[Elecraft] K2 and HW-101?

Wed Jan 16 19:53:02 2002

At the risk of beating this subject to death, another approach is to use a
200-ohm resistor but omit the transformer.  The KAT2 should be able to match
to it easily, there is no additional inductance, and 10 watts into 200 ohms
would produce the necessary 45 volts of RF on the grids.

----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: Wednesday, January 16, 2002 1:22 PM
Subject: Re: [Elecraft] K2 and HW-101?

In a message dated Wed, 16 Jan 2002 11:25:29 AM Eastern Standard Time, Vic
Rosenthal <[email protected]> writes:

 > [email protected] wrote:

 > > K2VCO said:
 > > >  Well, you could just use a 1-4 toroidal transformer
 > > > between
 > > >  the input and a 200 ohm swamping resistor.

 > > That might work, if the toroidal transformer can drive the capacitive
load of
 > > the tubes over the frequency range. Neutralizing would be disabled and
a TR
 > > system installed.

 > You might have to add a small inductance to tune out the reactance the
 > grid-cathode capacitance on 10 meters, which is effectively in parallel
with the
 > swamping resistor.

Where would you put the inductance?

>  This is annoying, because we are trying to get away from
 > input circuit bandswitching.

 Why are we trying to do that?

As I recall the HW-101 circuit, the 80 meter coil in the 6146 grid circuit
has a link on it that is used for receive antenna input. The other coils are
switched in parallel to reduce the inductance. Why not just keep the grid
coils and feed the RF in through that link via a suitable T pad (to absorb
some of the K2's output and reduce impedance variation)

What I'm beginning to envision is this:

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.

5)Power supply can be HP-23 if you have one or homebrew if you don't.

Waddya think, sirs?

--

 An even stranger version:

Get a torn up Johnson Viking 2 and use just the final. Will work 160 thru 10
and the WARC bands. They are well shielded, rugged and easy to work on, but
real desk-crushers. BA purists will recoil in horror at the idea, anyway.

 --

It's legal for us hams to do this as a homebrew project for our own use, but
not legal for Elecraft or any other company to
do it, either as a kit or an assembled unit. Something
wrong there.

73 de Jim, N2EY

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