[Amps] 3CX1500A7/8877

[Jeff Blaine]

Bill,

Curious:  Was that a tuned input or a swamped resistive type?

73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie

-----Original Message----- 
From: Bill, W6WRT
Sent: Monday, July 30, 2012 2:24 PM
To: AMPS
Subject: Re: [Amps] 3CX1500A7/8877

ORIGINAL MESSAGE:
On Mon, 30 Jul 2012 08:03:41 +0300, Alex wrote:

>Russian GS35b triode is close to 8877 and works up to 1000MHz and able
>to  run 1.5kW easy with 3kV plate voltage.

REPLY:
GS35b's work but they are relatively inefficient, IMO. I built an amp and
swapped between a GS35b and an 8877. In order to get 1500 watts of carrier 
out
of the GS35b, I had to drive it till the DC input was 3000 watts, an 
efficiency
of 50%

I then changed the socket and filament voltage and put in an 8877. Now to 
get
out 1500 watts, I only had to drive it till the DC input was 2500 watts, an
efficiency of 60%. And the drive power required dropped from about 85 watts 
down
to about 45.

In both cases, I used two different tubes, all four were brand new.

One other European ham confirmed he had about the same results.

You pays your money and you takes your choice.

73, Bill W6WRT
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