Mystery Electronic Device

[hardpanman]

Can anyone help me identify this small battery-operated device? Detachable antenna, on/off switch, maybe a tiny speaker hole on the bottom. Quality metal construction, and a fancy box. The battery compartment will hold neither a AA nor a AAA battery. I even tried two MN21/23s. No dice. Some sort of vintage tracking device? It measures 2-1/2 x 1" x 1/2".

 

[JimB]

Looking at the components on the circuit board, it appears to be a low power transmitter,
so my best guess is that it is a bugging device.
The small hole which you describe as a "speaker hole" is more that likely a microphone hole.
In the bottom left hand corner is what appears to be an electret microphone.

JimB

 

[augustinetez]

Does the bottom red section lift up?
Instruction leaflet might be in there.

 

[AnalogKid]

Agree about the electret mic. I count 8 adjustable components. That seems like a lot for a simple wireless mic or bug. Any way to see what's stamped on the crystal?

ak

 

[Nigel Goodwin]

Agree about the electret mic. I count 8 adjustable components. That seems like a lot for a simple wireless mic or bug. Any way to see what's stamped on the crystal?

ak

Actually it looks perfectly normal for a 'proper' transmitter, as opposed to the 'toy' bugs that you usually see, the multiple adjustable coils and capacitors are for aligning the multiplier and output stages.

Neat little unit though

 

[hardpanman]

JimB, you are right. Once I had the proper phrase to research (bugging devise) this very unit popped up twice on this website (attached). It should be easy to track down the maker, with that B logo. Thanks.

 

[hardpanman]

AnalogKid, the crystal is marked 14.7496 SCX

 

[Nigel Goodwin]

AnalogKid, the crystal is marked 14.7496 SCX

It's likely to be multiplied by 8 (118MHz) or by 12 (177MHz), so in either case outside the range of a normal FM receiver, it will also be NBFM (Narrow Band FM). If you're planting a bug, you don't want it so it can be accidentally picked up with a domestic FM radio.

How long is the aerial?, that should tell you which of the two likely options it is.

 

[JimB]

t's likely to be multiplied by 8 (118MHz) or by 12 (177MHz),

I think more likely X12 multiplication to 177MHz which would put it into the general highband VHF area, whereas 118MHz would put it in the bottom end of the aircraft band which would be rather naughty.

I also agree with NBFM.
Using a crystal oscillator for frequency stability has the effect of limiting the amount of deviation which can be applied, also a frequency multiplication factor of 12 means that the small amount of deviation which can be obtained at 14MHz is also multiplied by a factor of 12.

JimB

 

[Nigel Goodwin]

I think more likely X12 multiplication to 177MHz which would put it into the general highband VHF area, whereas 118MHz would put it in the bottom end of the aircraft band which would be rather naughty.

It's an illegal bugging device, using an illegal band, in either case

I doubt that's of much concern to the makers or sellers of illegal equipment, but I agree that 177MHz is probably more likely.

As for the aerial, 177MHz is about 40cm and 118MHz is about 60cm.

 

[hardpanman]

I'm back home now. the antenna is 7".

 

[Nigel Goodwin]

I'm back home now. the antenna is 7".

In which case it might be a helical aerial?, as it's too small for a quarter wave whip at either of those frequencies.

For a whip 7 inches would be about 400MHz, but the coils in the transmitter look too high an inductance for 400MHz.

 

[AnalogKid]

Often in devices such as this, the antenna is inefficiently short to aid concealment.

OTOH, there is a connector-looking metal band around its base, suggesting a connector, suggesting a helical.

ak

 

[Nigel Goodwin]

Often in devices such as this, the antenna is inefficiently short to aid concealment.

OTOH, there is a connector-looking metal band around its base, suggesting a connector, suggesting a helical.

ak

Where's a frequency counter when you need one?

 

[AnalogKid]

A friend of mine got a cute little 1 GHz spectrum analyzer for $80 on ebay. I used it to tweak wireless doorbell transmitters from different manufacturers to work interchangeably.

$80. Absolutely disgusting. Now I have to get one.

ak

 

[hardpanman]

Solved. Cryptomuseum has a full description of this AU-015 Universal UHF/FM Bug Transmitter:

AU-015

www.cryptomuseum.com

 

[Nigel Goodwin]

Solved. Cryptomuseum has a full description of this AU-015 Universal UHF/FM Bug Transmitter:

AU-015

www.cryptomuseum.com

Cool, right frequency for the aerial being a quarter wave whip