Motion Detectors
A common force multiplier deployed in static positions(such as Safe Houses, RON sites, LP/OPs, etc.) and to monitor avenues of approach are motion detectors. One of the most popular ones on the market is the Dakota Alert MURS motion detector.
They can be quite useful and are commonly found in rural areas as a driveway monitor. One of the biggest complaints about them is the terribly short range. This is attributed to one factor:
Notice the pitifully small telescoping antenna? Yep, that’s why it gets horrible range.
Maximizing your gear
One of the biggest things about being a Survivalist is making the absolute most of what you have. In the context of this motion detector, it’s actually very simple to maximize this device’s capabilities. It utilizes a BNC connector on top of the unit to mount an antenna. Pick up some RG-8X with BNC connectors, 20ft or so should do.
Remember the Jungle Antenna?
You can build one for the MURS frequencies. If absolute low profile is what you’re after, you can build a simple dipole, looking like this:
The duck tape is simply for writing what frequency this is cut for; it came from another kit for another purpose. Were it going in a tree, it’d be camoflaged.
For maximum efficiency, suspend the dipole vertically instead of horizontally like most associate with dipoles. The reason for this is so you can keep both your radiating signal(from the detector) and your receiver(your monitoring set) both on the same plane. It makes a difference in your ability to receive.
MURS
The Multi-Use Radio Service is five VHF frequencies just above the 2M Amateur band and just below VHF Marine. Legally it requires no license and allows a maximum transmit power of 2W with an antenna of no higher that 60ft. It is channelized:
| Channel | Frequency | Authorized bandwidth | Channel Name |
|---|---|---|---|
| 1 | 151.820 MHz | 11.25 kHz | N/A |
| 2 | 151.880 MHz | 11.25 kHz | N/A |
| 3 | 151.940 MHz | 11.25 kHz | N/A |
| 4 | 154.570 MHz | 20.00 kHz | Blue Dot |
| 5 | 154.600 MHz | 20.00 kHz | Green Dot |
While there are potentially severe pitfalls to using open-source channelized frequencies for security, the MURS motion detectors are a decent starting point. Building a good antenna enhances the capabilities offered and maximizes the device.
You should be looking for ways to make the most out of everything you have.