Mystery Electronic Device

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hardpanman

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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".
 

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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
 
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
 
AnalogKid said:
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
Click to expand...
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
 
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.
 

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hardpanman said:
AnalogKid, the crystal is marked 14.7496 SCX
Click to expand...
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.
 
Nigel Goodwin said:
t's likely to be multiplied by 8 (118MHz) or by 12 (177MHz),
Click to expand...
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
 
JimB said:
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.
Click to expand...
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 said:
I'm back home now. the antenna is 7".
Click to expand...
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.
 
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
 
AnalogKid said:
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
Click to expand...
Where's a frequency counter when you need one?
 
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
 
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