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Re: [Amps] Drake amplifier

To: Gary Schafer <>,
Subject: Re: [Amps] Drake amplifier
From: Steve Katz <>
Date: Mon, 23 Jul 2007 09:11:57 -0700
List-post: <>
The low output is attributable to the low plate voltage.  3-500Zs are rated
400mA Ip per tube.  A pair of them at 2450V (* 800mA) = 1960W input power.
At 60% efficiency, which is about as high as it can possibly be, output
should be 1960*.6 = 1176W.

But methinks that Ep is on the low side.  I don't have an L-7, but could
swear the L-4B Ep was more like 2.7 kV key-down...might be related to line
voltage and which transformer tap you're using.


-----Original Message-----
From: Gary Schafer [] 
Sent: Monday, July 23, 2007 9:21 AM
Subject: [Amps] Drake amplifier

I have a drake L7 amp.
How much power out do you typically get from a drake L4 or L7 amp? I have 95
watts drive and get just short of 1100 watts on 40 meters.

The amp's wattmeter and a bird wattmeter with a brand new slug agree almost

This seems a little low or is that about all that can be expected from the
3-500Z's. They run at 2450 volts on the plates and 230 ma grid current.

Gary  K4FMX

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