You have to explain what you mean Robert. I have not been on this reflector
long enough to know what you fellows have been discussing earlier. Hej de
Hans SM5KI
>Från: "Robert Kirkland" <w5pvr@earthlink.net>
>Till: <amps@contesting.com>
>Ämne: Re: SV:SV:SV: [AMPS] Tetrode Amp Help
>Datum: ons 15 dec 1999 15.26
>
>
>
>----- 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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>> >
>> >
>>
>> --
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>>
>>
>
>
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>
>
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