[AMPS] Help building mono band amp

wlfuqu00@uky.edu Wlfuqu00@uky.edu
Fri, 12 Oct 2001 08:26:40 -0400

    Why not start with a pair of 4-125A's in grounded grid...
They will give you the same output as a pair of 813's and 3KV plate voltage
is within their spec.
Later by simply beefing up the plate supply and filament transformer and
choke you can
upgrade to 4-250A or 4-400A or 3-500Z with out changing sockets. You will
probably be content with
a pair of 4-125A's for some time.  Also, don't forget to make a window so
you can enjoy the red glow of you
         4-125's are cheap because very few people use them and you are
more likely to get
new ones than the 813's. Many of the 813's I have gotten at hamfest were
abused and usually low on emission.
Hams used to push them hard since they were cheap in the 50's and 60's

Bill wa4lav

At 09:37 PM 10/10/01 -0700, Geo Clute W7LFD wrote:

> >-----Original Message-----
> >From: owner-amps@contesting.com [mailto:owner-amps@contesting.com]On
> >Behalf Of Mike Baker
> >Sent: Wednesday, October 10, 2001 10:37 AM
> >To: AMPS REFLECTOR; Jean-Michel Bombar
> >Subject: Re: [AMPS] Help building mono band amp
>  For any band up to 20 meters they kick butt and love high voltage.
>The 813's typical operation is to 30 MHz. I ran a pair on 10 meters
>with 3350VDC on the plates.
>Drove them with a Swan 500cx until the carbon plates many red
>hues...Couldn't burn them out.
>1983 "The Radio Amateur's Handbook"
>Freq.: 30 Mc.
>Plate V. 2500
>Plate MA 125
>Screen ma. 20
>fil 10v 5A
>Screen Volts 800
>Cin PF 16.3
>C gp PF .025
>C out PF 14
>Typical output AB2 two tubes is 650 W
>Geo W7LFD
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