[AMPS] Q Swing

Wed, 20 Aug 1997 22:13:54 +0000

Carl,

Your nasty index is rising, but there is one good technical point 
hidden inside:

> Maybe in your version of reality but not in the world the rest of us
> inhabit.
#One.

> As hams we are not striving for some Nirvana level of perfection nor
> interested in a constant barrage of bull. 
#Two

> Follow the classic articles and you wont go wrong. Follow the crap and
> you will wind up with a Mississippi Nightmare....or worse. 

#Three .... and then a technical point

> Tom makes a few very good points but since the average ham has no access
> to the lab test equipment it is mostly moot. 

Anyone owning  a GDO, a simple common antenna analyzer, or a 
transceiver and a low power SWR meter, and a few capacitors could 
measure the inductance with great precision.  Most Hams own 
transceivers with some sort of SWR meter, and Silver Micas are cheap.

I hardly think any of that is "lab equipment".

>A reasonable error in the L
> will make very little difference in reality. As Tom has mentioned
> recently,  a Q of 8 or 12, etc is no big deal. 
another technical point...that's two

That's right, IF 8 or 12 is high enough to match the load and source 
Z. 

If the goal is getting close to what you want, it would be MUCH 
better to calculate the values of caps. If you know that, by leaving 
the tube, choke and stuff disconnected, and putting a small silver 
mica from the tube end of the tank to the chassis and another one at 
the loading C location instead of the loading C, you can do the 
whole tank without ever having the tube filament on!!

The tank is terminated at the tube end by a small carbon or film 
resistor, of the same resistance as the estimated tube operating  
impedance. 

Then the tank can be driven from the load end with a cheapo antenna 
analyzer (or a transceiver and the inductor trimmed to perfect size, 
with all sheet metal and covers in place, starting from the lowest 
band and working up. Safe, fast, cheap, correct, accurate, and easy.

Or you could use the method requiring testing the tank with power 
on, AFTER everything is soldered in place. 

>If your variable C cant
> handle that much of a fudge factor then YOU have a problem that needs
> correcting.   
# Four.

> A select few have strived to put amp design into an arena reserved for
> the self annointed gods.  
#Five

> And learn to seperate the chaff from the chiff...or is it the other way
> around?
#Six.

In the middle of all the unnecessary nastiness, there was still two 
areas where something can be learned. Nastindex of  6 over 2...or 
three. ;-)

73 Tom

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