Back then I think very few understood what PEP was. Still today many don't.
In the 1962 (16th edition) Bill Orr radio handbook they have an 813
amplifier project article. It is described as providing "1500 watts PEP
input (750 watts single tone) with 2500 volts on the plates and 2000 watts
PEP input (1000 watts single tone) with 3000 volts on the plates". The
thinking back then was that whatever the dc input was, PEP was automatically
twice that no matter what.
We all know that a pair of 813s tuned to 1000 watts input with a single tone
is not going to provide 2000 watts PEP input.
Even in the 1977 ARRL handbook their description of PEP is a lot of mumbo
jumbo and hand waving to try and describe it and still not coming up with
the correct explanation.
But I don't remember the FCC having anything in the rules about PEP until
the rules finally changed to what they are today to specify PEP output.
Under the old rules the only definition for amateur power was 1 kw DC input
as read on the plate meters that could not have more than a .25 second time
constant. I don't remember anything prohibiting pulse tuning back then
either.
In all reality an amplifier that would run a legal 1kw input should have
been capable of at least 3 to 5 kw PEP input to avoid flat topping.
Just look at how low the plate input power is on an amp that runs 1500 PEP
output which is close to 2500 watts input. The average power as read on the
meter (without processing) is going to be quite low.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of jeremy-ca
> Sent: Monday, July 23, 2007 4:23 PM
> To: Roger; amps@contesting.com
> Subject: Re: [Amps] Drake amplifier
>
> Your slight technicality is a later revision to the regs, the FCC was
> having
> a problem defining the power so that advertising wording and tuning
> instructions didnt break rules.
>
> In 1963 1000W DC input meant exactly that. Key down, A0, steady carrier,
> however you want to define it. Pulse keying tuning was also illegal except
> into a dummy load.
>
> National was questioned about their 2KW specs by the FCC, ARRL (for ad
> purposes), and many hams. Nationals defined voltage and current in the SSB
> position easily exceeded 2KW; 2500V @400ma indicated on voice peaks since
> key down in the SSB position barely got the voltage down to 2500 @ 900ma
> and
> output was typically 1400W. They used a very healthy xfmr and a slow
> meter.
>
> National and others forced the FCC to clarify the rules. There are still
> on
> the air and Internet arguments as to what defines PEP.
>
> And then RF speech processors came along in that year such as the Comdel.
> I
> still have mine!
>
> Now they have amps advertised regularly that will do 2200-2500W out and no
> one cares any longer. How many out there drop the drive to their 8877 amp
> to
> 60-65W in order to be legal?
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Roger" <sub1@rogerhalstead.com>
> To: <amps@contesting.com>
> Sent: Monday, July 23, 2007 3:59 PM
> Subject: Re: [Amps] Drake amplifier
>
>
> >
> >
> >
> >> 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
> > limit.
> >
> > 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.
> >
> > 73
> >
> > Roger (K8RI)
> >> Carl
> >> KM1H
> >>
> >>
> >> ----- Original Message -----
> >> From: <Gudguyham@aol.com>
> >> To: <garyschafer@comcast.net>; <amps@contesting.com>
> >> 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,
> >>> garyschafer@comcast.net 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
> >>> http://discover.aol.com/memed/aolcom30tour
> >>> _______________________________________________
> >>> Amps mailing list
> >>> Amps@contesting.com
> >>> http://lists.contesting.com/mailman/listinfo/amps
> >>>
> >>
> >> _______________________________________________
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> >
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> >
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