[Amps] SB-200 Problem

[Richard]

>Rich said;
>
>>EUR  no RF input is needed when it makes its own.
>
>I would be inclined to do the first sets of tests with a 50 ohm load on the
>output, and the transceiver connected to the input (transceiver in 
>transmit, but
>delivering NO power). That way, the amp is seeing something like reality 
>as far as source and load impedances are concerned. When it's stable that 
way, 
>you can try the 'no input - no output load' - it ought to be stable like 
that.  

€  the sticky wicket is that the c. 100MHz energy never sees the 50‡ load 
because the tank is a low-pass filter config.

>572Bs aren't the easiest of bottles to tame as far as parasitics go - the 
internal
>structure has a lot of inductance, 

€  amen 

>and if new ones have a bit higher gain, it
>could easily tip the balance. I suspect that the amount of suppression
>inductance needed ends up being such that of necessity, a fair amount of 
>power will get dumped in the suppression resistors. This means that 10metre 
>efficiency will be down, although the suppressors will help keep the room 
warm.......
>
€  However, the loss of a couple of percent of P on 29MHz is probably not 
going to be noticed on the Rx end. 

>I believe that 572Bs were originally intended as Class B zero bias (or nearly
>so) AF power tubes for AM modulators.
>
€  So it seems.
cheers, Peter

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
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