Telegraph key

It started with spark gap and graduated to tubes that back then were called valves. Triode tubes
were used in the 20s and 30s, like the O1A, 30 tube, the 27, the 45 tube in both receivers and transmitters.
Hartley and Colpitts oscillators were popular as well as tuned plate-tuned grid and TNT. Some used
a transmitter called a MOPA which is an acronym for master oscillator power amplifier. I have built several
of those and they are still in use today.


IMG_0213_1.JPG
This is the transmitter I will use with the new telegraph key. It is a MOPA design using two 211 tubes(VT4C). The coils on the left are for 160 meters, the ones in the transmitter are for 80 meters and the coils on the right are for 40 meters. The grid current meter on the top left came from the local dump at the time and was part of the remains of an old Ritter dental X-ray machine. It easily works from coast to coast on
ten watts of RF input power.


The world as we know it today could easily be transformed back to the stone age by an EMP (electromagnetic pulse) or an overhead
nuclear explosion. Cell phones would become useless. Cars wouldn't run. Anything with solid state technology would be
destroyed. But, tubes would not be affected! So anyhow if things go bad, a few of us will still be able to communicate.
Of course the receiver would have to contain tubes as well. I'm not a doomsday person at all but it doesn't hurt to know that
things could radically change our lives in an instant. The sunspot cycle is on the increase. A CME(coronal mass ejection) is
a real possibility in the coming 11 year cycle of old sol.
 
Cathead,
Did you use one of those old Grid Dip Meters to tune your coils, or was it just done straight from the math calculation?
Based upon your use of language, and technology, I would put your age in the range of my father. He is almost 90.
Those old tube rigs (like the MOPA) were laid out in a way, which was often quite artful. I only built two tube transmitters,
one was for 11 meters, the other was the license-free range for QRP. After that it was all transistors, as I recall with the old
Motorola Planar transistors for some of my first "higher power" designs.
 
addertooth said:
Cathead,
Did you use one of those old Grid Dip Meters to tune your coils, or was it just done straight from the math calculation?
Based upon your use of language, and technology, I would put your age in the range of my father. He is almost 90.
Those old tube rigs (like the MOPA) were laid out in a way, which was often quite artful. I only built two tube transmitters,
one was for 11 meters, the other was the license-free range for QRP. After that it was all transistors, as I recall with the old
Motorola Planar transistors for some of my first "higher power" designs.
Click to expand...

This was back in the days when RF was referred to as the "ether". It was all trial and error back then and still can
be if you want to play old time radio. It's not too hard to take an educated guess on the amount of inductance and capacitance
required when building a tuned circuit. Once it oscillates, it's easy to find it on a receiver. If the frequency is too high, one
needs to add more capacitance or inductance or maybe both to lower the frequency to what you need. You don't need a
grid dip meter or even mathematics to do this. By the way, if your dad is almost 90, you could easily be older than me.:grin:
 
Very nice Cathead. I am a CW enthusiast and a retired RF/Antenna design engineer. I have a small collection of Vibroplex semi-automatic keys.
 
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