Transmitters using tank circuit or RF transistors are called?

Some do, some don't, plus there's a whole bunch of generic classifications it depends the exact arrangement of components in the circuit. One of the best and easiest to use sources for that type of info would be the ARRL Handbook.

Thanks for reply. I have a copy of RSGB radio communication handbook and I bet that has some clues for me if I can dig them out. I wonder if I am right in thinking that pushing a lot of energy into a LC circuit using thermionic valves is what was done before RF transistors existed because it was the only way it could be done? Could early valves oscillate at say 150MHz? Thanks for your time. david

Early valves could go a lot higher in frequency too. Think of the early radars. These valves were shielded to keep the radiation in the box.

David, There was a whole world of RF communications well into the UHF range using tubes, solid state devices merely extended the upper limit, making it easier to use in everyday devices like cell phones. Alan

Alan thanks for reply. I wonder why then in a transmitter like this the valve drives the

big tank circuit presumably at a frequency much lower than the LC resonant frequency. Why not have the valve/tube run at higher frequency and feed RF directly to the antenna? Is there an impedance match problem? Thanks for reading. david in u.k.

The upper limit to regular vacuum tubes is about 30MHz. That tank circuit looks to be within that range. An antenna must be impedance matched for good power transfer. Also you don't want to lower the Q of the circuit with the load from the antenna. With more tubes you can have a power output stage. How old is that transmitter? About 1940?

Thankyou StandardsGuy. That gives me some good clues. The photo is not mine but one found at random because I just wanted to show the sort of devices I was thinking about. I do own a couple of old handhelds though. One modern 2m and one 1980 with xtals and a RF transistor output.

SG, The upper frequency limit of tubes is a function of the physical dimensions of both the tube and the circuit that it operates in. Commercial FM broadcasting (which goes as high as 108mHz) started in the late 30's, about 15 years before transistors were invented, so everything was tube-based, commercial and military based tube designs went much higher, especially during WWII.

There are small valves that will generate output up to 3GHz, and travelling wave tubes (TWTs) that will provide larger powers in the GHz range.

A tuned tank circuit used with valves is also designed to limit the frequency output over a small range. Harmonics are limited by the Q of the tank circuit (typically in the range Q=10 to Q=12).

An antenna is a low resistance device, varying from say one Ohm up to 75 Ohms, or with coupling devices/transformers antenna input can be pushed to higher Ohmic values. Valves are high impedance devices, usually needing loads in the region of hundreds and thousands of Ohms, at least those producing only a few kiloWatts at most.

Transistors are usually set up broadband, using coupling transformers to connect to antennas. Add-on filters are used to limit the band they operate over. Transistors have low impedances similar to antennas (and lower).

Thankyou Phaddy. I think when I first asked this question my mind was foggy and I could not figure out right thing to even search for in google but your answers and others have cleared fog enough see a bit. Thanks.