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Old 16th Oct 2018, 4:59 pm   #1
terry vin
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Post Looks like a valve?

Does anyone on here know what this is please Marconi 3099.4 KCS.

Terry
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Old 16th Oct 2018, 5:01 pm   #2
Ed_Dinning
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Default Re: Looks like a valve?

Possibly a plug in crystal in vacuum; 3.0994 MHz

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Old 16th Oct 2018, 8:20 pm   #3
m0cemdave
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Default Re: Looks like a valve?

Yes, definitely a quartz crystal unit, for setting the frequency of an oscillator.

Another view (at 90 degrees to the picture) should show a thin plate of quartz, with gold plated terminations connected to two of the pins on the base.
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Old 17th Oct 2018, 9:42 am   #4
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Default Re: Looks like a valve?

The pic is a bit hazy but is the area encompassing the "CO" of marconi, behind the vertcal wire. a convex plate? If so, I would suggest a phot electric cell as used in 16mm sound projectors.
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Old 17th Oct 2018, 9:43 am   #5
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Default Re: Looks like a valve?

Crystal without a doubt,frequency written on it.
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Old 17th Oct 2018, 12:57 pm   #6
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Default Re: Looks like a valve?

Photo cells from projectors are very different.
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Old 17th Oct 2018, 2:10 pm   #7
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Default Re: Looks like a valve?

Quote:
Originally Posted by Ed_Dinning View Post
Possibly a plug in crystal in vacuum; 3.0994 MHz

Ed
Do these have vacuum? One of mine has broke at a pin. I taped it up and it still works well, but obviously no vaccuum now. Another one I have, at audio frequency, can be readily heard when the oscillator is working. The oscillator works with very low drive, taking nearly a minute to startup so is probably not excessive running.
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Old 17th Oct 2018, 2:25 pm   #8
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Default Re: Looks like a valve?

AFAIK, these do have a vacuum. Loss of the vacuum should have no near term consequences, but would probably impair long term accuracy and stability.
Alternatively they might be filled with inert gas like an electric lamp.

Quartz and gold plating are both reasonably inert and little influenced by air or moisture, but some slight inaccuracy might be introduced by moisture or dirt.
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Old 17th Oct 2018, 4:00 pm   #9
John M0GLN
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Default Re: Looks like a valve?

Quote:
Originally Posted by broadgage View Post
Loss of the vacuum should have no near term consequences,
The millions of old FT-243 crystals just worked in air, they could be taken apart by undoing 3 screws and then adjusted and re-assembled in their plastic case and lid without any seals, it's not something I've done myself but it's detailed in many Radio Amateur publications.

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Old 17th Oct 2018, 4:11 pm   #10
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Default Re: Looks like a valve?

Yes they should have a vacuum: apart from preventing contamination causing frequency-drift or 'sleeping-sickness' which sometimes affected HC6/HC18 type crystals, one thing to note is that these vacuum-encapsulated crystals need very careful driving as apart from conduction through the supports and direct radiation there's no way for any heat to escape.

Don't try using one of these in the classic 'single-valve' 6V6-style HF transmitters!

[Sidenote: there were some similar-looking glass encapsulated crystals produced for precision frequency-meter use. Instead of a vacuum the encapsulation contained a small amount of an inert gas such as neon or Argon. When energised by an external RF source at the correct frequency, the gas ionised and the crystal glowed!]
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Old 17th Oct 2018, 6:29 pm   #11
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Default Re: Looks like a valve?

Quote:
Originally Posted by G6Tanuki View Post

[Sidenote: there were some similar-looking glass encapsulated crystals produced for precision frequency-meter use. Instead of a vacuum the encapsulation contained a small amount of an inert gas such as neon or Argon. When energised by an external RF source at the correct frequency, the gas ionised and the crystal glowed!]
Does this mean that the ionisation was used for amplitude stabilisation?
Runing in a vacuum should increase the Q.
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Old 17th Oct 2018, 6:43 pm   #12
G6Tanuki
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Default Re: Looks like a valve?

No, these frequency-standard crystals were designed to be energised by coupling to the output of a transmitter or similar: the idea being that when the transmitter was operating at the crystal's resonant frequency the crystal presented a high impedance so you got a local high-voltage RF field around the resonant crystal, high enough to ionise the gas and cause a glow.

Handled properly they could let you tune your transmitter's master-oscillator to within 100Hz or so of the crystal's frequency.
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Old 17th Oct 2018, 6:49 pm   #13
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Default Re: Looks like a valve?

Not heard of this...
I have some in the junk box I assumed to be not filled by anything but vacuum.
Some testing is required!

Last edited by Jon_G4MDC; 17th Oct 2018 at 6:50 pm. Reason: spelling
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Old 17th Oct 2018, 6:55 pm   #14
G6Tanuki
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Default Re: Looks like a valve?

Unless it's specifically identified as a reference-indicator crystal I doubt you've got one!

They were only something you'd find in industrial/military/broadcast circles in the 1920s and 1930s.
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Old 17th Oct 2018, 7:23 pm   #15
Jon_G4MDC
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Default Re: Looks like a valve?

Thanks, mine are in some swag from Holland.
Scheveningen or Kootwijk Radio throw outs - age is unkown.
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Old 18th Oct 2018, 3:35 am   #16
terry vin
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Post Re: Looks like a valve?

Thank you for all the information regarding this would be valve the "pretender" that turned out to be a crystal in vacuum.

Many years ago (late70's) my Father used to go to a motor auction in Rothwell near Leeds and I would some times go along. It was always full of ex BT and British Gas Vans and cars plus Police and Ambulance vehicles. Most of them didn't run and sold for very little.

One time I went and a Blue I think RAF Ambulance was going in the auction, it wouldn't start so was pushed through it had fitted a Pye radio that looked like a CB, and in the back two more of these Pye radios just sat on one of the seats.

If I remember correctly it sold for £25 and I asked the new owner if I could buy the "CB"radio's in the back he said "you can have them" I remember them being Blue and Silver with the name Pye mobile radio.

I never got them to work or pick up anything, but I still have the glass plug in crystals if anyone wants them FOC.

Terry.
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