[Amps] triode or tetrode

[Jim Thomson]

Date: Thu, 26 Aug 2010 06:33:06 -0700 (PDT)
From: Jim Hoge <knowkode at verizon.net>
Subject: [Amps] triode or tetrode

I am kicking around the idea of a new amp ( I want 160m capability which my 
current amp doesn't have) and have a few questions for the gurus and those that 
have theses beasts. Am I better off with a triode or tetrode based amp? Does it 
really matter? How about a one or a two holer amp? How much headroom should I 
look for in a legal limit amp? Some designs are nearly at the limit of the 
tube(s). How about auto tune capability? Do the amps that have this feature find 
the best match or will an override/manual tune do a better job? Any other 
tidbits of wisdom? 


Tnx,
Jim W5QM

      Alpha 9500 Auto-Tune
      HF Amateur Service
      1.5 kW RF Amplifier $7,950 +
      shipping and handling 
      Alpha 8410 Manual
      HF Amateur Service
      1.5 kW RF Amplifier $4,995 +
      shipping and handling 


##  how much money do you want to spend ???? 

##  A GG triode is the way to go.  Forget the 2 x holer.   If you need more HP, you don't put
2 engines under the hood of your truck.  200 w of drive into a  YC-156 will peg a 10 kw slug,
and you can get a YC-156  for  $200.00  to $300.00    200w  into a 3CX-3000A7 will peg a 
5 kw slug.  No socket, and no parasitic suppressor required for the YC-156.  Used vac caps
are cheap. A  4800 vac  10 kva  hypersil pole pig  [120 lb, 1 cubic foot]  will run a YC-156
nicely.  1/4"-3/8"-1/2" copper tubing is dirt cheap at home depot.  Gigavac G-2 vac relays
are cheap for hams.  6A10 diodes are cheap. HV 450 v lytics are cheap..esp the 2000-4000 uf
variety. 

##  You can beat Alpha, et all, at their own game, and get 6-8 X  more power to boot.   You will get
30k hrs  from a new 3CX-3000A7.  Lowest imd tube, period. [-58 db pep].  Use a PI net, with
a low tank Q..like 8-10..and it will be very broadband.    A  L-PI is used on the upper bands. 

##  You can use the 225W  CCS  grid in the 3x3  as a dummy load for your XCVR. Since the grid is
bonded to the chassis via a grid  ring, the grid diss is actually a lot higher.  A simple grid fuse + cathode
fuse provides ample protection.  A high power Glitch R + HV fuse provides the protection in the B+ portion. 

##  I use the Array Solutions wattmeter  for the hi-swr protection.  

## Then you end up with the...'real deal'.  The metering is simple.  I use  separate grid/plate current
meter's.. and ditto with B+.  You won't get this kind of satisfaction from an Alpha, or any other
amp.   Want  QRP... use a 8877, or any of the other fine tubes out there.  I end up using vac caps
either way, so it's a moot point.  Chinese 3CX-3000A7 / 3CX-6000A7's  are cheap... and will last
a lifetime.   GS35B  is a good tube too, no suppressor required either. 

##  Do you want a...'me too'  shoe box on the desk ?    There are plenty to pick from.  

Later... Jim   VE7RF