I truly enjoyed the article.
When I played the vimeo video of ½ λ dipole antenna electric field propagation I reached
for my headphones hoping to hear dark side of the moon. No dice. I get antennas and their physical characteristics and I am always intimidated by the math behind digital signal processing (DSP). Again, great article.
Radios, how do they work?
41–50 of 114 posts
Re: Radios, how do they work?
#42Earlier quoted context omitted.
AM peak detector is probably the easiest and primitive AM demodulator: it's basically made by a diode, a capacitor and a resistance. I implemented it when I was in the high school and I was making the first physics experiments. The idea behind this demodulator is quite easy: the diode filters out all of the negative part of the signal, then the positive signal charge the capacitor and the energy is released in a quit…
I was trying to say that a capacitor and diode (detector) is not a complete receiver.
You will need also a resistor otherwise the capacitor is not going to discharge, but the resistance is the easiest component :)
Re: Radios, how do they work?
#43Another trick, which I haven't really appreciated for a long time, is that it's VERY dark in the radio frequencies. Black bodies radiate barely any energy there. It's quiet so if you shout even moderately loudly you can be heard halfway across the globe. It's permanently night and even small lamp shines quite far.
Re: Radios, how do they work?
#44Magnets
Came here to see this. Thank you.
Re: Radios, how do they work?
#45I work RF world pretty regularly, and I still consider the Superheterodyne Receiver to be tantamount to magic. Edwin Armstrong was a brilliant brilliant man.
Not that it matters much, but it seems to be somewhat unclear who came up with the idea for the superheterodyne receiver first. Could be Armstrong, or Lévy, or even Schottky. The patent in the US was eventually awarded to Lévy.
Armstrong definitely was a genius though. Before the superheterodyne receiver he also invented the regenerative receiver.
And you're right, the superheterodyne is such a marvelous technology. The principles it's based on aren't super complex in itself, but the combination of them is genius.
https://en.wikipedia.org/wiki/Regenerative_circuit https://en.wikipedia.org/wiki/Superheterodyne_receiver
Re: Radios, how do they work?
#46Earlier quoted context omitted.
AM is quite easy (a diode and a capacitor can be enough), an FM receiver need a local oscillator that require some active elements (transistors) and a more complex circuit.
Under what circumstances is a diode and a capacitor enough to make a radio receiver?
I read "AM is quite easy" as "AM demodulation is quite easy".
Re: Radios, how do they work?
#47Their primer article [1] is also really nice. > Today, I’d like to close this gap with a couple of crisp definitions that stay clear of flawed hydraulic analogies, but also don’t get bogged down by differential equations or complex number algebra. Related: many, many years ago, when Facebook didn't exist yet, Google still passed as a "good" company, and hobbyist electronic geeks had almost only PICs to choose from, I…
I guess the original "NEETS" content is this: http://compatt.com/Tutorials/NEETS/NEETS.html Content updated in 2011.
THAT'S IT!!!
Thank you so much! I've been looking for this for at least fifteen years!
And there are even links to previous HTML versions (this one is PDF)... amazing!
Re: Radios, how do they work?
#48For sure they do not work the way the "Path Loss Equation" would have you believe they do. The path loss equation violates conservation of energy ie the frequency or wavelength term depending on how it's structured cannot be in the equation. And the receiving antenna does not have any 'gain' other than physically getting bigger or smaller, though the transmitting antenna can have gain depending on shape and size. That is, the transmitting antenna and the receiving antenna work very differently. Yes, end to end the path loss equation gives the right answer but in between it's scientifically illiterate.
Re: Radios, how do they work?
#49This reminds me of a really cool video on superheterodyne receivers that Technology Connections did. https://www.youtube.com/watch?v=hz_mMLhUinw
Re: Radios, how do they work?
#50For sure they do not work the way the "Path Loss Equation" would have you believe they do. The path loss equation violates conservation of energy ie the frequency or wavelength term depending on how it's structured cannot be in the equation. And the receiving antenna does not have any 'gain' other than physically getting bigger or smaller, though the transmitting antenna can have gain depending on shape and size. Tha…
> The path loss equation violates conservation of energy ie the frequency or wavelength term depending on how it's structured cannot be in the equation.
Why is that?