6L6 VS 6AG7 for Xtal Osc

[Carl WA1KPD]

I'm getting my Hallicrafters HT-9 back on the air and I have wondering about the 6L6 it uses for the xtal oscillator.

I am under the impression that the 6AG7 is much kinder on crystals. So I'm thinking about building another stage
(without hacking up the rig) that feeds the crystal input of the 6L6, or replacing the 6L6 with a 6AG7, as again as an external plug in.

Schematics attached. The osc coil plugs in to the first stage. I am only planning to use it on 160- 40

I welcome your thoughts.
Carl      

[WA5VGO]

You're right. The 6AG7 will have much less crystal current. It's also has higher efficiency when used as an oscillator. I'd build an adapter and plug it into the existing 6L6 oscillator socket. If you do, keep the leads as short as possible. I'm pretty sure you'll have plenty of drive.

[Carl WA1KPD]

Thanks,
The adaptor route was what I was thinking
73
Carl

[k7mdo]

I think the Heathkit AT-1 uses the 6AG7 and it would give you some starting component parameters.... just a thought.

Tom

[W9GT]

I had the same concern /problem with the old John Meck T-60-1 transmitter.  I just rewired the socket for the 6L6 oscillator and changed the circuit a little to accommodate the 6AG7.  I used the same circuit as that used in the Johnson Adventurer/KnightT-50.  Works great with either the xtal or VFO.  Much better performance than the original oscillator and no extra holes or noticeable mods required.

73,  Jack, W9GT

[N3GTE]

If the voltage aren't too high you can try a 6Y6 or 6W6. Same pinout as the 6L6 and easier on the xtals.

Terry

[w1zb]

I have no problems using the older style FT-243 xtals in my HT-9 with the original 6L6 oscillator. Works with all my 160, 80 and 40 crystals. The 6L6 oscillator works fine with either a crystal or VFO. I wouldn't use the smaller QRP crystals that are available now.
I ran my HT-9 during the AM Rally and had a lot of fun. Good luck with yours.

73 Jerry W1ZB

[Carl WA1KPD]

Hi Jerry,
Never had a problem, just wondered if it was a precaution worth taking as crystal suppliers go away. I don't want to change the rig at all, so it would be a separate chassis possibly inside the voluminous rig!
Carl

[W3RSW]

Meant to add this earlier for why the superiority of a 6AG7 or miniature Version 6CL6 in an electron coupled oscillator.   This site's been mentioned on this board several times but still
Fun and informative.  Truncate the URL for Lattias' Frostburg.edu. Other neat engineering and physics pages and projects.

Neat site even includes an ad copy of the 6CL6 when First brought out.

http://faculty.frostburg.edu/phys/latta/ee/6cl6xmtr/6cl6xmtr.html

Here's GE's ad if your in a hurry.

http://faculty.frostburg.edu/phys/latta/ee/6cl6xmtr/6cl6adlarge.jpg