Not necessarily. Altho the average rice box has far worse IMD than say a
SB-220 it is far less tolerant of reflections from the amp which further
aggravate the IMD.
A pair of 3-500Z's can easily handle 150W of drive but in a SB-220 that
would result in severe PS regulation problems. Even at 100W drive and a full
on compressor the PS is up against the wall and even a slight gain reduction
is a benefit.
Carl
KM1H
----- Original Message -----
From: "Joe Subich, W4TV" <lists@subich.com>
To: "'Jack Shirley'" <jcshirle@gmail.com>; <amps@contesting.com>
Sent: Friday, July 31, 2009 2:05 AM
Subject: Re: [Amps] grounding grids
>
>> This was done to match the output power of the TR-3 and TR-4.
>
> This would also indicate a value to removing the negative feedback
> circuit with modern 100 Watt output solid state transceivers. With
> their three finals, the TR-3 and TR-4 were capable of 150+ watts
> output and the L4/L4B were designed when 1000 Watts plate input was
> the rule.
>
> 73,
>
> ... Joe, W4TV
>
>
>
>> -----Original Message-----
>> From: amps-bounces@contesting.com
>> [mailto:amps-bounces@contesting.com] On Behalf Of Jack Shirley
>> Sent: Thursday, July 30, 2009 11:00 PM
>> To: Thomas Carlsson
>> Cc: amps@contesting.com
>> Subject: Re: [Amps] grounding grids
>>
>>
>> The answer is:
>>
>> to provide -2db negative feedback. This was done to match the
>> output power of the TR-3 and TR-4.
>>
>> Also of note; it was the first 3-400/500 amp to have tuned
>> input circuits,
>>
>> The output circuit was designed to match a 2 : 1 SWR at all
>> impedance's and phase angles.
>>
>> He also designed the MN-2000 which will match a 5 : 1 SWR at
>> all impedance's/phase angles.
>>
>> At one time they were getting L-4s in for service which had
>> the pi wound grid chokes where the windings were " slammed
>> together" .. This was from plasma arcs inside the tube going
>> thru the grid. He called EIMAC about this and they said when
>> the 3-500z are being vacuumed sealed, they put high voltage
>> on all the terminals to burn off the metal whiskers which
>> form during the process. Eimac said " guess we will have to
>> let them burn off longer " . After that the problem went away.
>>
>> The cost of a 3-500 was 24.50 then.
>>
>> Any other questions?
>>
>> 73 Jack N8DX
>>
>> On Thu, Jul 30, 2009 at 10:00 PM, Thomas Carlsson
>> <thomascarl@gmail.com>wrote:
>>
>> > Interesting addition: LK-500 and its brothers have Grids direct to
>> > Ground, no components. Cathode resistor only 0.15ohm/3W. SB220 and
>> > L4(B) both 1ohm in cathode and they have the same grid
>> components, on
>> > schematics I have the RFC and C's are copies of each other. 73,
>> > Thomas, PY2ZXU/SM0CXU
>> >
>> >
>> > On Thu, Jul 30, 2009 at 8:25 PM, Jack Shirley <jcshirle@gmail.com>
>> > wrote:
>> >
>> >> I looked at the various 3-400 and 3-500 circuits in the
>> Eimac Amateur
>> >> Service Newsletters and did not find this mentioned anywhere.
>> >>
>> >> If the SB-220 and L4 use the same grid circuit, I could ask the
>> >> engineer who designed the Drake L-4 as I know him personally. Any
>> >> interest?
>> >>
>> >> 73 Jack N8DX
>> >> On Thu, Jul 30, 2009 at 6:48 PM, Ward Silver <hwardsil@gmail.com>
>> >> wrote:
>> >>
>> >> > > perhaps somebody with an SB-220 and a spectrum
>> analyzer needs to
>> >> > > do an IMD profile using each grid circuit and SEE which one
>> >> > > produces the cleaner output.
>> >> >
>> >> > What?! And ruin a perfectly good thread?
>> >> >
>> >> > 73, Ward N0AX
>> >> >
>> >> > _______________________________________________
>> >> > Amps mailing list
>> >> > Amps@contesting.com
>> >> > http://lists.contesting.com/mailman/listinfo/amps
>> >> >
>> >> _______________________________________________
>> >> Amps mailing list
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>> >>
>> >
>> >
>> >
>> > --
>> > Thomas, PY2ZXU/SM0CXU
>> > Member of the PW2D Team
>> >
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>
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