From: semra@ral.arc.nasa.gov (Donald K. George)
Newsgroups: rec.radio.amateur.packet
Subject: Re: Anybody tried packet with Tandy 100?
Date: 21 Jul 92 12:20:00 GMT
Organization: NASA Ames Res. Ctr. Mtn Vw CA 94035
News-Software: VAX/VMS VNEWS 1.41

In article <01GMJ45VJAPC90NW41@biotechnet.com>, VIDGAMES@biotechnet.COM (ANDY EDDY, VG&CE EXECUTIVE EDITOR) writes...
> 
>Chris Blackmon, N4VGK, asks:
>>Has anybody tried mobile packet with a Tandy model 100? Just curious.
> 
>I haven't yet, but as soon as I can get my radio (Yaesu FT-411e) hooked up
>to my MFJ 1270b TNC, I'll give it a try. I know there is a Model 100 program
>on CompuServe, and I have a modem cable that I know will go between the TNC
>and the 100. I'm having trouble getting the cable between the radio and TNC
>working without interference. (First I had nothing passing between the radio
>and the TNC; then I had it receive okay, but not activate PTT; then I had
>PTT work, but there was so much interference passed from the TNC to the
>radio [at about S7, and confirmed by moving the cable nearer and away from
>the radio, then shutting off the TNC].) Give me a yell in a couple of weeks,
>because I'm deep in a book project, and don't have a lot of free time right
>now. I think the 100 and an HT, if I can get the TNC battery powered too,
>will make a hot little portable packet system. I think 73 had a similar
>article last year.
>=-=-=-=-=-=-=-=
>Andy Eddy-WB1FNV/6, 7J1ALH    Beverly Hills, California   
>Exec. Editor, VideoGames & Computer Entertainment Magazine
>Internet: 70007.3554@compuserve.com or vidgames@biotechnet.com
>Delphi: VIDGAMES      CompuServe: 70007,3554      Prodigy: CKJB66A
>GEnie: VIDGAME      MCImail: VIDGAMES      America Online: VIDEOGAMES
I've tried my M100 with an MFJ-1274 and a Yaesu FT-727.  After a minor mod
to the TNC (changing a resistor value I think) had no trouble keying the
radio.  Unfortunately, so much RF interference came out of the TNC cables, 
that it made it virtually impossible to receive anything unless you were
almost on top of the transmitting station.  I verified this by removing all
the cables from the TNC and sticking a battery pack inside.  Just a couple 
of flat 4 AA cell holders from radio shack is all that's required.  Of course
since I was hunting for interference, and since the batteries weren't 
rechargable, I didn't connect the power cable.  This eliminated the interference
but obviously didn't make the TNC very usable.  You still need an RS232.
My solution was to get the antenna far enough away from the TNC so that the
RF isn't a problem.  It seems to work, but I don't use the M100 for this 
anymore.  Looking at the 1274 unit and schematics, I can't figure out how
the RF is getting out in the first place.  There appear to be RF bypass caps
on all lines going into and out of the unit.  If anyone out there has found
a better solution to this problem, I (and I'm sure others) would love to
hear about it.  It's a shame to homebound this quite portable packet station.

I've also written some software for the M100 to deal with the Computer
Aided Tuning (CAT) system for the Yaesu.  If there is some interest,
perhaps I can post it/send it to an archive site/BBS.

					Better Luck to you,
					Donald K. George (KB6ZHN)