Re: TAN; Tram passing a Radio Station.


Yes, I'm well aware of directional antennas--- my whole career was in the engineering side of broadcasting and television. I was involved in the design, construction, and adjustment of several AM d/a's. Directional antennas are quite complex things and it's sometimes difficult to achieve the design objectives.

The transition from Altona to Lower Plenty must have been a frustrating episode for the Packers. Initially the plan was to simply raise the power from 500W to 5kW by the simple expediency of installing a new transmitter. However they were restrained from doing so by the (then) ABCB (Australian Broadcasting Control Board). One of the planning guidlines for new or upgraded AM transmission sites went someting along the lines that "not nore than 5% of the potential listening audience can lie inside the 2mV/metre field strength contour". I'm relying on memory for these figures but the up-shot of it was that 5kW at the Altona site would not have complied with this regulation. The maximum permissible power increase represented such a modest improvement that it was judged not worthwhile.

Another ploy to extend transmission hours in the early morning was to commence playing music half an hour or so before the official opening time with the announcer saying at intervals "this is 3AK testing". Understandably 2BS complained to the ABCB who jumped on 3AK. I think they then limited pre-transmission "testing" to about 5 minutes.

After purchase of 2BS, all efforts were directed to installing d/a's at both stations. I don't know the background of the land acquisition at Lower Plenty but in the fullness of time the site proved not ideal, causing yet more frustrations. The problem was the the 3AK directional antenna was too close to the 3KZ omni-directional antenna, and the latter caused significant difficulties in meeting the specified radiation pattern. Various attempts were made to make the 3KZ mast "dead" to the 3AK frequency so that it would not influence the tuning of the two 3AK masts, but with little success.

How it was all resolved I don't know. I was not involved with it, and all this is based on my recollections of discussions with interested parties.

I visited both the Altona and Lower Plenty sites, and also the Grey St and Bendigo St studios. In the last few years of "Mack" ownership, there was an afternoon program called "3AK's Bonanza" (a sort of music/phone-in/give-away affair) which was quite popular, but all this ended with the Packer buy-out.

For what its worth, trams in Wellington Parade (East Melbourne) passed close by a radio station in Jolimont which no longer exists. But evidence of it can be seen in a posting by Noel Reed a few months back. Noel's photo concentrated on trains in the Flinders St yard, but a tall tower is visible in the distance. In the 1950s the national office of the PMG Department's "radio branch" was located at Jolimont. Somehow the money was found to commence an experimental FM broadcasting station which carried the program of the (then) ABC classical music station 3LO. It was never publicised and only hobbyists or classical music buffs equipped themselves with an FM receiver. The tower in Noel's photo carrried the transmission antenna for this service.

In the early 1960s TV was being extended to country areas and it became apparent that additional VHF TV channels were needed to allow for this expansion. The government appointed a Professor somebody to figure out how to find the additional channels. His solution was to take over the FM band for TV which brought to an end the experimental FM service in Melbourne, and the tower was taken down. Of course there were complaints from listeners but these were rebuffed by the Post Master General who stated something along the lines that "hardly anyone listens to FM and there is no interest or pressure from the public or the broadcasting industry for FM in Australia".

As is all too often the case, sentiments espoused by politicians turn out to misplaced or just plain wrong, and the Australian public would not now tolerate their FM broadcasting service being switched off again.

Roger Greenwood
----- Original Message -----
From: Stuart Turnbull
Sent: Monday, September 17, 2007 7:07 PM
Subject: Re: [TramsDownUnder] TAN; Tram passing a Radio Station.

Of all the Melbourne stations, 3AK must surely have the most chequered history. I don't know how long Akron ran it but sometime during the period when its transmitter was in Balwyn it was a night-time only station. When I moved to Melbourne in 1953 it was owned by the Mack Furniture Company in Flinders Lane and was a day-time only station, i.e: sunrise to sunset. During winter it closed at 5:00pm but in summer it stayed on until 7:00pm. Every day the last half-hour of transmission was occupied by a gravelly-voiced gentleman with a thick accent who espoused some obscure religion.


There is a technical reason for the day time and night time only broadcasts from 3AK.

3AK was at 1500kHz frequency; this frequency was shared by 2BS, Bathurst NSW. As 3AK had such a low output, its signal was swamped at night-time by the more powerful signal from Bathurst (which must be 6-700 km away over several mountain ranges) hence the day time only operation. I suspect in the early days 2BS would have shut down fairly early in the evening, meaning 3AK had to use the night time and later the situation was reversed as AM signals don't travel so far by day but became a problem when the sun went down causing interference.

Mr Packer solved the problem by purchasing both 2BS and 3AK (not at the same time). He then installed "directional aerials" on the transmitter masts which pointed the signals away from each other. Still strong enough to be heard all over Melbourne but it solved the night time interference and 3AK went to 24 hour operation.

It's a bit "Off topic" from the trams but well within the "era of significance" for those of us who admire the MMTB and trams in general.