You know, I ran a pair of 250THs grounded grid back in the 60's driven
by
a pair of 6146Bs at 1kW plate input power.
That was before I knew that you could not do it. I wonder if it I could
do
it again knowing it will not work. Hi Hi they have a mu of 37.
In one of the Radio Handbooks by Bill Orr, there is an example of a GG
304TL. It did require 200 Watts drive
for 900 Watts output, but back then the tubes were very cheap.
But as far as the 833, I see no advantage of running them in GG due to
the grid plate capacitance. Either a single or
two in push pull would be better. I am not aware of any hams getting good
results on 10 meters however. Some have been
built for 80-20 meters but the output drops a bit on 20.
73
Bill wa4lav
________________________________________
From: Amps [amps-bounces@contesting.com] on behalf of Hsu
[hsu4qro@gmail.com]
Sent: Monday, January 26, 2015 5:44 AM
To: Mike Waters
Cc: amps@contesting.com
Subject: Re: [Amps] 833A GG
Hi Mike, Thanks for your very good and useful information.
Yes, you are right.I'll not think off this tube.
833C's manufacturer nearby my home( 300 mtrs apart!)
They made 3-500Z too, in past two years, Almost all over the world
3-500C
from this manufacturer.There is a version of rugged 833C, anode diss. and
filament current increase 30%-35% , they renamed it FU-501
http://hgdzg.com/a/english/Products/blg1/2014/0614/121.html,
There is a more powerful triode FU-605, same as Jananese 6T51
,http://hgdzg.com/a/english/Products/blg1/2014/0613/118.html
the amplification facturer is 48,maybe it is suitable for GG ,its anode
diss is 800W.
anode to filament capacitance is 0.21p, maybe this tube is better?
73!Hsu
-----原始邮件-----
From: Mike Waters
Sent: Monday, January 26, 2015 5:01 PM
To: amps@contesting.com
Subject: Re: [Amps] 833A GG
Not recommended for GG on ANY band.. Not enough gain, for one thing; it
would take several hundred watts of drive power to obtain the legal
limit.
Another issue is that the feedback capacitance is quite high.
Some tube data sheets I've seen imply that it can be used above 10
meters.
However, you'd almost certainly have to run two in P-P, beside using
neutralization, not to mention careful attention to every last detail
such
as layout.
Now, I do know of a guy that did build a working GG 833 amp, but it was a
monoband (75m) amp. His 833 amp used a tuned input and required 600 watts
of drive power, IIRC. But it could put out more than the legal limit,
even
by today's standards. I forget whether he used one or two tubes. I forget
his call, but he used to hang out on 3895 in years past. The last I knew,
he (Frank?) listens a lot on 3890 or 3892 at night.
I built a homebrew legal limit amp using two 833Cs in parallel,
swamped-grid-driven. I've used it successfully on 160, 80, and 40.
However,
it's kind of touchy on 40; the grid impedance drops too low there, for
one
thing (one sign that it needs neutralizing). It's kind of a work in
progress, but it works perfect on 80 and 160. Future plans are to
neutralize it with a tertiary winding in the broadband input matching
transformer connected to the plates through a HV neut cap, and eventually
see if it'll play on 20m.
Details and photos of the 833C amp are on www.w0btu.com if you're
interested.
The graphite plate version of the 833A is actually an 833C, BTW.
73, Mike
www.w0btu.com
From: Hsu <hsu4qro@gmail.com>
To: <amps@contesting.com>
Date: Mon, 26 Jan 2015 14:13:55 +0800
Subject: [Amps] 833A GG
Anyone have experience about 833 works on GG configurtion?Is it can
work
10 mtrs?I just contact with the manufacturer, the factory new tube
graphite
anode,only $50/ea, ,dirt cheap
Hsu
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