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Author Topic: Electronic Keyer using tubes...  (Read 1486 times)
K7XID
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Posts: 11




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« on: November 20, 2017, 03:14:10 AM »

Many years ago I had an home brew electronic keyer which used two little russian tubes I can't remember. Now I would like to find the diagram and try to build it ... any help? 
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N3QE
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« Reply #1 on: November 20, 2017, 06:29:05 AM »

March 1967 QST shows a two-tube keyer (12AU7 + OB2) with a lot of nice features like self-completion and single knob for speed control.  http://www.cqham.ru/forum/attachment.php?attachmentid=96946&d=1322076726

It is possible that a modern 48V coil relay (like Omron LY series) would sub in for the Sigma 2300-ohm coil relay specified in the original project. The 48V LY coil is speced to be 2600 ohms and just might not require much tweaking of other elements.
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K7XID
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« Reply #2 on: November 20, 2017, 06:54:38 AM »

Thanks a lot for the info!... will check it!

73

Raúl, also CO8ZZ
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N3QE
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« Reply #3 on: November 20, 2017, 07:12:43 AM »

Thanks a lot for the info!... will check it!

73

Raúl, also CO8ZZ

Oh wow Raul, I had no idea K7XID was CO8ZZ was you :-) . Thank you for the 42 RTTY and CW QSO's the past couple years!

If you come across any links to Russian tube keyer designs I would really like to see them.
« Last Edit: November 20, 2017, 07:22:38 AM by N3QE » Logged
K7XID
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« Reply #4 on: November 20, 2017, 03:47:14 PM »

Hi Tim!... Yes, for sure!... let me try to find something printed down here... Best regards!
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W6EM
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« Reply #5 on: November 24, 2017, 11:44:05 AM »

March 1967 QST shows a two-tube keyer (12AU7 + OB2) with a lot of nice features like self-completion and single knob for speed control.  http://www.cqham.ru/forum/attachment.php?attachmentid=96946&d=1322076726

It is possible that a modern 48V coil relay (like Omron LY series) would sub in for the Sigma 2300-ohm coil relay specified in the original project. The 48V LY coil is speced to be 2600 ohms and just might not require much tweaking of other elements.

Most of those older 12AU7-like tube keyer projects used plate voltages around 130-135VDC as I recall, having built one when I was a kid.  The relay might just draw a little too much current for the coil....and zap open.

If you were to put two 1N5366 39V 5W zener diodes in series with the relay, they would drop the voltage to the relay coil down to about 48VDC across the coil.  Dissipation would be about 0.7W per diode.

Lee


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KM1H
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« Reply #6 on: November 30, 2017, 02:20:02 PM »

Or you can take it to the next level and build a TO clone which was a QST feature and then licensed to Hallicrafters. I have and use the HA-1 with vintage tube gear.

http://bama.edebris.com/manuals/hallicra/ha1/

Carl
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G3RZP
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« Reply #7 on: December 01, 2017, 03:20:30 AM »

Rather than put zeners in series with the relay, use a resistor of the right value to give 48 volts on the relay coil. Using a higher voltage and a series resistor means the relay pulls in faster.
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N4MQ
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« Reply #8 on: December 01, 2017, 05:31:47 AM »

How does a resistor or zeners affect the speed??  Current is all that causes the relay to close and if the current is the same.....as defined by the voltage dropped across the coil in steady state conditions = seems to be the same to me. Woody
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K3UIM
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« Reply #9 on: December 02, 2017, 12:15:06 PM »

Or you can take it to the next level and build a TO clone which was a QST feature and then licensed to Hallicrafters. I have and use the HA-1 with vintage tube gear.
Carl
Whoa!!! You mentioned "TO' in ref to the keyer and I just purchased an unmarked "ham unit" (home-brewed) on Ebay that had "TO9" marked on it.
It was built by a ham I would guess during the early 60's, when I was also active. I figured out it was a keyer by looking over the circuit and seeing where the jacks connected, etc.
The "TO9" sounded very familiar, but I cannot remember where or when I became familiar with it. I was going to check my cd of several of the ham mags of that period for those letters and number. I'm pretty sure I'll find it there!
Small world!!!
Charlie
« Last Edit: December 02, 2017, 12:19:29 PM by K3UIM » Logged
WB6BYU
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Posts: 17187




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« Reply #10 on: December 02, 2017, 12:39:26 PM »

Quote from: N4MQ

How does a resistor or zeners affect the speed??  Current is all that causes the relay to close and if the current is the same.....as defined by the voltage dropped across the coil in steady state conditions = seems to be the same to me.



Pull-in is time is determined by transient conditions rather than steady state.

The current through a coil when first powered on is a function of time that depends
on the voltage across it.  Initially there is no current, since the current through a coil
can't change instantaneously.  The higher voltage allows the current to increase faster,
and the voltage drops as the current increases due to the series resistor.
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W6EM
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Posts: 1666




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« Reply #11 on: December 02, 2017, 06:51:20 PM »

Quote from: N4MQ

How does a resistor or zeners affect the speed??  Current is all that causes the relay to close and if the current is the same.....as defined by the voltage dropped across the coil in steady state conditions = seems to be the same to me.



Pull-in is time is determined by transient conditions rather than steady state.

The current through a coil when first powered on is a function of time that depends
on the voltage across it.  Initially there is no current, since the current through a coil
can't change instantaneously.  The higher voltage allows the current to increase faster,
and the voltage drops as the current increases due to the series resistor.
The time constant of a series RL circuit determines how quickly the current rises from time zero.  Since the time constant is L/R, in the case of zeners-only, assume R to be just the coil resistance.  In the case of using a series dropping resistor, total R would be 2.8 times coil resistance or 2.8R.  So, since L is constant, the time constant shortens by 1/2.8.  Thus, RZP's comment is correct.  Faster closing, since current climbs faster to steady state values, which are the same for either method, zeners or resistor.

Although, I doubt seriously that the difference would affect anything at CW keying rates.

However, probably not relevant here, but at time zero, with resistors, the coil sees 135VDC momentarily.  With zeners, it should only see 48VDC instantaneusly.  I doubt that the insulation level of the coil would be exceeded, but something to consider at higher voltages.  Somewhat akin to choosing a solid state device to switch high voltage tube circuitry.
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K8BYP
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Posts: 16




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« Reply #12 on: Today at 12:52:37 PM »

Its not possible to make a "real keyer" with such a simple circuit. Yes, two timers, but thats not quite "keyer" in the modern sense.

Keyers are several functions all at once, and complitcated to do in discrete circuitry:

Dot interval
Dash interval
Dot-Dash ratio
SILENT SPACE BEHIND EACH (so they arent run together)
Lockout of the opposite oscillator when the first is running (again, so Dot and Dash dont run together)

The last two are the "gotchas"!

That is a job ideally suited for a microcontroller. The fact a micro can "only do one thing at a time" takes care of some of the problems.
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