PH2LB shack on the internet.

K2 digimodule

This page was last updated : 28-Mar-23 13:21:07

 

I really love my Elecraft K2 but was missing a line out/in/ptt option to work audio driven digital modes like PSK31, RTTY (no FSK), WSPR, FT8 etc, so I started to design my own K2 Digimode breakout PCB.
This PCB has the following components : 

• a balanced input buffered amplifier for the AF out based on a LM386 (with limited gain).
• a connector containing AF-out, AF-in (microphone level) & PTT (and of course GND) so I can have a read panel connector having those signals.
• a microphone configuration breakout so I don't have to remove the entire front panel when I want to use a different microphone / interface and also includes AF out to have AF-out on the microphone connector when required.
• a zero beat LED circuit to have a visual zerobeat indicator (just because I like it on my FT897D) based on a LM567/NE567.
• a simple 5V power supply so I don't have to steal VCC from the microphone connector.

TODO : add photo's, explain schematics etc.. 

AF amplifier 

 

Zero beat detector

 

Microphone and audio / ptt connector

 

Powersupply

First prototype PCB design

 

First real-life prototype test.

Injected 50mVpp and could have a output put to 1200mVpp (way to much the AMP is working). Modulated the frequency over the audio spectrum (10Hz to 3KHz) and at the range of 630 to 580 Hz the zero beat detection activated the LED.

Current draw with a output of 200mVpp and zero beat LED locked : only 26mA.

Next step : building it into my K2

And I couldn't :-( I made made the PCB with the wrong dimensions and it couldn't fit against the side.

So back to the drawing board. 

 

Second prototype PCB design

Second proto type construction. 

 

PDF's of the schematic and PCB can be found : here (schematic) and here (pcb)

First real-life prototype test.

Injected 50mVpp and could have a output put to 1200mVpp (way to much the AMP is working). Modulated the frequency over the audio spectrum (10Hz to 3KHz) and at the range of 630 to 580 Hz the zero beat detection activated the LED.

Current draw with a output of 200mVpp and zero beat LED locked : only 26mA.

Next step : building the second prototype into my K2

TODO 

 

Future : Where to buy 

When this PCB works out, the left-over PCB's of the small prototype batch will be sold through the For-Sale page on my website. When they are sold out and there is a demand, I might be ordering a new batch of PCB's to sell them. So when they are old out and your interested, let me know.   

The design will be publicly available (use the For-Sale page  to request GERBER files) so you order your own PCB's at OSHPark or a other PCB factory of your choice, but licensed it Attribution-NonCommercial-NoDerivs 3.0 Unported (CC BY-NC-ND 3.0).
Meaning : 

• Attribution — You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
• NonCommercial — You may not use the material for commercial purposes.
• NoDerivatives — If you remix, transform, or build upon the material, you may not distribute the modified material.

It's not to be childish but it now happened a few times that a  designs I made was sold by other people just because is was "Open source, so I can do anything I want with it" without any credits or even a token of appreciation. 

When you like the design and PCB's. a small fee as a token of appreciation / commission to support my work is very appreciated (see : Support & Tip Jar).

---