Signals Intelligence Resources

Building your own Signals/Communications Intelligence(SIGINT/COMINT) capabilities is one of the cornerstone messages of this blog- trust me, you’re going to be doing a lot more listening, interception and analysis than you will be doing shooting.

Along the way, I’ve learned quite a bit about communications and communications intelligence, from a humble teenage beginning with a Radio Shack CB, K40 mag mount, and a RS Pro-96. Everyone starts somewhere.

Where to Begin

Listening is 2x more important than talking. Your first purchase should be a general purpose scanner. Poke around Radio Reference, searching your area code, to find out what type of modes local emergency services are running. If it’s digital, such as APCO/P25, you’ll need a digital scanner. Yes, they are kinda pricey. Poke around though, they can be found fairly affordably(~$200) if you look hard enough. Most of the models built in the past 10 years have a feature known as “close call”, which switches the receiver directly to the frequency transmitting closest to the scanner. This is a nice feature that definitely will come in handy. Don’t discount the older non-digital sets; they have plenty of uses for monitoring traffic other than emergency services, including the license free bands, Marine band VHF near water ways, and air traffic.


Have a Shortwave Receiver. Shortwave broadcasts sit sandwiched within the Amateur HF bands. They range from broadcasts from fringe elements to international news. If you didn’t already know, domestic US news is highly condensed and biased towards a marxist agenda, normally offering a “version” of events that are contrary to the facts. At the minimum, you’ll receive the other side of the story. The set pictured is the venerable GP-5, it receives both AM and SSB, the mode which most Amateur traffic is transmitted. The cost is about $80; you should have one. Have a look around HF Underground, a neat forum that logs Shortwave broadcasts, commercial, pirate, and numbers stations. These are clandestine broadcasts that send encrypted messages via OTP and are intriguing to listen to. For all of you that continuously refer to One Time Pads as the solution to every single crypto need, you’ll get an idea of how they’re done in the real world.

Getting more advanced- Field Worthy Kit


Invest in a Wideband Communications Receiver. These may seem redundant at first; they both scan and receive Shortwave traffic. Like any jack of all trades, they are a master of…well, a few. These are actually much more suitable to use in the field than either of the aforementioned devices. Sometimes referred to as bubba detectors, they’re great for monitoring common FRS/GMRS/MURS traffic used by the uneducated. Most on the market are fairly ruggedly built, and several higher-end HTs also include wideband receiver features, to varying degrees. Personally, I like having a separate device to listen with than communicate with.

The model pictured is an Alinco DJ-X11, which receives all modes including SSB, and has a hidden transmitter(“bug”) detector built in. Both AOR and Icom build compact models as well(AR-Mini and R5/6, respectively), that are both excellent values at around $160 new. The Alinco is around $320, but the addition of SSB reception means it can receive HF amateur traffic as well as Shortwave like the others can. I greatly value the ability of my gear to be as redundant as possible.

Other sets can serve this purpose adequately as well; the Yaesu 817 makes a decent enough receiver on its own. As I stated, I’m not a huge fan of putting all my eggs in one basket, but knowing that your equipment can wear many hats is always nice and becomes a force multiplier at otherwise inopportune times.

arrow.jpgA portable Yagi Antenna.  Your signal collection team is not complete without one. Most folks use these to “beam” transmissions towards certain azimuths, and that’s a definite consideration for communications, but it also listens much better in the direction of which its pointed; giving a rough bearing on the direction of which a transmission is originating. 

This makes not only listening to bubba but finding out where bubba is much easier. Coupled with the directional communications capability, this is a piece of kit that a clandestine team should not leave the wire without. They’re also relatively simple to homebrew. On these notes, your individual kit is not complete without a compass; without the ability to get a decent bearing, you’re wasting your time. “Over yonder somewhere” ain’t gonna cut it in a formal intelligence report.

writeintherain.jpeg An all-weather notebook to write down what you hear and not have it get ruined if it gets wet. Without the means to copy what you hear, including call signs or other identification, type of traffic, type of voice or mode(male/female/CW/Digi, etc), and azimuth,you’re listening for nothing. Remember that this information will go into a detailed SALUTE report, and the more detail offered the better the results will be in the end. The more detail you can give to an analysis cell, the more effective your operations will be later on. Included in your notebook should be a simple band plan and detailed info on past positive ID’d signals; the ability to quickly identify signals, possible sources, and previous users will make life much easier on the interception end. In addition, information on antenna lengths and types should be included to help positive ID targets and their equipment. Again, the more details you can include, the better off the mission will be.

SIGINT/COMINT Teams in the Field

The Army’s Intelligence Units break down SIGINT guys into teams which collect signals known as Low Level Voice Intercept, or LLVI for short. This skill set is so important that Special Forces include what’s known as SOT-As, which like their LLVI cousins, collect signals intelligence in small teams on the ground, reporting their findings to an analysis cell. Both are typically composed of four men; two buddy teams switching off to keep continuous surveillance on a target. It’s boring and repetitive, but it’s critical, hence why it takes very disciplined soldiers to competently complete the tasks.

A clandestine setting, like an overt setting, postures a small team shadowing other elements for other purposes. Like cogs in a machine, they’re just one piece, but when they don’t function, the machine may not run. In addition, a lost or compromised signal team is a huge detriment; in addition to the lost time it takes to train, it also compromises your capabilities. Your men have to be among the best in your formation, bar none.

You should be doing this now-

Signals and interception training, unlike shooting or bushcrafting, can be done anytime, anywhere, and besides the cost of equipment, is free. It’s low profile, and likely no one is going to call the police if you’re doing it in public. The only way to get good at it is through practice.

You can keep hoping for miracles or begin making your own.

32 thoughts on “Signals Intelligence Resources

  1. Scott freah

    Just got a digital scanner uniden trunk tracker v. This scanner is p25 1and 2 capable. Can I direction find w a digital scanner? If so what antenna would be best? Thanks for your help. I really enjoy your website, very timely and extremely needed.

    1. Yes you can; use a Yagi. Like with directional transmissions, the antenna creates nulls in all directions except the one the driven element on the yagi is pointed.

      In common man english, this means it receives in the rough direction you’re pointing your antenna.

      1. Bob

        Hi. Do I have to worry about being tracked ( directional finding) with any if these radios ?

        How do you prevent that too

    2. RuralAz

      As long as it has a signal meter you can DF with it. You can without one too , but you need experience in how to orient the radio/antenna. I DFed narco spotters up in the peaks surrounding the Vekol Valley in AZ . Used a whistler that had band scope and signal strength.

  2. With the enormous amount of RF spectrum those mentioned radios cover (the Alinco DJ-X11T tunes 50 kHz to 1300 MHz), knowing where to tune is paramount. Time spent in gathering frequencies to monitor is time well spent. There are sources that list the frequencies the police, fire and etc. use, but listening is better. Scanners miss brief transmissions, especially if you’re scanning wide chunks of spectrum.

    If your intent is to listen for FRS radios in the UHF spectrum, I think something like the Arrow interlaced 144/440 yagis would be a good choice. It will give you VHF and UHF capabilities. Yes, you’ll have to rotate the antenna to get the right polarization, but you really should do that with the 146-3 you mention.

    1. Agreed. That’s why it takes a good chunk of time developing a working list of frequencies to keep an ear on with notes as to why. It’s not just something folks can jump into out of nowhere- hence why it takes so much time to train guys in this art.

      1. Gatorbait3014

        NCSCOUT, that is why tell people: “Map the RF TERRAIN now, before you need it!” As so you won’t have to develop the information on the fly, or worse, under duress.

        Then, go back an review it for accuracy and changes at least once every year. (2x a year is better!)

        And don’t forget the AM/FM broadcast bands. Especially AM. If your area/region is without electrical power on a wide scale, the ability to hear news and information from other regions of the county is priceless. By knowing where to listen, saves time and electrical power.

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  5. PSYOP

    Question about the alinco/icom rigs: Would it make much difference to connect a pigtail to it, then connect to an ldg 4:1 unun and a long wire for better rx or just stick to stock antenna?

    1. It may very well overload it- the handheld RX are great, but once overloaded you’ll get a lot of intermod and bleedover. Basically, it won’t be as selective, and you’ll get crazy signals from everywhere they don’t belong.

      What you can do, and what *just may be a post* soon, is building a RX/2M TX wire discone for that handheld scanner, which some students found out not too long ago in a recent hands-on exercise can be quite the arrow in the quiver. 😉

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  8. Bob Martin

    Posting on CommRadio CTX-10 is closed for comments. I’m working with developer of CTX-10 and can provide lots of updates and technical info. I’ve got S/N # 2 under test right now.

  9. Bob Martin

    An alternative to a yagi, smaller physical size and more directional for more accurate direction finding is:
    Being a non-resonant antenna it’s usable over an extremely wide frequency range. The only downside is that is receive only. Although experienced users can do great work with a yogi and body-shading, a novice can do great with one of the fox hunting loops.

    1. I’m actually using the UHF Loop with my Alinco DJ-X11. There’s been good results with both it and the homebrew Moxons used in the same way. In fact, both are part of a Signals Collection class that I’m putting together to compliment the RTO course.

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  12. So, do you have any clever tricks for connecting my (brand spanking new Arrow) Yaggi to a GP-5? I could rig a BNC to mini, but that would just be AM (unless I misunderstand)…

  13. Mike

    Anyone use the Kenwood TH-F6A? Besides the 2 meter, 1 1/4 meter and 70 cm transceivers, it also has 0.1 to 1300 mhz receive, am, fm and ssb.

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