A Scanner for TEOTWAWKI – Part 3, by Tunnel Rabbit

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

External Antennas, Detecting Potential threats at greater distances

When using a scanner to sweep the band, or scan a list of frequencies, the scanner is much more sensitive and hears weak signals as well as strong signals. When using the Close Call feature that also sweeps the band, only strong signals that are very nearby (within 100 to 200 yards), might be detected. Some brands of scanners other than Uniden, may also have a similar Close Call feature, and might have more a sensitive receiver Sofware Defined Radio (SDR) frequency counter or a better antenna so they could intercept traffic further away.

To greatly increase the possible range of detection of our Close Call feature, and that of the standard scanner, it should be connected to an exterior antenna that is mounted above the roofline and otherwise, as high above the ground as reasonably feasible. Watch out for power lines, and mount it preferably, at least 15 feet above the ground for the best reception at the lowest height. Remember that in the radio world, height is might. Cable loss will be higher with longer runs, but the height attained can more than offset that line loss. Those interested in the weakest signals could go all out and use LMR400 cable. Folks like myself can use cable TV antenna coax. There are coax connector adapters from ‘F’ type to BNC so that one can easily utilize this cable. Use one antenna per scanner, unless the proper splitter is used, and those splitters should not be the simple cable TV type.

Any antenna that is approximately 18 to 19.5 inches in length will work much better than the attached antenna, and it does not have to be tuned. But if it has a magnetic mount used for vehicles, then attach it to a large metal can, or best yet, a pizza pan, or other sheet metal of similar large size. This kind of antenna needs such a ground plane to operate at it’s best. A high gain dual banded UHF/VHF ground plane antenna can be purchased with an attached ground plane and the correct mounting hardware for building installations, will work even better.

My favorite homemade antenna is the Slim Jim, or lower-cost J-pole. These are ruggedly built and have a gain of about 2.1Dbi. Use one tuned for UHF with a center frequency of 465.000MHz to listen to both UHF and VHF, if only one antenna can be purchase. Use a second one with a center frequency of 149MHz to listen to the VHF band. These make good all-around antennas with a low signal-to-noise ratio.

If an external antenna is needed for a transmitter for 2 Meter, MURS, or GMRS, the scanner can be removed and a transceiver connected to the appropriate antenna. These can be purchased on the Internet from KB9VBR. The frequencies of most interest for preppers are in the UHF/VHF bands good all around, all band antenna made for scanners is the discone type, such as the Tram 1141.

Any external antenna is a game-changer. The Close Call feature, depending on the terrain and foliage, might now pick up 5 watt transmissions from a handheld up to a mile away, instead of only a few hundred feet. It would pick up traffic further away if the signal might be from a mobile transceiver on its highest power setting. That would typically be from 25 to 70 watts depending on the model. The Close Call feature requires a strong signal that exceeds its threshold before it will record the transmission. Putting it on an external antenna on it, greatly increases what the scanner, or any receiver can ‘hear’.

Uniden scanner’s Close Call feature, does provide an advantage, yet I would not rely upon it to hear the very low powered FRS/GMRS radios that transmit at a maximum of 1/4 watt. The Close Call feature could prove to be a lifesaver, however, as with most things, we should understand its limitations. Uniden scanners with the Close Call feature, can be programmed to cover only one, or the other band: either UHF, or VHF, but not both simultaneously. If possible, it would be good to have at least two Uniden scanners that have the Close Call feature, one for VHF, and one for UHF, each on their respective antennas for their band. If I could only have one, then it would be set to VHF frequencies, and I would use a standard scanner to scan a list that includes FRS/GMRS frequencies.

Conduct an RF Survey of your AO

To test how far away the Close Call feature and the standard scanning function will work at your location by using your own transceiver, first on high power, then low power. Periodically transmit to see how far away we can be from the Close Call scanner antenna, before it can no longer hear the call. We can test the OEM rubber ducky antenna that comes with scanner, and then again once an external antenna is installed. I’ve done surveys using a digital recorder with the VOX on, so when the recorder hears a noise, it automatically begins to record.

During the test call, give the location and time, and power setting used. Test the area from every avenue of approach on a MURS frequency, and then use a FRS radio, and from different parts of the property, and then further out in your AO. When nearer to the receiver, use the terrain and buildings to obstruct the signal. Is it possible that a savvy operator just might use a metal building, or small hill to block his radio signal while surveilling your home before an attack.

FRS/GMRS transceivers are very low-powered radios. And these are the most likely radio that would be used, because they are familiar, easy to operate, and an easily obtained handheld transceiver. They are truly ubiquitous, just about everyone owns one. The concern here is that FRS/GMRS transceivers are difficult to intercept especially in certain terrain, such as conifer-covered and hilly terrain. If a receiver hears a signal from these transceivers, it is in most cases, close by. It would however be advantages to be able to hear the weak signals from FRS/GMRS transceivers at range that is further from us, so that our defense has more time to respond. And if we are capable of performing patrols well outside a perimeter, the patrol should monitor these very low-powered, and other frequencies by carrying a handheld scanner.

Detecting potential threats at greater distances is the furthest most outer layer of a defense. If living in a remote area where there a few neighbors whom are close by, connecting a scanner, or other receiver to an external antenna would greatly increase the distance at which the weak signals from FRS/GMRS, or any transciever, from a possible threat or our friendly neighbor, might be received.

Advanced Techniques, Rough Bearing Acquisition made simple

Usually a yagi-type antenna is used in this role. This is an invention of my own that is intended to be used by untrained persons, and those with minimal equipment. With that said, it would be advantageous to put two separate recievers on two opposing Moxons oriented along the axis of the major road providing access to the area. Set up this way, these two antennas, together would provide omnidirectional coverage. A Moxon antenna has a gain of around 6Dbi, and would ‘hear’ two and half times (2.4 times) better than a 1/4 wave omnidirectional antenna. It transmits and recieves in a pattern that is analogous to how a flashlight shines it’s light. In the case of the Moxon, it’s pattern is a very broad 180 degrees, akin to a floodlight. See the radiation pattern here.

A Moxon tuned or ‘cut’ to receive FRS/GMRS (center frequency is 465.000Mhz) will also pick up the typically stronger VHF frequencies that are harmonically related. The pine tree needles around in my AO soak up UHF signals exceedingly well. Any UHF signal in pine forests are greatly attenuated, and the range is at least less than one-half that of a similar in strength VHF signal, or less. A 250mw or less, UHF signal out of an inexpensive fixed antenna could have an Effective Radiated Power (ERP) of less than 250mw (1/4 watt), and be very hard to detect in a pine forest. 250mw is the maximum allowed for FRS radios.

With this arrangement, we would be much better able to detect the most common handhelds that are FRS/GMRS, MURS, as well as 2 Meter and 70cm, or whatever you wish to monitor, and instantly eliminate 180 degrees of the compass, and begin the process of determining or improving our rough bearing, that is, to get a better idea of the general direction from where the signal originated. For example, if the threat is approaching from one direction, or the other of the road that passes by a location. Is it coming from the West, or the East? This capability could determine if the primary, or alternative defense plan should be used, or not. We may not get a second chance to get a better rough bearing, but at least we can alter our defense based upon this information. If there is additional traffic, we could also employ a yagi, and get a better rough bearing, but the Moxon method can be used by an unskilled attendant who only needs to note that one scanner received traffic, while the scanner on the other antenna did not, or one scanner was louder than the other.

Using this method, not only is detection possible at extended ranges due to the antenna’s high gain of 6dbi, one might also hear the chatter from neighbors who are at a greater distances as well, and better than can be detected by a standard omnidirectional antenna. If their traffic is normal, then the threat environment is normal. And, if we can hear them, we also might be able to talk to them.

Anyone who can sweat a copper pipe joint can construct a durable Moxon antenna using 1/2” copper, and 1/2″ black thin-wall poly pipe used for drip irrigation. An SWR meter is not necessary if the antenna will only be used by a receiver. Simply cut lengths as determined by the Moxon Antenna calculator, and you’ll be close enough, and good to go.


At the very least, get one inexpensive and easy-to-use analog scanner, and an external antenna so that low-powered, and distant radios can be heard, when otherwise they might not be. The Tram 1141 and other discone antennas made for scanning, often come with a very long cable and BNC connector designed to connect to a scanner. Why? Because security will be job #1.