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(Continued from Part 2. This concludes the article.)

A Low Cost, and Simple-to-Operate Simplex Repeater

We can use a simplex repeater such as the Argent Data Systems ADS-1 Simplex Repeater. This is essentially a sophisticated digital voice recorder that is superior in quality to the Surecom, and other cheap Chinese renditions. We must have a reliable system especially when it is relatively difficult to access and a linchpin in importance. Using a simplex repeater in conjunction with a cross-band repeater can confuse the RDF analysis further.

This ‘repeater’, is actually a digital voice recorder that provides many useful functions. For the sake of this article, it rebroadcasts seconds after receiving a transmission. It rebroadcasts on the same frequency as the sending station. This means we can use transceivers that are not repeater capable. Transceivers that are not ‘repeater capable’, such are most GMRS/FRS radios, and all MURS radios (transceivers). Common transceivers, including CBs, can use this kind of repeater system. A repeater for CB is less likely to be necessary as CB propagates much better than UHF in mountainous terrain and uses 4 watts of power. This simplex ‘repeater’, the ADS-SR1, will be used in my AO to ‘connect’ three small mountain communities that will use very low-power GMRS transceivers.

The ADS-SR1 recorder is presumably legal for use on GMRS and MURS, since this device is not actually a repeater. These communities would otherwise not have communications between them. I use this on line tool to conduct a virtual Radio survey to identify a repeater site, or propagation ‘problem’ areas, or RF holes, or ‘dead spots’. The utility of this tool can not be overstated.Continue reading“Mitigating the Drone/RDF Threat – Part 3, by Tunnel Rabbit”

(Continued from Part 1.)

Down and Dirty, Remotely Controlled Transceivers

Armed with the axiom that if something is ‘stupid, but works, then it is not stupid’, we can become creative. In the most austere environments where field expedient and unconventional means are the only means, I should mention that a Citizen’s Band (CB) radio with a Public Address (P.A.) function, or a hard wire intercom can also be used with the VOX feature of a transceiver to cause it to transmit. Using these means, we can transmit remotely, yet we can only receive via a transceiver located at the base station. This is not optimal, yet in many situations, it could be perfectly good enough. When it comes to field expedient means, keep in mind that “perfection is the enemy of good enough”, especially if it can save lives.

We can also operate two separate CB radios over two separate runs of WD1a wire as a crude phone system whereby each station can communicate. An intercom can perform similarly, as well. And we can use a C.B radio’s P.A. function to deliver instructions remotely at a checkpoint safely from an LP/OP. Field phones can assist at a checkpoint as well and in conjunction with a P.A. system. It would be good to be able to interview (interrogate) persons at the front gate from a safe distance, especially if overwatch is not available.

RF Propagation Techniques as RF Camouflage

Historically, RF propagation techniques were practiced extensively on the battlefield and were once SOP for our military, from WW2 through Vietnam and a bit beyond. Nothing I’ve mentioned is new under the sun, but proven. How we use it, could be another matter, so it would be good to define what it essentially is: RF camouflage.

Moving beyond field phones, we can use propagation methods as part of a defense. As a metaphor, these methods should be considered as a sort of electronic/RF camouflage that can be deployed on an electronic battlefield. Using one’s imagination, we might be seen or heard, yet we may not necessarily be identified or located. That is what camouflage does in the physical/visual realm. Camouflage does not actually make us invisible. Rather, it confuses the viewer about what he is observing. What kind of camouflage should be used will depend on the terrain, and circumstances.Continue reading“Mitigating the Drone/RDF Threat – Part 2, by Tunnel Rabbit”

Introduction

This is an extension to my recent SurvivaBlog article titled Advanced Field Telephone Techniques, yet it examines and details the topic in the context of a specific threat. It often pays to reiterate and reinforce. While partly an intellectual pursuit, this discussion is grounded in decades of real world experience, sans actual battlefield experience, or military training. With this disclaimer stated, we can rest assured because the method of remotely operating transceivers via field phones was once SOP (Standard Operating Procedure) for U.S. military forces. It is well-proven on the battlefield as method of avoiding RDF, and subsequent direct attack by enemy forces.

It is also a method that can be used as a substitute for a radio repeater. However, in this modern age, we should be aware that the best that we can attempt is mitigation, and should not expect that we can totally avoid the threat. At any time that there is RF generated by any device to include, for example, the charge controller of our PV array, there exists RF (Radio Frequency) energy that could be detected. Total RF silence at a base station should be in effect for best results. I, therefore, use relatively RF-quiet charge controllers, the Morningstar TS-45/60 with the PWM switched off to lower my RF footprint. Typically, many MPPT-type charge controllers are relatively RF noisy.

JWR Adds:  Even the local oscillator within a radio receiver produces detectable RF energy  — but minuscule, compared to what you’d produce in operating a transmitter.

Understanding the Threat

Drone technology is here to stay and drones will increasingly become problems in many ways. They can be used to gather intelligence visually, day and at night. Thermal imaging can be used both during the day and at night. And now affordable drones have Radio Direction Finding (RDF) capabilities. Drones are increasingly used for intelligence gathering, and kinetic (offensive) measures. An ability to use doppler RDF technology, allows drones to locate a potential target. Learning how to deal with such a growing threat will be an ongoing process. As technology advances, we can adopt low-tech practices that can help us conduct a more secure communications plan. To better understand the threat and the measures proposed, we need to understand how drones are used in RDF operations. There is an excellent video on how RDF using drones works. Please first view this instructional video from S2 Underground, and then come back to this article:

Radio Direction Finding: AKA How “They” Can Find You

A drone does not necessarily need to have RDF capability to be a threat. Rudimentary direction-finding methods involving a yagi or a moxon antenna, and a handheld receiver with a strength meter, or simply a good ear, and a map of the area, can give the user a rough bearing as to where he should fly his drone to pinpoint a retreat location visually. If the location has enough electrical power to run a radio, then it is of interest as it likely has other desirable or essential supplies to attract looters.

Remote Transceiver Operation Using Field Phones

We begin with the most effective method that is available, one that may work for most people without much background in the subject. Field phones, and the devices mentioned, are relatively simple devices, devices so simple, that as a child, I was ‘messing with this stuff’. If I can, then you can. I would encourage anyone with any understanding of electrical circuits to use these methods. The terms mentioned in this article might be new and strange to the reader. But do not be discouraged, since this stuff is not rocket science. Anyone who can connect two wires to a field phone could be in business. And that is the beauty and strength of field phones, rugged simplicity that is sustainable low technology that can defeat the highest tech, and cutting edge of surveillance means and methods. It is a 25-cent solution to a million-dollar problem.Continue reading“Mitigating the Drone/RDF Threat – Part 1, by Tunnel Rabbit”