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Vintage Amateur and Military Radio Amateur/military receivers and transmitters, morse, and any other related vintage comms equipment.

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Old 5th Aug 2021, 3:17 pm   #1
G6Tanuki
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Default Wood&Douglas 144SY25 and VCO3

I acquired recently what appears to be a rather ramshackle homebrew 2M-band FM transceiver - it's got a 2-digit 7-segment LED display and thumbwheels for channel-selection, and inside are two diecasr boxes housing rather-non-ramshackle PCBs - one marked VCO3 the other 144SY25 - along with the W&D logo.

There's also what must be the receive strip - a single board with a couple of discrete transistors/open-wound coils as the front end, a 7.5KHz ITT 'block' filter, a circular TO5-type RCA IC as the IF amp, a CA3089 discriminator and a LM380 audio stage. Can't see a part-number on this, nor on the PA module which uses a SD1143 transistor.

Google only finds one reference to the 144SY25 - from a 1980 Practical Wireless - which suggests it's a synthesizer programmable for a range of different RX/TX output frequencies, with repeater offsets and 1750Hz toneburst, suggesting it could be used to replace xtals in conversion of surplus two-way radios.

Anyone got any circuits or other details? I suspect the boards and displays were part of a "supply your own switches/case/heatsink" kit some time in the late-70s/early-80s but info on early Wood&Douglas stuff seems very sparse!
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Old 5th Aug 2021, 3:22 pm   #2
Jon_G4MDC
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Default Re: Wood&Douglas 144SY25 and VCO3

Had paper copies of this. If they haven't been eaten by the shack mice it might be possible to find and scan them.

I put one on a TR2200GX in place of the proper VFO30G. The locals didn't appeciate it much (WB noise) now it has the genuine VFO30G instead.
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Old 5th Aug 2021, 3:28 pm   #3
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Default Re: Wood&Douglas 144SY25 and VCO3

A bit of digging shows the 144SY25B and VCO3 description [but no details] in a 1984 W&D catalog on the BATC website; I wonder if maybe the 144SY25B was an improved version with less noise?
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Old 5th Aug 2021, 3:45 pm   #4
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Default Re: Wood&Douglas 144SY25 and VCO3

It was a design of it's time. I think it was VCO running at 45MHz RX & 48MHz TX divided by 4 for the 12 MHz TX drive which was required by the 2200.
The reference frequency was 25/3 = 8.333kHz I think.

At least with a phase modulator in the TR2200 you didn't have the issue of the phase locked loop removing any direct modulation.

Last edited by Jon_G4MDC; 5th Aug 2021 at 3:52 pm.
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Old 6th Aug 2021, 9:49 am   #5
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Default Re: Wood&Douglas 144SY25 and VCO3

Thinking on this a little more (soft memory).

I think the issue was probably with reference spurs rather than wideband noise. The effect was being audible on the adjacent and 2nd adjacent channel (for very near stations). Was it that the loop filter was not that good? Was it general coupling + decoupling in the box?

Won't ever know. It's long gone.
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