[AMPS] More t'bolt questions

[2]

>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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