Back in 1977 in parallel with writing the Gunnplexer textbook I was writing my first computer textbook using the then new Radio Shack TRS-80 Model 1. I received the first one delivered in New York State and decided to write a series of textbooks using the new Zilog Z-80 microprocessor on the subject of assembly language programming using a novel technique for teaching the subject. My approach was to disassemble Bill Gate's tiny 4K bytes of Basic program ROM code and start the reader off as simply as possible; i.e., to sequentially display text from location 'x' till it was terminated with a zero just call 28A7H. The same approach was used for all the functions in the Basic ROM such as single and double precision add, subtract, multiply, divide, square root, log and so forth.
The original 1977 Radio Shack TRS-80 was the joy of my life. It is illustrated below. The disk drives and expansion interface shown were added in 1978. Just 32K of RAM was considered a big deal at that time and quite expensive. Each of the 5 1/4 inch disk drives held a maximum of about 75K if I recall correctly, but compared to using tape on a cassette to save your programs were a giant step forward. Eventually I purchased the Radio Shack Models 2, 3 and 4 TRS-80s which I kept till about 1984. There were Apple lovers and TRS-80 lovers. I am happy to say I was one of the latter. Radio Shack had excellent TRS-80 computer service and repair centers around the U.S. which I seldom needed
The volumes 2 and 3 I wrote went into greater detail and were much more like any standard assembly language textbook. Volume 4 covered transmitting and receiving Morse code in assembler and the last one, Volume 5, covered transmitting and receiving radio teletype with the TRS-80. In 1979 Bill Gates had read my volume one and told a friend of mine, "that's my Basic ROM code. You cannot use it." I thought that Bill ought to drop dead and there's no law against teaching assembly language using small pieces of his code as examples. I was delighted that I never heard from the founder of Microsoft again! He seemed to have forgotten that his BASIC was copied from Dartmouth College's freely available and earlier BASIC written by Professors Kemeny and Kurtz.
Just like the Gunnplexer Cookbook promotions all my textbooks were advertised in 73 magazine and QST, displayed in my booth at the Dayton and Buffalo hamfests for several years, and a lecture given at each hamfest.
PACKET RADIO USING THE VANCOUVER PROTOCOL:
Amateur radio packet radio is a giant step forward compared to Baudot radio teletype. Essentially it transmits groups/packets of encoded ASCII or extended ASCII characters of varying length with a CRC (16 bit Cyclic Redundancy Check), at the end of each packet to see wheter the packet was received without error. If so, the receiving station transmits a short acknowledgement that tells the transmitting end of the connection it is ok to send the next packet. If not or no acknowledgement in a short period, then the transmitting station resends the packet.
Douglas Lockhart, VE7APU, in Vancouver, British Columbia in Canada wrote the Vancouver Protocol in about 1981/1982 which was the first standard used by the first amateur packet radio pioneers. Normally, an amateur packet radio station consists of a computer, a a keyboard, a video display and in those days a modestly expensive TNC (Terminal Node Controller), that converts the keyboard output to the protocol being used, generates the cyclic redundancy check and then modulates the user's transmitter with a series of mark and space tones. Mark tones = 1200 cycles and space tones = 2200 cycles. To make a long story short, I had the idea of replacing the TNC with assembly language software using a Radio Shack Model 1 or Model 3 TRS-80 microcomputer. With the help of my good friend, W2EUP, Gil Boelke in Buffalo, New York, I was off and running. In 1983 I finished writing the textbook 'Packet Radio Using The Software Approach - Vancouver Protocol' ..... all 300 pages of 'how to' do it. I sold about 500 copies at $25. each postpaid which was not exactly a resounding success. There were a number of radio amateurs in the Toronto, Canada, area running the Vancouver Protocol on the amateur 2 meter band.....144 to 148 Mhz so I purchased 2 each LONG Yagi (22 feet in length), moon bounce antennas figuring I could work them 120 miles distant via extended ground wave from my home at Chautauqua Lake, New York. I could and I did. My two Boomer moon bounce antennas at my home at Chautauqua Lake, New York, are sketched below.
During the same time frame an American packet group ginned up the AX.25 protocol which was derived from the widely used existing X.25 protocol. The 'A' stands for 'amateur radio.' It is the protocol still widely used today. Following the AX.25 standards I wrote Volume 2 of the 'Synchronous Packet Radio Using the Software Aprroach - AX.25 Protocol.' It was published, all 300 pages spiral bound, in January 1984. Like all my previous books it was advertised in Byte magazine, 73 magazine and QST at a price of $25. postpaid. It went through a total of 8 printings of up to 2000 copies each as below:
1st printing: January 1984
2nd printing: July 1984
3rd printing: October 1984
4th printing: December 1984
5th printing: April 1985
6th printing: August 1985
7th printing: February 1986
8th printing: September 1986
Amateur radio packet operation has progressed significantly in the past 10 - 12 years. It has speeded up from the original 1200 Baud to 9600 Baud and who knows at what speed it will top out. I had a great deal of fun playing a very small part in its growth many years ago.
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