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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 16th Oct 2017, 5:20 pm   #1
G6Tanuki
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Default What was this used with?

Frobbing about in my big box of old-PMR-bits I came across this little thing: from the wiring inside [where there's a 741 IC] it's clear that the 2-pin Molex is a +12V input. The socket labelled "Mic" is 3-pin and looks like it's designed to supply an electret insert [there being a voltage on one of the pins], the 5-pin RT socket would logically connect to a transceiver, being the same as the standard Pye mic-connector.

Can't see how there would be any 'press-to-talk' function though!

So - anyone got a clue what it would have been used with? The "Home Office" designation implies police/fire-service but I never recall coming across anything like it in my days playing with such gear.

Was there any such gear in the 1980s/early-1990s that used VOX switching?? "Sonic communications" still exist, and offer "covert audio" stuff: http://www.sonic-comms.com/index.php...s/covert-audio
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Old 16th Oct 2017, 6:49 pm   #2
Jon_G4MDC
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Default Re: What was this used with?

Maybe for motorcycle set?
PTT on handlebars I believe...
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Old 17th Oct 2017, 10:37 pm   #3
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Default Re: What was this used with?

The HO part number ending in MO means it's an ancillary for whatever the same part number for the main equipment ending in MM is/was, which might help tie it down...

I am trying to recall what the HT prefix represented in the vocab. F's were fixed and M's were mobile, so hand-portables perhaps? In which case it *could* be part of a covert (Cougar maybe) install?
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Old 18th Oct 2017, 12:19 am   #4
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Default Re: What was this used with?

The HO part # in the pic ends in MQ before someone sets off on the wrong track.

Although that still doesn't help identify it and I'm pretty sure the Home Office isn't going to tell.

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Old 18th Oct 2017, 9:49 am   #5
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Default Re: What was this used with?

Quote:
Originally Posted by Terry_VK5TM View Post
The HO part # in the pic ends in MQ before someone sets off on the wrong track.
Well spotted! Same principle applies, that means there could be another couple of ancillaries used with whatever the HT0228MM part number was. With the move to Airwave and two or three company changes since the HO days I would think it is unlikey any stores vocabs still exist, unless someone had the foresight to preserve a set...?

And just for the record, later HO and DTELS part numbers were 8 alphanumerics. The first two letters loosely related to the equipment type, from a 6BA nut or OC71 to a 150W fixed transmitter. For example, AF for Antenna, FL for Filter, FR for Fixed Receiver, MX for Mobile Transceiver, RR for Resistor, WR for Wire etc, the 4 numbers were allocated to a specific unit, the last two letters started at MM and were changed to MN etc for versions of, or ancillaries to the main equipment part number. The stores vocabs, and there were quite a few, listed these with a description (occasionally useful...) and a cross-ref to any previous HO part number.

I was once told they were 8 alphas long because stores computers at the time used an 8-bit bus...
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Old 18th Oct 2017, 11:17 am   #6
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Default Re: What was this used with?

Quote:
Originally Posted by G6Tanuki View Post
Frobbing about in my big box of old-PMR-bits I came across this little thing: from the wiring inside [where there's a 741 IC] it's clear that the 2-pin Molex is a +12V input. The socket labelled "Mic" is 3-pin and looks like it's designed to supply an electret insert [there being a voltage on one of the pins], the 5-pin RT socket would logically connect to a transceiver, being the same as the standard Pye mic-connector.

Can't see how there would be any 'press-to-talk' function though!

So - anyone got a clue what it would have been used with? The "Home Office" designation implies police/fire-service but I never recall coming across anything like it in my days playing with such gear.

Was there any such gear in the 1980s/early-1990s that used VOX switching?? "Sonic communications" still exist, and offer "covert audio" stuff: http://www.sonic-comms.com/index.php...s/covert-audio
I am inclined to think that this " box" has been modified, the sockets are on top of the labels? the IC and power socket seem to be unlikely in a vintage looking unit, be interesting to hear what it really is or was.
MM0HDW
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Old 18th Oct 2017, 2:13 pm   #7
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Default Re: What was this used with?

Thanks for the suggestions - I'm not sure what I will do with it!

I guess it depends on your definition of "Vintage" - I'm suspecting it dates from the 1980s/early-1990s, back in the days of Marconi 640s/690s and the like - which is definitely "Vintage" in PMR terms! The overall styling is definitely in line with "made for Military/Government agency" stuff of the era so I reckon it's 'original' not modified.
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Old 18th Oct 2017, 2:28 pm   #8
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Default Re: What was this used with?

Sonic Communications have been in the specialist PMR install game for many years now. They used to fit out motorcycles and produced all the interfacing tricks etc. It's possible that it was for a police bike as those connectors seem familiar and I think they were used on sets like the 690 in the post high band police change over. The die cast box spec is certainly familiar with Home Office gadgets of the time.
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Old 18th Oct 2017, 3:04 pm   #9
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Default Re: What was this used with?

Has the same air as this (see photo) at the Thames Valley Police Museum. Rather surprised an old Triumph alternator could cope. Having owned a few it was hard enough to start in the morning by foot let alone the "electric assist" start.
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Old 18th Oct 2017, 3:24 pm   #10
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Default Re: What was this used with?

That's a late-1960s/early-1970s Pye Westminster motorbike set; its connectors were water-resistant and *not* the same as those used on ordinary Wessies (and also on on my little box). Pye etc. continued using the standard Wessie-style connectors right through the M290/MX290 series until the late-80s when the "FM1000" came in which used a RJ45-style plastic connector.

I still reckon my little box dates from the 90s.
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Old 18th Oct 2017, 5:10 pm   #11
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Default Re: What was this used with?

A lot of the old Police motorbikes had an up-rated alternator. The standard alternator on my BSA C15 would hardly point the ammeter into the plus never mind run blue lights and a radio! I'm pretty sure it was six volt anyway. I think Sonic used to fit out the crash helmets with comms gear too. The Honda Pan-Europeans the Ambulance Service used were fitted by Sonic if I remember right. These were fitted with a standard Motorola MC Micro turned down to about 10 Watts. I think the preferred connector for interfacing was the metal locking DIN plug/socket as they could stand up to the vibration on bikes. I remember fixing comms faults on the old BMW boxer twins and the first thing you heard was all the screws rattling about loose inside the radio when you removed it from the bike. That used to stop it working.
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Old 19th Oct 2017, 11:38 pm   #12
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Default Re: What was this used with?

Philips did make a vox unit for use with mobile cross-band repeaters. I can't remember its name but we did away with them and took a squelch line from the FM91s and 92s they were used with to make something an order of magnitude simpler and more reliable - a pot, two transistors, a switch and a relay.
Anyway, this isn't it...

73,

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Old 23rd Oct 2017, 5:26 pm   #13
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Default Re: What was this used with?

I asked one of the ex-HO vehicle installers if he recognised the box. He's pretty sure it's a mic amp used with covert or overt mics fitted in, on or behind the sun visor. Still trying to find out what the HT0228MM was...!
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Old 23rd Oct 2017, 7:26 pm   #14
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Default Re: What was this used with?

It may also have provided a phantom supply for an electret mic element, as I seem to remember the new generation HO spec radios were designed to work with the old type dynamic elements to be compatible with legacy telephone style handsets. They must have had bucket loads left over in stores to do that.
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Old 24th Oct 2017, 4:30 pm   #15
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Default Re: What was this used with?

Quote:
Originally Posted by Sparky67 View Post
I asked one of the ex-HO vehicle installers if he recognised the box. He's pretty sure it's a mic amp used with covert or overt mics fitted in, on or behind the sun visor. Still trying to find out what the HT0228MM was...!
OOh thanks!

AQnd yes it does have provision for a 'phantom' bias for an electret. I guess that's why there's a 741 in the box too - to give a bit of audio-boost if the operator has to speak quietly to avoid being noticed 'talking to himself'.
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