mstechca said:I wonder if the breadboard is causing difficulties, because I'm doing alot of my testing on a breadboard.
How many times have you been told you can't use a breadboard at VHF?, do you never listen to anything you're told?.
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mstechca said:I wonder if the breadboard is causing difficulties, because I'm doing alot of my testing on a breadboard.
The tuned high impedance tank is supposed to be at the transistor's high impedance collector. The quenching parts are supposed to be at the transistor's emitter to "quench" or cutoff the transistor when its signal gets high.mstechca said:He is agreeing with me.
I think it is just two components (resistor and capacitor), and you are saying it is the capacitor and inductor.
My resistor capacitor and inductor are connected together the same way. except the other end of the inductor is connected to collector and the resistor and capacitor are pull-ups instead.
The emitter inductor is supposed to be a high impedance choke, not a tuned tank. The high value of 1uH makes a pretty good choke.When the emitter inductor is at 0.1uH I hear more "hum". When I replaced it with a 1uH inductor, I hear more stations.
When are you going to learn that high frequency radio circuits don't work on a breadboard due to its very high stray capacitance and inductance.I wonder if the breadboard is causing difficulties, because I'm doing a lot of my testing on a breadboard.
Single-tuning is intentional. I want to add a poor-mans varactor arrangement to it later.Your circuit has only a single tuned circuit so its selectivity is pretty low.
Which then requires more mathematical equations.Real radios have many tuned circuits for good selectivity.
That's ok, as long as it can detect ANYTHING in the VHF/UHF range, I'm happy.Your circuit detects AM
You must be one of those guys that stick with the books. :LOL:Put the tank at the collector where it belongs and put the quenching parts at the emitter where they belong.
When are you going to learn that high frequency radio circuits don't work on a breadboard due to its very high stray capacitance and inductance.
mstechca said:You must be one of those guys that stick with the books. :LOL:
A huge advantage with using a breadboard is that I can test 100's or even 1000's of circuits on the same breadboard before it is toast. On a PCB, I'll be lucky if I can test a few variants of the SAME circuit (namely replacing parts with different part #'s).
Sometimes he says it works.Nigel Goodwin said:Except you CAN'T build VHF circuits on a breadboard, it's yet another reason they don't work.
audioguru said:Sometimes he says it works.
I think it is just a crystal radio. A tuned LC and a transistor's junction as an AM detector diode.
I wonder if it works better without a power supply.
audioguru said:MStechca,
Here is an article about "How to design a super-regenerative receiver".
**broken link removed**
It has the normal circuit of an oscillator with the tank at the collector and the quenching parts at the emitter.
It has the normal supply bypass capacitor that your circuits never have.
IT HAS FORMULAS and MATHEMATICAL EQUATIONS for you to guess about how much is your stray capacitance and inductance.
Nope.mstechca said:It looks like I'll have to generate my own equation.
So far, one equation that is close to working is: carrier frequency / Hfe = Quenching frequency.
I'm still unclear with "modulation frequency". Is it the oscillator frequency?audioguru said:2) The quenching frequency must be at least 2 times higher than the highest modulation frequency to avoid beats. Make the quenching frequency at least 4 times higher than the highest modulation frequency so you can use a reasonable lowpass filter to remove the quenching frequency from the output.
Modulation is the information in the transmission. If it is ordinary audio then it could extend up to 20kHz which is as high a frequency as you can hear. If it is a stereo FM or TV broadcast then it has mono audio from 50Hz to 15kHz, a 19kHz stereo pilot signal and 23kHz to 53kHz stereo subcarrier sidebands. It might even have data modulated up to 100kHz.mstechca said:I'm still unclear with "modulation frequency". Is it the oscillator frequency?
I learned about FM stereo when it was first broadcast and I built a kit FM stereo multiplex adapter to go with my kit FM tuner. Its detailed operation is in Google, search for FM Stereo.mstechca said:how did you know the other information? I can't seem to find it anywhere on the net.
FM stations used to broadcast SCA "restaurant" music around 67kHz. Now they have data that says their type of music.are there any other modulation frequencies of interest out there?