Hi Carl,
6T51's mu=48, 250TH only 38 ,450TL only 18, and 6C21 only 30.
Are your sure it duo to low mu and not exciter's problem?low mu means
high driving level,means driver 's outpu is very dirty too.
6T51 is dirty cheap now.it similar 7092 and TB5/2500,but higher mu.
Hsu
Carl <km1h@jeremy.qozzy.com> 于2020年1月25日周六 上午10:34写道：
> 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@mwt.net>
> To: "MU 4CX250B" <4cx250b@miamioh.edu>; "Yueh Hsu" <hsu4qro@gmail.com>
> Cc: "Amps" <amps@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@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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> >>> Amps@contesting.com
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> >
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> >
>
>
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