ID This Device?
2 Attachment(s)
Can any anyone ID the (possibly military) gizmo in the attached photos? It is mostly brass with an ebonite or similar top and the base has four non-brass solid pins in a British B4 pattern, all drilled into the base. The insulated top has a single terminal and the base and top are riveted together.
The top is marked "X1141" and "958" is also scratched onto the top, possibly a serial number. The "anode" pin of the B4 is marked as "5" and finally the middle of the underside is drilled for a 4BA screw. Plugging this into a B4 base would obviously short all the pins together, so a piece of test gear comes to mind. There is no electrical connection between the terminal and the base and pins, measuring on the highest range of my mulitmeter and there is no discernable meter "kick" which might mean there is a capacitor inside. Any ideas? 73 Roger/G3VKM |
Re: ID This Device?
Xtal?
Lawrence. |
Re: ID This Device?
If not a Xtal than possibly a Coil? What does a meter reading give on Ohms?
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Re: ID This Device?
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I will try hooking it to my crystal tester. Roger |
Re: ID This Device?
In the 2nd photo what's the four brass looking things on the top?
Lawrence. |
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I'm betting that it's either a crystal or some sort of plug-in capacitor: I recall that WWII-era transmitters sometimes used plug-in "antenna-shortening" capacitors (in series with the antenna) to help a radio designed for short whip-antennas (well less than 1/4-wave) to match a longwire that may be more than 1/4-wave long. |
Re: ID This Device?
If they are then it doesn't look like B4 to me, needs confirming maybe.
Lawrence. |
Re: ID This Device?
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Roger |
Re: ID This Device?
Thanks, it's a mystery so far.
Lawrence. |
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The pins in the base definitely fit snugly into a B4 base, if by B4 you mean a PM2 valve base. It's not the American 4-pin base which has large and small pins. The base pins do not align with the (?) rivets on top, which are at 90 degree points around the board. If I get chance tomorrow, I will hook it up to my sig gen which has a crystal tester built-in and I will also try it on my capacitance bridge. If it does have a antenna shortening function then I would expect the capacitor to be of a low value, 100pf at most. 73 Roger |
Re: ID This Device?
Spark gap for lightning arrester?
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Re: ID This Device?
One thought occured to me is that "X1141" referred to an RAF aircraft serial number but searches on-line seem to indicate that serial was never issued.
Roger |
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Have had a close look at the thing this morning with a magnifying glass but, other than the number "5" next to the "anode", pin I can't see any marks other than those in my O/P. Roger |
Re: ID This Device?
OK, it is a crystal! Oscillates at 2017.88 kHz on my tester. I can't see that the X1141 and 958 numbers on the top have any relation to the frequency it works at.
Presumably, there was a B4 crystal holder or holders in the equipment and selection was made by a flying lead. The freq may indicate marine band but also older military kit, something like the early numbers of the Wireless Sets range? OK, so we know what it is but what does it belong to!? ??? 73 Roger |
Re: ID This Device?
That was my initial thought, it looks very Marconi (ish)
Lawrence. |
Re: ID This Device?
Yes, Lawrence, a good guess! I've had a quick look thru Wireless for the Warrior Compendium 1, which covers the Spark to Larkspur era and I cannot see anything that resembles the crystal. Most of the post-WW1 sets had master oscillators and only the later WS No 1 and 3 onwards had crystal oscillators as an option.
If it is marine band, then a pre-WW2 list of ship working frequencies might show the crystal as being for a ship TX. I have some data on that subject, if I can find it! Cheers Roger |
Re: ID This Device?
Crystals have two resonance modes, series and parallel, and it could have been used on either. So does either mode land on a popular maritime frequency?
David |
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Do we think so for such an early one?
And at such low frequency, would that be significant? I'm happy to bow to greater knowledge but I would have thought a few 10's of PPM at the most. I will say have never seen one like that before all the same! |
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Roger |
Re: ID This Device?
That's a big gap. I wonder when the "trawler band" was assigned? I've found references to the date of ending 2182, but not to the start. Someone must have been using 2.xxxMHz for some purpose?
As a kid with an AR88 in the sixties, fishfone improved my vocabulary no-end. Anyway, even old crystals have both series and parallel resonance modes The spacing depends on the holder capacitance and the motional inductance. Probably a few kHz. David |
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