[Amps] QRO 2500DX MARK lll 4CX800

[Jim Thomson]

Subject: RE: [Amps] QRO 2500DX MARK lll 4CX800


<Of course any of these amps when married up with a modern SDR exciter
<running Pure Signal IMD cancellation feedback produce truly 
state-of-the-art
<performance.

<In the Tx tetrode tube space today there are very few choices to be 
had.....

<Leigh
<VK5KLT

##  The only modern  SDR  xcvr   for sale on the market right now, 
with...Pure signal... is the  ANAN   7000  + 8000  xcvrs,
which,imo, are not ready for prime time.  Esp judging by the  37 K postings 
of various issues..on their yahoo group, that I belong to.
Pure signal will really take ahold when  Icom, Yaesu, Kenwood   start using 
it in their future products.

##  Heres  my take on tubes Leigh.   Why mess  with a tetrode in the  1st 
place ?    Tetrodes offer  ZERO
advantages  over a   high mu  GG triode.   Heck, you dont require a socket 
on  some  triodes,  nor regulated screen  supplies,  regulated
bias supplies, screen and  anode current protection,  +  compensation on the 
input for stray  tube C,  + neutralization etc, etc.

##  A  dead simple,  single chinese  8877   GG  triode amp makes more sense. 
2 x  3-500Z is also dead simple..and instant on, no grid current
protection required..perhaps a simple  fast  3agc  grid fuse  at most.

##  From a HB perspective, why bother with a complicated  mess, like the typ 
tetrode ?   A  simple  3CX-3000F7 requires no socket,  instant on,
rebuildable,  5-8 kw pep out..or  CCS cxr,  and  -59db  IMD-3.   Most hams 
will die before the tube  does.   Moot point, cuz your kids can have it 
rebuilt,
use it..then  pass it on to their kids.

Jim   VE7RF