Teletype Model Hookup

common RS-232 levels of â computer interface, all that is left to do is make the computer speak 110 baud of ASCII. The ASCN part should be easy; it s the native language of most computers. As to the 110, it depends on the computer. We covered the CoCo in this column several months ago. Program 1 is a simple scheme to aHow the CoCo to output at 110 baud through the "bit banger" serial port on the rear apron Similar schemes should be just as easy for other computers. Even my old 6800 would slow down with the flick of a jumper

\ hope this material will help those of you wno have been trying to get a Teletype Model 33 interfaced. Remember to measure all points for dangerous voltages before you hook up the computer. I don't mean you should take the "smoke tost" literally! And please, let me know your experiences

Moving right along. r,j have asked for some opinions, now and then, on a variety ot RTTY topics. One of them has been packet radio. Are you interested or will this be the NBVM (who remembers that one) ot the future?

Wendeil Larsen W31RX of Upper Black Eddy PA has taken the challenge. Wendell says that he is "currently on HF and VHF RTTY with an IBM PC and Hamcom software11 and has been contemplating getting on packet Ho one yet has satisfactorily clarified his questions about this mode

WendeU writes, 'Essentially, what does ft provide to justify the cost? Supposedly, it will enable countrywide 2-meter digital communication capability. I question this since it appears difficult if not impossible, to establish effective links, at any time, even on the East Coast. I realty can't see how error-free communication is possible if the link cannot be established

'Now packet operation on HF may hold some possibilities for point to point without intervening digi-peaters. Tm constancy hearing local 2-meter packeteers enthusiastically proclaim that they made it as tar as New York or Florida Even then, the path was so cluttered that nothing practical couJd be accomplished."

Well, Wendell, from the packeteers I ve talked to, it sounds like we are looking at two different systems! I don't know what the closest digi-peater is in Upper Black Eddy PA but here in Baltimore establishing a link with a machine doesn't seem to be much of a problem. Now, I grant you, what hams talk about on packet is not likely to be any more stimulating than what hams talk about on RTTY, FMk SSBt AM, or CW. I am leaving ATV and SSTV out of this because they at least have pictures.

But the mode itseif promises great potential, with the proliferation of digi-peaters, t think back to my early days on 2 meters. On AM, getting a signal from Silver Spring MDh a suburb of Washington DC, into " the District," (as residents term DC) was a real thrill, When the first FM repeater was established midway between Baltimore and Washington, I drove to a hill near my home to try to make the repeater, and with it, Baltimore Now, 2 meter repeaters are so common that sitting here in my den I can pick up a handheld two-meter rig and trigger five or more machines, with a geographic range of Washington DC to York PA.

This is the ground floor of packet 'dom. If it takes ofl, it won't be for present convenience, but for future promise, LetHs hear what

RS-232 Drive


TTV Loop

RS-232 Drive

Fig 2

others have to say on the subject. We all would like to know.

Regards to David Berger WD6EUC of Sunnymead CA David has joined the ranks of C-64 owners, and is looking for a way to put his computer onto RTTY. Well, David, I hope the review of C-64 and VIC-20 software covered here a few months ago was a help to you. I also suggest that you ask around at your local ham ctub for someone who uses this setup. The C-64 ts a popular small computer, and I am sure that you It find someone in your area who is using it on RTTY, Lei me know how you make out.

Another fan, Jerry Valentin! KC2IO of Jersey City NJ is running a TRS-80 CoCo, and is looking for a disk-based program to run RTTY, Well, sorry to say, Jerry, not much is available commercially at this time. A scheme was presented here a few months ago to convert Clay Abrams program, NEWRTYCW, to at least load from disk, and I have sent that along to you. Hope it helps.

Jerry also askeo about keyboard replacements, a topic that I have addressed for several computers. Well, if you can find it, the fabled $5 Radio Shack replacement keyboard certainly represents the best value per doltar ratio. You can identity it by the red BREAK/ESC key in the upper right corner, an ALT key next to the G, a CTRL key next to the A. the CLEAR key next to the and the cursor arrows relocated to a diamond configuration on the right side of the keyboard It also sporls two tunction keys, la^ beled F1 and F2. at the lower right. If you can't find that one at Radio Shack, don't buy any of the other Radio Shack keyboards; they were made for a variety of other computers, and won't fit the CoCo,

Instead, you'll have to choose from the $5 keyboard being sold at a higher price, as advertised by severaf national advertisers, or one of the "expensive" keyboards that cost more than $50. At that point, it really becomes a matter of personal preference To get a ieel for typing on one, see if anyone near you owns any of the replacements. Good luck.

As you can tell, many of the (oiks writing in this month were helped by material presented in this column in the past. Many ol the more requested topics are in the reprint series I have put together. A list of reprints, each of which is available for a self-addressed stamped and $2 to cover costs, can be had for the SASE alone. Just send it to me at the address at the top of this column, and ask for the list of available reprints. I always welcome questions, of course, and try to answer them in the column as soon as possible, ff you want a personal response, be sure to include that all-important SASE. I can also be reached on CompuServe, ppn 75036,2501, either oni EasyPlex or often on the CoCo SIG (GO COCO),

Topics are flying by these days, and next month promises to be a winner. Be sure your subscription io 73 is up to date; you wouldn't want to miss next month's RTTY Loop!




50 POKE &H954,&H01 POKE &H96,&HF6:,110 BAUDS





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