recently my friend designed a small diy am reciever for fun and my question is will it even work since im not 100% it will actually work.
After simulating the amplifier in ltspice it works but im not sure about the radio part.
After simulating the amplifier in ltspice it works but im not sure about the radio part.
Well its great to see you doing something like this 🙂
On the amplifier... it is very inefficient and the two 47 ohm resistors mean it will use a relatively high current for not very much output. A PP3 type battery won't last long. Current gain of individual transistors might also mean the operating points are a bit different (set by your 1 meg resistors).
Something like an LM386 chip would be better all round tbh, or you could copy the simple output stages of transistor radios of years ago.
The 1000nF cap looks a bit large. I would have thought 100nF would be plenty for AM radio bandwidth.
I'm no expert on what is really a 'crystal set' front end but I wonder whether the loading by the pot and 2nF will effectively reduce the sensitivity a lot.
On the amplifier... it is very inefficient and the two 47 ohm resistors mean it will use a relatively high current for not very much output. A PP3 type battery won't last long. Current gain of individual transistors might also mean the operating points are a bit different (set by your 1 meg resistors).
Something like an LM386 chip would be better all round tbh, or you could copy the simple output stages of transistor radios of years ago.
The 1000nF cap looks a bit large. I would have thought 100nF would be plenty for AM radio bandwidth.
I'm no expert on what is really a 'crystal set' front end but I wonder whether the loading by the pot and 2nF will effectively reduce the sensitivity a lot.
Remember the ZN414:
https://en.wikipedia.org/wiki/ZN414
As a youngster I never had much luck trying to make a working radio 🙁 (but don't let that put the op off)
https://en.wikipedia.org/wiki/ZN414
As a youngster I never had much luck trying to make a working radio 🙁 (but don't let that put the op off)
For the 1000nf its actually 100nf its a error in the schematic. And it isnt powered by a battery but a 0.5A power supply. So my question is will it work im not chasing high quality or efficiency but just wondering if it works
If you have simulated the audio section and it works OK then its going to work or be easily got to work in a real build.
You just posted 🙂 the LM386 makes more sense all round.
Superreg you mean?
For what frequency band is the circuit of post #1 meant? For the medium-wave broadcast band, I would expect something like 175 uH and a 500 pF tuning capacitor, with the antenna connected to a tap of the inductor or to the top via a 47 pF series capacitor.
Last edited:
It's a crystal set. That means it needs to receive quite a strong signal. That means you're looking at a proper broadcaster with ERP of many tens of kW. And that usually means MW and LW. I never measured the inductance, but I used to reckon that thirty or forty turns of 26swg enamelled copper wire on a 30mm core (a plastic pepperpot) tuned by a 50-500pF variable air-spaced capacitor and coupled to a few metres of aerial and a decent earth (central heating pipe) would work for MW. A germanium diode (OA91) was needed. With care, in the 70s, I could receive Radio Luxembourg in North London (UK) directly into a crystal earpiece - no amplifier or power source required. The RF part probably won't work, let alone the issues others have raised about the audio part. Sorry.
It will probably pick up the Spanish-speaking stations that some of my early amplifiers used to pick up. Without intending to of course. I’ve often wondered what the actual frequencies were, or if they were in the spectrum space that they were supposed to. My amps never seemed to pick up any of the strong megawatt local pop, country or talk radio stations (we did have some even on AM) - just stuff of unknown origin that may or may not have originated in the country.