[Elecraft] noodling with K1 VFO range

[Wallace, Andy]

In the CQWW contest, I was hearing interesting DX at the limits
of my K1 80 kHz VFO range. This past weekend, I decided to see
how I liked the extended 150 kHz range by putting a bigger cap
at C2 (68pF = 80 kHz, 120 pF = 150 kHz).

I pulled the stock cap and saved it. I then installed a 
68pF surface mount cap on the back of the board with a jumper
wire to connect the other lead to the hole for C2.

On the top of the board, I stuck a two-position jumper in one
hole for C2, and ran a wire toward the other hole. Then, I experimented
with cap values to use between the wire and the other C2 hole. 

It sounds confusing the way I am writing it but basically I have two
caps in parallel (which adds), one on each side of the PC board.

With a jumper installed, I get the pair paralleled. Without
the jumper, I get just the bottom 68pF cap and the stock ~80 kHz 
range.

I settled on a 47pF cap for the top side jumper. This gives 
enough overlap that I can calibrate things and still have about
150 kHz range. 

Now, remember if you change caps, you'll have to redo the VFO range
(adjusting toroid spacing) to have the counter-clockwise end meet
3.100 MHz; redo the band OPF calibrations, and redo the OFS offset
adjust. Your RIT range will change, also. My idea of using the 
jumper means that I will have to redo all these if I decide to
change back to 80 kHz -- still, easier than getting the soldering
iron and solder sucker out during a contest.

NOTE: it's not necessary to change the 30m crystal if you had previously
installed the one for 80 kHz range starting at 10.100 MHz. The only
loss here will be that you'll be tuning 10.100 - 10.250, and won't get
WWV at 10.0 MHz. 

How do I like it? Well, the jury is still out. I'm getting about 16 kHz 
per revolution on the VFO, which is not too bad. However, it is tougher
to zero beat the other stations (but still possible). There are also some
nonlinearity "jumps" at one end of the VFO but it may be because I have
worn my pot down after months of steady band cruising. ;-)

The activity up to the ~150 kHz range of the bands has not been
overwhelming.
I did hear an HK station on 21.135 the other night, and I still need 
Colombia, so I guess I'll leave it in for now. If I decide I like it 
overall, I'll pull my jumper setup out and just install the stock
factory 120 pF polystyrene cap. Obviously the K1 was designed with
this in mind and it IS perfectly usable, but the 80 kHz range
makes things even smoother.

-Andy