Albert H wrote: ↑Wed Nov 22, 2017 10:57 am We used infra red lasers back in the 80s. We used a pair of beams about a metre apart, so that there was no interruption if a pigeon flew through the beams. We got it to work - in mono - from block to block in Shepherds Bush. It was tricky to set up and noisy when it rained!. The only thing that it did for us was allow us to use a studio in one block and broadcast from the next. We abandoned the idea after about 10 days, and went back to very low power Band III.

Albert H wrote: ↑Fri Nov 24, 2017 1:07 am Do you remember CDR? Came from Norland mostly. It lasted about a year. The two kids who had the studio lived in the next block, one floor down from the top. We had endless trouble with noise on Band III links, mostly because of the two stations on the Harrow Road who used insane amounts of power out of their studios and had plenty of spurii all over Band III. When I got a couple of Spectra-Physics lasers, we decided to give an optical link a try.

The modulation scheme for the two 5mW HeNe infra-red laser tubes is still secret after all these years, since it was used a year or so later for the first ever scattered light audio surveillance monitor system, and is still in use to this day by some security services. Some really weird technology came out of the stuff we tried to conceal links. I've still got one of the receiving telescopes we used. I found it in a box of miscellaneous optical bits and pieces when I was having a clear out, and couldn't figure out what it was, for a while! The optical link worked quite well - when it was correctly aligned - but really got noisy in heavy rain!

CDR was also (probably) the first station to try a mains link from their studio to the lift room two floors above. The original system was at about 140kHz FM and went up the Neutral and Earth. The circuit was based on a thing published in the National Semiconductor data book for a "Remote Loudspeaker". It worked quite well, but could be susceptible to mains-borne interference, particularly from the heating system.

They were also early adopters of the Band IV gear we hacked together from surplus Pye Pocketphone PF1s. The only real problems we had with the Band IV gear was hacksawing the boards in the right place! We used to chop off the crystal oscillator and phase modulator from the TX, and feed a rock-bound PLL board into the multiplier chain. The receiver used the original crystal oscillator and multiplier, together with the front end and first IF stage. All the squelch and audio stages were cut off since they were designed for narrowband speech and wouldn't support quality audio.The crystal filter was removed and the IF then went into a standard 10.7MHz IF strip - the Ambit kit one was always a favourite. On later builds, I added a 3SK88 pre-amplifier with a critically tuned filter to massively improve the receiver sensitivity, and I also did a couple of the transmitters with additional grounded-base, push-pull 2N3866 "power" amplifiers, to get the original 80 - 100 mW up to close to a Watt. These UHF rigs were always matched to 75Ω to allow the use of Belling-Lee TV aerial connectors, TV aerial downlead and TV Yagis. The telly aerials were very cheap and really directional and never looked out of place on a rooftop! I have to thank BDHK for the idea of using the TV aerial hardware.

I've just remembered what "CDR" stood for: "Community Development Radio". Some of their guys subsequently went on to other stations and the two original kids moved to Fulham - near to the end of the Kings Road - and did "Lovelight Radio" for a while. I lost touch with them in the late 80s when I moved abroad for a while. I heard that they had a RH-built rig removed from one of the Brentford blocks because it was entertaining the commercial pilots on final approach to Heathrow....

In those days, it was possible to cover a significant proportion of London with as little as 40 or 50 Watts - there were big gaps in Band II and the noise floor was very much lower. Happy days!

stevemay wrote: ↑Fri Nov 24, 2017 4:14 am Breathtaking you seem to have lost your mind to the point of no return. Cdr I don't recall that does anybody else? What frequency?

Albert H wrote: ↑Fri Nov 24, 2017 11:36 pm

stevemay wrote: ↑Fri Nov 24, 2017 4:14 am Breathtaking you seem to have lost your mind to the point of no return. Cdr I don't recall that does anybody else? What frequency?

No "Steve May" - you have. I don't recall a "Steve May" around the west London radio scene in the 80s. I remember a lot of other people though - many of whom are still friends of mine (and one or two I don't get on with, but that's life!). I also remember the grief that we old hippies got from the newer breed of "radio entrepreneurs" in the late 80s - when the fun went out of it.

FYI CDR came from Shepherds Bush, usually on 92.8 MHz, and was the reason that AVM and I found a huge drum of UR67 in a cupboard in the "Community Area" on the top floor of Norland. It was too heavy for the two of us to remove, but we supplied lots of other people with offcuts from that reel. We supplied everyone with aerial cable for ages!

Thinking about it, the only Steve May I recall was over in Mottingham -near Five Ways - who had a bad rep for "recycling" rigs that had been removed from the tops of blocks. Last I heard, he'd fried his brain with lots of noxious chemicals and had taken up cross-dressing.