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In Keeping with 813 thread......6MJ6 pair




 
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Author Topic: In Keeping with 813 thread......6MJ6 pair  (Read 552 times)
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WA4WAX
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« on: October 19, 2022, 05:00:19 PM »

I am thinking about a pair of 6MJ6.

Should be good for 300 watts out on CW with 900 VDC anode voltage in class C

Screen modulated AM should be around 75 to 100 watts out. 

RTTY should be OK around 150 watts if transmissions not too long.

Thoughts?
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K9MB
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« Reply #1 on: October 19, 2022, 11:16:37 PM »

I am thinking about a pair of 6MJ6.

Should be good for 300 watts out on CW with 900 VDC anode voltage in class C

Screen modulated AM should be around 75 to 100 watts out. 

RTTY should be OK around 150 watts if transmissions not too long.

Thoughts?

Those outputs seem very optimistic for a pair of tubes with 30 watt dissipation.
These sweep tubes have very high peak current capability, so they can put out a lot of audio as strapped triodes but seems like outputs should be about half the amount you mention. Maybe I am missing something?
73, Mike
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WA4WAX
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« Reply #2 on: October 20, 2022, 05:53:14 PM »

Hmm........I will walk that back to 250 out on CW if in deep class C.  Of course, tune up with a clicker.

Maybe 70 watts screen mod.

The more I think of it, two 4D32;s sound better.

The 6MJ6 is an industrial version of the 6LQ6.....much more reserve.
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KD6VXI
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« Reply #3 on: October 21, 2022, 09:02:47 PM »

The RCA 6MJ6 with the black plate cap and two connections to the plate (the RF rated tube) is amazing.

It's more a 35 plus watt tube.  It has some serious emissions capability.  It needs decent colling (a good stiff breeze, constant on TX).

That said, I think you need a third or fourth tube to see what you want to see.

At least.

4D32s are a better idea.

--Shane
WP2ASS / ex KD6VXI
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K1JJ
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« Reply #4 on: October 21, 2022, 09:39:19 PM »

Hmm........I will walk that back to 250 out on CW if in deep class C.  Of course, tune up with a clicker.

Maybe 70 watts screen mod.

The more I think of it, two 4D32;s sound better.

The 6MJ6 is an industrial version of the 6LQ6.....much more reserve.


Hi Matt,

If you're thinking of a 4D32, I highly reccomend it.  It's in the elite tube class -  I have one in each rig:   4-1000A, 813, 4D32.

Here's "Summer Breeze" -  a single 4D32 class C AM rig I built last year that may be of help to you.  Page 2 shows a lot of action.

http://amfone.net/Amforum/index.php?topic=45973.0

Good luck!

Tom, K1JJ
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Use an "AM Courtesy Filter" to limit transmit audio bandwidth  +-4.5 KHz, +-6.0 KHz or +-8.0 KHz when needed.  Easily done in DSP.

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K9MB
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« Reply #5 on: October 22, 2022, 12:05:20 AM »

Hmm........I will walk that back to 250 out on CW if in deep class C.  Of course, tune up with a clicker.

Maybe 70 watts screen mod.

The more I think of it, two 4D32;s sound better.

The 6MJ6 is an industrial version of the 6LQ6.....much more reserve.


Hi Matt,

If you're thinking of a 4D32, I highly reccomend it.  It's in the elite tube class -  I have one in each rig:   4-1000A, 813, 4D32.

Here's "Summer Breeze" -  a single 4D32 class C AM rig I built last year that may be of help to you.  Page 2 shows a lot of action.

http://amfone.net/Amforum/index.php?topic=45973.0

Good luck!

Tom, K1JJ

A pair of 4D32s is a different matter. They are rated at 50 watts dissipation and can easily put out 200 watts high level AM.

You can get 300 watts on CW, also.
Downside is the surplus market has dried up and they are more than $50- $75 each now.
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W3SLK
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« Reply #6 on: October 22, 2022, 11:20:59 AM »

If you are bent on using the 4D32's you might also want to seek out advice from Brett, N2DTS. He did/does a lot of work with 4D32's and 4CX250's and is quite knowledgeable.
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
WB3JOK
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« Reply #7 on: October 31, 2022, 08:04:59 PM »

I think the highest-dissipation sweep tube is the 6LF6, rated at 40 watts. But they're pricey these days too. You could save some by using the odd filament voltages like 20v or 40v (assuming you have an appropriate filament transformer).
Just put three 40LF6 in your amp and you won't need a filament transformer  Grin
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