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SWEEP TUBE DATA SHEET QUESTIONS

Stellasstillarat

Stellasstillarat

Active Member
Aug 14, 2014
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I'm trying to uderstand if sweep tube data sheet dissipation ratings, that I'm assuming were created many yesrs ago and mostly for the television industry reliable when the tube is being used in a transmitting application?

Or does that 40 watt rating change + / - when the tube is not being used for it's intended use and used for transmitting?
 

Ratings are ratings. Sweep tubes are generally run at anything other than rated specs and their life span reflects that. Sweep tubes were meant as the amplifier in the horizontal deflection amplifier in televisions and were found to be useful at RF frequencies and were much cheaper than regular RF tubes hence the popularity of them. They tend to be rugged and will take short overload conditions for brief periods hence the proliferation of them in 11m amps. Cheap and plentiful meant profits. Today they are scarce and expensive so treat any sweep tubes nicely lest they go bye-bye.
 
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Sweep tubes were never designed to 'amplify' RF, never were.

Go from there, go solid state
 
space cowboy said:
I know el519's are rated for 35 watts, but can put out L/H 200/400 when transmitting.
Click to expand...


What they CAN put out and what they SHOULD put out are two different things. An EL519 at 2-400 watts out apiece are simply screaming. An 811A with 65 watts plate dissipation is screaming at that output level. Ameritron runs four 811A's in their AL-811H and is rated at 800 watts pep. Even the amplifier designer admits the tubes are running well beyond what they should be at that level.
 
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space cowboy said:
oops.
those are wattages for the amp, not the tube. cut the wattage I posted in half. so only 100w peak on low per tube.
Click to expand...

In that case they are being run about the same on LOW as the 811A is in the Ameritron AL-811H, at about three times output as the plate dissipation rating is. The Ameritron amp designer still says this is running outside the design limits of the tube.
 
Interesting read "Some thoughts on sweep tubes" contained in your link Space Cowboy that I have read previously. Thank you.

I am not a fan of sweep tubes in linear PA service due to the potential for higher IMD (distortion) yet I am somewhat hypocritical in that I own a few Yaesu FT101's that have them in there. I understand that many folks have there first exposure to RF amplifiers with sweep tubes due to the shear quantity of those boxes still out there, so I don't want to dis them entirely.

That being said, I will never run an amp that has them... as I have seen the light brothers and sisters... on my portable spectrum analyzer... when I visit folks that run those jagged splatter sweep tube distortion boxes...Amen :notworthy:
 
One of the big problems is that most people run the piss out of their sweep tube amps and IMD goes completely out the window. That same amp run in a more sane fashion will have much better IMD figures, not real great mind you, but much better. Of course the same can be said for all types of amps however the sweep tube amps have relatively poor IMD figures to begin with. This leads to the next problem which is that most operators don't have a clue what IMD is and even when they do find out they take on a "Well it doesn't affect me so WTF"attitude.
 

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