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I took over the broadcasts from Wally Coxon (VK6AG). At
first the broadcast went out on 40 metres only using an AT 20, a huge
ex RAAF base transmitter which had parallel 813s in the final modulated
by another pair of the same. The output was 400 watts AM. While the
broadcast was being made none of the family could use any electric
appliance (toasters, electric kettles etc.) in the kitchen as the main
fuse to the house power would blow.
 AT 20 Transmitter The news was read by me into a microphone live. There were complaints from country areas that 40 was unreliable at 9.30 AM and I then built an audio distribution device so that I could run simultaneous transmissions on 80 and 40. We got rid of the AT20, all 1/2 ton of it and the Division bought a Geloso for the 40 metres transmission and a tape recorder on which I recorded the news and put it out on the two bands, 40 AM and 80 SSB on my home brew phasing transmitter. VK6BO took the transmission from one of these for 144, another amateur (forget his call) relayed it on 160 metres and later another (VK6RU??) put it out on 20 metres for the north. For a brief period I also transmitted on 6 metres FM. So we had the spectrum well covered. After the news portion of the transmission the tape recorder was turned off and a transmission from VK6GH, George was rebroadcast for technical notes. I found out later that simultaneous transmission was a no-no as far as the Radio Branch was concerned as also was transmitting speech from a tape recorder. The technical authorities were very slow to catch up with technical advances. A good example of this was when a senior radio inspector whom I will not name came to inspect my station. The conglomeration of gear had him rather worried as he found it hard to measure my DC input to my final (limited to 150 watts at this time) on my HF rig as it ran SSB not AM. He asked the usual question "What are your modulators" and I replied "A pair of OA90S". He raised his eyebrows and said, "But those are diodes!". I replied "Yes, but I am using a balanced modulator for SSB." He didn't get that at all and asked a lot more questions and finally said, "What are your plate current and anode voltage when you run CW?" I replied", 1500VDC at 100 mA". "OK, he said, "But we will put it down as 1400 volts. 1500 is getting too close to the limit." The Inspector went away satisfied. I continued to do the broadcasts until I transferred to Albany in 1971. To list the gear used for the broadcast: Phasing rig - my home station rig 80 metres SSB (later replaced by the Division's Swan 350 transceiver.. Geloso transmitter 40 AM For a time 6 metres on FM car phone (forget the breed but it had a QQVO3/20 in the final) Tape recorder into a single audio in, four audio outputs to distribute the audio to the transmitters. The HF SSB homebrew power supply was twofold, 250 DC for the low power stages and 1500 volts for the final. Rectifiers 866As which could be purchase ex disposals for 10/-. The final tube was an HK 257B which was also disposals for 10/- each. |