--- In ham_amplifiers@..., "Robert B. Bonner"
<rbonner@...> wrote:
Yeah Mike it does take an EGO defect of some kind to build the
heavy iron.
### ego has nothing to do with any of it. It's a case of
practicality. IF u decided to build a hb 2 x 3-500Z amp.... u
could have easily just bought a sb-220 and been done with it. IF
u decided to build a 2 x 4-1000 Amp.... u would end up with 2 x
sockets, 2 x chimnwy's , 2 x tubes, 2 x anode suppressor', 2 x fil
xfmrs... 2 x variacs [one per fil]... a big HV supply... vac tune
and vac load caps... and the same 2 x broadcast caps and tapped 4 uh
coil.. for the tuned input.
### The 4-1000 chimney's are 6" diam EACH... and gobble up a lot of
chassis space.
### My conclusion after 30 yrs is this...... if u are gonna HB an
amp... you may as well build a BIG one. Yoy are just gonna end up
using the same vac tune and vac load caps... big hv supply, etc.
The one big tube approach... means NO socket, one tube, one chimney.
one fil xfmr... etc. Simple.... uses the SAME 2 broadcast cap +
tapped coil for the tuned input set up.
### IE: you can simplify the design with just one big triode...
easy to trbl shoot too... and no need for matched tubes, etc.
### You are gonna put just as much time and effort into building a
2 x 3-500Z amp or a 2 x8877 amp.... as a 3x3 or a 3x6/YC-243.. or a
YC-156.
## The YC-156 is about as simple as it gets...... just whack a hole
in the chassis, bolt the tube in.. no parasitic suppressor.. and 10+
kw out with just 200 w of drive.
### Ego has nothin to do with it. It's just as easy to build a big
one... as a small one.... in fact easier.
### These GG triodes are pretty simple... just add fil v and plate
V... grid is chassis grnded. The plate + grid metering hasn't
changed in 50 yrs. The HV supply is simple. You want more
power... order a bigger plate xfmr. Throw in the tuned input... and
the pi net ouput.. a few t/r relays... some bias.... and all in a
box.... zero rocket science...... zero ego. You get personal
satisfaction from it. Most people will never see it... maybe hear
it... that's it.
### Better to do in now.... than wish you had done it... when ur 78
yrs old.
But what the heck, by the time my next life comes around there
probably wont be ham radio to do it again.
So we have to do it now.
### agreed. If u think 1500 w is enough.. go for it. I find it
gets boring really fast. Just copying something from the handbook
is fine for a 1st project.
### Personally.. I like the challenge of the bigger amps. You
won't find em in any handbook either. Just developing some
techniques along the way is fun enough... like fully adjustable
bias. On a 2 x 4-1000 amp I had... I had 2 x variable bias setups..
one per tube... plus sep fil xfmr's and variacs... plus one plate
meter... and 3 x shunts.... then u can read plate current on tube
1... tube 2 tube 1+2... and tweak idle current the same etc.
### The entire tuned input u see in typ arrl projects from yrs
ago... with separate bandswitched pi nets... each consisting of the
typ Millen 60496 slug and fixed silver mica's on each side... is
enough to put anybody off of building a GG amp. Arco compression
trimmers on each side was the next improvement.
### Now imagine trying to build tuned inputs for each band.... but
ones that will handle a kw ?? Hence the easy way out.... just 2 x
broadcast caps [padded for 160m] and a simple tapped 4 uh coil.
### 3/8" and 1/2" tubing is dirt cheap at home depot... so pi
net tank coils are not an issue... and there are plenty of surplus
vac caps out there. Having a MFJ-259B and a digital LCR meter +
GM3SEK's excellent spreadsheet is probably the biggest improvement
for me anyway.... in the last 30 yrs. You design it on his
spreadsheet.... measure the values on the LCR meter.. tweak the
taps... verify everything using the MFJ 259/resistor setup... and ur
99% homefree.
## It's straight forward to calculate all RF currents through all
the various components.. ditto with peak voltages... so correct
sizing is no longer guess work. None of it needs to be guess
work. That PI spreadsheet of GM3SEK's will save one hrs of time...
esp if using a tiny bit of uh b4 the main pi-net. I used to
calculate that portion by hand... using the formulae in the ARRL
handbook... which literally took hrs on end.
### Throw in some protection circuits and metering everything is a
bonus. Stuff like blower over run, fil step start, HV step start,
etc...high swr shutdown, relay sequencing, is pretty straight
forward.
### There is NOTHING here that could not have been done 25 yrs
ago ! None of it is really "new".. it was just never published
b4. Toss in the internet and pix.. and other's idea's/
experiences... and we are better off now... than at any time in the
past.
Later... Jim VE7RF
BOB DD
