ARRL CW transmitter 6GK6 and 6146 (1973).

[oh6cn ham]

Hello dont know if this is the right forum but anyway has someone made a cw transmitter with the 6gk6 as crystal osc .I am trying but cannot get it to oscillate Regards Greger

[Bazz4CQJ]

I cannot recall that valve being used in any British designs. I cannot recall a design published in UK mags using 2 valves, with the 6146 as output, in which I guess the oscillator valve needs sufficient "muscle".

Are you sure your valve and crystal are in good condition?
What frequency are we discussing?

B

[Julesomega]

I can't find my ARRL Manual from about that time, but a very early postwar Manual has "6V6, 6L6 or 6F6 or glass equivalents" as both crystal oscillator and power amplifier, so I don't think it can be at all critical

[Julesomega]

For the reference, here's the Beginners Transmitter article. I love the old ARRL designs for their utmost simplicity suitable for home construction, while meeting the claimed specifications

[Terry_VK5TM]

This appears to be the transmitter that Greger is referring to https://w7ekb.com/glowbugs/projects/75to120wattcwxmitter.pdf

[Bazz4CQJ]

Looking at modern European options (and a 6146 is a modernish valve), there's a thread on this forum where 6Tanuki reports using an ECL80 as a crystal oscillator/driver for an 807. I think there were published designs doing something similar. ECL80's are pretty cheap valves.

B

[Radio Wrangler]

These transmitter designs were aimed at beginners, and back in the sixties and seventies, 6146 were expensve valves. Beginners were more likely to go for commonly available surplus valves.... like the 807, 6L6 (on lower bands), 5B254M, TT21 etc.

Higher power crystal oscillator circuits do not work well with modern HC6/U and smaller cases, where they tend to significantly exceed the recommended max power dissipation in the quartz. Higher power valve oscillators worked best with old FT243 type large crystals. I've autopsied failed crystals from various people and founs cracked qurtz inside.

A lower power oscillator citcuit nd a buffer stage before the PA would be gentler on the quartz and give more drive allowing a lower gain (cheaper) PA valve, but it would have looked more complicated on the printed page. Unfortunately it isn't so easy to gauge the amount of trouble likely in getting something going just from a schematic. I suspect that although that design exploits a (then!) modern power output valve, it may be best with vintage crystals.

The ARRL have always been pretty good ar checking designs, buying equipment for review instead of testing loaners from manufacturers etc, but this may be a case of changes in the world since publication. Disclosure... I have in the past worked as an author for the ARRL.

David

[oh6cn ham]

Hello and thanks for all the inputs so far I have the Old FT 243 crystals I have checked them with a Heath HW16 and they work OK.

[G6Tanuki]

6GK6 is pretty much the same as the EL84 but with different pin connections. I used its buddy the 10GK6 (10V heater) in a few things because they were very cheap!

My ECL80 oscillator and driver used the triode as a Miller type oscillator with the crystal between grid and anode, capacitively coupled to the pentode. Triode anode and pentode screen fed from a 150V Regulator. It happily produced enough RF to light a 12V 2.2W bulb to impressive brightness, and at least 5mA grid current in the PA stage.

Some of these 'classic' valve circuits extract the second or third harmonic of the crystal from the driver and then feed that to the PA grid. Probably not a good idea, you can never really be sure what the PA is amplifying..

[Joe_Lorenz]

From today's point of view the acquisition of a vector network analyzer shall be very helpful to sort out your builds quickly. They can be had for little money now, in comparison to the valve era.

Many years ago as a young lad I made similar experiences building (not so legal) AM transmitters using cheap valves like PC88, EQ 80, EL84 and RS292, just what I had. Sometimes causing trouble regarding TV reception or turning neighbour's Hammond organ into a rock music radio. Without proper test equipment much was hit-and-miss!

Joe

[Richard675]

Your crystals are OK so experiment with values of C1 and C2
I’d start by fitting a 100pF variable at C2. You just need to get the feedback correct for your crystal.