Electronics > RF, Microwave, Ham Radio

Radio from first principles ?

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jwhitmore:
I probably need a good book rather then pestering you people. I'm starting out and I could get into HAM radio by spending money on an expensive radio and all the gear. I'm afraid I'd learn very little that way so I want to do it from first principals. Almost follow the evolution of Radio so to speak. Most books seem to be at a higher level then that. Like getting an SDR up and running. I'll get there eventually I hope.

So I'd like to put up a self build antenna and just plug it into my Rigol 1054Z and be able to understand what I'm looking at. Then go from there amplify and filter and all that stuff.

So my question would be book recommendation and what "bandwidth" antenna should I start with. I assume Morse in the 20M band and stretch a piece of copper wire out across the lawn or something?

MrSlack:
It's a little more complicated than that but not much.

A good book - yes, but I suspect we're fine being pestered :)

I'd suggest grabbing a copy of the ARRL Handbook which is published yearly (mine is 1995 - old ones are fine). It's chock full of the fundamentals of radio. Digest some of that before you look at the signals on a random wire antenna.

You can do exactly what you have described but a time domain instrument like a scope isn't really very good for looking at what comes in on the wire. You need to at the very least stuff it through a resonant filter and detector/demodulator, resulting in a "crystal set" and observing the reuslt of that. You can build one of these with a schottky diode, a variable capacitor and a coil of wire. Then stick an LM386 AF amp on it. That will be far more useful than a scope for early experimentation.

A scope is going to do the majority of its work if you move to a direct conversion or superhet receiver.

40m CW (morse) seems to be the easiest place to pick anything up reliably but you will need to use a BFO (beat frequency oscillator) with a crystal set to actually hear any CW as the carrier is modulated on and off which has no audio component. On this basis I'd try and build a shortwave broadcast receiver which uses AM modulation and works fine on a crystal set. You can then bodge it with a BFO later (most of RF is progressive bodging I find :))

hendorog:
An easy way to start might be to use the HAM exam training material - e.g. for NZ it is here:
http://www.nzart.org.nz/assets/exam/Study_Book_14022013_Teachers_Edition.pdf

Section 15 (Page 90) onwards is where it talks about how transmitters work, antennas etc.

You should be able to get a quick overview of what is involved, what you already understand and what you need to learn about. Then go and find more detailed info on the bits you are missing.

uncle_bob:
Hi

Well, a lot depends on just how "first principles" you want to get. Physics is a good starting point for a lot of the basics of radio ...

That said, I think you would have a lot more fun doing it with some of the stuff targeted at Ham radio. The basic stuff for a license course is not a bad way to get the introductory stuff.

Bob

mtdoc:
I bought but have not yet read Build Your Own Transistor Radios. 

It gets good reviews and the author, Ronald Quan is a bonafide ex-HP analog guru. He was interviewed on the AmpHour a while back.

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