Superregen radio

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zachtheterrible

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I went against the better judgement of some members of this board and built a superregenative radio receiver, not becaue i'm rebellious, but didnt have much else to do. I also wanted to see how it performed so that someday I can incorporate it into a proper radio receiver that actually uses IF amplification for gain, so that I can have an even more sensitive receiver.

I can hear aircraft very clear with this thing, but I can not hear my bug very well. I practically have to shout into it to hear over the radio. I imagine that maybe I need to lower the resistnce of that 47k that biases the oscillating transistor or something?

thanx :lol:
 

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The BC547 has a very wide range of DC gain unless you are using the B or C grade, so Q2 could be saturating. I would try a larger value for the base resistor.
 
What I do is start with the basic-most FM transmitter found on University of Guelph's site. Do a search for ~antoon with google, and you should see a link pointing to a website dedicated to circuits. On that site are 4 FM transmitters, none of which performed satisfactory for me. So what I did was take his simplest one and rip everything to the left of the coupling capacitor out and plugged in a complimentary-symmetry (push-pull) amplifier, and placed the microphone at the input of the push-pull amplifier with a 1.5 Megaohm feedback resistor.

You might want to check out Harry's Homebrew Homepages as well.
 
Hi Zach,
The super-regen radio receives AM, which is what aircraft use just above the FM broadcast band. A super-regen doesn't receive FM very well, you have to tune it to one side of the station so it "slope detects". Maybe you have tuned the side where the AM part and FM part of your transmitter cancel.
 
I just discovered something that might narrow things down, before I go and do circuit surgery.

The transmitter will not make the oscillating sound unless it gets really close to a speaker.
when i cut the power to the superregen though, the transmitter can be pretty far away from the speaker, and will oscillate for a second until all the power is gone from that 1000uf capacitor.
In other words, it seems that the superregen will receive the way I want it to for a second after the power is cut off.

btw, ive been listening to airplanes for a couple hours now, I drove around a bit and was listening to them. it was sooo cool! One time I heard something really weird. This guy comes on and starts talking about "launching" something, and I heard what sounded like a launch code, a series of numbers, read off very slowly. Then I heard things about "bravo".
 
Congratulations. Now if you want to change parts, only change the values of the tuning capacitors and the sensitivity resistor. It seems that the higher the value of the sensitivity resistor, the more stations you could get, but then some local stations could jam if you are close enough to them in frequency.

The transmitter will not make the oscillating sound unless it gets really close to a speaker.
Click to expand...
I find it much better to use small values for the capacitor connected between the battery and the transistor's base. Also, I use a 0.1uH inductor because Big resistance to me means less power.

You will need to experiment with the values of your parts. Try to not go under 500 ohms in resistance in any circuit or something might blow up or fail to work.

and btw, is your battery fresh?

A large value capacitor connected in parallel with the battery can help alot since the capacitor stores the energy from the battery.

And check your antennas. They should be between 6 and 12 inches. If you follow the wavelength formula, (where antenna metres = 300 / frequency in megahertz) then you will get a nice long antenna (2 - 3M), but you will receive better reception and transmission.

And for the transmitter, an antenna is necessary.
 
It seems that the higher the value of the sensitivity resistor, the more stations you could get, but then some local stations could jam if you are close enough to them in frequency.
Click to expand...
Really? I'll have to try that.

Ive been slapping in different capacitor values and have goten in the whole FM band, but like audio said, i can't hear it very well.

I'm going to try to get my transmitter working with the receiver before I do anything else.

I don't think this is true because I've tried tuning it to different parts of the signal and nothing.

Russ, Im not sure if what you said applies because this transmitter works just fine with regular radios. Should I still try that?

btw, I am using 2n3904's for the transistors of the transmitter.

EDIT: Just found out something interesting. when turning up the sensitivity of the receiver, you can get the the highest point, turn a little more, and the receiver will stop working. If I turn the receiver to the highest point of sensitivity, i hear the oscillating sound normally, but it has to be extremely precise, too little and you have to shout over it, too much and the receiver stops working. THIS IS DRIVING ME INSANE!! wuts a matta??
 
Ive been slapping in different capacitor values and have goten in the whole FM band, but like audio said, i can't hear it very well.
Click to expand...

lower capacitor values give higher frequencies, and higher capacitor values give lower frequencies.

Regular radios may have special circuitry inside them. If your transmitter works well with a regular radio, place your superregen the same distance from the transmitter. If the response is the same in both units with the exception of volume, then you should be OK.

Let's solve 1/2 your problems right now: Cut the cable off one of your computer speakers that you normally use. Open it up and you will see 2 wires inside. If one looks like it has enamel on it, sand it off. The enamel is there to prevent a short circuit. Now replace the microphone in the transmitter with the two wires you have revealled. Now turn your computer on, and have it play music continuously. Now adjust only your receiver's tuning dial and your computer's volume control. If you can hear the music in your receiver, then you are on the right track.
 
 

As Audioguru said, a super-regen is an AM radio receiver, so it will have very poor performance with an FM signal. Slope detection probably won't work very well because of the pathetic selectivity of this type of receiver.

zachtheterrible said:
I went against the better judgement of some members of this board and built a superregenative radio receiver
Click to expand...

So why ask questions about it?, we told you it would be crap, you built it - it is crap!, as it was going to be!. There's 'no magic cure' to make it wonderful, it's probably as good as it's going to get.
 
hey audio, ill have to pick up a 10k POT at radioshack *shudders*. ideally i think I'd try to get a 15k, but thats the closest theyve got, and i dont feel like making an online order and waiting . . . For the resistor in series with it, will 47k work?

Nigel, you sir are a wet blanket :lol: . Like i said, I built this for fun! when i found out it could receive aircraft, i really wanted to build it. I also thought it was worth a shot to see if my transmitter would work with it, and it seems that it might! I've already gotten better range with this than with a regular radio. The sound quality is just crap, which I'm trying to fix. Besides, the oscillator that that transmitter uses is supposed to put out as much AM as FM so why shouldnt it work?
 
Hi Zach,
The bandwidth of a super-regen reduces as its sensitivity is increased, so it will sound very distorted and muffled with no treble. It will sound like CRAP!

As I said before, measure the resistance of the existing pot when it is adjusted to max sensitivity, and if you use a 10K pot, use a series resistor that is the resistance that you measured minus 5K.
It probably won't have enough range of adjustment to be able to reduce the sensitivity for strong signals. Battery voltage will also affect sensitivity and it probably won't work any more when the voltage drops a bit.

I took a "real" scanner radio to the airport one time. The chatter was interesting.
 
Sure, but then it won't have any "gain". Reducing the Q of the tuned circuit will be like turning down the sensitivity control.
 
Well, i give up :lol: . I did what you said audio and got it to oscillate, but it's still nearly impossible to find the transmitter for one thing because I have to mess with sensitivity AND find the station @ the same time. and when I do find the station, its very hard to keep it there. and yes, sound quality is crap. don't rub it in too hard nigel :lol:

But im still happy I made it! I'm listening to aircraft as i type this. I can't believe I can actually hear jet airliners! like southwest. Do pilots communicate pretty much only when they are landing and taking off? Because if this is so, I am hearing from the airport in San Diego, which is an hour away at least from where I live.

EDIT: I tried using a 100k resistor in series with that POT to see if i could get beter sensitivity. Doesn't really seem to make all that much of a difference, but I'm not sure. What value would be best for optimum sensitivity and performance?
 
zachtheterrible said:
I am hearing from the airport in San Diego, which is an hour away at least from where I live.
Click to expand...
He, he. It's CRAP alright! Lots of fiddling. We told ya so!

I just got my old slide rule calculating that the airport must be 550 miles away because jetliners fly that fast. You must be at the top of a mountain.
But then again, the San Diego airport might be only about 3 miles away if you're walking for an hour to get there.
Are you the guy with a scooter or maybe your sister has a scooter? Nah, it must be Johnny down under. It would reach about 10 miles in 1 hour at top speed.

It would be cool (but unfortunate) to hear, "Mayday. This is 123 heavy and we've lost all hydraulics (or fly-by-wire on new planes). I'm going to attempt a landing by controling the aircraft using engine thrust only!" It was done and hundreds of lives were saved.
One jetliner had its elevator stuck in the extreme down position while in flight. The pilot managed to get it flying upside down pretty well but made a lousy landing.
How about the Concorde? Control tower: "You're on fire!" Pilot: "Fire? What fire? Oops!"
 
lol, that would be unfortunate :lol:

i heard somethin REEALY funny today. First I keep hearing someone saying: "what about that low flying aircraft over elsinore?"
Then the guy that was flying low says: "oh sorry"
Other guy: somethin about "you're in my way"
low flying guy: in a really annoying voice: "am i out of your way now?"
other guy: he just about cussed but held his tongue
low flying guy: "am i out of your way now?"
other guy: "GOD!"

i live about 40 miles from the airport i'd say.

So what about that question about thee 100k resistor and better sensitivity?
 
it was an edit, you must not've seen it:

EDIT: I tried using a 100k resistor in series with that POT to see if i could get beter sensitivity. Doesn't really seem to make all that much of a difference, but I'm not sure. What value would be best for optimum sensitivity and performance?
Click to expand...
 
Hi Zach,
100K in series with the pot is much too high since the original pot was 50K (on the schematic) and its setting for max sensitivity was much less.
Put a resistor in series with one end of the new 10K pot and its slider. The other end of the pot is one terminal and the other end of the resistor is the other terminal. With the pot set at half-way, the resistance between the terminals must measure the same as the resistance of the original pot when it was adjusted to max sensitivity. The smaller-value pot in series with a larger-value resistor reduces the range of the pot's setting so it is much easier to set to max sensitivity.
 
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