Don’t forget the Vacuum Tube

My XYL (Ham operator’s term for wife – “Ex Young Lady”) who is also an amateur radio licensed operator, was asking tonight about the local club’s growing interest in CW operation.  That is “Continuous Wave” or “Code” operation.  That is where the operator uses code operation to communicate with other hams.  Using a key (switch) the person sends a series of short on-off pulses which represent the letters of the alphabet.  CW code is a language that, once learned, allows one to communicate with other operators around the world.

Even newly licensed technicians have certain areas of the amateur radio spectrum where they are authorized to transmit and receive code. There is no microphone required. There is no speech amplifier, compressor, modulator, or phase shift networks required.

Now, if we consider that we only have to switch a circuit on or off,  we can consider the vacuum tube.  There is much being said about the power tubes in audio amplifiers as used on guitar amplifiers, HI Fi amplifiers, low distortion, and so on.  In  CW work, we are operation our vacuum tubes as switches.  The tube must simply transmit when we hit the key, and not transmit when the key is off.  If we keep this in mind, the tube characteristics (and somehow the resulting price) are not so important to the CW operator..

Long story short,  if your CW transmitter uses a 6V6 or 6L6 tube for the ‘final’,  don’t hesitate to purchase on at the local hamfest and give it a try in your rig.  You may find the power output is as good or better than that more expensive tube advertised for its great audio characteristics.

The 12K5 “LookMa” CW  transmitter kit sold by Pastime Projects is an under thirty dollar kit which will produce a signal in the 40 meter ham radio  band. Its enough of a signal to be heard across your ham shack in a nearby receiver. You can use it for code practice.  It does not have enough power to be heard on the air at any distance, so don’t expect to work DX with it. All you need is a CW key, a 12 volt power supply,  and a 50 ohm resistor for a dummy load, and you can practice code to your hearts delight using your 40 meter receiver. It comes with a crystal! And a great manual. Most often, we even wind the coil for you to save you a little time.    73 Glenn  pastimeprojects(at)yahoo(dot)com


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