Some miscellaneous gear including Pye MX294.

[storrington_rad]

Just sharing some miscellaneous gear which I've recently rescued from my garage for general interest.

[Jon_G4MDC]

There's an AVO to fix then.
Maybe an IC2E. What band are the MX294s?

[Sparky67]

I could probably recreate that image from my garage. And raise you a Pye Vanguard!

[SiriusHardware]

For anyone interested in the MX294s I have a small stock of the N82S129N PROMs which are used for channel programming. They can hold up to 32 channels (the channel switch is 16 way but there is a high / low bank link near the channel switch which you can use to switch between two blocks of 16 channels).

You can also use an EPROM wired into the PROM socket - a bit messier, but you can't see it when the lid is on.

[Jon_G4MDC]

Don't tell the video game restorers about the 82S129s. I gather they are unobtainium.

I love the MX series and I have many. I do not love love those 'kin one time programmable ROMS. For that reason I don't love the NJ8813 divider either since they want the data provided in those 4 bit nibbles now now now and now! (BCAD?)

I once tried to replace the NJ8813 with ADF4111. It looked like you should be able to program it just as a divide by N and not need a prescaler. Well it beat me at the time. No guarantee my chips were genuine... Anyway - Fail! The kludged in EPROM method works OK, I have several of those too.

Anybody up for a redesign of the PFX logic board? They used much the same setup. I want a PIC and
ADF4111 version - obviously with the same LCD but with scanning and CTCSS etc etc A bit off topic but hopefully not too much.

The big issue with an IC2E these days it that it is almost impossible to make it work on 12.5kHz channel spacing. That change to the band plan was perhaps justified at the time but these days is probably worthy of a re-think. Here 20 miles from London - I hear a lot of nothing.

[SiriusHardware]

Actually, I think the PFX and the rarer MX294s fitted with 40/80 channel front panels or electronic control heads used the N82S185N which could hold up to 100 channels (if addressed by BCD codes). I do also have some stock of N82S185 as well.

[Radio Wrangler]

Originally Posted by Jon_G4MDC

The big issue with an IC2E these days it that it is almost impossible to make it work on 12.5kHz channel spacing. That was justified at the time but these days is probably worthy of a re-think. Here 20 miles from London - I hear a lot of nothing.

The need for 12.5kHz channels never really got going. We could revert to 25kHz and enjoy clearer audio. It would also put a lot of existing radios back in the game. The narrow bandwidth kills off the "FM Advantage" almost completely so we get muffled audio from the bandwidth truncation, along with worse S/N ratios in the received audio. Lose-lose.

I don't see this happening, though.

David

[Jon_G4MDC]

arrgh - 82S185s - please don't tell me this!
I can't program them these days anyway.

I still want to do the PFX board all the same.

David, yes that change was stupid, pointless and unnecessary. Why?

And now we can have digital splurge too! - absolutely excellent. I'm working on something like the Crud-O-Ject seen in American magazines. It will detect digital mod and shut the squelch. I will not hide behind a CTCSS gate. I want to hear the channel minus crud.

[storrington_rad]

I'm happy to see the level of interest in my pile of random stuff! I've been working on the AVO today and it's back to some semblance of life. Will post more details of the MX294 soon.

Good points about the IC2E and 12.5 kHz channel spacing. Sigh.

[SiriusHardware]

arrgh - 82S185s - please don't tell me this!

Too late.

I do still have the means of programming them, so if you can generate the necessary code file - bear in mind you have to get it right first time as they are one-shot devices, drop me a PM about it.

[SiriusHardware]

Unless the MX294s happen to come from the VHF marine band (some did) their receivers will be filtered for 12.5KHz channel spacing by default.

[G6Tanuki]

Pretty much all VHF PMR stuff was specced for 12.5KHz from the mid-70s onwards. Though a 25KHz-spacing version of the Pye Westminster apparently exists according to the manual, I never came across one in the flesh. Given the widespread use of Wessies, Olympics etc by hams on 2M, 12.5KHz filtering was already well established before the switch to actual 12.5KHz channels some time in the late-80s.


I remember the coming of the M294 series; they were essentially DIN-car-radio sized, which was handy. Back then many vehicles had 'low line' and 'high line' radio/stereo options; the low-line was a single-DIN radio/cassette, the high-line version fitting a better radio/player with separate amplifier (to drive extra speakers) occupying the second DIN slot below the radio. This slot was blanked with the low-line [or van] option, but the blanking plate popped out and the space revealed happily took a 294.

[storrington_rad]

The MX294 is telling me that it has ch 1 is at 170.5 MHz, though I haven't attempted to power it up to verify yet. Watch this space. The other unit is a 3 channel M294E.

Somewhere I have some original manuals though don't rate my chances of finding them - can anyone point me to a working online source?

I had the privilege to do a little bit of development on the MX series at Pye back in the day - but please don't blame me for the channel programming complexity!

[Jon_G4MDC]

What was so silly about it is that 25kHz filters (10.7MHz & 455kHz) were the holy grail to convert 12.5k stuff to suit 25kHz. A good source was UHF versions which were almost always 25kHz.

Then you had all the fun of modding them back the other way to downgrade the performance when the channel spacing changed.

If you need manuals for those two please PM your Email address.
The synthesiser wasn't your fault. We have Plessey to thank for that.

[SiriusHardware]

The M294 is a sheep in wolf's clothing - it's the earlier crystalled version, probably not economically worth recrystalling with actual crystals.

The MX294 - 'X' signifying synthesised - is obviously a 'High VHF' (A?) band example. It should have a specific type code - 'A0', possibly, engraved on the rear plate which covers the cable junction box. The rarer 'B' band ones (at the lower end of the VHF high band) are the most ideally suited to conversion to 2m, but I have several 'A' band examples on 2m myself.

[storrington_rad]

Originally Posted by SiriusHardware

The M294 is a sheep in wolf's clothing - it's the earlier crystalled version, probably not economically worth recrystalling with actual crystals.

The MX294 - 'X' signifying synthesised - is obviously a 'High VHF' (A?) band example. It should have a specific type code - 'A0', possibly, engraved on the rear plate which covers the cable junction box. The rarer 'B' band ones (at the lower end of the VHF high band) are the most ideally suited to conversion to 2m, but I have several 'A' band examples on 2m myself.

Yup, they are indeed both "A0" units. 2m conversion of the MX294 might be fun.

[Jon_G4MDC]

It's easy. You can just add capacitors where things don't quite tune.
An A0 works but it can be made better.

I had an MX295 (Band III) which I put on 6m, just for fun. The varicap tuned front end it had was a definite advantage to be able to cover the full band.

Manuals sent. The one for MX294 is a bit large for email. It might stick in the works.

[SiriusHardware]

2m conversion of the MX294 might be fun.

If you are serious, I could make you a 32-channel 2m PROM for it but I would need an explicit list (written down) of the TX and RX frequencies for each channel and I would need to know the colour of the channel switch spindle - red, or black? (It matters).

[Jon_G4MDC]

And to be double sure maybe the colour of the HEF4750 board and Ref Crystal frequency?

[SiriusHardware]

Indeed, although I'm not sure I remember how to cope with any differences arising from variations in those. It's more than 20 years since I was really actively mucking about with these.