KG4CNA's PSK31 Interface Box

Okay fellow hams and hamettes! Here is the interface I built for working digital on my HF radio.

First up is the schematic I used to build it. I got this from a quick Google search on easy PSK31 interfaces.
I did NOT design this interface and I do not know who the author is, otherwise I would give him name
credit here...but many thanks to him. If I can find out, I'll put proper the recognition here.

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My parts list included all that you see on the schematic PLUS, six panel mount RCA type phono jacks, seven RCA
type phono plugs, two stereo 1/8 mini plugs, two mono 1/8 mini plugs, one 4x2 piece of perf board with solder
rings, 20 feet of 3 conductor shielded audio cable AND one small project box (black plastic) measuring 4"x2"x1"
to put it all in. NOTE: I used the DB9 connector, NOT the DB25. All of the parts are readily available at your
local Radio Shack. The part numbers for the transistor (Q1) ARE Radio Shack part numbers.

The 1/8 mini plugs are for the audio connections to the computer sound card and for the data port and external
speaker on the back of my Yaesu FT-900 radio.

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Here is a picture of the empty case with the panel mount RCA jacks already in place. The terminals have been
tinned and are ready for connections.

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The audio isolation transformers (T1 & T2) are hot-glued to perf board to slide into the slots in the case.

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The switching circuit (2 diodes, 1 resistor and 1 transistor) completed with hook-up wires ready to be installed
in the project case.

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The switching circuit mounted in the case with connections made to the RCA jacks.

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One transformer installed.


Here are the audio transformers mounted and connected to their respective jacks

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Everything is in the case! Nice and neat! AFTER I make sure it works properly, I'll put a dab of hot-glue
on the edge of each perf board slot to keep the boards secure. Almost there...gotta make the cables now.

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Cables are done and have been tested with an ohm meter to make sure they are ready!

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We're all done! Overall, this project was very easy to build. Had I not messed up the first project box by
getting the holes aligned wrong, I would not have had to spend extra on it...but it was worth it.
A little descriptive info since it's not labeled...the jacks on the left side of the box go to the radio, the
right side to the computer. The top two jacks on each side are audio in and out from the radio and computer.
The bottom left jack will connect to the PTT and the bottom right will go to the computer's com port. My
computer is a bare-bones kit system I built in 1999 that is running Ubuntu Linux 8.04 LTS. I'll be using
LinPSK to make contacts.

Keep in mind, this interface should work with almost any HF rig. I wired this one for a Yaesu FT-900 radio.
It has the data port as well as external speaker and PTT connections on the rear panel.

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Here are some more photos. I lableled it so I know where the connections go.






Here we are hooked up and in action in the shack with a screenshot of LinPSK as well as what my shack
looks like.












Hopefully, you enjoyed my photos and information on this easy to build PSK31 interface. I hope to see you
on my waterfall display soon!