>Rich said:
>
>>Why did the tetrode amplifiers that I built become less linear with grid
current?
>
>Did you follow all the requirements?
The requirement in the 8170 spec sheet was 0mA grid current. When I ran
grid current RF output and IMD increased.
>That includes adjusting the zero signal
>plate current to the correct value for AB2. See the reference.
>
The ZSAC was adjusted to 0.5A @8400v.
>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.
>
The person who designed Ameritrom/MFJ's sans-VHF suppressor 8877 eating
amplifier still works for the company. [see Figures 24 & 24.1 on my Web
site].
> >>>// 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.
>
For AM linar sevice, yes. For SSB linear service, no.
> >// 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.
Without a choke that is resonated with a capacitor c. 2.2x the electric
mains frequency,, there are significant output V-transients as the load
current varies.
>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.
M-i-c-k-e-y M-o-u-s-e.
>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.
Undoubtedly.
>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.
>
I have observed the output potential of such with an oscilloscope.
> >>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,
Indeed
>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.
>
agreed, Peter
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
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