John's radio

[Analyser]

Anyone know if John's radio in West Yorks is still going these days? He still has a website but phone just rings and the equipment list doesn't work any more.
Used to get some test equipment from them back in the day, he was trying to retire then, and that must have been 15 years ago!

[shorty]

That names a blast from the past, they used to be based in birkenshaw, i had a drive over in the early 90's to pick up an old spectrum analyser, next time i'm up that way i'll have a drive past to see if there still there.

[Albert H]

I got a few bits of gear from them! I don't know if they're still in business. If you find out Shorty, please let us all know!

[Analyser]

John's warehouse was a great place, absolutely full of the finest test gear courtesy of our MOD. John himself was a tad grumpy and got pretty annoyed if you tried to bargain with him but the lady working downstairs, called Pat, was great. She would say "I'll have a word with him" if there was something you wanted an John was in a grumpy mood.

Another blast from the past was J.Birkett in Lincoln. I did a search yesterday and (in 2013 at least) he was still open. Apparently even a few years ago he was in his mid-eighties so not sure how long he'll still be in business. Might try giving him a call later in the week to see if there's any goodies for sale...

[thewisepranker]

I bought one of my spectrum analysers from Stewart of Reading. He was happy to do a cash deal and as a result I effectively got a TTI frequency counter, Farnell dual power supply and Kenwood 2 MHz signal generator for "free".

[shuffy]

For the last few years I've been using Stewart. It's a bit of a hike from here but I'd assumed John's was long gone! It's pot luck what he's got in stock but you can stay as long as you like and check stuff out as I've been able to do. Also do remember J.Birkett, I think it was him I bought an oscilloscope from in the early 90's when I was living darn Sairf...

[Albert H]

Birkett's! Wonderful - they used to stock the 587BLY - a stud-mounted version of the BLY94 (sort of). Birkett claimed that these were "30 MHz" devices. I found that they'd give around 90 Watts at Band II with the right drive. Birkett sold them for £3 for one-off, but I did a deal for 400 of them, and got them for £1.25 each! They were a 28V device (though they didn't fail until about 36V on the supply).
The circuit I came up with used a 2N3866 for 100mW to 1 Watt, a 2N3375 to take the 1 Watt to about 9 Watts, followed by the 587BLY. The 2N3375s I got were the batch sampled ones from Texas Instruments in Bedford. They'd been soldered-to so couldn't be sold as "new" - I got them for 40p each. The 3866 was about 50p in quantity. The PA board fitted straight between the middle fins of a standard (cheap) Redpoint heatsink, and had four trimmers - input match, two interstage ones, and an output one.
There was a three coil lowpass filter on the end of the thing. The harmonic performance was excellent, with nothing worse than about -62dBc at the bottom of the band, and getting better than that as you went up in frequency.
The whole PA cost about £20, which was pretty exceptional for 90 - 100Watts from 100mW input. The most I ever got from one of these was about 125W by raising the supply voltage, but it wasn't worth the risk of destruction for the few extra Watts.
This PA circuit was replicated by loads of builders all the way through the 80s and into the 90s.
In those days, my whole rig design used a tripler topology, with the oscillator at one third of the output frequency. Colpitts oscillator, un-tuned buffer with equal collector and emitter resistors, tripler, then two stages of filtering and amplification to 100mW. All the transistors were BF494 except the final which was a BSX20 with a little heatsink. The PLL take-off point was the emitter of the buffer stage, and that went into a little board full of 74LS-series logic ICs.
An old friend brought two of these 80s boxes 'round a while ago to move their frequency, and I was delighted to discover that these were as good as the day they left my bench - almost 40 years ago!