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Old 22nd Nov 2022, 9:43 pm   #1
livewireless123
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Default Crystal assembly

I have had this block of 6 plug in crystals in my bits box for many years.
I finally got round to plugging them into my ct432 calibrator and cheapo Chinese counter. they read from 148.500 to 152 .250 kHz spaced 750 Hz apart.
I vaguely remember that it came out of a piece ex gov gear that I bought
from a radio junk shop on London road in Manchester many years ago and dismantled as I did then.I think there were quite a few ef50s in there as well.
just out of curiosity I wonder if anyone knows what the item's function was,
Some sort of radar unit?
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Old 22nd Nov 2022, 10:09 pm   #2
Al (astral highway)
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Default Re: crystal assembly

So that’s on the long-wave spectrum.

Maybe from an old transmitter?

Far too low f for radar IF.
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Old 22nd Nov 2022, 10:13 pm   #3
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Default Re: crystal assembly

Could be a filter system. 750 Hz passband plus or minus.

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Old 22nd Nov 2022, 11:51 pm   #4
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Default Re: crystal assembly

+/-750 Hz would imply a 1.5kHz wide filter.... not bad for RTTY, and in government equipment that would seem to fit

A filter for teleprinter mode from some system with a 150kHz final IF seems possible.

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Old 23rd Nov 2022, 6:38 pm   #5
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Default Re: crystal assembly

They don't look big enough to be that low?
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Old 23rd Nov 2022, 9:40 pm   #6
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Default Re: Crystal assembly

I'm thinking of a radio navigation unit like one of the GEE or GEE-H variants. This sort of crystal would be used as a timebase for the timing function - and ultimately determine the accuracy of the radiolocation offered.

As far as I can recall the basic GEE Mk.II system started from a 150kc/s crystal and divided it down in the Indicator unit.

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Old 23rd Nov 2022, 9:53 pm   #7
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Default Re: Crystal assembly

Quote:
Originally Posted by trh01uk View Post

As far as I can recall the basic GEE Mk.II system started from a 150kc/s crystal and divided it down in the Indicator unit.
Nicely remembered, Richard! You're exactly right, Gee MK II had a Xtal oscillator 150KHz stage.

Link from VMARS here and close-up of the relevant page. 100V P-P sine wave from that stage, photo top left.



http://www.vmarsmanuals.co.uk/archiv..._GEE_MK.II.pdf
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Old 23rd Nov 2022, 9:57 pm   #8
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Default Re: Crystal assembly

Quote:
Originally Posted by Al (astral highway) View Post
Quote:
Originally Posted by trh01uk View Post

As far as I can recall the basic GEE Mk.II system started from a 150kc/s crystal and divided it down in the Indicator unit.
Nicely remembered, Richard! You're exactly right, Gee MK II had a Xtal oscillator 150KHz stage.

Link from VMARS here and close-up of the relevant page...

http://www.vmarsmanuals.co.uk/archiv..._GEE_MK.II.pdf

Well, I think I am on the right track. But GEE Mk.II had a single 150kc/s crystal. What we have here is a set of crystals carefully spaced around the 150kc/s point. I am thinking - speculating - that this is part of a later coding system (to fool enemy jamming perhaps).

And the crystal types make me think 1950s, so perhaps we are looking at GEE Mk.III, which I have never really paid much attention to.


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Old 23rd Nov 2022, 10:01 pm   #9
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Default Re: Crystal assembly

Quote:
Originally Posted by trh01uk View Post
[

Well, I think I am on the right track. But GEE Mk.II had a single 150kc/s crystal. What we have here is a set of crystals carefully spaced around the 150kc/s point. I am thinking - speculating - that this is part of a later coding system (to fool enemy jamming perhaps).

And the crystal types make me think 1950s, so perhaps we are looking at GEE Mk.III, which I have never really paid much attention to.

Well, a worthy contribution indeed. I'm going to go back through the manual, fascinating system.
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Old 23rd Nov 2022, 10:22 pm   #10
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Default Re: Crystal assembly

One of the crystals does have APR 56 marked on it so that might be an actual date - either crystal manufacture or installation date.
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Old 23rd Nov 2022, 11:18 pm   #11
Al (astral highway)
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Default Re: Crystal assembly

Well spotted Terry.

Here’s the cct. showing the X-tal oscillator that is used to generate sync pulses
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Old 23rd Nov 2022, 11:59 pm   #12
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Default Re: crystal assembly

Quote:
Originally Posted by Jon_G4MDC View Post
They don't look big enough to be that low?
Look inside your watch. There's a variety of crystal modes other than SC cut face-shear.

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Old 24th Nov 2022, 12:41 am   #13
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Default Re: Crystal assembly

Just noticed x-tal osc. photo didn’t upload. (#11) Here it is
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Old 24th Nov 2022, 1:33 am   #14
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Default Re: Crystal assembly

[QUOTE=trh01uk;1515924]
Quote:
Originally Posted by Al (astral highway) View Post


Well, I think I am on the right track. But GEE Mk.II had a single 150kc/s crystal. What we have here is a set of crystals carefully spaced around the 150kc/s point. I am thinking - speculating - that this is part of a later coding system (to fool enemy jamming perhaps).

Oops! On further investigation of the circuit, the X-tal in the GEE Mk. II had a fundamental of 75KHz and that is tuned to the 2nd harmonic, 150KHz. Text in photo here. T1 is visible in the photo in my previous post.
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Old 24th Nov 2022, 11:31 am   #15
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Default Re: Crystal assembly

I fondly recall GEE as I used to live a couple of miles from a tx at Worth Matravers. It sang away at 30.7 Mc/s and spread all over the band. A handy calibration reference!
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Old 25th Nov 2022, 1:51 am   #16
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Default Re: Crystal assembly

Quote:
Originally Posted by livewireless123 View Post
.
I vaguely remember that it came out of a piece ex gov gear that I bought
from a radio junk shop on London road in Manchester many years ago
Mazel Radio.
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Old 25th Nov 2022, 12:12 pm   #17
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Default Re: Crystal assembly

I believe Richard has cracked it. I just checked the circuit of the GEE Mk3 Indicating Unit Type 26, and that has a module containing six crystals all arounf 150kHz.

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Old 25th Nov 2022, 8:42 pm   #18
livewireless123
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Default Re: Crystal assembly

So it looks like it was gee equipment, I thought it was possibly airborne gear as it had a higher frequency power transformer in it. thanks for all the interest in this. Regarding Mazel radio, no, it came from a small shop further up. I don't think he lasted very long. I actually worked for Mazel from the early 60s to early 70s
Heres a pic of the shop,all gone now.JAK was the son of his lady friend
he moved to Southport and I followed him and worked for him for some time doing repairs. I kept in touch with him until he passed away earlier this year,
His grandson now runs his shop.
The pic won't load up, will investigate what's wrong and put it up later.
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Old 25th Nov 2022, 9:02 pm   #19
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Default Re: Crystal assembly

Now got the pic to load up
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