Multi-Purpose Key

Model MPK1

This MP-Key is a small and multifunctional help-mate for every HAM operator. It has several functions:
1. Keying of the transmitter, with side-tone, very useful for simple rigs without a side-tone oscillator.
2. Morse code practice, volume and tone range are adjustable.
3. Telegraph connection by wire-link, useful for training of new HAM operators, for antenna-tunning, sport-contests and childrens`-summer camps. You need two identical units, connected by two wires or one wire and a ground. With the one wire and ground you can do the connection (by the conductivity of the earth) at least 10  metres away. You can use the central-heating system of building as a ground connection.
4. Basic test of circuits and components: resistors, ellytic conds and semiconductor junctions, can be used as a cut-off testers. Suitable for beginner hams, because it is cheaper than profi measuring-instruments. By comparing the tone range of known and unknown resistors, you can find the proximate value. The one or several ohm resistor, provide the high tones, the large megaohm resistors do the flip-flap. For the tone comparision, It is advantageous to have a "calibrating resistor set". Proximate value of ellytic conds can be found by comparing of length of whiz, which is dependant on the load time. On semiconductor components (diodes, LED, bipolar transistors) you can test the junctions, npn/pnp type and Ge/Si type. The germanium type sounds even in a closed-direction.

 

The printed circuit after drilling and etching.

 

The base plate is made of 10 mm plastic, leaf spring is made of 1,5 mm Glasstextite.

 

Hardened rubber is affixed on the periphery of bottom side.

 

Assembled MPK-1.

 

The mystery of successful construction of the microswitch-telegraph keys is in a small plate affixed to the base plate. It takes up the key lift, so that it enables precise keying.

 

The terminal block for the transmitter and line connection is situated on the back side.

 

Six small cavities from FRB-connectors serve for inserting of testing parts. The magneto-dynamic transducer of 145 ohm resistance provides the device with sufficient volume.

 

 

Model MPK2

Construction of the MP-Key is very easy by using the integrated piezo buzzer. Type MPK2 has nearly the same functions as MPK1:
1. Keying of the transmitter, with side-tone. The same as MPK1.
2. Morse code practice. The same as MPK1.
3. Telegraph connection by wire-link. The same as MPK1.
4. Basic test of the circuits and components. Because the tone of the piezo buzzer is slightly dependant on the voltage, the MPK2 can only be used only for simple tests of conductivity.

 

The microswitch is used as the contact system. The flexible element is made from 0,5 mm glass-textite. The piezobuzzer is glued on it. The battery contains three alkaline button-cells. The cells are in vinyl tubes. Flexible contacts are made of phosphorous bronze. A four-pole terminal plate is used for connecting of cables.

MPK2, back-view.

 

MPK2, front-view.

Here you can see the both keys, side by side.