Date: Wed, 1 Aug 2012 19:37:39 -0500
From: Rob Atkinson <ranchorobbo@gmail.com>
Subject: Re: [Amps] The dilemma of Tx tube
The eimac triode connected g.g. cathode driven data sheet for the 4x1
has specifications for 3, 4 and 5 KV.
Rob
K5UJ
On Wed, Aug 1, 2012 at 4:07 PM, <Gudguyham@aol.com> wrote:
>
> If I am not mistaken, the 4X1 "typical" GG service is rated at 3KV. Pump
> it up with the proverbial "pole pig" power supply at 6KV and something has
> to go out of spec. Most likely IMD?
## If you looked at any Eimac catalog from the 1960-1995, you WON’T
see any GG specs for a 4-1000. I mean with screen + grid bonded to chassis,
and
run as a high MU triode. Einac did list some GG specs for hams
in the odd rag like CQ once in a while... like for 3-4-5 kv. That was just
a courtesy
thing. No ham was gonna buy a brand new Eimac 4—1000 anytime soon. For less
money,
you could buy a NEW 3-1000Z.... which IS rated for GG, and also rated up to 6
kv in GG.
## Fact is the IMD sucks on the 4-1000. A 160m, monoband single 4-1000
in GG was featured
in the ARRL handbook in the 80’s... and with just 900w pep out, the IMD was
horrible on it!
-30 db pep for IMD3. The 5-7-9-11-13 hardly drops at all on the arrl lab 2
tone test setup, as depicted
in the handbook article.
## I had several of em myself. The last one ran 4800 vdc no load, and 4400
vdc under load.
120 watts of drive and tuned input used for each band. Output was 1900 w pep.
I lucked
out, and obtained 2-3 brand new Eimac 4-1000’s. A broadcast eng buddy of mine
sent a few
my way, sealed in the box’s... and only built 2-3 months before I got em.
They were used,
4 at a time in some AM broadcast TX’s. 2 in parallel for the RF deck, and
2 more in PP, in the
modulator. That’s why you will see the odd ball fil xfmr in dahl’s
commercial catalogs.
208 or 240 vac single phase input..... and 4 x separate secondary’s, each
sec was 7.5 vac @ 21 A CCS.
## Even with only 4400 vdc on the tube under load, and brand new tube used,
the imd at 1900w
pep out was not spectacular. It didn’t help that the Drake T4XC and also
drake TR4 used to drive it
was only -30 db pep for IMD3. -24 db below one tone, typ of the sweep
tubes used by drake.
## NO tube maker will endorse tetrodes used as high mu GG triodes anyway.
In most cases, the
control grid hogs most of the .....“grid current” and the control grid diss
is exceeded.
4-1000 only has 25 w of grid diss vs the 50 w grid in the 3-1000Z
## Several folks also tried and used 4CX-5000’s in GG, with screen + grid
grnded to chassis, then
run as a GG triode. Typ was to drive it with a SB-220, in the CW position,
with 600w of drive.
7.5 kw pep out with lousy imd, but nobody cared abt imd back then in any
4-1000 amp. If you
had one... or a 2 holer, you were the kingpin in your town...and not to be
trifled with. And yes, mine
had a window in it. Local’s would stare in awe at it, running cherry red and
orange. No different
than muscle cars. Legal limit was for somebody else...still is.
Jim VE7RF
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