[Amps] anyone build an amplifier use 6T51 glass buble?

[Carl]

Good for AM, CW, RTTY and FT8, horrible for SSB due to low amplification 
factor, heavy drive requirement and horrible IMD

It  would be like using a 5867 or 5868 in place of a 3-500Z and 3-1000Z.
It is strictly a ISM tube..

About 10 years ago I removed a PP 250TH AM RF deck and installed PP 6C21's 
running as 450TL's.

The 250TH's were converted first to grid driven linear config and next to 
GG. I used 40M only, the original grid coil and a HB input network for GG. 
The bias supply was regulated and adjustable. HV was varied from 2000-3000V

In all Class B GG tests the drive needed was higher than my TS-940 could 
produce so that was cranked down and into a SB-200 I had kicking around.

IMD in all cases was horrible at anywhere near the 600W output level, 
around -18-20dB 3rd real IMD as per the commercial/military way of testing 
and not the silly ARRL method.

At about 400W out and in AB1 they looked decent and  in the -25 to -28dB 
range. They simply did not like grid current.
Maybe at 4000V (within ratings) it may have been better but I did not have 
that PS in the small test rack.

In Class C 1500W CW or AM carrier (pushing it a bit hard with modulation at 
~3500W PEP but wanted to confirm full emission tubes) was easily attained.

I built my first PP 250TH amp at 17 while in HS using military surplus thru 
the MARS program plus roaming the shops in NYC Radio Row on Saturdays. It 
was a short drive from LI.

Carl
Ham since 1955


----- Original Message ----- 
From: "Joe" <nss at mwt.net>
To: "MU 4CX250B" <4cx250b at miamioh.edu>; "Yueh Hsu" <hsu4qro at gmail.com>
Cc: "Amps" <amps at contesting.com>
Sent: Sunday, January 12, 2020 1:21 AM
Subject: Re: [Amps] anyone build an amplifier use 6T51 glass buble?


>2 KW+ OUT for 100 bucks?
>
> Hmmmm?
>
> Joe WB9SBD
> Sig
> The Original Rolling Ball Clock
> Idle Tyme
> Idle-Tyme.com
> http://www.idle-tyme.com
> On 1/11/2020 9:50 PM, MU 4CX250B wrote:
>> A cool tube, Hsu, kind of a throwback to the 1960s, when homebrewers
>> were running 3-1000Zs and grounded grid 4-1000As.  This is a BIG old
>> triode that I bet is a beauty to see lighted up with that nice
>> tungsten filament and plate glowing orange.
>> 73,
>> Jim w8zr
>>
>> Sent from my iPhone
>>
>>> On Jan 11, 2020, at 7:28 PM, Yueh Hsu <hsu4qro at gmail.com> wrote:
>>>
>>>  The datasheet here http://www.boezk.com/download_en/FU6051_EN.pdf, its
>>> mu=48,not too bad. it is a cheap tube . the manufacturer's list price 
>>> only
>>> $100+....
>>>            Hsu
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