Lifting the cover

1. Lift up the key arm half way
2. Push in the black serrated part (that is now exposed under the arm) with one hand
3. At the same time lift up the top cover with the other hand

Czech Morse Key with cover up

Key adjustments 

There are 2 adjustment screws under the cover. One adjusts tension and the other the gap ~ just make sure you tighten them after adjustment. You will need to make adjustments as the gap is set wide, and the spring tension high to minimise damage in transit. The more time you spend setting the key up for your style then the better the key will perform ~ this is time well spent!

Czech Morse Key showing adjustment screws

Setting up a straight key........

Setting up a straight key

Anti-Slip Mat

These are easily made from anti-slip matting available in hardware stores. They are washable, very cheap, easy to use and will be available at all radio rallies we attend.

Anti Slip Mat

SACKTA Mat (Stick A Czech Key To Anything Mat)

These are gell type mats used to hold mobile phones, etc to car dash boards. I thank David G3ZPF for bringing these amazing mats to my attention ~ they really are the business! They are washable, cheap, easy to use and will be available at all radio rallies we attend.
Stick Anything To Anything Mat

Using the original 2 pin plug 

The original 2 pin plug has 4mm diameter pins which neatly fit into standard banana sockets. The pitch of the pins is 20mm. So simply mount 2 banana sockets 20mm apart in a small box. Then wire your rig CW plug to the sockets. 

The simpler and cheaper alternative is to wire 2 in-line 4mm banana sockets to your rig CW plug. We have these in-line 4mm sockets available at £2 for 2 (or equivalent in Dollars or Euros), just add to your order.

4mm to 3.5mm sockets

The 2 spade pins in the top cover 

This is just a link wired in series with the key to prevent transmission when the top cover is lifted up.

The text on the key arm 

"Prijem" means Receive and "Vysilani" means Transmit in Czech.

The "key arm parked up" position 

I have seen some keys with a 4 pin plug. 2 pins of this plug are wired to a cam switch mounted inside the key, so that the action of raising the key turns the TX off and the RX on. This cam switch is fitted to the keys we supply, but as it’s only got a 2 pin plug the switch is left unconnected.

RM31 4 Pin Plug


  • Size 150mm Long by 65mm Wide by 50mm High
  • Weight about 470 grams
  • Khaki painted pressed MS base plate (secured with 4 countersunk screws) and arm
  • Bakelite type body and top cover with rubber type seal in the top cover
  • 30mm diameter Bakelite type key knob
  • 1 metre cloth covered lead
  • Cam switch operated by the arm in the Up Position (not connected)
  • Black painted pressed MS 2 pin plug with 2 phosphor bronze pins
  • Silver contacts

A piece of history

The key was made in the early 1950’s for the Czech armed forces, presumably for the army. It was part of an HF base station which was called Type RM31 (although this may have been just the receiver reference), so the type name
stuck and was then associated with the key. I now think the transmitter was called Type RS41. I have spoken to 
several Czech radio hams but they appear to know little about the keys history; although many have used the keys.

I would welcome any further information to add to this site............see (more to follow thanks to Karel OK1UHU) Czechoslovak People’s Army website on the RM31, etc  

The Art & Skill of Radio Telegraphy ~ ebook download........

The Art & Skill of Radio Telegraphy

ARRL site with CW MP3’s from W1AW........

CW MP3’s from 5 to 40 WPM

Internet CW........

Internet CW

Internet ICW2012........

Internet ICW2012

G3RID on 500KHz........

Maritime Radio

I took my CW test in 1985 at Humber Radio (near Sutton on Sea). Some years later I discovered that my Grandfathers brother (George Bowthorpe) opened the station in Dec 1927. Here is the photo..........

Humber Radio 7th Dec 1927

Czech Morse Key on You Tube, just click the links below..........Czech Morse Key Introduction

Czech Morse Key by YS1RS..........4 pin Czech Morse Key

A short piece of history...........Czech Morse Keys at GQRP Rishworth 2012

Simple Morse Oscillator........

2 Transistor Circuit

Built Oscillator

Simple RF Morse Oscillator........

555 Circuit

Low Cost ATU Build Info

ATU Notes

ERA Microreader MK2 Instructions

MK2 Instructions

Make a valve to go with your valve transmitter and your new key! This video is absolute magic ~ just watch it and smile.....

How to make a thermionic valve :-)



These keys are over 50 years old and some may have very minor corrosion on the of the steel base plate. The internals in all the keys we sell are in first class condition. All the photos taken are of keys taken straight out of the factory packing. The rusty keys we have for sale have clear signs of rust, but this can be cleaned and the bases repainted very easily. If you would like a specially selected key suitable for the serious collector complete with a 5 year warranty then these are available for $150 plus shipping. Please email for more information.