three antennas?

Thread Starter

mik3ca

Joined Feb 11, 2007
189
then we can say that my circuit works because the tank won't reach its resonant frequency when I tune, because the resonant frequency of it will be < 50Mhz. because the carrier frequency I am dealing with is > 100 Mhz, the actual AC resistance will be less than infinity.

So maybe one of my ideas is correct. Maybe I should after all, increase the inductor value, that way, the antenna (connected to the emitter) can control the circuit a little more. Come to think of it, I should see if I can make a 60Hz filter for the tank so that at that frequency, the detector won't do anything, and then maybe I won't hear ANY hum.
 

Audioguru

Joined Dec 20, 2007
11,248
I think your RF transistor acts like the AM detector diode in a crystal radio.

Why not make a super-regen radio exactly like the 3 that you have seen?
Then improve it with an RF amplifier.
 

Thread Starter

mik3ca

Joined Feb 11, 2007
189
I tried making it like the three circuits you showed me once before and I got worse results. I don't think I even got a signal once.

I was playing with the emitter inductor last night, and after I changed it from 1uH to 50uH, It seemed that I can pick up remote stations ok, but I am also picking up what sounds like shortwave. Sometimes when I tune (with the 50uH inductor in place), it sounds like I am almost changing stations on an AM radio.

so the value of the inductor is very important thing for me to consider. I think I will make it 2uH. I just have to remember not to make XL = XC.
 

Thread Starter

mik3ca

Joined Feb 11, 2007
189
Only use one RC lowpass filter.
you know that filter from Rick Andersons Superregen receiver page that AudioGuru boxed in red. Is it possible that I could maybe put two of those in series? so instead of having 1 resistor in my signal line with a grounding capacitor, I have two resistors in my signal line with two grounding capacitors, or will that make no difference?
 

Audioguru

Joined Dec 20, 2007
11,248
The de-emphasis lowpass filter in an FM radio is supposed to be only a single pole at 75us in North America. Its cutoff frequency is 1/(2 x pi x 75us) (2133Hz) and the single pole reduces high frequencies at 6dB per octave because FM transmitters boost high frequencies at 6dB per octave.

Two or more RC filters directly in series affect each other and the very droopy frequency response will have a steeper rate. Then the FM radio will sound worse than a lousy AM radio.

Andersen added an extra lowpass capacitor for stability. It severely cuts high audio frequencies but he doesn't care because aircraft pilots don't transmit music, only speech.
 

Thread Starter

mik3ca

Joined Feb 11, 2007
189
It seems that after adjusting multiple values, especially the capacitance that controls the quench frequency, I can pick up remote stations better. I even used lower feedback resistors, and it still works.

I guess the whole thing comes down to quench frequency.
 

Audioguru

Joined Dec 20, 2007
11,248
It looks like your super-regen radio is built upside-down.
Transistors have a small amount of current gain when they are connected backwards.

You have the tank at the emitter instead of at the collector and maybe the parts at your collector are the quenching oscillator parts that are supposed to be at the emitter.

The radio would probably work a lot better if the RF transistor was connected the correct way around and with very short wiring.
 
Top