[Milsurplus] Chirp in Crystal Control

[Ken Gordon]

On 21 Aug 2024 at 5:16, Rob Flory wrote:

> 
> Hi,
> 
> This conversation is reminding me of a couple things with military
> transmitters. 
> 
> TBX(0-6) and TCS both have limited keying rates in crystal control
> because of chirp.  In MO mode you can key faster.
> 
> I can't recall the name for the type of one-tube transmitter in the
> TBX with the 837 tube where the feedback of the oscillator is derived
> from one of the screen grids,   Maybe electron-coupled oscillator? 

Yes. Exactly. The ECO. The actual oscillator section is the "triode" formed by the cathode, 
grid, and screen, and the remainder of the tube constitutes the "amplifier", so you have a 
single tube doing double-duty. That way the :"oscillator" is very lightly loaded, yet the single 
tube can output significant power. This is one way you can get real power out of a crystal 
oscillator without overloading the crystal.

Furthermore, there is a "sweet spot" in the voltages involved in the ECO, in which  the drift 
caused by voltage changes is cancelled, since the screen voltage changes cause drift in one 
direction, while the plate voltage changes cause drift in the opposite direction. The RSGB 
Handbooks show a graph of this.

I have always regarded the ECO as one of the best discoveries in oscillators which has ever 
happened.

I have both a TCK-4 and a TCM-2, both of which I would LOVE to have on the air, and 
despite my advanced age (82) I plan to have on the air as soon as I can.

As far as I am concerned, the TCM-2 has more knobs and dials per inch of panel space than 
any other transmtter I know of.

And the TCK-4 has one of the best VFO systems in military transmitters that I know of.

Ken W7EKB

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