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Re: [Amps] 572B/T160L tube class C

Subject: Re: [Amps] 572B/T160L tube class C
From: Jeff Blaine <>
Date: Thu, 19 Aug 2021 21:33:09 -0500
List-post: <>
How much service do you expect from a new set of tubes?  It's one thing to know "it can do it, if I want" - but then not actually need the capability.  It's another thing if you are saying "I want to run a 572b 24/7 at full output."

About 10 years ago I was working on a SB200 which was initially setup to run RTTY.  I did quite a lot of profiling of those using the Chinese tubes of the era.  Watching very carefully to respect the Pd max of the tubes, I found a typical 25% drop in Po over about 100 hours of testing.  The testing was typically 3-15 minutes key down 100% carrier per interval.  Plus on-band rag chew, contesting & DX (this was pre FT8).

Carl is about a million times more experienced than I am but I think maybe the Pd spec vs. actual was a bit optimistic for the Chinese tubes I had because this drop off seemed excessive. However my abuse of those tubes, compared to typical ham use, was really bad.  Also the SB200 positions the tube horizontally which may be a factor as is the generally poor circulation even with my augmented cooling.

In the end, I abandoned the 572b and went with the GI7T which was an excellent performer by comparison although it required quite a lot of changes to the SB200.  Unless there is a specific reason to use the 572b, if I were building a high duty cycle amp in the future, I would probably want to use a metal/ceramic type tube instead of a glass one.

Good luck!


On 8/19/21 8:50 PM, Carl wrote:
That tube was designed for AM BCB service by Taylor but didnt catch on there or for AM hams as the T-160L in the late 50's.

It was later bought by and designated  the 572/T-160L for Unitrd Electronics alone. They couldnt keep up with demand and sold production rights to Cetron who had a much larger production facility.

UE then became the 572A and Cetron the 572B. The step top (shouldered) glass was Cetron and the round top was UE.

At some point the T-160L was dropped for both.

You may also find a 572B with the round top and the Cetron name, those were built by UE as the demand was even too much for Cetron alone at times....such as the SB-200 and the Clipperton L.

I have examples of both (no Taylor T-160L) as well as other versions including OEM named such as Dentron, Waters, plus Raytheon, GE, and several others who did not build their own.  The top shape ID's the source.

I cant remember ever seeing an actual T-160L spect sheet or the tube.

Ham since 1955

----- Original Message ----- From: "Fuqua, William L." <>
To: <>
Sent: Thursday, August 19, 2021 8:56 PM
Subject: [Amps] 572B/T160L tube class C

  I am looking for full power data for the 572B/T160L operating ICAS class-c CW and AM. The only thing I have found thus far is in an ARRL handbook, but it is obviously the 811A specs.
Not the full 160W plate dissipation specs.

Bill wa4lav

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