The HAM RADIO Autobiography of ZS6RO


I have been a Radio Amateur since the late 60's, first as ZS1RO, then ZS5RO, now as ZS6RO. I also have a M0HMB callsign. I still hold my ZS1RO callsign, mainly for sentimental reasons. Though I did my share of CW and SSB operating and even a bit of Satellite work, my favourite mode has been 'data over radio', or what is now commonly called 'Digital Modes' ... 

I experimented extensively with RTTY and Amtor in the 70's, and ran a totally home-brew SELCAL RTTY BBS, including the OCXO Xtal radio transmitter and receiver, on 14075 kHz for many years. Jim ZS2LR, Gerd ZS3B, Taffy Z21CE, Hofie ZS6CC and a few others also ran SELCAL RTTY BBS's on the same channel, all of different designs. Jim ZS2LR built up a SELCAL totally from electro-mechanical relays and it worked flawlessly!!

I had a lot of fun broadcasting the SARL HQ weekly bulletins, by first typing the text onto teleprinter yellow re-perforated tape, then using RTTY to transmit the bulletin, then taking reports afterwards from the 'RTTY listeners'. (There was quite a following of listeners).

I later used a genuine  APPLE II with home-brew plug-in pc-boards for the terminal unit (TU). The TU coupled the radio to the computer (similar to the packet radio TNC). This was all at a speed of 45.45 baud.

My first SELCAL consisted of some integrated-circuit (IC's) gates in what was called a 'bucket-brigade' configuration including a UART. wired up to accept the character sequence "ZS1RO-T" - this RTTY command when received would start a mechanical teleprinter reperforated tape reader which then ran a piece of 'looped' paper reperforated tape which had the sentence "The quick brown fox jumped over the lazy dog's tail NNNN" punched on the tape (This sentence has every letter of the alphabet in it at least once). This was transmitted over the radio as RTTY signals. The four "NNNN" was the sequence used to shut the reperf tape reader motor off! The loop was then ready for the next 'ZS1RO-T' request ("T " for TEST tape). The looped reperf paper tape was a blue colour which identified it as being thicker and stronger than the standard yellow reperf tape and could be used many times over without breaking. This 'test tape' setup was used extensively especially when newcomers came onto the channel. They would be able to adjust their own equipment without worrying anyone. The test signal was also useful to see how good the path was between ourselves.

Later one could get RAM (Random Access Memory) chips relatively cheaply. RTTY uses 5 bits for each character, not counting the start and stop bits. Using five of these RAM chips (each chip being 1024 bits) I exchanged this for the re-perforated looped tapes and with some additional IC circuitry, was able to send the test 'tape' out silently - this was progress! By dividing the memory into two banks, roughly 500 bytes per bank, I put the ZS1RO-T test message in one half of the RAM. Then using the command ZS1RO-S, any characters sent immediately afterwards was saved into the second 500 byte bank of the RAM. Four 'NNNN' closed the RAM from receiving any more characters and replayed the saved message. The command ZS1RO-R could also replay the message just saved in case it was corrupted by conditions. The ZS1RO-R command could be repeated any number of times and the last message stored with the ZS1RO-S command would be replayed over and over.

The ZS1RO-S and ZS1RO-R commands became quite useful. I suddenly became a RTTY 'repeater' , all on one frequency! Now two RTTY'ers trying to communicate with each other but were skip to each other could store a message in my RAM and then it would replay for the other guy. When it was finished, the other operator could reply by also using the ZS1RO-S command. We eventually had a number of RTTY 'repeaters' dotted around the country. Later my APPLE RTTY BBS took over all the electro-mechanical machines in my shack and I must admit it was a lot quieter! The APPLE also took over the various ZS1RO-S, ZS1RO-R and ZS1RO-T commands, including a few extra commands.  

When Packet Radio entered the scene, this opened up data communications like never before and it wasn't long before a VHF/HF Packet Radio Network started in South Africa at most of the major cities.

In the early days before Internet took off, forwarding traffic between BBS's was done on packet radio on HF. We quickly learned that OCXO Xtals was the order of the day if you wanted to stay on the channel frequency! BBS traffic forwarding on HF (300 baud) moved slowly during daylight hours and virtually came to a standstill during the night. Today the HF bands are still the same, but now we mostly fall back onto the Internet. VHF Packet Radio which the BBS users occupy is primarily at a speed of 1200 baud.

I had the first RTTY BBS and Packet Radio BBS in Cape Town, around the mid 80's. It was relatively simple in those days and only allowed one user at a time to be logged in! I had a homebrew HF radio (14MHz) and also a VHF radio connected to the BBS. The 14MHz HF channel was mainly for forwarding between ZS6 and my BBS and also between YB5 (AsiaNet) and my BBS. AsiaNet then connected to the rest of the Packet Radio world and forwarded any traffic I had passed onto it. (Internet hadn't been 'invented' yet!). I linked the RTTY BBS and the Packet Radio BBS via their respective RS-232 COM ports and arranged that the two BBS's could automatically update each other.

The BBS's updated themselves, either by radio (HF, VHF or UHF) or Internet (Internet from 1994) by E-Mail, or Gateways (Telnet Sessions). In Cape Town, the Packet Radio Network included a SATGATE that relayed traffic via Radio Amateur Satellites. This was sent out worldwide and allowed messages of a personal nature, or small bulletins of varied topics, to be conveyed to their respective destinations with very little delay. The Satgate is now closed due to the satellite not being available.

Nowadays the BBS 'Mail' gets through from one side of the globe to the other within a few seconds via Internet! The majority of these tasks are automated. BBS Sysops are a dedicated bunch of Hams and usually own, finance and maintain their BBS's to ensure that the 'Mail' gets through ....

I still run a Packet/HF Pactor Radio BBS and like most BBS's around the world including South Africa, a large amount of traffic passes through it on a daily basis. My BBS 'radio address' is ZS6RO @ ZS0MEE.SRJ.GAU.ZAF.AF ...

I also run a DX-Cluster Node ZS6RO-3 which is internationally connected to other DX-Cluster Nodes. One can log on, either via the Internet or by radio and watch the DX-Spots go by. If you are listening on a radio (HF/VHF/UHF) and hear a bit of rare DX, you can send a DX-Spot with the relevant info to a Node and this will in turn be broadcast to all other Nodes on the DX-Cluster network.

I have a WAP site running where a WAP enabled cellphone can log in and receive current DX-Spots. One can also search a Callbook database for other Radio Amateur's address information - useful for sending QSL cards! The Callbook service is also available on my BBS.

I have had a few Raspberry Pi's, credit card size microprocessors for a couple of years which run on Linux, a Raspbian Wheezy distro and has a Debian flavour. One RPi is running my ZS0MEE BBS, DX-Cluster, APRX Node, Web server and a WAP server. It consumes just 5 watts of power and is very efficient. I'm intending to set up another RPi with a VHF transceiver for an Echolink gateway.


73 de Dick ZS6RO / ZS1RO / ZS0MEE / M0HMB.