[Amps] HB amps

[Jim Thomson]

<<<<<You can't really compare hamfest scrounged parts to brand new. Would
you buy an amp from Alpha if they told you all the parts were
scrounged from a hamfest?

When a person finishes their scrounged-part amplifier, they are
basically starting off with a used amplifier. I am not knocking used
amps, just wanting folks to be aware of what they are getting for
their efforts.>>>>>

##  What would you like us to do, buy brand new Jennings /Comet
brand ceramic vac caps  for both the tune + Load ?? 

##  at  $3-5 K  each.. they are cost prohibitive new... which is why alpha  stopped
building the 77-dx.     Surplus, they are a bargain.    I picked up 4 x 12-500 pf  @  15 kv
ceramic vac caps [ Jennings] new , still in box's.. and all hi-pot test well over  15 kv.

##  I also picked up [nib] 2 x 10-1000pf  @  15 kv ceramic Jennings caps.. and these are motor driven.
also got a 25-1000 pf  @  15 kv, non motor driven  [ measures 17-1056 pf] 

##  as for vac load caps, I managed to get a pair of Jennings   50-4000 pf  @  5 kv ceramic caps,
and 1 x 50-3000 pf @  5 kv  Jennings.   Fair radio had NIB  50-2000, and also  50-2300 pf  @  10 kv
glass vac caps.   The glass ones are padded  on 160m.. with paralleled NPO  5 kv  ceramic  doorknobs [HEC HT-50/58]
8-10 x 100-160pf

##  15-25-50'  rolls of  cu tubing is cheap at home depot, lowes, etc.  Just cuz Alpha  uses  undersized  3/16"
tubing on 20-10m doesn't mean you have to.  [ I use  1/2".. then I silver plate all of it]

##  Commercial ham amps will use every trick in the book to avoid the use of vac caps, etc. 

##  IMO... after doing this since 1972... I have come to the conclusion
that's its just as easy to build a big amp..as a  small one.

##  IF you don't have enough HP  under the hood of your truck, you don't 
install a 2-4 engines under the hood.... you get a bigger engine to start with! 

##  why mess with 2-4  tubes.... 2-4 sockets.... 2-4  chimney's....  2-4 parasitic suppressor's, 2-4 anode connector's
then  cross ur fingers and hope the [A]  drive  splits  2-4  way's... and [B] the 2-4  tubes match up...
and [C]  airflow  splits  2-4 ways, etc, etc  ?? 

##  A  single   $200.00   YC-156 is  simple. NO  socket required... just whack a hole in the chassis,
and bolt the integral grid flange to the chassis.   NO  parasitic suppressor required either. [ no anode connector either]

##  The mating SK-306  chimney is a dime a doz.   Fil requirements  are  miniscule. 

##  tuned input is simple.   PI net is simple... and uses vac caps..... [and so does my  2 x 4-1000 amp I built yrs  ago.]

## 1 cubic ft,  120 lb  hypersil  pole pigs are also a dime a doz.  [4160/4800 variety] .    

## 1 kv-6A  [400 A surge]  6A10  diodes    [ big bro to the 1N5408] are cheap in bulk... mouser.

## 2300-2500-3900 uf  @  450 vdc  electrolytics are available NIB, surplus, have 10A  ripple  current ratings,
and provide  for < 1%  ripple... and superb dynamic B+  regulation.  NIB, surplus contactors are easily
available.

##  don't like the loaded Q  for the tuned input / high powered PI net output... then re-tap the coil and change it.

## Once your all done.... you end up with an amp that makes the Alpha 77-SX  +  Henry  8-K.... both look 
like  sick puppies.   The re-sale value is also high.   Blower noise ?     Put it in another room,  and simply run in there
and ..'dial up the pre-set's.   Once tuned for say  14.200 ,  it's  good from 14.100  to  14.300   I can't squeeze
1 more  watt out of it, if I try and re-tune  at either  14.1.... or  14.3    [ assumes ant has flat swr across the same  200 khz]  

##  Trying to compare commercial made ham amps to hb ham amps is sorta  like apples and oranges.  The HB builder, is at 
liberty to use anything, and everything, at his disposal.  He can choose to cut corner's.. or not.   He can also up-grade any portion
at any time... and after the fact.   He's not trying to enhance profits.  AL plate  can be polished to a high luster, like  a mirror,
or chrome, or leave it plane, or do a brushed finish, like stereo amps  from the 70's.   See where I'm going with this? 

later........ Jim  VE7RF