Taking a Radio Camping | Hacker News Reader

Taking a Radio Camping

ewpratten.com

139 pointsewpratten50 comments

Back in the 70s when shortwave was still king, we used to pack communications radios, rolls of antenna wire and jump on a train to travel up to northern Scandinavia to listen to faraway exotic stations on the medium and shortwave bands. It was an ideal environment with no electronic noise, mainly due to scarce population, and we were free to roll out 500 meters of longwire in various directions without upsetting anybody. Fun times indeed!

I occasionally get a long wire between buildings and listen to shortwave and bands. Sometime I’d like to get a HackRF and try out SDR and GNU Radio.

HackRF isn't the only way to go. There are other projects like T41-EP that can give you a really nice software defined platform as well.

Check it out here: https://www.4sqrp.com/T41main.php

(hint: you know it's a group of hams as soon as you see the colored fonts and grey background)

yeah you can also get an RTL-SDR for like $30 USD (or something) and listen to a pretty wide range of frequencies - definitely good enough to get started with a very small cost.

Not for shortwave. They don’t work below 50Mhz

Rtl-sdr blog v3 has a direct sampling mode that will get you into the single-digit mhz.

I assume that the v4 does as well. The earlier versions apparently also have this mode but it requires opening the devices up and a bit of soldering here and there.

I have an RTL-SDR and an upconverter. Pretty nice setup if you don't need the ability to transmit.

They do indeed, with the RTL-SDR Blog V3 and "direct sampling" mode! I think it's the only one at that price point that you can directly listen to HF/shortwave.

I have a couple of the super cheap ones I got for like $12 years back. With a simple mod you can get direct sampling and listen to any frequency. Works great.

The best radio for shortwave is without any doubt the Belka. It costs around 200€, but the quality is fantastic. The new versions cover also LW/MW and have an IQ output, so you can use as SDR as well. Otherwise you can find some Chinese clones of SDR play that are really cheap, but I am not suggesting those from a ethical standpoint

In the 90s I spent a few years working on the Jindalee Over-The-Horizon-Radar. It's in the HF band and located in a quiet spot in the middle of Australia. At that time it wasn't fully operational, so there were substantial periods where the research team had exclusive access. One of the techs was a keen radio amateur and used to patch his HF kit into the beamformed antenna array. Subject to the ionosphere not being complete rubbish he could roam around to his hearts content. A further bonus was real-time access to one of the world's best ionosonde networks. It was HF nirvana.

The variation in local noise between different locations is huge. As an apartment dweller and radio amateur, this is something I am fighting every day and in a densely populated environment, the noise floor changes all the time, depending on which neighbor operates which electrical device at the time...

The amateur radio community is very aware of the problems and several initiatives have been launched to quantify the effects. One of them is the DARC's ENAMS, which is described in detail here:

https://web.tapr.org/meetings/DCC_2020/DK5HH/F_ENAMS-DCC-DK5...

Have you tried a QRM Eliminator? I haven't tried one myself yet, but I hear good things about them. Also, some really simple things can be really noisy. Cheap LED bulbs for example can be super noisy. I had one above my desk that was terrible.

I think that's a phasing device. You attach an auxiliary antenna specially to pick up the noise. The signal from that is phase shifted and mixed into the signal from the main antenna. The phase shift circuitry has knobs to vary the phase and amplitude. You adjust them so that the noise cancels out.

That can be effective but it's really only useful for cancelling out one noise source. I once used a similar device when there was something bad happening on a power pole down the street. It's no use if you have general noise from multiple directions.

This would be an effective method against Iran’s scrambling of satellite TV

A buddy of mine uses one and it is effective. Most of your noise will come from buck converters and other cheap power supplies in the near field. Cell phone chargers, 120ac to 12vdc PSU, computer PSU, and fluorescent lighting ballasts are big culprits. Plasma TVs will generate more noise as they age. Pole-mounted cable repeater PSU go bad and start heating up, generating a shitload of noise. Any arcing on cracked insulators will generate RFI and can be easily located by driving around with a clear AM channel on your car stereo. Report these as they must also be repaired. Cheap solar panel inverters are also noise generators. A process of isolating house circuits helps identify the offending devices if they are in the home. In most cases, it is unlawful for devices to generate spurious emissions. In the case of solar panel inverters, they must fix/replace them if you complain. Another thing to check is cable tv leakage, which is less of a problem today, but can still cause interference. Unterminated cable coax can radiate lots of noise in the 144mhz band, and also on other channels. Great article about RFI hunting and elimination: https://www.arrl.org/files/file/RFI/Thompson%20Noise.pdf

Wow! Thats a very cool device. I'll be investigating further for my at-home setup.

I plan to write about my home setup, which is... a little crazy antenna-wise.

The noise here is really bad due to my area and the construction of the building I live in. Much creativity is required to get QSOs from here.

A big part of Ham radio today is what are known as POTA (Parks on the Air) activations where hams go to different parks to make contacts with other hams. These are often low-power transmissions (Known as QRP, or 10W or less). I think a big driver of this is the fact that our cities have become so noisy.

https://parksontheair.com/

Side note: if you read Hacker News, enjoy tinkering with electronics, and want to meet/talk to more people like you, I recommend becoming a Ham. The Technician and General exams from the FCC are relatively easy if you have any technical background and it's a great outlet for experimenting.

I actually intended to make these proper POTA activations, but I couldn't figure out the park identifier due to lack of cell service, and I also didn't bring anything for VHF to try doing so over APRS.

Next time I guess.

Nice article, btw.

But I am very curious. Did you use a balun or antenna tuner?

Thanks! I used the integrated tuner in my KX2. Worked perfectly.

If you find the park reference you can submit logs to pota.app after the fact. Any qso counts.

Thanks for pointing that out. I will do so

This has been on my list for a while now, and I've played with radio in various forms (allowed...) for the past few years and have quite the collection of baofang, many sdrs, a dish collecting goes16 images 24/7.. etc.

I am however, for whatever reason, adverse to the social, or seemingly kinda social, aspect of the proctored exams.

Am I just making a mountain out of a molehill?

You just go and take the test. The guy administering it may want to talk about his granddaughter's wedding or his prostate or whatever but you can just take the test and go home. It's not illegal to be rude. You never have to see him again.

It's really not a big deal. They just watch as you take the test and then you go home. There's very little socializing (unless you want to, hams seem to love to talk to each other).

Also, you can take the tests online as well, you usually just have to have a camera setup so they can see you aren't cheating: https://hamradioprep.com/ham-radio-license-test-online/

I have a question for amateur radio enthusiasts:

Let's say "radio 1.0" is as it existed since radio was invented: convert raw analog or digital packets into a signal of a given wavelength as assigned by the FCC for the "type" i.e. nautical, hobby, aero, etc. Roughly associated with physical distance.

It's obvious we have the technology at this point where multiple streams of information can be reconstructed from one wire/pipe. My cable internet is mixed with thousands of other users and yet the cable internet system delivers me just my data.

Why is the airwaves not just another physical medium (metal wire, fiber optic, air)?

If I want to build an amateur transmitter to airstream my Twitch to my friend in Brazil, the FCC would say no, because

1. Can't clutter up the airwaves (the FCC manages the wavelengths) 2. For "safety" (government wants to monitor the stream)

In "radio 2.0" I can build my hobby hardware to whatever transmit power I want and use whatever wavelength I want because air is just another medium for the same signal. My question is roughly, why cant the organizing principles of my router, isp cable internet system, etc apply to over the air transmission?

Is it a physics limitation? Or a "we always did it this way therefore you can't have it" (FCC, etc)

Let's say I hypothetically have a high power handheld transmitter in my pocket powered by modern batteries, the FCC doesn't exist, and the power is the best that the modern batteries can provide, with the only tradeoffs being weight of the transmitter and duration of batteries, i.e. physics based tradeoffs.

Don't we have the technology to mix thousands of such handheld transmitters so that everyone can carry one, broadcast their own stream, and intermix the streams, and deconstruct the stream back to my own data?

The same principles are used and airwaves are just another physical medium. The problems are this is shared media with everyone else and also it's somewhat inefficient media (EDIT: and noisy).

Your hypothetical high powered handheld transmitter (e.g. you cellphone?) is limited by the amount of power from your batteries and other factors.

EDIT: The bandwidth of radio waves is also limited and there's noise which limits the total amount of data you can broadcast.

The purpose of the post is trying to understand 1. can a viable mesh-network exist 2. does the mesh network not currently exist because it's artificially suppressed by centralized networking (i.e. cellphone service providers' influence over the FCC), or 3. Does a mesh network not exist because physics

On point 3, we have made huge strides in miniaturization of electrical components since the dawn of radio; we have also made huge strides in battery technology.

That would suggest it's physically possible to build better devices, so maybe the limiting factor is more #2 nowadays, the ability to innovate is capped not by physics but by regulation.

Sure, things like LoRa exist, but are not widely useful.

If iPhones were a little more brick-like, maybe we wouldn't need to dump money into ISPs pockets; we could just have a standard communication language to bounce packets around. Then we don't need to pay cell phone bills, just buy new batteries.

I'm a big fan of the idea of a mesh network. That said you're probably not going to replace fiber optic networks (e.g.) with a mesh of wireless devices. But having a dynamic peer-to-peer wireless mesh to augment physical media is probably something that improves the overall network.

I tend to agree that likely regulation is part of this but maybe a counter example is people opening their WiFi networks, which isn't regulated against, but people generally don't do. OTOH we could have regulation forcing all WiFi networks to be open? With some mechanism of paying people for bandwidth usage? But who would drive something like that? I think that's not different than me going through your phone on the way to the next hop? You will need to give me some battery life, and some of your bandwidth, so what do you get in return?

802.11s

https://en.wikipedia.org/wiki/IEEE_802.11s

https://en.wikipedia.org/wiki/Wireless_mesh_network

The limitation is probably Metcalf's Law. It's difficult to mesh enough users to get the value of the network to match that of the cellular network, so the cellular network wins.

You might be just describing packet radio, which does exist, but it's extremely slow due to the physical size of the radio waves involved, as I understand it. The frequency of the waves, due to their extremely long wavelength, is very low.

The trade-off for the long wavelengths is better permeability of the signal, which is why the author of the article is able to transmit so far on seven watts, but your Wi-Fi (high frequency and very short wavelength) has trouble getting through walls.

Packet doesn’t have to be in any particular frequency band, e.g. not in ELF-MF (3Hz-3000kHz).

It just implies packet switching instead of circuit switching or message switching, and can be done at any frequency.

APRS is packet; anything that hears a position report can decode the data and decide what to do with it, as a unit. This is versus circuit switching or message switching-circuit switching being a dedicated channel (e.g. a phone call, regardless of what the underlying protocol is, since I know we can do things like VoLTE where the underlying network packetizes and multiplexes traffic) and message switching being like email-routed all together somewhere, perhaps via multiple hops.

Well the whole HF band is a tiny fraction of cable bandwidth, plus a LOT more natural and manmade noise, plus some of it only works during the day, some at night, some mostly at the right time of the solar cycle... And THEN remember that it's "one cable" you are sharing with up to the whole world.

Can anyone recommend something (as in radio type or particular device) for relatively portable battery based comms between two hiking groups? The use case is a big group hike that often gets separated into two or more smaller groups walking at different speeds, but wanting to still be able to check in with each other every so often. There's no cell reception out there.

Basically just want a glorified walkie talkie with a bit more range (a few miles through woods and across hills of possible).

I just got my GMRS license and some cheap 5W handhelds to experiment with, but I'm not sure if that is the best option.

We might also have the option of setting up a "base station" at the trailhead (our cars or someone relaxing at a picnic table) to act as a higher powered repeater if that would help.

How much of it is frequency (radio type), wattage, line of sight, operator skill. etc.?

I'm not very familiar with GMRS, but your scenario is what that license is designed for. So I'd recommend it.

I think in some places you can set up a repeater for GMRS? You'd have to check up with the local regulations.

Of course, you could get everyone (or a few designated people) ham licensed. In many areas, operators are allowed to let other people use their radios under their supervision, so you might not need to even get every single person licensed.

Frequency plays a very big role, and the rest "depend".

There are some frequencies that'd just simply be impossible to use for communication that close (in the grand scheme of things) and others that would struggle to penetrate the trees.

Without knowing the area, I'd guess that 2 or 6 meters would be your best bet. (Probably 2m)

Your next challenge would be getting good antennas. The antenna matters a lot (even more than power output. (See me hitting Australia with 7w))

I'm always available for questions via email. You'll find it in my website.

Thank for you the response! If this GMRS stuff goes well (getting the radios in a few days, hiking the week after that), a HAM license sounds like a fun thing to look at next. But from the movies, it always seemed like that was more of a way to chat with random strangers around the world (like this "Parks on the Air" thing), rather than coordinating hikes between specific individuals. Is that accurate at all?

> Without knowing the area, I'd guess that 2 or 6 meters would be your best bet. (Probably 2m)

What is this in reference to? Is that a measure of wavelength (e.g. 2-6m ~= VHF?) or did I misunderstand? I thought for longer-range comms, you would want to utilize not just repeaters but things like ionosphere reflections and HF. Are you saying that's actually not the best thing to use for wooded areas a few miles apart?

I appreciate the info :) If I really get into this as a hobby, I'd love to hit you up via email. Please give me a few weeks to test the waters first.

You might want to check out lora devices like Meshtastic.

https://meshtastic.org/

This is interesting, thank you! It seems like LoRa operates in the UHF frequencies, and is an encoding scheme for data packets...? Does that encoding system also affect its usable range, or can any two radios in the same frequency generally send/receive over those distances?

A 50kb/s bit rate is fast enough for texting, but I guess it'd take some specialized voice protocols to do a walkie-talkie over that.

Regardless, thank you for sharing.

You can trade range for bandwidth by playing with the spread factor, an encoding tunable: https://meshtastic.org/docs/configuration/radio/lora/#modem-...

But generally yes, latency is too high and bandwidth is too low for synchronous voice. The upside is that real-world performance often exceeds the range of analog UHF even at significantly lower frequencies, e.g. GMRS.

> I had originally intended to spend this trip operating FT8 and CW, but for some reason I found myself really enjoying FT4 (a mode I had never used before), so I spent most of my day camped out on 14080Kc, and then shifted to 10136 and 7074 in the evening.

As a non-radio enthusiast, I was following along until this sentence.

FT8, CW and FT4 are all types of modulations, or ways of imprinting information onto a radio signal. They offer different performance under different channel conditions.

14080Kc ( = 14080 KHz = 14.08 MHz), 10136 (=10.136 MHz) and 7074 (=7.074 MHz) are the frequencies of the radio channels being used.

The ionosphere (which is partly powered by the sun) tends to dissipate at night and not reflect higher frequencies as well. Thus one tends to use lower frequencies during the evening/night and higher frequencies during the day.

As an aside, an ionosonde is a radar which can measure and display the reflectivity of the ionosphere in real-time as function of things like height/range, radio frequency and direction. Not many people get to play with them, but they are a great tool to learn how the ionosphere works. You can sit in front of the display and watch in real-time as the ionosphere's response changes and it's height increases as night approaches and see how it varies from day to day. Beats reading about it in a text book and it's fascinating to watch.

Here's a link to an online ionosonde, displaying ionograms in real-time, updated every 5 minutes:

https://www.sws.bom.gov.au/HF_Systems/1/3

Haha, I saw this comment coming as I wrote this sentence. I tried to link to everything you might find relevant in the text.

The other comment under yours does a great job explaining things too.

As an additional note KC (Kilo Cycles) is the old way of writing Kilohertz. I just happen to prefer writing Kc for some reason even though I know it's no longer "correct"