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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 9th May 2014, 3:28 pm   #1
David Simpson
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Default Spark Gap Valves

Info required please on some old Spark Gap valves :-
CV488's - made by BTH, and some wee 7248's - made by Western Electric ?
What equipment used them ?
Regards, David
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Old 9th May 2014, 3:40 pm   #2
Jeremy M0RVB
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Default Re: Spark Gap Valves

I have CV488 specs at http://www.tubecollector.org/cv488.htm but I've no info as to what these were user in.
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Old 9th May 2014, 4:03 pm   #3
G6Tanuki
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Default Re: Spark Gap Valves

Some of the very small ones were used in microwave radar systems as "T/R Switches".


See here for explanation.

http://www.tubecollector.org/tr-cell.htm
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Old 9th May 2014, 5:31 pm   #4
David Simpson
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Default Re: Spark Gap Valves

Thanks guys. Just wondering if they were out of some sort of test set. Or prahaps an emergency wartime Naval or Maritime WT set. I understand that Marconi Spark Gap Tx's were still in use in the 40's on vessels.
I've already looked at the valve info sites, but they dont tell you much. There are some being sold on ebay. But who would use them & what for, I wonder?

Regards, David
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Old 9th May 2014, 5:37 pm   #5
turretslug
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Default Re: Spark Gap Valves

With the voltage rating and duty cycle quoted, could the CV488 have had application in radar modulators?
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Old 9th May 2014, 6:17 pm   #6
kalee20
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Default Re: Spark Gap Valves

Don't know about these types, but glass-cased spark gaps are used as part of the ignition system to fire up jet engines. My company makes the electronics - a fly back converter charges a capacitor (1uF) to 3kV at which point the spark gap triggers and dumps the energy into the igniter plug. It repeats at the rate of about 2Hz.

I have also come across spark gaps to fire up xenon arc lamps in cinema projectors. Again, a capacitor is charged till the gap fires, the capacitor is then discharged via the gap into the primary of a Tesla coil. The secondary voltage, around 25kV, is fed to the Xenon lamp, breaks down the Xenon gas, at which point hopefully the thing avalanches and the running condition of 30V at 60A establishes.
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Old 9th May 2014, 7:07 pm   #7
Jeremy M0RVB
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Default Re: Spark Gap Valves

I just checked the CV data sheets, CV488 is based on CV295 which is described as a protective spark gap. Unfortunately the spec data never tells you what the things are actually used for!
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