[Elecraft] Re: CW tuning indicator for Elecraft K2

[Tom Hammond]

Hi Charlie:

At 06:45 PM 4/6/05, W0YG, Charlie Summers wrote:
>Being a newbie and just getting SN 4853 going, I don't know what this 
>tuning indicator you have referred to is.  I would like to know a bit more 
>about it.  Is there some place I can read up on this modification.
>
>SN 4853 is on the air!  I am now building up the KPA100 module.  When 
>completed, I am going back through the alignment/tuning procedure once 
>more then wrapping this project up.  It has been a hoot!

Congratulations on having completed s/n 4853!!! You'll love the rig.

And, tanks for asking about the SMD LED CW (Zero Beat) Tuning Indicator... 
sometimes I tend to forget that no everyone was around when this subject 
first came up, or when it reappeared most recently...

About 5-6 years ago, Jerry Henshaw, KR5L, designed a PLL circuit which took 
a little signal from the K2's AF output and drove a PLL which would blink a 
LED when the radio was tuned closely (generally +/- 50Hz, if I recall) to a 
signal which matched the K2's sidetone... thus indicating that the K2 was 
close to being zero beat with the received signal. It was meant as a tuning 
aid for some operators who had difficulty achieving a good zero beat by ear 
(by matching the K2's sidetone against that of the receive signal.

I designed a small PC board for Jerry, using thru-hole components, and I 
believe he sold a dozen or so (maybe) of the boards over the next year. 
After that time, the circuit kinda lost interest and little was said about 
it for another year or two.

Then, I somehow found (or was directed to, I forget) a similar circuit 
which was offered by Bob Wolbert, K6XX, on his web site, but which seemed a 
bit nicer than the original design. I made up a few (thru-hole) boards, and 
offered them to builders. Sold a few. but the PC board was still a bit 
larger than might have been desired.

So, for the first time in my short life, I decided to try designing the 
same circuit using surface-mount devices (SMDs), in an effort to get the 
board size down a bit (slightly larger than a large postage stamp), AND to 
add a small degree of challenge to the building of the kit.

With the help of several Elecraft builders, we devised installation 
instructions for the kit into all of the Elecraft transceivers (K2, K1, and 
KX1), and the K1 installation docs also can be used as a general set of 
installation instructions for just about any other radio as well.

THIS time, when I offered the PC board for sale, a number of folks groused 
about having to first find and then order the components... so I caved in 
and started kitting the project at a complete kit.

I was amazed that the project took off... I sent out over 360 kits in the 
space of 3-4 months...!!! And to date, I know of no complete failures... 
though they may not have been reported to me... <G> A couple builders had 
problems with solder shorts between components, and one PC board (which I 
supplied) which had a broken land, and another one which had two shorted 
lands, but otherwise I know of no problems... so far.

Once I got the 360+ kits made up and sent out, I'd had about as much 'fun' 
as I could muster (and a LOT HIGHER REGARD FOR THE FOLKS WHO MAKE AND SELL 
KITS FOR A LIVING!), and I now only offer the bare PC boards for sale. The 
documentation which appears on my web site  www.n0ss.net  included a 
complete parts list and the Mouser part numbers so builders can order the 
components from one location with as little pain and suffering as possible. 
The docs also offer complete assembly and alignment instructions.

Though assembly does require a steady hand, and either good eyes or a 
decent magnifier, assembly of the kit is not difficult, and alignment is 
fast easy as well. And only four (4) wires are required to attach the kit 
to your radio. KX1 owners will require two (2) user-supplied 1/4W resistors 
to go with their installation, to drop the AF output lever before it gets 
to the indicator. Oh, I almost forgot, K1 owners will have to supply an LED 
of their choosing as well.

In the K2, the tuning indicator is usually installed such that it will 
blink the 10th LED of the S-meter LED to indicate when you're tuned to the 
other guy's signal. Don Wilhelm, W3FPR, tells me he prefers to use a 
separate LED for this purpose, and he mounts a mini-LED inside the K2s 
[LOCK] button. Of course you, the builder, can choose how you wish to 
implement the LED indicator.

In the K1, the user-supplied LED can be mounted in a hole you'd have to 
drill in the case, or you can use the suggested implementation which mounts 
the LED AGAINST the existing RIT LED and illuminates the RIT LED by 
radiated light. Seems to work nicely.

In the KX1, the existing MAP LIGHT is utilized as the indicator, allowing 
for installation without having to drill holes or having to add a 
user-supplied LED.

So, that's it. Hope this has given you enough info. If not, please feel 
free to ask.

Complete docs are available at  www.n0ss.net

Write me if you are interested in a PC board. They're $6 ($7 DX) postpaid 
to your stateside mailbox.

73,

Tom Hammond   N0SS