $88 ALinco HT on 9600 Packet downlink:

Good news:  The Disc output is easy to get to, and looks linear.
            Its easy to mount a SIP header pair through the side
            of the case for easy interfacing.

Good news:  The sensitivity is as good at 436 for satellites as 446 MHz

Bad news:  After adding an external ANtenna connection, I measured the
           receive sensitivity at -116 dBm.  That's 6 dB worse than my
           Kenwood THD7 (with built in 9600 baud TNC) but still usable
           with a preamp.

The Kenwood can get good data with a 3 element handheld beam.  The alinco
will need more elements or a preamp to get to the horizon.  But still good
for briefcase portable on the 9600 baud birds.  The 5 Khz steps seemed
adequate to keep the pattern on a scope  clean.

I am not configured for PACSAT Protocol and was only viewing packets on
a dumb terminal screen.  So I dont know how many packets I got.  Saw lots,
but doubt it was 100%...

DISC OUTPUT:  THe DISC output is easy to find.  Open up the back and right
in the center, just above the VCO metal box is printed "SQ" and "RT3".
The chip capacitor to the left of the "RT3" is a blocking capacitor
between the discriminator output and the Squlech POT just above it.  The
end closest to the "RT3" is the DISC side.   I broke off two pins of a SIP
header socket and melted it slightly into the lower case just above the
VCO can.

The lower pin goes to the DISC, and the upper is soldered to the VCO can
as ground.  This also provides solid mounting for the plastic header.
Then I cut out a matching slot in the back cover so that it fits back on.

The result is a flush mounted barely noticible 2 pin SIP socket into which
you can plug your 9600 baud TNC.

I visually observed DISC noise components no shorter than  80 us which
sure enough equates to 12.5 KHz.  So this is a narrow receiver... and
others may be able to draw conclusions as to the overall viability of this
radio for 9600 baud use.  

For an external antenna, there is a SIP header on the board with 2 pins
just for this purpose.  I soldered a short 3 foot pigtail with a BNC on
the end to this point, just long enough to reach a handheld antenna.
Sorry, I dont have any more time for further testing, but it appears as a
low cost entry into the 9600 baud downlinks.. (How many are there now? 5?)

I'll bring it to the AMSAT COnference

de Bob, WB4APR

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