This is an update of some of our activities in the month of February, 2024.

Did an introductory video-conference presentation about ham radio to a group of comrades in the Northeast.

Two of us worked together remotely to get set up using CAT control and JS8call on one of our stations. CAT control works. However, the contact failed due to suspected coax problems. It was too cold outside to check. It was also suspected that one of the rigs suffered internal damage due to high SWR, but the problem appears to have been solved by a factory reset.

A second attempt was made a couple weeks later, this time using a Linux command line tool called minimodem which is a general purpose audio FSK modem capable of sending at very low bit rates, which, in theory should allow for a message to cut through very high noise levels. Experiments with very low audio (not RF) between two computers in the same building yielded promising results. We set our radios to VOX control and let it rip. No joy. One of the antennas was simply not radiating. The endfed random wire antenna that is proving to be problematic will likely be replaced with a soe form of multiband resonant dipole when the ice melts. Minimodem may get its own post in the future. There’s something to be said for such a simple and flexible command line utility, as opposed to more complex GUI applications such as FLDigi and JS8Call.

Solar powered Meshtastic modules have been ordered and should arrive soon. One Meshtastic device was given to a comrade who lives just beyond line of sight. Arrangements will be made to install the device on a mast, and attempt experimental contact when both parties have time. They are hopeful, as the mesh network is expanding in their localities and contact should be possible through at least two hops.

None of us have been affected by the AT&T outage. Although, it does serve as a stark reminder that whether due to disaster, malice, or sheer incompetence, governments and private corporations cannot always be trusted to maintain critical infrastructure.

This is an update of some of our activities for the month of January.

Shortly after tabling at an Anarchist book fair in December, we released an updated version of the zine, For an Anarchist Radio Relay League on this site.

One of us built an LCR meter from a kit. An LCR meter measures inductance, capacitance, and resistance of electronic components. It also tests transistors and crystal oscillators, as well containing a few other functions. This should help to adjust hand-wound inductors, and also to help identify mystery junk drawer components.

A few of us participated in Winter Field Day from our various locales. One of us made 47 contacts in one hour, the furthest being over 6,000 miles away Brazil.

Experiments with LoRa Meshtastic and Reticulum continue.

This is somewhat less of an activist-oriented post, because shit would honestly have to be pretty fucking dire in the world for CW (we’ll get into why we call it that in a bit) to actually be practically useful. Not that such situations are impossible, and of course it’s worth thinking about and imagining, but we just don’t find them terribly likely. For a lot of people, Morse Code scratches an itch on a part of our brains that loves learning languages and sending secret codes. Anyhow, Morse code is cool and fun.

Hams call it CW, which stands for Continuous Wave. That’s because rather than modulating in response to the oscillations of a human voice or multiple tones of a digital signal, it uses one continuous tone generated by an oscillator. The oscillator is either On or Off. The circuit is either open or closed. The differences in the amounts of time the radio transmits is what creates the language.

And yes, it is a language. A relatively unique one, too because it’s neither a written language, nor a spoken one. It is sent by the hand, but also it is meant to be heard and experienced in time, not seen as dots and dashes on a piece of paper.

Now, CW is not unique in the sense that many other languages throughout the world have been developed for communicating over long distances using tones and rhythms. See African Talking Drums, and the abeng used by Jamaican Maroons to send coded messages.

Each combination of fist, key, and radio system has a “voice” which is as distinct as a human voice, and can be picked out among a pileup of other voices.

It is not exactly binary, even though it is regarded as the first digital mode. If anything, it’s Ternary. The “dits” and “dahs” are not equivalent to zeros and ones, because the gaps in between the tones are just as important as the tones themselves. For example “dah dit dah dit … dah dah dit dah” is “CQ” which is basically a way of saying “is anyone out there?” But if you change the timing to say “dah dit … dah dit … dah dah … dit dah” it says “NNMA” which probably doesn’t mean anything to anyone.

Computers aren’t very good at decoding CW. CW decoders do exist and are quite common, but they require a certain set of conditions in order to work properly. They expect tones in a certain range, a clear strong signal without any interference, and a very regular cadence. When CW is sent by a real human (especially with a straight key) on the real airwaves, using low power, a computer is of very little help. The human ear is much better at decoding this than a computer.

As far as radio communication goes, CW is the most efficient mode there is, by many standards.

Bandwidth: CW uses the smallest amount of bandwidth. Usually only about 500 Hz. Compare that to the typical 2400 Hz bandwidth of an SSB phone transmission.

Signal to noise: some “low signal” digital signals such as FT8 can be decoded by computer when it’s so deep into the noise that it can’t even be heard by the human ear. However, a skilled CW operator can decode CW that sounds exactly like static. That’s not easy to do with the human voice, and computers are not good at decoding messy CW.

Efficiency: You can probably squeeze more miles per watt out of CW than any other mode. Moreso, the equipment can be extremely small and lightweight.

A word about keys

There are several different types of CW keys, but most people either use a “straight key” or an “iambic paddle”. The straight key is the one most people are visually familiar with.

The straight key produces “dits” and “dahs” by pressing down the key for shorter or longer periods of time.

Back when Morse Code was still a primary mode of long-distance communication, telegraphers – especially postal workers – primarily used straight keys. Prolonged use of straight keys caused a repetitive stress injury known as “glass arm”. To prevent this from happening, keys were made which relied on a side-to-side motion such as semi-automatic keys called “bugs” and then iambic paddles.

Most modern radios have circuitry inside them which allow you to set the sending speed, so the duration of the “dits” and “dahs”. This enables the use of iambic paddles.

Iambic paddles are pretty good. One of the paddles is “dit” and the other is “dah”. You can press them at the same time send “dit dah” or “dah dit” depending upon which paddle was pressed first. Very convenient. They allow you to send well formed characters very easily.

The dis/advantage of straight keys is that they almost force you to send slower. You also have to be very conscious of how long your dits and dahs are. On the air you can often tell when you’re talking to someone using a straight key because they can lean on the “dah” for what seems like an eternity once you get into the groove. The sounds may not be consistent relative to each other. A consistent and legible operator is said to have a “good fist”. The irregularity of the straight key may or may not be desired.

How to learn the Code:

The most important things to do are listening to and sending CW.

There are three main methods of teaching CW which are generally accepted: Koch, Farnsworth, and Instant Character Recognition (ICR). They’re all slightly different and tedious to explain, but we thought we’d point that out as they are terms you might come across.

Many tools exist to help people learn Morse code. Below is a non-exhaustive list of some options that are out there.

Videos:

Morse Code Ninja, Farnsworth Method

Websites:

Learn CW Online and Morse Code World are good learning tools. Morsle.fun is a game kind of like Wordle.

Software:

Morse Mania is an app for Android and iPhone. It’s good at teaching letters using the Koch method, but they want you to pay for numbers and punctuation. Rather than paying for software, you may want to move on to Morse Trainer (Android) which is open source and also uses the Koch method, but in a slightly different way. There are many different mobile applications

Learn from people: The Long Island CW Club and CW Academy are two groups that meet online and teach CW in different ways. Participation in both of these groups pretty much requires that you have both a Key and either a dedicated oscillator or a radio with a practice mode.

Long Island CW Club has regular Zoom meetings where people practice sending back and forth. There is no curriculum. You just show up to whichever meetings are convenient for you. There is a membership fee for LICW.

CW Academy is free, but it’s more structured. Students sign up for an 8 week long course consisting of two one-hour Zoom meetings per week.

How NOT to learn the Code:

Most skilled operators will advise that you NOT try to learn it visually. CW is an audible language, not a written one. Do NOT rely on a sheet of paper with the alphabet as a list of dots and dashes. The reason is basically that when you memorize the symbols in a visual way, you will always try and decode using a visual reference to each corresponding symbol, which is much slower than hearing the sound of each symbol.

Conclusion

So, while CW may not be particularly useful in the day-to-day, consider some of the information above. CW rigs are small and light. They don’t require computers or other equipment. The transmissions are very narrow-banded. CW signals can get out in very poor band conditions, when almost no other signal can. It’s a great emergency mode, and just another great skill to have.

It didn’t take long after the attacks on the power substations in Moore county, North Carolina for the old Civil Defense guys in the ham radio community to start ranting about the “Shit Hitting The Fan” in their email lists. Talking about how State emergency response groups are woefully unprepared or – more to their point – disconnected from the ham radio community.

While we disagree with the statist approach to their solutions, they’re not wrong about the problems. If power, Internet, and cellphone systems all go out, that leaves people vulnerable. Elderly people, people with disabilities, people living with food insecurity, etc. You know, the working class.

Prior to 9/11, the number one threat to national security in the eyes of United States government was not from Islamic Extremists, nor “Illegal Aliens”, nor “The Chinese”, but from American white supremacists. The anti-Black racism, homophobia, xenophobia, and hatred of poor people that existed before 9/11 never went away. Instead, it was redirected towards a War on terror, a War on Drugs, and a War on “Illegal Immigration”. The hatred was focused on external perceived threats to cishet white male Christian hegemony.   
So now, there are power substations being attacked, likely by white supremacists.  

In the case of Moore county, North Carolina there’s a possibility that the ideological target was the local LGBTQ+ community due to a drag show that was happening at exactly the same time. The physical target, however, was anyone who uses electricity.   
While the motivation for the attack in Moore County is yet to be confirmed, the plausibility of terrorist attacks on critical infrastructure targeted at marginalized communities in both the present and future is very real. Regardless, the effect is the same.

Due to the known fact that many police and their ilk are either fascists or simply sick bastards in their own right, it should be understood that state-based solutions to communications outages are neither tenable, nor necessarily desirable for many people.

With that said, it may be obvious to us that having a ham radio base station at the local police department monitoring for emergency traffic may not be so desirable. What may not be obvious is that police departments tend not to want people calling them over the radio either.  

https://unicornriot.ninja/2022/the-far-right-fascination-with-the-electric-grid/

So what is to be done? The short, very general answer – and probably the most important – is to build dual power in the form of networks of solidarity and mutual aid. But here are a few ideas.

What already exists? NCPACKET, APRS, solar panels, batteries, flashlights, candles, heaters. 
What should we build? As always, build community, bases of knowledge, networks of mutual aid and solidarity.  
What does that look like? Queering ham radio  and building Community mesh networks.

Pick up some FRS, MURS, GMRS or CB radios for your friends and neighbors. Come up with a comms plan and practice.

http://tarpn.net/t/packet_radio_networking.htmlhttps://unicornriot.ninja/2022/the-far-right-fascination-with-the-electric-grid/​

Following the police murder of a comrade at the Weelaunee Forest, we endorse the statement which can be found below.

As for our own words, we support the rights of people to communicate freely and to enjoy nature. We oppose mass surveillance and the Carceral State. Aside from that, we love trees. They hold our antennas.

We call on all people of good conscience to stand in solidarity with the movement to stop Cop City and defend the Weelaunee Forest in Atlanta.

On January 18, in the course of their latest militarized raid on the forest, police in Atlanta shot and killed a person. This is only the most recent of a series of violent police retaliations against the movement. The official narrative is that Cop City is necessary to make Atlanta “safe,” but this brutal killing reveals what they mean when they use that word.

Forests are the lungs of planet Earth. The destruction of forests affects all of us. So do the gentrification and police violence that the bulldozing of Weelaunee Forest would facilitate. What is happening in Atlanta is not a local issue.

Politicians who support Cop City have attempted to discredit forest defenders as “outside agitators.” This smear has a disgraceful history in the South, where authorities have used it against abolitionists, labor organizers, and the Civil Rights Movement, among others. The goal of those who spread this narrative is to discourage solidarity and isolate communities from each other while offering a pretext to bring in state and federal forces, who are the actual “outside agitators.” The consequence of that strategy is on full display in the tragedy of January 18.

Replacing a forest with a police training center will only create a more violently policed society, in which taxpayer resources enrich police and weapons companies rather than addressing social needs. Mass incarceration and police militarization have failed to bring down crime or improve conditions for poor and working-class communities.

In Atlanta and across the US, investment in police budgets comes at the expense of access to food, education, childcare, and healthcare, of affordable and stable housing, of parks and public spaces, of transit and the free movement of people, of economic stability for the many. Concentrating resources in the hands of police serves to defend the extreme accumulation of wealth and power by corporations and the very rich.

What do cops do with their increased budgets and their carte blanche from politicians? They kill people, every single day. They incarcerate and traumatize schoolchildren, parents, loved ones who are simply struggling to survive. We must not settle for a society organized recklessly upon the values of violence, racism, greed, and careless indifference to life.

The struggle that is playing out in Atlanta is a contest for the future. As the catastrophic effects of climate change hammer our communities with hurricanes, heat waves, and forest fires, the stakes of this contest are clearer than ever. It will determine whether those who come after us inherit an inhabitable Earth or a police state nightmare. It is up to us to create a peaceful society that does not treat human life as expendable.

The forest defenders are trying to create a better world for all of us. We owe it to the people of Atlanta and to future generations everywhere to support them.

Here are some ways to support the defense of the forest in Atlanta:

Donate to the Atlanta Solidarity Fund to support legal costs for arrested protestors and ongoing legal action.

Call on investors in the project to divest from Cop City (list of APF investors). Call on builders of the project to drop their construction contracts.

Organize political solidarity bail funds, forest defense funds, and forest defense committees where you live.

Participate in or organize local solidarity actions.

Endorse and circulate this statement of solidarity. Email defendweelaunee@riseup.net.

The Narrow Band Emergency Messaging System is probably one of the easier digital systems to implement. In its simplest form, all you need is your radio and an Android device running AndFLmsg. Simply type your message in the app, hold your radio up to the phone speaker and press the PTT button while the encoded message plays over the speaker. This method is called “audio coupling”.

The downside of audio coupling is that it makes a lot of audible noise in your local environment. The sound is pretty annoying, too. It’s also possible for environmental noise to interfere with a good copy, although some of the modes used with NBEMS are fairly robust against noisy environments.

There are a few ways to solve this, but they all involve either more equipment, more capable radios, or both.

If you’re using a Baofeng UV-5R or similar HT, you could use an audio interface cable such as the BTECH APRS-K1. This cable is usually used for APRS, but it does work for AndFLmsg. One end plugs into the Kenwood connector socket on the radio, and the other connects into your phone with a 3.5mm TRRS connector. If your phone does not have a 3.5mm audio jack, it may be possible to use a USB-C to 3.5mm adapter, but it seems like a lot of people have trouble with this. Besides, that’s a lot of cables and connectors at that point.

Speaking of a lot of cables, you could also use a sound card interface such as the Digirig Mobile, the Wolphi Link, the AIOC, or possibly the EasyDigi if you want a more DIY option. It’s similar to the APRS cable, except that it’s more modular and can be used between various devices and radios, provided you have the right cables to go between them.

The downside to the BTECH APRS K-1 cable is that you either still have to manually push the PTT button, or you have to put the radio into VOX mode. This means that the PTT is triggered by audio rather than by pressing the button. This can cause the beginnings of messages to be cut off, or (in my experience) cause the radio to overheat and kill the battery, or it may completely fail to trigger the PTT at all. The other issue – and Baofeng radios are notorious for this – is that the VOX circuit may be quite laggy, which might cause the first part of a message to be cut off. To overcome this, it may be a good idea to start a message with some junk data, such as a bunch of zeros or just jumbled letters, in order to give the VOX circuit the split second it needs to activate the PTT.

Audio interfaces such as the Digirig shouldn’t give you this problem, as they are able to send the RTS signal to the radio, which activates the PTT much like a radio with built-in CAT control would be able to do.

As of this writing, it seems that the Mobilinkd TNC3 does not work with AndFLmsg.

AndFLmsg is based on a more feature rich suite of free and open source programs called FLdigi. AndFLmsg basically consists of FLmsg and FLwrap. The full desktop version can be a little more complicated to set up, but FLmsg and AndFLmsg are capable of talking to each other.

Sending text

The first thing AndFlmsg shows you is a simple screen that looks like a chat interface. A mostly empty screen with a text field at the bottom where you type the message to be sent. For quick, informal messages that need to be sent from one person to another, this is perfectly acceptable.

However, AndFlmsg also supports forms. These are pre-formatted XML files, often made for particular organizational purposes. The most common form is the ICS-213 “General Message” form. (It is also possible to create custom forms, but that’s beyond the scope of this post.)

It takes about 3 minutes to send the text of John Brown’s last speech using a mode called MT63-2000L. With the BPSK31 mode, it takes almost 11 minutes to send the same text. AndFlmsg supports dozens of different modes that have varying levels of robustness, and transmit at various speeds. You’ll want to research the different modes and decide which is most appropriate for your group in any given situation. Take into consideration the length of the messages you’re likely to be sending back and forth, how long you can sit in one place waiting for a message to be transmitted, as well as both audible and RF interference in your local environment that you’ll have to deal with.

Sending images

To send and image in AndFlmsg, go to the Compose View and scroll down to select the “picture.html” form. Fill out the form, and attach your picture. Tap “save to outbox” and it will take you to the Outbox view. Select your message, and then tap “TX OVER RADIO”. The encoded message will begin to transmit.

When sending images which contain text using AndFlmsg, we have observed that rotating the image 90° so that the text is vertical makes the decoded transmission 100% more legible. However, sending images with text should probably not be your primary purpose for using this system. It could be useful to send images of injuries, an area affected by flood or fire, the face of a missing person, maps, or aerial photographs for instance – in other words, things which can only be effectively expressed through images. It took more than 3 minutes to send the black and white images above.

Sending text is bound to be faster, more efficient, and less prone to error than sending images, at least in most cases we can think of.

https://www.arrl.org/nbemshttps://www.arrl.org/files/file/On%20the%20Air/Tutorials/Introduction_to_NBEMS_ARRL.pdf

https://www.arrl.org/files/file/On%20the%20Air/Tutorials/Advanced_NBEMS_3_0.pdf

Edit: another application has become available, quite similar in concept and usage to AndFlmsg, called Rattlegram (on Google Play Store or wherever you get your APKs). It uses a method called Coded Orthogonal Frequency Division Multiplexing (OFDM), which makes it quite fast. However, as far as we can tell, it is only possible to send text (and emojis!) not forms, images, or files.

Send SMS text messages via ham radio using APRS.

SEE UPDATES AT THE BOTTOM OF THIS POST!

We know that police and the State can shut down cell towers at any time, basically by asking the telecom companies nicely to “pretty please turn the tower off because there’s an emergency”. We also know that not every protest takes place in an urban setting with cell and Internet service on every block. At pipeline protests, railway blockades, and forest occupations, cell service can be anywhere from spotty to non-existent.

With ham radio and APRS, it is possible to get a message out to people who need to know what’s happening when you’re in the digital dark. The best part about this technique is that the people you contact basically don’t need to know *anything* about ham radio.

You need:

1. a valid call sign (sorry pirates, sometimes that’s just how it goes.) (UPDATE: I actually tried setting up APRSdroid with a fake call sign, and NOT entering an APRS-IS password, and it seems to have worked fine. I did not transmit over RF. Tired old reminder that illegal things are illegal, own risk, etc.)

2. a device with Internet access, and a device capable of sending and receiving SMS text messages.

3. Important phone numbers. National Lawyers Guild, outside support team, a friendly reporter, your mom, etc. You’ll be adding these as “aliases” later on.

4. a VHF radio with APRS capability. This can be:

-A Baofeng or other basic HT, an Android phone or tablet with APRSdroid installed, and an APRS cable or AIOC.

-A Baofeng or other basic HT, Android phone with APRSdroid installed, and a Modem/TNC such as the Mobilinkd. (There are options for iOS, but I don’t know what they are)

-A VHF transceiver with APRS built in, such as the Yaesu FT-3DR, the Yaesu FTM-400, or the Radioddity GD-AT10G.

How to get set up

1. Get APRS working. You can start with APRSdroid using the APRS-IS service in order to avoid transmitting your phone number on the air for no reason, and for the sake of using a stable Internet connection rather than RF. It’s up to you. However, once this process is all done, MAKE SURE you can actually send and receive packets VIA YOUR RADIO (not the Internet. [I made this mistake.])

2. Send a message (any message) to the “SMS gateway” service by entering in the callsign SMSGTE. The message format should be “@5551611312 some message”. Use your phone number, or a number you don’t mind being associated with you for a while. You have to do this at least once.

(Note that you can actually stop here and use the SMSGTE service without registering, but the following steps will add a little tiny bit of privacy, at least against anyone within RF range listening to APRS traffic, or watching a site like https://aprs.fi. And by itself, this is still useful. If a comrade really needs to get a message to their partner or family member for example, you could let them borrow your device, type in the phone number and message and hit ‘send’. They do have to know the number, or be able to find it in their contacts.)

3. Go to https://SMSGTE.org and create an account. Follow their instructions, as part of the registration process involves sending at least one APRS message.

4. At the top of the page, go to ‘User Tools’ and ‘Alias Manager’. You should see an empty list with “Name, Number, SSID” at the top. SSID isn’t necessary, but will make it easier to manage multiple conversations in your chosen APRS interface.

Example entries:

Alias	Number	SSID
NLG	5551611312	LG
MyCrew	6667654321	MC
Mom	5551234567	MA
TeenVogue	1234567890	TV

Doing all this allows you to save contacts and conversations as distinct message threads. So when you want to send a message to the NLG phone number, you can send it in one of two ways:

With just the Alias,

Callsign: SMSGTE
Message: @NLG My name is X, we're at Y, some of my friends have been arrested. Please send help.

or with the SSID

Callsign: SMSGTE-LG
Message: My name is X, we're at Y, some of my friends have been arrested. Please send help.

Receiving SMS messages via APRS.

When someone receives a text message from the SMSGTE service, it will look like

@[CALLSIGN-7] message

If the person you sent the message to wants to reply, they *must* begin the message with your callsign and SSID such as “@[CALLSIGN-7]” otherwise it will just go straight to the SMSGTE number and never be transmitted back to you.

@[CALLSIGN-7] reply

Pros and Cons

1. APRS is basically GPS. Even though the “P” stands for “Packet”, it’s often referred to as the “Automated Position Reporting System”. As such, most APRS devices periodically beacon out your GPS location while it’s running. This includes APRSdroid. Radios with APRS built in may be set up differently and have different options. To mitigate privacy concerns, APRSdroid has a GPS ambiguity setting, which in my experience has abstracted my position by as much as 34 miles from my actual location. so that’s…something. Location beaconing can also be set to manual.

2. APRS would be good for coordinating logistics that are legal, like water, food, first aid, legal observers, and media. It is extremely important to understand that these messages are sent in the clear, and over the airwaves, AND over the Internet, AND through unencrypted SMS messages. So this is very much a technique to use when the grid is down and you have an emergency.

3. APRS being useful is still reliant on beacons that are run by volunteers. There is no guarantee that wherever you go, there will be an APRS Igate that’s running and within RF range. Remember that getting your antenna as high up as possible will help you get out farther. Raise your radio up over your head, stand on top of a car, climb a tree. Do whatever you have to to get the signal out.

4. If you are within RF range of an APRS beacon, it’s possible that you will be able to *send* SMS messages, but not receive them. Unfortunately some Igates only *receive* and do not transmit.

5. while SMSGTE is automated, it is also a *service* that is run by *human* *volunteers* who can forget to pay the phone, server, or electric bill, or trip over a power cord, or get struck by lightning or any number of other things, just like anybody else. This service is correspondingly vulnerable. It’s pretty robust, but it’s not bulletproof. Hardly anything is. https://SMSGTE.org has a donation link near the top of the page.

Videos about SMSGTE:

Videos about APRS more generally

UPDATE #1 (11/13/2023): The FCC is at it again. The SMSGTE service has been shut down for over 6 months. From smsgte.org:

“The SMSGTE service us currently offline. New regulations put into place in the US, Canada and other jurisdictions along with some recent abuse of the service to send SPAM have forced me to shut the service down. I am currently searching for a solution to restore service. If there is a club or HAM organization interested in assisting, one that is a legally registered business or non-profit, please contact me.”

As such, we will leave this post up for posterity, and will update it either when the service comes back online, or when a solution arises. In the meantime, consider our later post on how to Send text messages via email – over ham radio as a sort of workaround.

UPDATE #2 (12/18/23): A solution has arisen. http://aprs.wiki/SMS/ This system works pretty much the same as SMSGTE, the difference is that people have to enter their phone numbers to opt in ahead of time to receive messages. When the number is entered, they will receive the following message:

“You have opted-in to the APRS to SMS Gateway Service. To opt-out, reply STOP. To opt-in again, reply START. See http://aprs.wiki/SMS/ for more information.”

It is also possible to create aliases using the SMS service. However, so far it is only possible to do this from the APRS network itself, not the webpage.

Here is a video about the new SMS service.

Before the bombs started dropping on Ukraine, I was trying to write something about the ban on ham radio there.  Now I’ll do the same thing, but not try to be clever or funny about it. I don’t know that this information will be particularly useful to the people of Ukraine *right now*, but it might come in handy for any of us later on.  

1. Jamming: basically, jamming is the deliberate interference of a radio signal by transmitting on the same frequency as the target signal, usually at a higher power. So, if you are transmitting at 5 watts, a 6 watt signal on the same frequency would drown you out. Or even a 1 watt transmitter if it is very close to the receiver. This is especially easy on FM due to a phenomenon called the “capture effect”.  

 

2. RF direction finding: in movies and TV shows they often call this “triangulation” and it’s a real thing. If you’re on VHF/UHF your antenna most likely transmits in an omnidirectional radiation pattern, meaning your signal travels roughly the same distance in any direction. The signal is strongest at the source – near the antenna – and gets weaker as you get farther away. An attacker can find the source of your signal by the use of one or more *directional* antennas. These are antennas that have a more focused RF radiation pattern for both transmission and *reception*. Two common types of directional antennas are the Yagi-Uda antenna (featuring a large pole with a handful of smaller perpendicular bars) and the more well known satellite dish. The attacker would sweep an area, swinging the antenna in different directions to find out where the signal is strongest.