I have worked in Broadcast Television at NBC for over 30 years and always wondered how a radar CRT scanned like it does. I figured it might be a moving coil and your video just verified my theory. Thank you so much for your demo. I guess somehow the motor is synchronized to the actual sweep of the dish using selsyn motors?.
I am surprised how hard it is to find out this info on Radar equipment (Classified? I doubt it :-P) but spinning magnet coil was my FIRST GUESS TOO! Cool :-)
There were three ways of doing a Plan Position Indicator Display. Rotating Magnetic Coil as shown, FIxed Coils and Electro-static plates. The Rotating Coil and Electro Static Plate methods were first thought up by Germans in 1936. The British came up with the rotating Coil in early 1938. The fixed coil was thought of in Britain in 1940. Germans built their first prototype PPI display in 1938/39. The British didn't build one until they had developed long after glow phosphor in 1939/1940 and their first PPI display was built in May 1940. The British were the first to use it in very early 1941 with the AMES Type 8 GCI radar. Selsys were used to sync the display coil and the turning gear of the Radar Aerials / Antenna.
I had always wondered how these worked, and had kind of always assumed some kind of rotating coil with how crude the tech was when radar was 1st invented. Either two somehow synced motors, or just one motor driving the dish and something like the speedometer cable on an old magnetic drag cup speedometer going to the radar display to rotate the coil in sync with the dish. Then the only timing you have to get right is the sweep from center to edge. Probably basically start a new sweep every time a pulse went out the radar and light up a blip on the CRT when the return echo came back as the sweep progressed. As someone else posted in here, not a whole lot of info about how early radar worked.
Would make a nice Audio Oscilograph with the circular trace :-) What would it do when you make the sideways deflection accept an audiosource, and let the coils spin? Makes for a nice Amoeba effect.
The trace moves from the centre of the ppi to the circumference in a radial direction. Could you please clarify if its moving in a straight line(at pulse repetition frequency but moving with respect to scanner and deflection coils) or spiralling outwards( at each pulse a trace is sent out spiralling outwards towards circumference, and is visually seen by the eye as a straight line because it's so fast)?
I have worked in Broadcast Television at NBC for over 30 years and always wondered how a radar CRT scanned like it does. I figured it might be a moving coil and
your video just verified my theory. Thank you so much for your demo. I guess somehow the motor is synchronized to the actual sweep of the dish using selsyn motors?.
I am surprised how hard it is to find out this info on Radar equipment (Classified? I doubt it :-P) but spinning magnet coil was my FIRST GUESS TOO! Cool :-)
There were three ways of doing a Plan Position Indicator Display. Rotating Magnetic Coil as shown, FIxed Coils and Electro-static plates. The Rotating Coil and Electro Static Plate methods were first thought up by Germans in 1936. The British came up with the rotating Coil in early 1938. The fixed coil was thought of in Britain in 1940. Germans built their first prototype PPI display in 1938/39. The British didn't build one until they had developed long after glow phosphor in 1939/1940 and their first PPI display was built in May 1940. The British were the first to use it in very early 1941 with the AMES Type 8 GCI radar. Selsys were used to sync the display coil and the turning gear of the Radar Aerials / Antenna.
I had always wondered how these worked, and had kind of always assumed some kind of rotating coil with how crude the tech was when radar was 1st invented. Either two somehow synced motors, or just one motor driving the dish and something like the speedometer cable on an old magnetic drag cup speedometer going to the radar display to rotate the coil in sync with the dish. Then the only timing you have to get right is the sweep from center to edge. Probably basically start a new sweep every time a pulse went out the radar and light up a blip on the CRT when the return echo came back as the sweep progressed. As someone else posted in here, not a whole lot of info about how early radar worked.
Would make a nice Audio Oscilograph with the circular trace :-) What would it do when you make the sideways deflection accept an audiosource, and let the coils spin? Makes for a nice Amoeba effect.
Wow I didn't not think of them doing it that simply.
Thanks for sharing.
Could you provide more details on the model of the radar unit and how you powered it up?
To think about this, F117 Nighthawk was actually made to defeat old school radars like this one.
This is absolutely sick! I love it! Get some modulation on that beam and show some real data!!!
A brincadeira ficou legal. Parabéns criou um bom efeito! Abraço
please share how you did this please!
The trace moves from the centre of the ppi to the circumference in a radial direction. Could you please clarify if its moving in a straight line(at pulse repetition frequency but moving with respect to scanner and deflection coils) or spiralling outwards( at each pulse a trace is sent out spiralling outwards towards circumference, and is visually seen by the eye as a straight line because it's so fast)?
It's a noisy business rotating those deflection coils !
How did you build it?
SWEET! Very nice indeed.
Just need a functioning antenna and a smattering of ufos.....
Your scope needs oiling.
Maravilhoso