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Re: Fm Stations in the 80's
Posted: Mon Dec 02, 2019 7:22 pm
Albert H wrote: ↑
Thu Jun 20, 2019 9:58 am
RFM - "Your All-Weather Station" - was the only thing on the air on the morning after the big 1987 hurricane! Dave & Andy used a couple of car batteries to power the rig and link receiver up a block in New Cross and linked on UHF for about a mile.....
The London "Veronica" spent one Sunday jamming Q102's link - playing Elvis Costello's "Veronica" repeatedly on a tape loop - since they were annoyed that Q102 had flattened their piss-poor signal over most of London. We got to the Palace on the Sunday evening, and installed a rather different link receiver to the Q102 site, and normal service was resumed. "Veronica" moved frequency the next weekend!
Chicago 87 was also on air before, during and after the hurricane, I know because I was building all the gear and engineering for them at the time. They were putting out dead air in the morning and not answering the phone. So I went over to Plumstead on my motorbike, a car wouldn't have got through. Trees across roads everywhere, the massive oaks on Plumstead common were on their sides. When I got there, nobody was in the studio. So I threw a tape in and left it running. Turned out during the worst of the storm they panicked and went home, I would've stayed put.
BTW Sam the 819 TX at Simla House behind Guys was 'The Edge' not RFM. 15watt rig built by Kenny Myers.
Re: Fm Stations in the 80's
Posted: Mon Dec 02, 2019 10:25 pm
We'll have to change the name of this thread, since we're talking about AM!
"The Edge" rigs were built by Andy Allman. Dave Fuller still has one of the spare ones in his garage. They had a 6.552MHz rock divided by 8, using a 4060. The 819 kHz squarewave drove a BFY51 medium power transistor, into an IRF640. The '640 had a modulated supply from a TDA2040 on a big heatsink. There was crude envelope feedback, using a couple of germanium diodes into an op-amp, feeding into the inverting input of the '2040. The link receivers were Band III modules (the ones that came in little tinplate boxes that you might remember). The aerials were always "tower block slopers", with the ground of the rig connected to the lightning conductor, and the RF output going into a quarter-wave(ish) (around 91 metres) of wire off the top of the block and tied off with fishing line to a lamppost or other suitable object. On the bench, the rigs developed a carrier power of about 18 Watts, and could do about 70 Watts on mod peaks. They were housed in blue metal-lined plastic boxes. AFAIK, there were six of them built. The audio quality was remarkable for medium wave.
The antenna - if you got the angle right - was pretty close to 50Ω resistive, and was astonishingly effective! These little rigs put a good daytime signal into most of London and out into the countryside in many instances. I remember hearing it near Reading on my car radio.
"The Edge" used (as I recall) three sites - Guys Hospital ("Dennis' Block), one in New Cross, and one in Hackney. The station closed down and became "Countdown Radio" in the weeks before the Law change in 1985 - "The station where you're never more than a minute away from another minute"! Presenters on Countdown included Myers, Allman, Ashton, Fuller, Hugo LJ, Dave C, John Smith, Bubbling Bob, The Beachcomber, Chris England and many more of your "old pals". Countdown used the remaining "Edge" rigs.