----- Original Message -----
From: "sm5ki" <sm5ki@algonet.se>
To: "Lamb" <k7fm@teleport.com>; "AMPS" <amps@contesting.com>
Sent: Wednesday, December 15, 1999 10:10 AM
Subject: SV: SV:SV:SV: [AMPS] Tetrode Amp Help
>
> Amen and thank you. Now lets discuss G2DAF and super cathode grounded grid
> amps.
>
> 73 de Hans SM5KI
>
> >Från: "Lamb" <k7fm@teleport.com>
> >Till: "AMPS" <amps@contesting.com>
> >Ämne: Re: SV:SV:SV: [AMPS] Tetrode Amp Help
> >Datum: ons 15 dec 1999 14.43
> >
> Oh no! Hans how could you, now this one really will stir the pot
Bob,w5pvr
> >
> >We have probably beat the screen regulation issue to death - but the very
> >nice Collins S-line and M-2 series did not use regulated screen voltage
on
> >their final 6146's.
> >
> >As a matter of fact, they were poorly regulated - but the Collins always
> >sounded superb - partly because they used rf feedback which improved the
imd
> >by 10 db and actually reduced distortion.
> >
> >Bill Orr ran an article in Ham Radio and scrutinized the 3rd order imd
of
> >the Collins. He noted that by removing the screen from the original
> >configuration of a series resistor and attaching it to the low voltage
> >supply (which had less variation), he reduced imd by a few db.
> >
> >Unless the driver transceiver uses feedback or high voltage transistors,
> >almost any amp (except a sweep tube amp) will have better imd specs than
the
> >driver - meaning the results will be irrelevant no matter how the screen
is
> >regulated if a proper tube is used. The 4CX1000 is a poor tube to use
> >without feedback. The 4CX1500 is excellent. Today, many of the high end
> >transceivers have superb 3rd
> >order imd specs, meaning that the amp is now becoming the weak link.
> >Amateurs are still way behind commercial units. The standard for ham
gear
> >is a -30 db whereas I believe most commercial equipment is a -45 db. If
you
> >listen on the ham bands, you can tell the difference.
> >
> >The bottom line is that amateurs are experimenters. Excellent tetrode
amps
> >can be made without a regulator - if the builder is prepared to test and
> >document the amp. under actual conditions of use. Without the testing,
it
> >is better to follow the lead of someone else.
> >
> >A real advantage of the screen regulator circuit is that it provides
> >absolute protection in case the plate voltage is lost for some reason. I
> >have built amps without electronic regulation on the screen that had
> >excellent imd performance - but there was no protection for loss of plate
> >voltage until I used a relay operated by the plate bleeder to give some
> >protection. However, if the rf choke had opened, I would have been in
> >trouble. There are some fine regulator circuits and boards available and
> >they are highly recommended.
> >
> >Colin K7FM
> >
> >
> >--
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> >
> >
>
> --
> FAQ on WWW: http://www.contesting.com/ampsfaq.html
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>
>
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