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 Multi-Key Patch Box
A Q&D interface project by N1FN

Morse Express Showroom

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Create a quick'n'dirty patch box to connect a variety of keys and paddles to a single electronic keyer or code practice oscillator.


My shop includes a showroom where folks can lay hands on a variety of keys, bugs, paddles, and associated keying equipment.  The demo keyer is the LogiKey K5, which also functions as a code practice oscillator.  Equally useful would be the GHD GR301A Morse Training Unit, which is designed first as a code practice oscillator but includes a practice keyer.  I also have a Katsumi EKM2B code practice oscillator which direct-connects to the binding posts on keys, but it could as easily be connected to the patch box.

Several of the keys are demonstrated more frequently than others, so a single box to plug the keys and paddles into seemed to be a very useful idea. And it can be adapted to shack situations where you want to connect more than one keying device to a single radio.

Keys, bugs, and paddles come with a variety of connection methods.  Some have binding posts, some have cables with plugs on them, some have cables which require you to attach a plug, and some have solder terminals for permanent connection of the cable.  Plugs for paddles will always be "stereo" or two conductors plus a shield or "common" wire.  Plugs for keys can be stereo or mono, or RCA.  Stereo and mono phone plugs can be 1/8" or 1/4".

In order to simplify, I went with the most common-- 1/8" stereo jacks, with 6 of them wired for "mono" plugs and six for stereo.  In a more permanent installation (e.g. a radio shack) I would install the specific jacks required for my equipment.  

In many cases a mono plug cannot be used in a stereo jack.  That's because the plug will short the ring connection to the sleeve inside the jack.  In other cases the ring connection is not used, so it doesn't matter.  There is a surprising variety of possible combinations of plug type, conductors, and wiring, but electrically the circuit is very simple and easy to diagnose or verify with a multimeter or even by trial and error.    

I didn't have a lot of time for this so I went with materials that were on hand and easy to work with.

Project box:  MX-H804 6x3x1 Hammond molded styrene with cover

Cable for keyer:
MX-C8S 3' shielded, 1/8" stereo plug.

Jacks for keys and paddles:  1/8" stereo panel jacks

Wire: 20 awg tinned bus wire or any convenient hookup wire, about 18"


General Comments:
I decided to set up 6 jacks for paddles (stereo) and 6 for keys (mono), and drilled the holes in the lid more or less free-hand-- I drew two lines along the axis of the jacks, and marked the individual jack positions with a pencil.  Of course you could make a drilling template and label if you are concerned about how it looks.

 (Click here for the related Control Panel article.)

The connecting cable enters through a hole in the end of the box and can be secured with a cable tie or a blob of hot-melt glue.

Tinned bus wire is very easy to work with in this situation, as it is a continuous run that is soldered to the appropriate terminals on the jacks.  If you use ordinary hookup wire you will need to cut small pieces to go between the jacks, or strip "spots" along a continuous wire.

In the case of the jacks to be used with mono plugs (straight keys), the ring connection is not used.  I wired the tip connections in common with the ring connections on the jacks to be used with stereo plugs (paddles).  With the Logikey Keyer in "hand key mode" either the tip or ring (dot or dash side on the paddle) will act as a straight key, but many keyers and radios require the use of "bug mode" in which case only the dash line acts as a straight key. In that situation the plug would need to be stereo, and you would plug it into one of the stereo "paddle" jacks.


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