Date: Fri, 12 Nov 2010 22:27:09 -0500
From: "Roger (sub1)" <sub1@rogerhalstead.com>
Subject: Re: [Amps] 2010 ARRL Handbook
On 11/12/2010 9:49 PM, Carl wrote:
> Is the D7 amp the same one that was in a few years ago and got pulled
> when the tube was NLA?
## Correct. Same one as in my 2006 book. It also uses the non existent
LGC auto tuner board as a 'tuned input'.
Now that its available again, at $1200, what
> is the purpose except as a showcase for the author?
## I paid $1100.00 for my new Eimac YC-243, which is the socketless
version of a 3CX-6000A7. I paid $1200.00 for a 2nd one. Rebuildable
till hell freezes over. I paid $650.00 for a new Svetlana 3CX-3000A7....and
$500.00 for a 2nd new one.
If I follow all of it, the D7 is quite different than the 8877. It uses
the same socket as the 3-500Z, has a 5V Thoriated Tungsten filament at
30 A. Same voltage and current as a pair of 3-500Zs and was designed to
replace a pair of them. Except for price I'd pick one over the 8877.
70 watts of drive gives about 2 KW out with 930 watts of plate
dissipation. Oh! The grid dissipation is 50 watts. 3rd order are -29
and -34 dB at 3 and 4.5 KV respectively 5th order are -43 and -37
respectively.
## 50 w of drive = 1.5 kw out on a 3x3 or 3x6. 100w of drive = 2.5 kw
150w of drive = 3.5 kw. 200w of drive = 5.2 kw...[that's all at 4.8 kv].
600-700 w of drive = 12 kw out, on a 3x6. [6.5 kv]. Imd on a 3x3 is -59db
pep for
3rd order imd @ 5.2 kw pep out. The imd, when run at 1.5-2.0 kw out is even
better.
That makes it the cleanest GG triode, period..limited only by the xcvr's imd.
Grid diss is 225 w CCS... and way more, when the grid flange/grid ring is
bolted
directly to the ice cold chassis. You can use the grid as a dummy load for your
FT-1000-D. Both tubes have a 50 ohm input Z. A simple 3agc fast grid fuse is
all
that is required for grid protection.
## Even Henry Radio said a new 3x3 is only $50.00 more than a new 8877.
The 8877 is a 'throwaway' tube. The 3CX-1500D7 might be a good tube, but
for $1200.00 ....and being yet another throwaway tube, I'd say it's not
exactly a
good bang for the buck. <4 kv, the smaller tubes have the advantage being able
to use
a vac cap for the tune control. But even that is questionable, since air caps
up to 9 kv
[1/4" spacing] are readily available].
## IMO, when u start spending $1200.00 for a tube, at least get a real one,
regardless
of power level.
Jim VE7RF
OTOH "Typical operation" under 30 MHz is 5 kVdc on the plate, 0.710 A
anode current, where 95 watts of drive gives 2400 watts out with 1220
Watts dissipation at 3760 Ohms load impedance.
However the max ratings are for 100 MHz unlike the 8877 which will
easily go to 2-meters IIRC.
CPI has the data sheets in pdf.
73
Roger (K8RI)
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