The video should say it all
https://www.youtube.com/watch?v=5rG75IRtew8
Cheers, Art.
edit: (updated video).
https://www.youtube.com/watch?v=5rG75IRtew8
Cheers, Art.
edit: (updated video).
Last edited:
That's a crude but cool tuner. How do you suppose it works? My guess is that a simple AM detector creates the telltale voltage that signals the presence of a station.
The closest I've been of something like that was a small console (seemed to be kind of an embedded module) that the operator used to "dial" the frequency he needed the xmtr to transmit at.Back in the 1930s they really did make radios with motorised tuning.
You had to preset (program?) the stations,though!
I think they discovered it was too fault prone & expensive,& it died out.
Much simpler mechanisms were used in the "Pressmatic" car radios & many European domestic sets.
The button "push" provided the mechanical power to shift the tuning!
When I first joined the old PMG's Dept,we had Auto-tune HF ISB Transmitters as a standby to the landlines between Perth & Melbourne,& Perth & Exmouth.
The Melbourne one,made by STC,would tune itself up using phase comparators,which controlled "Carpenter" relays,which,in turn controlled the tuning motors.
After it tuned the PAs it would adjust the Loading (Coupling).
It was so sensitive that if the wind shook the Rhombic around a bit,it would make a minute readjustment to the Loading.
The PA tuning on the AWA one for Exmouth were just presets,but it had an auto load circuit,& would do the same "Twiddle" when the antenna moved in the wind.
The Standby for this service was a smaller AWA one which had all the same "goodies" as the STC,but used power transistors in place of the Carpenter relays.
We had a lot of problems until we replaced all those transistors with better ones.
An interesting touch with this one,is that it would "wind" its own PA coil.
The former rotated ,& a Beryllium copper strip would be drawn out of a "reservoir",so that you had the correct number of turns.
The scanner with my car radio has two buttons. Push the right arrow button if you want to scan upward with respect to frequency, or the left to scan downward. This would mean two debounced switches on two pins of the microcontroller. The logic is a simple program. Press the right switch and the stepper rotates the tuner in the direction of higher frequency. When a station is sensed via the detector it stops. If you don't want that station just push the button again and up the tuner goes until another station is detected, and so on.You should already have a detector to do that.
Most radios have either an additional diode for AGC,or take a sniff off the regular one.
When you are tuned to a station,the AGC voltage adjusts the Radio's IF & (in most cases) RF gain,so that Stations all have pretty much the same audio---this saves messing with the volume control,which you need to do with simple receivers.
You should be able to use that to tell your micro that you are on frequency.
Obviously,you need to be able to defeat that function while you are actually
tuning,or the thing will always stop at the first station it comes to.
The scanner with my car radio has two buttons. Push the right arrow button if you want to scan upward with respect to frequency, or the left to scan downward. This would mean two debounced switches on two pins of the microcontroller. The logic is a simple program. Press the right switch and the stepper rotates the tuner in the direction of higher frequency. When a station is sensed via the detector it stops. If you don't want that station just push the button again and up the tuner goes until another station is detected, and so on.
That does sound like something I want to do... hope you'll be around to help
But I want to add a magic eye first and go from there.
Not to tune the radio from, but to build the initial list of frequencies.
An idea my ham club trainer had is compiling a list of all AM radio stations and
their frequencies in my continent (Australia), and a radio should be able to roughly
determine it's location based on what station it can receive without any need for GPS.
Cheers, Art.
Or a four track with simul-syncBack then, to do multi-tracks; you had to use at least 2 separate tape machines.
It sounds like we're reinventing the scanner. I think Art wants to do something entirely different. Once you catch on to microcontrollers it seems like the sky is the limit. I was thinking of making a miniature elevator from floor to ceiling; it would have to be a show piece in order to really wow people. Maybe like a cuckoo clock -- a bird came out and cuckooed each time the car stopped.PLL radios also have presets which store a frequency.
It might make a more impressive demo to do the scan,
but once you have your favourite stations it would be quicker to enter them on a keypad,
or to enter a number (say 0-9) that represents a preset frequency.
I suppose it wouldn't hurt to do both once the second part of the circuit is done.
PRS.. with regard to your other thread about antennas.. funny thing..
This morning I took the longest ferrite loop antenna I have (from a 60's radio),
connected it's coil parallel to another old tuning gang I have,
then connected that between the earth and antenna connections of this radio.
Best tuned AM broadcast antenna I've got yet!
I've read that you can connect them internally, replacing the first coil in
pre-ferrite loop AM radios.
If you were around for valves/tubes, you might have called it a cat's eye:An arbitrary entry? I'm sure you already know you'll need a keypad, Art. Just what is a magic eye?
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