The 3CX3000A7 (and the descendant 3CX6000A7) can't give 2A plate with 100W
drive, but perfectly deliver >2KW out with 100W in and 6.7 Kv plate.
At 100W drive its gain is typically 13dB in Gg.
No way less power than 2KW if tube is OK and PI tank well designed.
73,
Mauri I4JMY
----- Original Message -----
From: "Bob Marston" <k1ta@contesting.com>
To: "G SEVEN" <superiorwavelength@prodigy.net>
Cc: "AMPS" <amps@contesting.com>
Sent: Sunday, March 11, 2001 4:49 PM
Subject: Re: [AMPS] 3CX3000A7
>
> GSeven wrote:
>
> > I thought it would tune around at least 25pf bit its back all the way
out.
> > What should I expect to see with say 100 watts provided the tank is
right?
>
> Answer Not much The 3CX-3000A7 is notorius as being a Pig to drive. The
> spec sheet states that 410 watts is required to drive it to 2.0 Amps of
> plate current. With 100 watts don't expect much more than 500 mils of
plate
> current with the tube biased correctly.
>
> As to 10 meters not tuning that is also predictable. The 3000 has an
> inordinately high output capacitance. 38pf Compare this to the 8877 and
> 4CX-1500A which each have values of 10 pf and its understandable that you
> are not able to tune 10 meters.
>
> Finally the plate voltage that you state you are using (6700 volts) is a
> full 33% over the manufacturers Maximum recommended Plate Voltage of 5000
> Volts. BE CAREFUL !
>
> It appears that Eimac intentionally developed this tune with the objective
> of keeping it out of the hands of Hams and CBers. My recomendations, if
you
> have this Amp running on all bands but 10 declare victory and leave it
> alone. Drop the Plate Supply to 5000 volts and limit the service of this
> amp to 14 Mhz and below.
>
> 73s
>
> Bob K1TA
>
>
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