Rich said:
>Why did the tetrode amplifiers that I built become less linear with grid
current?
Did you follow all the requirements? That includes adjusting the zero signal
plate current to the correct value for AB2. See the reference.
I tend to believe guys who have designed large numbers of amplifiers to meet
definite commercial specification requirements: thay tend to have a history of
either getting it right or starving.
>>>// A swinging choke filter produces constant V-out Only when the
load
>>>current is constant.
>>
>>In that case, you could use a resistor.
>// 0.01-ohm should do it - provided it's in parallel with the choke
Your comment was that "A swinging choke filter produces constant V-out
Only when the load current is constant.".
If the load is constant, so is the current. So there's no variation anyway.
Which is why you can use a resistor.
>// So Continental, Harris, Hughes, Henry Radio, and Collins made a
>mistake when they utilized a resonant-chke filter in their anode
supply?
Of course not. The advantage of a tuned choke is that you can make a small choke
look like a very much bigger inductance. If you actually resonate it, you can
get enormous voltages, as Tom Rauch has told us he found the hard way.
Incidentally, if you negative lead filter with a tuned choke, you can rectify
the volts across the choke to provide a bias supply. In this Tbolt case, finding
room to add a suitable capacitor to tune the choke at low currents could well be
a problem, and a swinging choke isn't ideal for tuned choke applications anyway.
Don't forget that the choke input filter relies on the choke having more than
the critical inductance to maintain constant current through the choke
throughout the cycle. As the current increases, the critical inductance
decreases.
>>the choke serves the purpose of dropping the
>>volts without screwing up the regulation in the way a resistor would.
the idea is that a 4800 volt centre tapped transformer bridge rectified with a
capacitor load will give 7200 volts. With a choke input filter, it will give,
provided that the choke inductance exceeds the critical value, about .8 times
4800 or about 3840 volts, which is acceptable for the 4-400s. (Might offer a
problem for plate tuning caps - was the Tbolt plate modulated?)
> Rich has called me a liar
>// Quote please
Alright, intimated, rather than called outright. That was 13 June 1997 - no I
haven't remembered the date, I looked up the archive. This was during the same
old discussion on AB2 amplifiers. (Shortly followed by a similar debate on tuned
chokes in power supplies)
>>The G2DAF was not Class C.
>// The three I was familar with were seemingly Class C. One of them
was
> pretty close to Class D. (the one that could be heard for 150kHz on 75m)
>
Actually, once you've got in to Class C and hard clipping, you won't get it any
worse, but I know what you mean. See the report by George and Wood, Ideal
Limiting, Part 1, Washington D.C., U.S. Naval Research Lab, AD266069, October 2,
1961 for an analysis of limiting on multi frequency signals.
We've been through all these arguments before. I doubt it's worth doing it
again.
73
Peter G3RZP
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