[AMPS] parasitic suppressors

[Jon Ogden]

>€  With the tube not in a state of regeneration, a spectrum analyzer can 
>see trains of damped vhf waves coming from the anode-resonant circuit.   
>The only requisite is that DC current transients be passing through the 
>resonant circuit.  The same phenomenon can be simulated on the workbench 
>with a vibroplex key, a vhf resonant circuit, a resistor and a LV source. 

Hey Rich, do you have any plots from the spectrum analyzer of this?  I don't doubt you, it would just be interesting to see.  And you can satisfy a lot of curious on lookers by posting something like this to your website.

>  
>
>> Nor in the ARRL lab reports published in QST. 
>
>€  The ARRL Lab tech. who tested the Ameritron AL-1200 told me that he 
>observed intermittent tank spitting that he suspected was caused by an 
>intermittent parasite.  This information was not published in QST.

To me, he term "intermittent" parasitic oscillation says that the gain and phase margins of the amplifier are right on the border line.  Perhaps some thermal noise and temperature or input signal conditions are enough to start the amp oscillating, some aren't.  What I don't like is this idea that there are parasites hiding somewhere in a tank circuit waiting to jump out when you least expect them.  I would call this a conditionally stable amplifier.  Fixing an amp on the edge of stability is quite possibly easier than fixing one that is horribly unstable.

73,

Jon
KE9NA
 


--------------------------------------------------------------------------
Jon Ogden

jono@enteract.com
www.qsl.net/ke9na

"A life lived in fear is a life half lived."


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