From: btbg1194@uxa.cso.uiuc.edu (Bradley T Banko)
Subject: Re: Ramsey IBM PC packet TNC any good?
Organization: University of Illinois at Urbana
Distribution: usa
Date: Thu, 21 Jan 1993 15:42:49 GMT

In article <1993Jan20.214812.6731@allegra.att.com> rfc@allegra.att.com (Robert F. Casey) writes:
>At a hamfest last weekend I saw, at the Ramsey electronics table, a TNC
>kit.  This TNC is designed to connect (and get its power from) the serial
>port (think it was the serial port, it's been a few days ago!).  "No
>adjustments, all feeqs are crystal referenced", "platform for 'poor man's
>packet'".  price: $60.  connects to radios and HTs.
>
>Anyone buy and build this thing?  Any good?  for the money?

I have the Ramsey packet modem.  It is basically the same design as
you see that comes with the Baycom software... a TCM3105 modem chip and
a CMOS buffer to bring the serial RS232 lines down to TTL levels.
I couldn't get mine to work in the Baycom mode... the Baycom software
comes with a warning (in poorly translated from German English) that
the Baycom software won't work with all serial UART chips (in your PC).
It didn't work with mine (a Goldstar 386sx machine), *but* to the credit
of Ramsey, they also provide a simple alternate wiring diagram to 
interface the modem to your parallel port for use with Poor Man's Packet
software (which they *don't* provide... you can hunt it down on the
net if you have access).  The Baycom software is supposed to be better
to use, but I have been satisfied with the PMP software, and the PMP
software C source is also available, whereas the *Baycom* software
source code is *not* available.

All in all, I would probably either *build* a TCM3105 modem of my own
rather than pay Ramsey $60 for it *or* buy a PK88 for $100 rather than
buying the Ramsey kit.  The TCM3105 chips are available for $15 or so
from Arrow Electronics (St Louis) among other places, and circuit
diagrams for the Baycom and PMP designs are available.  You might still
be able to get a hold of a PMP *kit* for around $30-$40 from Kevin
Feeney at Cornell (one of the PMP authors).  Powering the
modem from the serial line is a perfectly valid thing to do... the
RS232 spec rates the lines at 500 mA with the ability to survive shorts,
but if you can't get it to work with your serial port, it doesn't make
much sense to tie up a serial port *just* for power... I wired a 9V 
battery connector behind the 5V regulator and can get buy for at least
a week or more on a battery (use rechargeables).

Oh, yes.  Connecting to the HT was something of a hassle, but mostly 
because I was having trouble with the serial line not working properly
to activate the PTT, so I didn't recognize it.  I was able to connect
my Standard HT to the signal lines directly (PTT & Mic/Spkr).
My HT also works with the "Yaesu/ICOM" configuration which is described
in the back of the AEA PK232 manual with our club's PK232.  AEA also
offers custom cables for connecting HT's to their TNC's which is another
advantage of going that route.  TNC's also have features like mailbox
and can take messages in standalone mode with the PC off or disconnected.

(One drawback of the PK88 is that it has some birdies in 2 meters which
can interfere with communications.)

Good luck!

KB8CNE, Brad Banko
Urbana, IL

-- 
Brad Banko;  Dept of Physics;  U of Illinois;  b-banko@uiuc.edu
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Tatiana Gutsu for President!                     73 de kb8cne @ n9lnq.il
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