[HN Gopher] Practical Radio Circuits (2003) [pdf]
___________________________________________________________________
Practical Radio Circuits (2003) [pdf]
Author : _Microft
Score : 143 points
Date : 2024-11-02 07:34 UTC (6 days ago)
(HTM) web link (www.fracassi.net)
(TXT) w3m dump (www.fracassi.net)
| tessierashpool9 wrote:
| 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 transmitting sth
| like base64(videoclip). that would be so cool.
| jsilence wrote:
| Internet via Ham Radio aka Packet Radio is a thing:
| https://themodernham.com/ip-over-ham-radio-via-new-packet-ra...
|
| Pair it with the Gemini protocol and you're there:
| https://en.wikipedia.org/wiki/Gemini_(protocol)
| michaelt wrote:
| Isn't ham radio no-encryption-allowed, no-commercial-use-
| allowed?
| myth2018 wrote:
| It is. That doesn't disallow mesh networks, but Gemini
| would be off-limits due to TLS. Gopher would be OK.
| deknos wrote:
| Signatures are okay though.
|
| And you can do encryption, when you have to control remote
| devices which belong to you.
|
| and internet still can be non commercial.
| bityard wrote:
| Sort of, yes, but it's quite a bit more nuanced than that.
|
| The actual rules say you're not allowed to obscure the
| meaning of a message. Use of encryption itself is not
| specifically prohibited, but you're not allowed to hide the
| information being sent. So, "encryption" is technically
| allowed for things like authentication and signatures,
| under most interpretations of the rule.
|
| It is correct that you're not allowed to use your ham
| license for any commercial purpose. But again, there are
| narrow exceptions: a teacher getting paid to teach a class
| on amateur radio or science in general can transmit to
| demonstrate the technology, or an astronaut or military
| member making contacts with amateurs for goodwill purposes
| or as part of an exercise.
| tessierashpool9 wrote:
| at the risk of this not flying well with some ham people
| here but i'd say the heck with those regulations i'm
| encrypting and that's the end of the story it's called
| clandestine for a reason after all
| bityard wrote:
| "Not flying well" has nothing to do with it. If you are
| transmitting on the amateur bands without a license,
| that's illegal. If you do it with any regularity, you are
| causing interference and some hams are better than you'd
| think at locating sources of unwanted interference.
|
| There are plenty of other anything-goes bands for you to
| use, there's literally no reason to do your pirate radio
| on the ham bands. Except to get those warm fuzzy counter-
| culture feels I guess.
| tessierashpool9 wrote:
| then let's go off-ham
| tonyarkles wrote:
| That's the tricky part... if you're going for legal and
| license-free you're pretty much left with the ISM bands
| and very limited transmit power. There's nothing stopping
| you from getting a real spectrum license and narrowband
| licenses in the 2m and 70cm bands aren't actually that
| expensive but there's also equipment certification
| requirements, generally.
| cruffle_duffle wrote:
| The 'no encryption' rule in ham radio is intended to
| encourage experimentation and openness. Ham radio has
| always been about exploring, learning, and sharing
| knowledge, much like open-source software. If
| transmissions are encrypted, it becomes nearly impossible
| for others to decode, learn from, or experiment with
| them. The idea is that anyone with the right knowledge of
| the protocol should be able to communicate with anyone
| else on the airwaves, supporting the spirit of why this
| spectrum is reserved.
|
| That said, balancing this with modern needs for security
| and privacy is a real challenge. Good communication
| protocols today are designed with these protections in
| mind, and the inability to use encryption arguably limits
| what amateur radio enthusiasts can do with newer radio
| technologies.
|
| Privacy, however, has traditionally not been part of ham
| radio--this is why you're required to identify yourself
| with a call sign, and contact info is publicly available.
| The identity of the sender is expected to be open. Maybe
| there's room to allow for some privacy around the content
| of the message itself, but the sender's identity should
| still be clear. I'm not sure what the right balance is,
| but simply allowing complete encryption that hides the
| message, the transmitter's identity, and the transmission
| protocol itself doesn't seem to align with the purpose of
| amateur radio.
|
| The 'trash bands' (ISM bands) are probably a much better
| place for experimenting with full-bore encryption and
| privacy. From these experiments, we might learn a
| balanced approach that could be backported to the amateur
| spectrum, preserving the spirit of why these bands exist
| while adapting to modern privacy needs.
| bityard wrote:
| Ham radio is actively unfit for the requirement of
| "clandestine" for the parent commentor's purpose.
| wildzzz wrote:
| Too many narcs on the ham bands would track you down for
| operating encrypted ham packet radio. You're better off using
| something like LoRa over the ISM bands. Build out a network
| of hidden mesh nodes over the area you'd like to operate and
| that's probably the closest you'll get to a true clandestine
| network. Of course the major issue with transmitting any RF
| energy is that someone can watch the spectrum and look for
| those transmissions and eventually track down your nodes.
| LoRa uses DSSS which if operating at minimum power, could
| help hide transmissions.
|
| If you want to add some illegality to the system, you could
| piggyback on amsats or open relay satellites like FLTSATCOM
| to expand your network and hide better.
| hbrav wrote:
| This should interest you: https://meshtastic.org/
| tessierashpool9 wrote:
| looks interesting. a network of maybe solar-powered scrapped
| commodity hardware or cheap raspis. maximum of 1kB/sec
| bandwidth. fully encrypted. no logging. all peer to peer
| networked. messaging / chat, text-based websites. maybe some
| simple images (black / white, svg) but optional.
|
| i don't think this would be in and off itself a game changer
| but it could be a seed for further development of anarchistic
| technology culture.
| cushychicken wrote:
| Reticulum qualifies as that. It's designed to run over LoRA.
| (The radio protocol, not the LLM thing.)
| tessierashpool9 wrote:
| i can't help it but hear LoRA spoken by a parrot in my head.
| LoRA, LoRA, ...
| cushychicken wrote:
| Great, now I can't help it either.
| seiferteric wrote:
| 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
| the air...
| tessierashpool9 wrote:
| that sounds interesting. never heard of that. are those
| conductors passive? just a mesh of copper wire or sth like
| that?
| wbl wrote:
| 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.
| carltg_ wrote:
| While 9kHz[3e-7/cm] (for an earth mode radio example) is
| lower than the plasma frequency of the ionosphere,
| 9MHz[3e-4/cm] (critical so that the ionosphere acts as a
| waveguide), would this be significantly lower, and hence
| have a high attenuation--a large imaginary component to the
| refractive index? If so, would this excite the ionosphere?
| Genuinely curious
| wbl wrote:
| The earth ionosphere capacitance. See longwave for
| details
| itomato wrote:
| Check out the DigiPi and all it can do.
| cushychicken wrote:
| 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.
| zh3 wrote:
| 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).
| elzbardico wrote:
| The 2024 version of the crystal radio. :-D
| accra4rx wrote:
| are there any good circuits for radio transmitter (circuit
| for low freq esp 60KHz)
| zh3 wrote:
| 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.
| aidenn0 wrote:
| 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?)
| zh3 wrote:
| Yes, depends of course on distance, aerial layout and on
| the decoding technique. Anything over a few hundred miles
| needs amplification/attention to aerial resonance etc,
| simply mixing (multiplying) the received signal wth a sine
| wave close to the same frequency results in a quite audible
| signal (strength varies throughout the day though).
|
| Used to be easy to pick up Loran signals in the same way
| (esp. with untuned aerials) but they're all turned off now.
| JKCalhoun wrote:
| The regenerative receiver, followed by the superheterodyne
| receiver? Edwin Howard Armstrong might be the man who fell to
| earth.
| mannykannot wrote:
| And FM. Tragically, he was driven to suicide by his battles
| with Sarnoff, principally over the IP rights to his own
| inventions.
| hezag wrote:
| Loved this practical guide publication format. Anyone know other
| magazines like this Everyday Practical Electronics?
| zh3 wrote:
| There used to loads of magazines like this. 'Everyday Practical
| Electronics' was from the merger of Everday Electronics and
| Practical Electronics IIRC, separately just in the UK there was
| Practical Wireless, Wireless World, Electronics International
| and many others (I may be getting the names a bit wrong here,
| but I have Practical Wireless dating back to 1963 or so -
| mostly valves then of course!). Elektor [0] is still around
| (online), also see things like the ARRL Handbook and associated
| publications (plus RSGB [2] in the UK, plentyof others out
| there).
|
| [0] https://www.elektor.com/collections/magazines
|
| [1] https://www.arrl.org/
|
| [2] https://rsgb.org/
| buescher wrote:
| Some thoughts - this is a good overview of how stagnant the
| hobbyist state of the art was 20 years ago. You could probably
| have built all of these circuits with the those exact parts in
| 1973. Pretty much everything in this collection but the superhet
| and direct-conversion receivers is obsolete and was at best
| obsolescent at the time. You can think of a typical SDR as a
| dual-conversion receiver with a conversion stage in the digital
| domain. Superregens were used in remote controls right up through
| the turn of the century, but by the time this was written no one
| was designing new ones. I saw a TRF front end on a commercial
| ultrasound device in that era but it was not typical.
|
| Many RF transistors are no longer available in through-hole
| though you can probably find small quantities for hobby projects.
| The msph10 is long gone. And good luck sourcing dual-gate mosfets
| even in smt. Infineon might still make a couple.
|
| As a digression, it does make me think TRF receivers are probably
| a better learning tool than the my-second-radio regenerative
| receiver. Crystal radios, of course, are pure magic and it's sad
| that so few people get to build them as kids.
| drivers99 wrote:
| 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 doesn't work very well.
|
| I do have an RF design book I haven't started (by Chris Bowick)
| as well as this PDF now, which should be even more practical, so
| I'm hopeful I can figure it out. I also have some test equipment
| such as nanoVNA, tinySA, and an oscilloscope which makes it
| possible to get visibility into how stuff behave beyond "I don't
| hear anything; no idea what's wrong." I was able to see how the
| tank circuit was behaving as you tune it.
| buescher wrote:
| 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.
| wbl wrote:
| Application notes can be pretty informative. Also ARRL handbook
| drivers99 wrote:
| 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.
| rjsw wrote:
| 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...
| drivers99 wrote:
| 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.
| styczen wrote:
| where can I buy new these f&* _(_ ( headphones
___________________________________________________________________
(page generated 2024-11-08 23:01 UTC)