[Elecraft] K2 and HW-101?

[Don Wilhelm]

Folks,
With my junk box filled with stuff from the 1960 through 1980 era of ham
radio, I don't think I would cannabalize my HW101 or SB401 (yes, I have
both) for an amplifier for the K2.
The pair of 6146 designs have been around for a long time and were more or
less standard fare for many transmitters - but I think there are easier
alternatives - such as something that will run class B with zero grid bias
(or some low voltage bias).  I am thinking that a triode like the 811A would
provide a much simpler approach and if the grid is driven (rather than the
cathode as in a grounded grid configuration), and would make a good
amplifier for the K2.  Finding a transformer to put 1200 volts on the plate
may be a challenge, but the 811 will work FB at 600 volts too and that can
be easily obtained from an old tube-type TV chassis if there are any left
around and run 2 811A tubes in parallel.  A bandpass network for the grid
input may be nesessary and would take some thought for bandswitching
techniques.

For those who want to go all the way with high power, there are several
class AB1 (or AB2) tetrode designs that will give 300 to 1500 watts output
with 5 or 10 watts input if one is willing to drive the grid circuit.  Check
out the older ARRL handbooks in the library to find these designs.  Even a
pair of 813s can provide the legal limit with just a few watts drive using a
grid driven design.

You folks are looking in the right ballpark, but unless you already have
many of the components in your junkbox or can find them at the next hamfest,
you would be better off waiting for the KPA100 to come out - high voltage
capacitors are becoming a rarity and are expensive too and doing QSK with
tube amplifiers may be challenging.  For myself, I am keeping all my HV
capacitors and large inductor stock to build antenna tuners when I get my
antenna farm developed - so none of mine are for sale - sorry, but anyone
wanting tube sockets -particularly octal sockets, just ask - I have many
that will likely never be used.

73,
Don Wilhelm  - Wake Forest, NC   W3FPR home page: http://www.qsl.net/w3fpr/
  QRP-L # 485   K2  SN 0020   mailto: w3fpr@arrl.net

----- Original Message -----
>
> 1)Get a basket case HW-100, HW-101 or SB series equivalent. Use a
hacked-up hangar queen, not one that has a decent chance of ever working
again. SB-400/401 might have possibilities, too.
>
> 2)Remove the meter, final amplifier and driver components ONLY. Sell the
rest to keep other Heaths alive.
>
> 3)Transfer these to a nice new chassis (could be a couple of pieces of
sheet metal held together by genuine Elecraft 2D connecters and panhead
screws, or 6-32 sized shameless copies if you have machine tool
capabilities). Original final cage and meter are reused, too. New front
panel with nice knobs and meter(s). Eliminate the troublesome "rubber band"
drive and the concentric plate/load nonsense of the HW series and have a
nice clean front panel. Tune, Load, Band, Meter, Mode, Power.
>
> 4)Design TR system to match K2 and bias system for various modes. One
possibility is to use the 160m/2nd RX adapter so that all the amp has to do
is switch between amp output and 2nd ant input.
>
>