Planning a heavy Transmitter build project, seeking circuit recommendations.

[steve_qix]

How well would a sweep tube (or several in parallel) work as a PWM modulator? The high peak current and voltage capabilities have me wondering.

They work very well.  I have used the 6DQ5 as a pulse width modulator for a pair of 6146Bs - Worked great!  You couldn't use a 6DQ5 for something like an 813 - too much average DC voltage for the modulator.  I used a 4-400 as a pulse width modulator for an 813 - again, it worked wonderfully.  No forced air needed on the 4-400, either - because the modulator was so efficient.

The discussion about alternative methods of AM is not necessarily trying to convince the original thread creator to use such methods, it is a "side" discussion, so to speak 

Regards,

Steve

[N6YW]

Steve
It is interesting and worthy of discussion even if I don't have a clue of how pulse width modulation works.
If it does the job of modulating the RF deck without the associated iron and costs, then by all means point us in a direction where this information exists. You have cracked the lid on my pushback Steve.

[W7TFO]

Might I suggest this:

It is pretty simple, good modulation without solid state or big iron.  All the tubes listed are available easily, and you could even make the final stage out of 810's as specified without breaking the bank.

Plenty of them around, they made a lot of them.

(They don't make 813's any more, either. )

[Opcom]

To clear it up, the series mod suggestion was only that, something different. I have no tried/working circuits, fiddled with it for a converted 807 TX once, blew up the PWM (555 and some transistors, the 807 mod tube lived), I did not get good results re; mod % with the 555 anyway, and gave up.

I was shown a 5K Collins BC TX and the engineer said it was a series PWM, I think 3CX2500's? - so nutty me I had to try it at home. Never mind - use what others say works!

[N6YW]

To clear it up, the series mod suggestion was only that, something different. I have no tried/working circuits, fiddled with it for a converted 807 TX once, blew up the PWM (555 and some transistors, the 807 mod tube lived), I did not get good results re; mod % with the 555 anyway, and gave up.

I was shown a 5K Collins BC TX and the engineer said it was a series PWM, I think 3CX2500's? - so nutty me I had to try it at home. Never mind - use what others say works!

That sounds like an expensive ouch!
I love challenges. I just took a 68 year old Collins ART-13 and restored it to great working condition. This includes building a kick ass power supply that matches the period styling but with modern components mixed with old school circuit topology. It was an epic journey and might make the pages of ER soon. The thrill of bringing that transmitter on air for the first time was a treat that money cannot buy although I spent quite a lot on the project, Hi! This got me into the idea of building a transmitter from the ground up, one that I could be proud of and never regret the choice of platform and performance. I think it's a good plan to ask other's for opinions because once you start on something like this, there is no turning back, at least for me. I want to make sure I am embarking on the "Right Stuff". I have built plenty of guitar amplifiers to know that planning is essential for optimal results. Nothing is more frustrating than wasting time... you never get that back folks, the meter is still running. You get my drift.
Thanks for all of the kind suggestions so far.