For 10kW PEP out, 600 volts peak to peak on the grid in AB1. At 30 MHz, that's
4.7 Amps of RF into the input capacity!
73
Peter G3RZP
========================================
Message Received: Nov 15 2013, 02:44 PM
From: donroden@hiwaay.net
To: "Amps" <amps@contesting.com>
Cc:
Subject: Re: [Amps] Passive grid stability calculation for a tetrode?
How much grid voltage swing for AB1 ?
( how many watts into a 50 ohm load )
Don W4DNR
Quoting Carl <km1h@jeremy.mv.com>:
> Even CBers can build stable grid driven 4X5's! It is a very hard
> tube to make oscillate.
>
> The SK300A socket requires good screen bypassing for RF.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "peter chadwick" <g8on@fsmail.net>
> To: "Markku Oksanen" <ww1c@outlook.com>; "Amps" <amps@contesting.com>
> Sent: Friday, November 15, 2013 5:44 AM
> Subject: Re: [Amps] Passive grid stability calculation for a tetrode?
>
>
>> Markku,
>>
>> It may be shown that (i.e. as the books say, it is left as an
>> exercise for the reader!) if you have H<2 as a result of solving
>> the equation H=gwCpgRpRg where g is the mutual conductance, w = 2
>> times pi times frequency, Cpg is the pate - grid capacitance, Rp is
>> the plate load resistance and Rg is the grid resistance, the stage
>> is stable. Arguably Rp should be the plate load resistance in
>> parallel with AC plate resistance of the tube, but sticking to the
>> load resistance gives a bit more stability.
>>
>> vy 73
>>
>>
>> Peter G3RZP
>>
>>
>> ========================================
>> Message Received: Nov 15 2013, 07:32 AM
>> From: "Markku Oksanen" <ww1c@outlook.com>
>> To: "Amps" <amps@contesting.com>
>> Cc:
>> Subject: [Amps] Passive grid stability calculation for a tetrode?
>>
>> All
>> I am back on my 4CX5000 project and as it not done yet, I am still
>> contemplating the circuit to be used.Earlier this year I got solid
>> info from this reflector for GG operation and that look like a
>> pretty good solution.However, I was wondering about passive grid,
>> grid driven also.
>> The question is: How do a calculate the stability? If I simply do
>> math for tube voltage gain I get something like 25.Then if I
>> calculate the feedback capacitive voltage divider, Grid to Cathode
>> 120 pf, Plate to Grid 0.7 pf, I get less than 0.01 for the ratio.
>> If the beast needs the voltage gain times feedback gain to be above
>> 1 to oscillate, to me it seems this tube is stable no matter what.
>> Where did I err if I did?
>> Thanks!
>> MarkkuWW1C
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 10.0.1432 / Virus Database: 3222/6338 - Release Date: 11/15/13
>>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|