Transmitter/Receiver Type 9AB (Army Tx/Rx 1946) No info found

[HamishBoxer]

A recent purchase for this small tx/rx VHF but a search finds nothing.

Does anyone have any info as to use etc 12V Vibrator psu built in.

I certainly have never heard of one before, perhaps the only one in the UK??

Thank you

David

[Station X]

Any chance of a picture?

[HamishBoxer]

Sorry Graham, there is a chance of a picture .Will do it now. The telephone type handset can be seen on the right hand side.

[G8BBZ]

Hi All,
Why do you think the set is an Army equipment? The type number sounds very Naval to me, there is a Pattern Number, and I see the tuning scale has an AP (Admiralty Pattern) number. I have a vague recollection of a set like this being used on Landing Craft but haven't been able to find anything on the HMS Collingwood site as yet.
Physically the set bears a resemblance to the BE610 VHF Set (which was Army) and is obviously intended for portable use.
I look forward to somebody making a positive identification.
cheers
Peter G8BBZ

[HamishBoxer]

Thanks Peter, silly me thought Army as that is what the guy had put in the advert! Sure you are correct saying Navy with the AP on it.

I should have known better.

[trh01uk]

Originally Posted by G8BBZ

Hi All,
Why do you think the set is an Army equipment? The type number sounds very Naval to me, there is a Pattern Number, and I see the tuning scale has an AP (Admiralty Pattern) number. I have a vague recollection of a set like this being used on Landing Craft but haven't been able to find anything on the HMS Collingwood site as yet.
Physically the set bears a resemblance to the BE610 VHF Set (which was Army) and is obviously intended for portable use.
I look forward to somebody making a positive identification.
cheers
Peter G8BBZ

Peter, I agree with you that its Naval equipment. The Pattern Number confirms that. It won't be the first time that an unknown set turns up that can't be correlated with anything on the Collingwood site - clearly the history of Naval electronics is very far from complete at the moment. It someone with a spare 10 years on their hands to do the equivalent for Naval kit as Louis Meulstee did with the Army stuff with his Wireless for the Warrior series.

I think we can say that this is an unusual, rare and potentially very interesting item. It could well be the only one in the UK - but that's impossible to prove of course. Not sure why anyone thinks its VHF kit - unless the innards clearly reveal that to be the case?

If it is VHF - and with a date of 1946 - that certainly makes it historically interesting, as the 1940s were the early years of (military/commercial) VHF equipment in the UK.

I note some odd features on the front panel - such as the two screwdriver adjustable controls marked "+ Net -". Apparently one for the transmitter and one for the receiver. And then there are the blue areas in the tuning controls - what is that about? And of course the serial number (M.F.5) is not what most of know as a "serial number" - looks more like an assignment to some specific unit perhaps?

As a last thought, I would point you towards a document on the Collingwood website entitled "Transmitter Nomenclature 1920 to 1950s". That might tell us the meaning of the suffix 'A' and suffix 'B', in the set type number: 9.A.B. What the document reveals is that 'A' means "An extempore W/T set made to Admiralty Instructions". The entry for 'B' is less helpful: "Spare Letter" !!

Richard

[HamishBoxer]

Certainly VHF at least looking at the inside which I must put another photo on our site.

Thank you for your interesting comments Richard.

Why did I buy it? because it was the year I was born!Though I thought at the time this is pretty rare.Also it has not been got at I don't think.

[M0FYA Andy]

I saw this advertised, and thought it looked extremely interesting. I was sorely tempted to bid, but reality took over, I've got enough projects to last more than one lifetime as Richard knows full well!
Most certainly early VHF, it would certainly be of great interest if you could put some good photos of the inside on here.
Good luck with it!
Andy

[HamishBoxer]

Thank you Andy, I must get the photos done on Friday.

[ms660]

More than one was made, mag page 514, right hand column, 3rd ad up from the bottom:

http://www.americanradiohistory.com/...WM-1963-11.pdf

And here some years on, mag page 57, Forth Motor Co:

http://www.americanradiohistory.com/...WM-1972-03.pdf

Lawrence.

[HamishBoxer]

Interior pics. Thanks Lawrence for those mags,all very interesting though strange till now I have never seen one before.

[trh01uk]

The pictures of the innards are interesting. The transmitter appears to be a pair of valves driving lecher lines, so possibly a free-running oscillator, with push-pull valves. The valves look like they may be DET20s - the valves used in the WS19 B-set at around 240MHz. These are triodes, and one top cap is the grid and the other the anode. Its clear that one top cap of each valve connects to the lecher lines - though I am less clear what is happening to the other top caps.

But then a question immediately becomes obvious - is there a modulator? Is it indeed an R/T set at all? If so, where is the microphone input? The "headset" connector has only two pins. If its CW, then there is no key input either.

The receiver is equally intriguing. At the moment I can't put a type number to the valve. It may be that it is a double-diode version of the EA50, with each anode connected to the receiver lecher lines. In which case, do we have some kind of crystal set here? In other words, the RF from the antenna goes to a tuned circuit (the lecher lines) and then is immediately rectified by the diodes? This would make some sense if extreme insensitivity in the receiver was just fine in the intended use. And the intended use might be a short range set, particulary at sea where propagation over open sea is about as good as it gets (unless you are in outer space!).

Richard

[M0FYA Andy]

The 'big EA50' valve looks like an NR88/EC53 triode to me.
http://www.r-type.org/exhib/aaa1627.htm
Andy

[G6Tanuki]

Originally Posted by trh01uk

But then a question immediately becomes obvious - is there a modulator? Is it indeed an R/T set at all? If so, where is the microphone input? The "headset" connector has only two pins. If its CW, then there is no key input either.

Looks to me like the wire-mesh grille on the left of the front panel is a loudspeaker? This would mean a headset was optional (for use only in high-noise environments?)

I guess the microphone is hard-wired.

With these relatively simple low-power kinds of transmitter crude-but-effective AM is often obtained by using a carbon mic and step-up transformer wired in series with the PA stage grid-leak. Grid-modulation isn't really elegant but it does give low component-count and minimal power-consumption which is of course important in portable, battery-powered kit.


Alternatively, an extra winding on the output-transformer (or using the existing primary-winding as a choke in "Heising" modulation) and a suitable switch can have the RX output-valve serve as a perfectly adequate modulator for a Tx that's only running to a couple of Watts of RF.

[HamishBoxer]

It has a wired in telephone type handset.Which resides in the r/hand side of the unit.Yes a loudspeaker on the left.

[trh01uk]

Originally Posted by M0FYA Andy

The 'big EA50' valve looks like an NR88/EC53 triode to me.
http://www.r-type.org/exhib/aaa1627.htm
Andy

Andy,

I suspect you are right - in which case the valve is not a double diode (probably) but a triode. In which case the circuit may well be a super-regenerative detector, and that would make the radio much more typical of other early VHF 2-way radios.

Richard