>
>Rich says:
>
> >? What is the Mu of the tube, Tom.
>
>The data sheet doesn't give it. It does give ra and gm, from which I work
>out
>mu = 9.
>
>I'll stick my neck out now:
>
>This is a very bad choice of tube for RF GG service. It is rated as an audio
>tube;it has four cathode pin connections and one grid pin connection, plus
>the centre spigot, so 'grounding' the grid correctly at higher frequencies
>will be difficult. It requires the grid to be floated at 100 volts or more
>negative to cathode; it has insufficient mu to be a good grounded grid
>stage, and insufficient grid dissipation capability to be run without some
>very good protection circuitry. ALC might save the grid, but will almost
>certainly lead to very bad intermodulation products, unless the grid supply
>is very 'stiff'. There are no RF ratings for this tube, and the absolute
>maximum plate voltage is 1800 volts. The listed 'output' capacity for
>grounded cathode (1pF) suggests that it could well have stability problems
>on the higher bands (21MHz and above)
>
>
>OK Rich, Tom, any comments?
>
You can't get an AB1 triode to turn on hard at zero grid-volts unless it
has a Mu of more than 4 or so.
AB1 triodes are problematic at frequencies over a few hundred kHz.
>
- later, Peter
>> ----------
>> From: Rich Measures[SMTP:measures@vc.net]
>> Sent: 27 July 1999 23:22
>> To: W8JI@contesting.com; amps; ohashi
>> Subject: Re: [AMPS] 3CX300A1 for AB1 GG
>>
>>
>>
>>
>> >
>> >> You are right if no ALC is used. My idea assumes 1-10 mA grid current
>> >> (yes, it is little bit AB2), but ALC reduces driving power from the
>> >> excitor, resulting total IMD is not so bad. Remember 6146 AB1 GC in
>> KWM-2,
>> >> same thing.
>> >
>> >First, ALC is not that fast. Most rigs can't even keep up with
>> >themselves, let alone a loop from an external PA.
>> >
>> >Second, any grid current will perturb grid voltage unless the grid
>> >comes from a supply with low esr and good dynamic regulation.
>> >
>> >Third, you are locked into cathode drive without complex circuitry.
>> >
>> ? What is the Mu of the tube, Tom.
>> >
>> >73, Tom W8JI
>> >w8ji@contesting.com
>> >
>> >--
>> >FAQ on WWW: http://www.contesting.com/ampfaq.html
>> >Submissions: amps@contesting.com
>> >Administrative requests: amps-REQUEST@contesting.com
>> >Problems: owner-amps@contesting.com
>> >Search: http://www.contesting.com/km9p/search.htm
>> >
>>
>>
>>
>> Rich...
>>
>> R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
>>
>>
>> --
>> FAQ on WWW: http://www.contesting.com/ampfaq.html
>> Submissions: amps@contesting.com
>> Administrative requests: amps-REQUEST@contesting.com
>> Problems: owner-amps@contesting.com
>> Search: http://www.contesting.com/km9p/search.htm
>>
>
>--
>FAQ on WWW: http://www.contesting.com/ampfaq.html
>Submissions: amps@contesting.com
>Administrative requests: amps-REQUEST@contesting.com
>Problems: owner-amps@contesting.com
>Search: http://www.contesting.com/km9p/search.htm
>
Rich...
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
--
FAQ on WWW: http://www.contesting.com/ampfaq.html
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
Search: http://www.contesting.com/km9p/search.htm
|