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Re: [Amps] Drake amplifier

To: <>
Subject: Re: [Amps] Drake amplifier
From: "Roger" <>
Date: Mon, 23 Jul 2007 15:59:48 -0400
List-post: <>

> 1KW input on CW, 2KW PEP on SSB was the FCC reg back then. For that reason

Maybe a slight technicality, but the power limit was "1 KW AVERAGE dc input 
measured using a current meter with a 1/4 aecond time constant. There was 
only one limit, not seperate ones for CW and SSB. In grounded grid you were 
supposed to add the exciter input to the amp input when figuring the legal 

PEP varied widely on input and output due to voice characteristcs.  On the 
two "legal limit" amps I ran back then I consistently ran 2 KW PEP "output"

> many amps of that era had a CW/SSB plate voltage switch. Many left it in 
> the
> SSB position irregardless of the mode (;  No sense in throwing away 3dB in 
> a
> pileup.

The CW position was also a tune-up position that allowed tuning for tilt, 
then switching to SSB with a higher plate voltage and not having to retune. 
Actually many of the amps used voltage doublers and if you tuned up in the 
SSB position it'd drag the voltage down to the point they'd be mistuned 
running SSB. My old Alpha 76A has a heavy enough power supply but the manual 
still has you tune in the CW position to prevent over heating the tubes.


Roger (K8RI)
> Carl
> KM1H
> ----- Original Message ----- 
> From: <>
> To: <>; <>
> Sent: Monday, July 23, 2007 12:33 PM
> Subject: Re: [Amps] Drake amplifier
>> In a message dated 7/23/2007 12:21:44 P.M. Eastern Daylight Time,
>> writes:
>> 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
>> exactly.
>> 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.
>> Thanks
>> Gary   K4FMX
>> Hi Gary, Yup, that is about right 110-1200 watts out with around 100 
>> watts
>> of drive.  If you have a look at an AL-82, it will do about 1600 watts 
>> out
>> with 100 watts in.  The difference is in the fact that the Ameritron 
>> AL-82
>> runs
>> the anode at about 3600-3700 volts.  The extra plate voltage really 
>> makes
>> the
>> 3-500Z's play great.  The "HOT" set up for the Drake L4 or L7  would be 
>> to
>> build up a better HV supply.  The Drake tank circuit can take  4KV no
>> problem.
>> But what you are seeing now is right on the money.   You have to remember
>> that
>> when the L4/L7 were made, the maximum power  permissible by the FCC was
>> ONE
>> KILOWATT DC INPUT.  That being so, the amp  companies did not run a pair
>> of
>> 3-500's to their full potential so they got by  with wimpy power 
>> supplies.
>> Put a
>> good power supply on an L4 and it will  perform nicely.  Easy legal limit
>> amp
>> plus.  Oddly, the Drake RF deck  makes a great conversion to an 8877 and
>> handles the 2KW easily.
>> 73 Lou
>> ************************************** Get a sneak peek of the all-new 
>> AOL
>> at
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