Having learnt a bit about AM radio receivers and how they work I decided to look at the other end of wireless communication, the AM transmitter.

Here is my experiment in creating an in house transmitter IHT (using valves of course!) to provide a AM signal for my little collection of radios.

As usual I have not much idea about what I am doing but get stuck in anyway, toss thoughts about, and make something work learning a bit along the way.

The Lever IHT

Any comments on any aspect is welcome.
Fred.

Fantastic work Fred!

I started with a AM TX kit called the "Spitfire". I know it uses those soft parts like transistors instead of valves, but after a few tweaks really does perform well. A simple change of the output stage to a DS548 makes a huge difference to the output distortion and power for example.

I have a few pictures of my rig here, but should update it one day with more info.

Love your documentation, and keep up the good work!

BeJay

Hi BJ that looks like a good project making a rack mount stack in MDF, good stuff. I like enthusiasts with ideas and the ability to carry them through. Even if the electronics has those funny little black centipede things in it. I still don't understand how a device works without a heater and cathode.........................only joking!
What "purists" don't understand is how much you learn from making a system whatever it is made from and battle through the problems make it match and work as a whole.
Cheers.

Are there still problems with the carrier waveform?
I’ve never seen or heard of ferrite rod antennas used for transmission,
and in fact, heard the complete opposite, never to do it! D

I wonder what the difference would be if you used a loop or just a resonant air core inductor?

Hi Art, I can do anything because I don't know what I am doing so I just do it. Ignorance is bliss!
I used a ferrite rod because it sounded like a good idea at the time.
In reality as I am not transmitting for any distance, NARROWCAST, so I don't need a tuned antenna with radiating properties. There is just about as much radiation from the 6V6 plate structure and the 1 meter connecting cable as from the ferrite which really only sharpens up the "Q" of the windings. So the ferrite is not a transmission part, the range of transmission is only FEET not MILES!
The carrier is simply a sine wave as the tank circuit comprising the tuning cap , the valve plate , the ferrite rod winding and cable are all a resonant structure.
When you view the carrier in the IF system of a receiver it looks just the same as the AM stations, that is a modulated sine wave.
If I wanted to BROADCAST the plate circuit of the transmitter would be very different which is what you are thinking about and there would be a solenoid air tank coil coupled to a 1/4 wave antenna and the ACMA would be around with the radio police in a trice! A ferrite rod could not be part of that so you are correct.
Fred.