[BC] Re: VP-50 vapor Phase and stuff.

[Xmitters@aol.com]

In a message dated 1/2/06 5:09:48 PM Central Standard Time, 
broadcast-request at radiolists.net writes:

<< The main disadvantage at 50 kW. was there were several tubes that could 
all  
 achieve 50 kW. with air cooling.>>

True but would that necessarily make it a disadvantage? VP type cooling is 
sure quiet and if that's important, then who cares about FA cooled tubes? I'll 
be glad to get rid of my FM-25K so I can take the family sized bottle of 
Excedrin off my operating budget. I sure hate the racket 1170 Sq feet per minute can 
make :-)
  
 The main disadvantage was tube costs, system maintenance -  water, 
 condenser, piping and that all components around the tube operated  at 212 
degrees F.
  
 <<The VP100 made a little more sense and I believed the added the trapezoid  
 modulation to that box.>>

VP-100 being PDM, true.
  
<< I am certain others will chime in, what was the RF driver, was the audio 
 drive solid state or tubes?>>

Not sure which transmitter you mean, but the VP-50 used a 12AU7 for input 
audio, pushpull 8122 for the next amp and another pair of 8122 tetrodes in a 
degenerative cathode configuration to directly drive the grids of the modulator 
tubes. this is actually the circuit I'm analyzing and why I was hoping to see 
one still in existence and still working. Modulator tubes, class B, were 
3CV30,000H3 industrial oscillator tubes according to the Eimac data sheet. Although 
Eimac did have tabular parameters for using the tubes as modulators. Not a very 
common pairing for intended service; A modulator or an industrial oscillator 
:-)

BTW, you guys that have actual experience with this box, do you have any old 
notes that would show what the modulator cathode currents were under 100% 
modulation with tone? My manual only gives zero signal typical meter readings. No 
"Simpson 260 readings" at all for the low power audio circuitry, which I miss. 
I wonder if this manual I have is a prototype; installation, parts list, 
schematics and discussion of VP cooling theory. No circuit descriptions in the 
manual at all. is your manual that way?
  
 You didn't save any power,  you didn't reduce tube costs etc.
   >>