amplifying to the extreme

Thread Starter

mik3ca

Joined Feb 11, 2007
189
I have discovered why my radio was too insensitive before.

but now, I want to maximize my amplification and signal strength.

I have seen single-stage amplifiers, two-stage amplifiers and three-stage amplifiers.

Just out of curiosity, what are the maximum stages I could possibly have for high end amplification? (in other words, I want to jack up the volume of my receiver).

I want to avoid adding excessive stages if they don't help me.
 

beenthere

Joined Apr 20, 2004
15,819
Signal strength is a function of the distance from the transmitter and the antenna characteristic. Sensitivity to the received signal is a function of tuning selectivity and even construction and layout details in the receiver. If the output is a headphone, one more stage of amplification should be enough.
 

Eyas

Joined Dec 23, 2007
10
Good day

As I understand from your question, you have a radio and you cannot get small signals.

If this is the case, then I just bought a project titled "AM-FM Antenna Amplifier" from Velleman-kit. the project number is K2622.

As I understand from that project, this project can be placed after the antenna in your radio to help you get small signals.
Respecting the rights of designing, I will give you this page and I will not give you the diagram of the circuit but it is only one stage amplifier.

See:
http://www.velleman.be/ot/en/product/view/?id=9054

GOOD LUCK
 

Audioguru

Joined Dec 20, 2007
11,249
Hi Eyas,
There are many high power FM radio stations and TV stations near the receiver. The wideband RF amplifier would be severely overloaded by them. An FM radio is supposed to have a tuned circuit then an RF amplifier then another tuned circuit. Then a very high gain IF amplifier that is also tuned. This super-regen receiver doesn't have them.

Hi Mik3ca,
Have you tried the two super-regen receivers exactly the way they are designed?
 

Thread Starter

mik3ca

Joined Feb 11, 2007
189
I tried one on a breadboard compared to my design. My design works OK on a breadboard, but the other designs don't seem to work so well, so I want to continue with my design.

I want to continue with superregen instead of a superhet because I want to minimize the number of elements I have to tune.
 

Eyas

Joined Dec 23, 2007
10
hi Audioguru

Thank you very much for the valuable information. However, I already aware of that but what I have written is what I read in the project guide I bought. To be honest, I have bought the project because I made an FM transmitter as project for a university course and there was a bounus for whome can increase the transmission range. I have connected the circuit but I did not test it yet. I hope that it can work.

Thank you very much again.
 

Audioguru

Joined Dec 20, 2007
11,249
Hi Mk3ca,
A VHF circuit usually does not work on a breadboard because the capacitance between rows of contacts and between wires is far too high.
Also, the series inductance of each connection wire is far too high.

You must use a pcb with a good ground plane. I was lucky with my FM transmitter project built on stripboard because I kept the wiring as short as possible.

The circuits that you have seen use low value ceramic capacitors as VHF bypasses. They have a very low inductance so their impedance at VHF frequencies is zero.
But you have high value electrolytic capacitors instead that are very inductive at VHF frequencies and have a high impedance.

The simple super-regen has a single capacitor to tune. My Sony Walkman FM radio is cheap but it has a pretty good super-heterodyne circuit and has a dual capacitor for tuning. One capacitor tunes the output of the RF amplifier transistor and the other capacitor tunes its oscillator so that every station produces an IF frequency of 10.7MHz.
Its RF transistor becomes overloaded by strong local stations because its input is not tuned. AGC would just reduce the sensitivity of all stations if one is strong. So it has a local-distant switch to select its sensitivity.

Good FM radios have a triple-tuned capacitor and AGC.
 
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