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Practical Radio Circuits (2003) [pdf]

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Re: Practical Radio Circuits (2003) [pdf]

#31

Post by buescher »

drivers99 wrote: post #29

A friend and I have been trying to build an AM radio. We got a few working, like the basic "crystal" (germanium diode) one with an earpiece, generally picking up 1 or 2 stations very faintly. Then some attempts with an AM radio IC (TA7642), some that use a couple diodes and LM386 op-amp but they're generally terrible, if they work at all. It seems that following random schematics off the web or a youtube screenshot d…

Ronald Quan’s Build Your Own Transistor Radios is pretty good but I have only read it, not built any of the radios in it.

The Bowick book is solid for fundamentals like impedance matching and basic filter design. The old brown edition is more concise than the new one.

Re: Practical Radio Circuits (2003) [pdf]

#32

Post by wbl »

drivers99 wrote: post #29

A friend and I have been trying to build an AM radio. We got a few working, like the basic "crystal" (germanium diode) one with an earpiece, generally picking up 1 or 2 stations very faintly. Then some attempts with an AM radio IC (TA7642), some that use a couple diodes and LM386 op-amp but they're generally terrible, if they work at all. It seems that following random schematics off the web or a youtube screenshot d…

Application notes can be pretty informative. Also ARRL handbook

Re: Practical Radio Circuits (2003) [pdf]

#34

Post by drivers99 »

wbl wrote: post #32
drivers99 wrote: post #29

A friend and I have been trying to build an AM radio. We got a few working, like the basic "crystal" (germanium diode) one with an earpiece, generally picking up 1 or 2 stations very faintly. Then some attempts with an AM radio IC (TA7642), some that use a couple diodes and LM386 op-amp but they're generally terrible, if they work at all. It seems that following random schematics off the web or a youtube screenshot d…

Application notes can be pretty informative. Also ARRL handbook

Application notes as in the examples on datasheets?

Cool, I do have the ARRL handbook (100th edition). I also got the 50th (1973) and 66th (1989) editions partly out of curiosity (for the 1973 one) and because someone told me a late 80's edition might be good for info about building stuff.

Re: Practical Radio Circuits (2003) [pdf]

#35

Post by wbl »

seiferteric wrote: post #18
tessierashpool9 wrote: post #2

i'd love to see some grassroots-powered clandestine para-web running at least partially on radio. obviously such a project would either immediately or at some point face the usual issues like: spam, cp etc. that's why i believe such a network would have to be slow. it would have to be so slow (and just fast enough) for text-based communication and simple protocols. and i mean text as in < 1kB ... not sufficient for t…

I always wanted to do something like this with "earth mode" radio. That is, signals sent through the ground. You can put a couple conductors in the ground spaced far apart and send signals into them and it can be picked up miles away apparently. Would be really slow, so probably text only, but also probably no one would notice. I also vaguely wonder if this would still be regulated by the FCC since it's not through t…

You end up exciting the ionosphere this way so it's regulated. But there is a band way down there to play with if you have your ticket.

Re: Practical Radio Circuits (2003) [pdf]

#36

Post by accra4rx »

zh3 wrote: post #22
cushychicken wrote: post #9

You can pick up a pretty reasonable amount of radio signal with the right length of wire and a properly tuned LC circuit tank. I didn’t believe it until I tried it, but it’s a surprisingly good first pass at an FM frontend.

If you're into receiving low frequency time signals, you can receive them directly with nothing more than a piece of wire connected to the mic input of a modern sound card (via a capacitor). Sample at 192kHz and downsample in software (simplest: mix with a similiar frequency sine and listen to the result, say 59kHz for WWVB or MSF).

are there any good circuits for radio transmitter (circuit for low freq esp 60KHz)

Re: Practical Radio Circuits (2003) [pdf]

#37

Post by rjsw »

drivers99 wrote: post #29

A friend and I have been trying to build an AM radio. We got a few working, like the basic "crystal" (germanium diode) one with an earpiece, generally picking up 1 or 2 stations very faintly. Then some attempts with an AM radio IC (TA7642), some that use a couple diodes and LM386 op-amp but they're generally terrible, if they work at all. It seems that following random schematics off the web or a youtube screenshot d…

I worked through this [1] book (PDF) as a child, everything worked fine but have no idea if component availability has changed.

[1] https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/M...

Re: Practical Radio Circuits (2003) [pdf]

#38

Post by aidenn0 »

zh3 wrote: post #22
cushychicken wrote: post #9

You can pick up a pretty reasonable amount of radio signal with the right length of wire and a properly tuned LC circuit tank. I didn’t believe it until I tried it, but it’s a surprisingly good first pass at an FM frontend.

If you're into receiving low frequency time signals, you can receive them directly with nothing more than a piece of wire connected to the mic input of a modern sound card (via a capacitor). Sample at 192kHz and downsample in software (simplest: mix with a similiar frequency sine and listen to the result, say 59kHz for WWVB or MSF).

Really just a piece of wire? I would have thought that there would be too much noise to pick up WWVB without a somewhat more selective antenna (loopstick maybe?)

Re: Practical Radio Circuits (2003) [pdf]

#39

Post by drivers99 »

rjsw wrote: post #37
drivers99 wrote: post #29

A friend and I have been trying to build an AM radio. We got a few working, like the basic "crystal" (germanium diode) one with an earpiece, generally picking up 1 or 2 stations very faintly. Then some attempts with an AM radio IC (TA7642), some that use a couple diodes and LM386 op-amp but they're generally terrible, if they work at all. It seems that following random schematics off the web or a youtube screenshot d…

I worked through this [1] book (PDF) as a child, everything worked fine but have no idea if component availability has changed. [1] https://www.worldradiohistory.com/BOOKSHELF-ARH/Technology/M...

Nice, I ran across that a month or two ago and it was great. I got to the OC71 germanium transistor and found out they're obsolete.

Re: Practical Radio Circuits (2003) [pdf]

#40

Post by zh3 »

accra4rx wrote: post #36
zh3 wrote: post #22

Earlier quoted context omitted.

If you're into receiving low frequency time signals, you can receive them directly with nothing more than a piece of wire connected to the mic input of a modern sound card (via a capacitor). Sample at 192kHz and downsample in software (simplest: mix with a similiar frequency sine and listen to the result, say 59kHz for WWVB or MSF).

are there any good circuits for radio transmitter (circuit for low freq esp 60KHz)

It's super-easy for very short range, super-difficult for long range. Reason is the wavelength is so long (speed of length/60KHz = 5Kms) that you need a massive aerial for lange range, however for short range you can feed the MW or LW coil of an AM radio to spoof a time signal (ideally make it resonant by adding the right amount of capacitance, look up "tank circuit"). Watch out if you add amplification though, due to the lnog wavelength and the high inductances involved (if you get that far) it is possible to end up with dangerous voltages at the aerial feed.

A sound card with a true 192Khz sample rate should be enough to fool a radio clock next to the transmitter coil - though be aware a lot of sound cards may not actually output the 60kHz carrier frequency required.

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