[Elecraft] K3: external VFO control (for EME)

[Edward R Cole]

I have final information for making the K3 work with MAP65v2 for 
those who are interested in working eme with their K3.

Trakbox: http://www.qsl.net/ik7ezn/Trakbox.htm
will send transmit frequency to the K3 via RS232 jack.  Trakbox reads 
azel.dat file produced by MAP65 to determine the frequency to operate 
(it can also point antennas).  Trakbox is fairly simple to setup, 
however is needs a dedicated RS232 line from the computer to the 
K3.  Since MAP65 also requires connection to the K3 serial port using 
RTS control lines to control PTT this presents a problem (but solvable).

Solution one:  build a PTT interface for the K3 using a 2n2222 and 1K 
resistor on the base which is connected to the computer RS232 line 
pin7 and gnd to pin4.  Set com-port on MAP65 to control this 
line.  Set Trakbox com-port for a separate RS232 line to the K3 
serial jack.  The 2N2222 shorts the PTT jack on the K3.  One can 
substitute an NPN opto-isolator transistor if you wish to isolate 
computer grounds from the K3.

Solution two:  Make a small box with two DB9 RS232 jacks to connect 
to two separate com ports on the computer.  Connect pins 2 and 3 of 
the cable that connects Trakbox to same pins on a third RS232 jack 
that will connect to the K3.  Connect pins 7 and 4 from the second 
jack connected to the other com-port controlled by MAP65 to the same 
pins on the third RS232 jack that connects to the K3.  This way two 
com-ports can simultaneously connect to the serial port on the K3 and 
requires no other interfacing.  Essentially a custom "wye connection box".

USB/RS232 conversion cables can be used between the computer ports 
and the "box" if the computer has no RS232 jacks.  Two cables required.

I received my first eme signal using MAP65 this morning.  I have to 
make up a box for solution-two before I have MAP65 fully interfaced 
for controlling the K3.  I plan to use my KX3 USB/RS232 cable for the 
second cable until I can purchase a dedicated cable.

Sorry for the extra bandwidth for this eme related info on using the K3.

73, Ed - KL7UW
complements to all who have offered help!


>Date: Tue, 11 Sep 2012 22:31:30 -0800
>To: Elecraft Reflector
>From: Edward R Cole <kl7uw at acsalaska.net>
>Subject: K3: external VFO control
>
>I guess this might be considered a subject covered by remote 
>operation of the K3, but I have a specific need to be able to 
>control VFO-A in my K3 from another sw program.
>
>I am implementing MAP65 vs 2 which performs JT65 over a 90-KHz 
>bandspan decoding every JT65 signal in the 90-KHz window, 
>simultaneously.  MAP65 has the ability to also transmit JT65 on a 
>specific frequency (but that requires frequency control of the 
>radio).  MAP65 currently is built to control SoftRock, FUNcube, 
>SDR-IQ, IQ+. and WSE.  I will be writing Joe K1JT about adding the 
>K3 to that list and he may need details on how to control the K3 VFO.
>
>This application to the K3 is not just a benefit to me as there are 
>several K3 owners that utilize JT65 and would use MAP65, as well.  I 
>should explain that MAP65 is primarily designed for eme use on VHF 
>(this has no particular application to JT65HF).
>
>73, Ed - KL7UW