Editor’s Introductory Note: This essay describes one approach to optimizing the performance, extending the range, and securing the signal of MURS band Dakota Alert intrusion detection sensors–and other low power transmitters.
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To begin, here’s some ground thruth on perimeter security: Security will be Job One. Everything else supports that objective. Manpower for most tasks will be greatly lacking. Every trick, hack, or tactic should be considered. If we don’t see’em, hear’em or smell’em coming, then it is over before it starts. You lose.
Organizing with your community is the best defense for those without their own manpower. Defend at a distance, not at the mail box. Don’t let them into the area in the first place. Thus, potential intruders will be reduced to a few potentially lawless neighbors.
One of the best plug-and-play force multipliers–often recommended by JWR–is the MURS band Dakota Alert system. We all should know about those by now. If not, then please see a video on it.
Although only a 1/2-watt transmitter with a limited range, external antennas can greatly improve the distance at which Dakota Alert sensors can be deployed. I make my own antennas, but I cannot beat the least expensive and most effective external antenna on the market.
When ordering these antennas, request the longest continuous cable length of at least 15 feet or more, if possible, specify the cable end, and the frequency it should be tuned for. In this case, a good center frequency should be 153.500 Mhz. A less expensive DYI antenna is a dipole made from RG58 coaxial cable, but you’ll need a Standing Wave Ratio (SWR) meter. The least expensive one on the market is the Workman 104.
I can make one of these antennas inexpensively by cutting a 20′ cable with two PL259 ends, and make two antennas for about 10 bucks each or less. Here is how.
And here is how to use an SWR meter when making antennas.
Milking Extreme Range
To squeeze every bit of range out these, put it on a yagi, or moxon antenna up high as possible, and install it parallel with the ground, in ‘horizontally polarized’ configuration, and point it at the crest of the hill that is in the way. This can be done to an equal effect using a vertically polarized yagi, or even using a slim jim that has a narrow take off angle or compressed pattern–hence additional gain. The signal will diffract at the ridge line, and may or may not bend enough to get the signal to the receiver. The signal will not be heard on the opposite side at the base of the hill or obstacle, but can be heard further away from the diffraction point.
A five element yagi has at least 7dBi of gain at practical heights, and will boost the 0.5 watt signal to an estimated radiated power (ERP) of almost 1.5 watts, if the cable is shorter, and if connections are not too ‘lossy’. If the transmitting antenna is horizontally polarized to maximize the range through thick forests, and to diffract over obstacles in it’s radio line of sight, and to reduce detection, then the receiving antenna must also be horizontally polarized.
To go to extreme ranges, the receiving antenna can also be a directional antenna! To save money, convert an old VHF TV antenna to be used on your receiver. Directional antennas are very hard to direction find (DF). The larger the front to back (F/B) ratio, and narrower the radiating beam, the better. Using lower power transmitters on a yagi, and signal received by another yagi, is stealthy way to secure radio transmissions. The ERP of a 1 watt hand held would be about 3 watts out of a 5 element yagi. If transmitting signal is horizontally polarized, the signal would be attenuated by 30db, if intercepted by a vertically-polarized antenna. This is whisper quiet in radio terms. If heard, the signal strength will like be below S-1 and more difficult to DF.
Home Brew Antennas
I make my own OWA (optimized wide banded antenna) 6 element yagis that are wide banded and direct connect, so no matching device needed. A moxon is much easier to make, however it has less gain and casts a broad 180 degree RF pattern, much like a 2 element yagi. However it has a fantastic F/B ratio. It is more wide-banded than than any yagi, and is also direct connect. Face the back side of a moxon toward the intercept station, polarized horizontally and you will be very, very quiet when using low power.
One can transmit directly at a intercept station with lower power, and not be heard if you know what you are doing. But please do not try this at home, or in a war zone, unless you are mobile and have no other way. If ‘shooting this signal’ by their antennas, then you must move asap at least 500 yards. Special order a yagi antenna from Arrow Antennas. This is a multi-purpose hand-held version.
Hoist any antenna as high as possible and the range could be improved as much as three times–as the terrain permits–or more if the antenna is above and is ‘clear’ of a previous obstacle that once blocked the signal. Using a high gain 5/8-wave folded dipole omnidirectional antenna, a slim jim, I have had reliable results out to 6 miles in ideal terrain. Place them along the road as far away as possible in pairs separated by 50 to 100 hundred yards. Used in pairs we now have ‘gates’ that allow the user to determine, direction of travel, number of vehicles, and speed of their approach. This also provides redundancy.
Redundancy!
Do not rely entirely on any electronic sensor. Rain causes the sensor to become somewhat unreliable, and can produce false alarms, or no alarm. The best way to deploy sensors is in pairs. Higher voltages improves the range and reliability in the cold and wet, yet that sort of alteration is not available to all. There is a number of simple ways to improve the power supply to increase range, reduce false alarms, and avoid frequent battery change, making the sensor generally more reliable.
Situation: The unit functions well, with no ‘false alarms’, for awhile, then begins to ‘alert’ frequently, and repeatedly issuing ‘false alarms’. According to the manual this the unit signaling that the batteries need to be replaced. Lithium batteries are usually worth the expense in this application. But if not, install fresh alkaline batteries, and see if it stops putting out ‘false alarms’. If it does not, then reinstall the ‘old’ batteries, and see what happens. If I recall correctly, when the 6 batteries only provide 7.2 or less volts, the unit will signal with a low battery alert. Eneloop batteries when fully charged will test at about 1.45 colts, versus fresh alkaline batteries that will test at 1.5 to 1.6. Rechargeable batteries do not last as long. If using the unit in the cold climates, battery life is also greatly diminished. So I would use the lithium type, if necessary.
Power Supply Options
There are several way to power these sensors. If using rechargeable batteries, one way is buy an aftermarket AA battery holder that has place for more than 6 AA batteries. To extend the time that rechargeable will power the unit, add one more rechargeable. For spots for any extra batteries that the holder can hold, you should have dead batteries wrapped in aluminum foil to serve as ‘place holders’. These place holders provide no power. The unit will tolerate more than 9 volts–perhaps even briefly 12 volts, but 12 volts may reduce the life of the unit. If we have a rechargeable battery with voltages of 1.4 volts x 7 = 9.8 volts, as compared to 6 fresh alkaline with 1.6 volt x 6 = 9.6 volts. Thus, by adding one more rechargeable battery we are near the same starting point as the set of alkaline batteries.
Another trick is to use a small 12 VDC SLA (sealed lead acid) battery, or car battery and a universal voltage transformer set to 9 VDC. The battery can be charged with a 10-30 watt solar panel using an inexpensive charge controller.
This 30 watt panel is the most cost effective and good for cloudy conditions, although ‘overkill’ for this application The panel has other uses.
Perhaps select a less expensive 10-watt panel that could be connected directly, and spare the expensive and complication of a charge controller, but only if it is used to charge a larger and standard 12 VDC automotive or marine battery. A marine battery, BTW is not a deep cycle battery!
This could be done with units that are set up at longer distances. Use an old and failing car battery that has a ‘bad’ cell or two, and tests between 8 to 10 VDC and power the unit directly. If charged by a PV panel, a universal voltage step down transformer should be use to limit the voltage. PV systems will produce 14.1 to 14.6 volts at the battery. There is often plenty of capacity at that voltage, even in cold temperatures to run these sensors that sip power, and an old failing car battery would have an extended life if supported by small PV panel that does not need to be regulated and can be connected directly.
If nothing else, watch the video!
Geese! Never runs out of power, sleeps in shifts, sees in Ultraviolet so excellent night vision. Cannot be bribed eats grass. Used as guard animals by Nuclear Sites in Europe, China and Russia.
I have watched a pair of adult Geese almost beat to death a large Doberman X-breed dog before it fled for it’s life. A Adult Goose hissing and charging you,YOU are in Trouble unless your ready to shoot it NOW.
Aside from the grass poop torpedoes they leave everywhere AND the fact UPS-FedEx makes me pick up in their office in town I love the privacy they give me.
You WILL however have to personally greet all your visitors as to have the Geese OK them. BTW you will have to greet them forever as next time with out your OK the Geese will not allow them out of their vehicle.
BTW for the techies among us radio direction gear WILL detect your MURS constant broadcasts. I’m not sure I want a constant broadcast if things get spicy and smart folks are searching for folks.
Re: Watt came first, the goose, or the egg?
Using the usually fox hunting techniques that most radio enthusiasts are aware of, these are very difficult to find, if not in reality, nearly impossible, unless the intercept is right on top of it and is setting the unit off, alerting defenders. Using a directional antenna on a these sensors, make them virtually impossible to find even with the best equipment available to any military. Few have sophisticated equipment that is equivalent to military equipment. After a collapse, fewer will be able to acquire such. In my estimate, the reward or advantage of using these sensors, far outweighs the risk or low possibility of detection. Try finding a weak, irregular, and broken signal that might be broadcast for only a few seconds in a 24 hour period with a yagi, and strength meter some time. Good luck!
It is only ‘theoretically’ possible, but in the real world, nearly impossible. I would never say impossible… Even a constant and strong signal needs to be triangulated, and that requires time and travel to get a good fix. It requires determination and skill few have. The best DF equipment, or just a Yagi, or any kind of equipment of any nature, used by low skill, or only mildly motivated operators, is a lessor threat.
If all this is just too technical, please see this great introductory video:
https://www.youtube.com/watch?v=UuJ0nZIeFoQ&t=322s
Re: Editor’s Note
Agree that this describes only one approach to optimizing a Murs Dakota Alert, specifically, how to optimize the long range potential, and gain as much of the benefits of an early warning as is possible from these devices. In this way we can reduce the effect of an attack that otherwise would be a total surprise. There are several other ways to improve use of these sensors, than is generally not understood, and might be considered unconventional as well. In these other situations that could be discussed, are where these sensors are deployed closer in one’s layer defense, and involve 360 degree coverage of a location using trip wire, relays to operate other methods of defense, camouflage techniques, and infrared lighting to improve area detection using this units that are limited by their design. Hopefully this winter I’ll have time then to describe more about this.
Someone already wrote that up for you, including the other power options like extra AA batteries or the use of 12 volt batteries, and the use of external antennas for greater range. https://modernsurvivalonline.com/mat-mods-enhancements-for-the-dakota-alert-murs-alert-transmitter/
I’ve been experimenting with these over the course of about 10 years, long before these were in wide spread use. I would not, however, recommend connecting directly to a 12vdc battery, or any 12 volt power source and would advise anyone not to do so. What the article recommends is risky. Therefore the heart of your contention is without merit. In the world of radio, attaching external antennas to transmitters to extend the range is common practice. I am not surprised that others might do so as well, and hope that they do so. My information is based upon my experience.
He said: “replace the 6 battery holder included with the MAT with two 4 battery holders wired in series instead.”
You said: “buy an aftermarket AA battery holder that has place for more than 6 AA batteries”
He said: “use automotive and lawn/garden batteries” and “added 5 watt solar panels to keep the batteries charged”
You said: “use a small 12 VDC SLA (sealed lead acid) battery” and “The battery can be charged with a 10-30 watt solar panel”
He said: “high humidity and condensation have caused them not to alarm when they should have on occasion, and the 12V power source seems to help in these wet conditions.”
You said: “Higher voltages improves the range and reliability in the cold and wet”
He said: “it will operate on voltages from about 7.2V (low battery) up to 14.8V (at least)”
You said:”when the 6 batteries only provide 7.2 or less volts, the unit will signal with a low battery alert.”
He said: “Replacing the standard antenna, or mounting it higher for greater range” and “Antenna height is the most important factor”
You said: “The external antenna can also be mounted higher for better range.” and “Height is might” as they say.”
Clearly you borrowed heavily the information and even the methods from the other article in writing yours. Denying it after your comment above about adding 360 degree trip wires, relays, and infrared lighting information in a future post, all of which are described in that article, proves that.
Go to the Dakota Alert Website, or read the manual and you’ll find similar information. Also visit Amazon and see the Q&A section, and you find once again, find similar information being exchanged by various persons. This technical information is widely available.
Yet I do my own testing and after years of experience, have confirmed that this information is generally accurate. Many persons have read about my early experiences that began in 2008. Perhaps the author benefited in some way from my early efforts to help others. I have witnessed that my ideas do indeed travel across a certain community on the internet. That is why we are here, to disseminate and share information so that we can learn from each other. This is not a complicated device, and is easily investigated and adapted, and there should be no surprise that others have had similar experiences, and found similar solutions to the limitations and problems of this now popular device. How technical information is packaged or presented, is by using a similar and accepted format that manages well, the logic and language, that will naturally appear to be of course, similar as a result. Most find the owners manuals of the various electronic devices they purchase to be boringly similar, and therefore avoid reading them as a result. Why? Because these manuals are predictably similar. The contentions made are again, without merit.
Many persons have similar interests, and approaches, and like to tinker. It is the American way. I certainly do not believe that I discovered anything new, and I shared this information not for my own benefit, but as a Patriot, attempting to help preserve our Republic, and American way of life. I claim nothing, and freely give my time in the hope others will find the information helpful in preserving their and lives and property.
I have several dakota alert sensors…however an inexpensive possibility is using the driveway alert from harbor freight. Put the alarm near enough to the sensor to assure contact. Then put a baofeng radio with the alarm set to transmit on vox,…put both the alarm and the radio under a bucket or something to protect from rain, then you have the effective range of the baofeng radios (one with the alarm and one on your person). I have a remote hunting property with only one road in. I am going to set this up to test it, the only drawback would be battery life.
Texas Prepper,
Although I am not familiar with the Harbor Freight driveway alert mentioned, the attempt to solve the short range of that sensor is at least recognition of the short fall of this device. However it is a radio of limited range, I suspect it is UHF. Like your idea and it would work for awhile, but the Baofeng transmitting so close to the sensor, would eventually damage it. In Texas, everything is bigger, including the ranch! I grew up on two small spreads and was riding at age 8. I would feel right at home in Texas! Anyway, the hat no longer fits, and I am in Montana, where there is still lots of ground around here. The problem of distance is a in your case might be best solved by a cross band repeater that is build into many low cost open banded Chinese radios such as the Anytone UT-5888. It require some technical ability to program, yet it is not so difficult that it can’t be done if one is motovated. Set the cross band repeater up in the house to receive the signal from the Harbor Freight sensor, and have it repeat on MURS to your Baofeng. The manufacture has the frequency of that sensor recorded somewhere in the provided literature. This stunt can also be accomplished with a MURS Dakota Alert sensor. Have the repeater receive on one of the MURS frequency, and then transmit out on a UHF frequency that could be a GMRS, business band, or if even on the Amateur 70 cm band frequency to your Baofeng. Radio can be fun! However note the the range from a 5 watt transmitter on a good antenna, can be much further than expected, and might pose the risk of detection and continued eavesdropping. Use another frequency for security traffic that uses low power and is much more limited in that would be from only hand held radio to another hand held radio, such as the Baofeng. Radio is wide open spaces can travel very far. For the purpose of improving security to nearer the immediate area of the house, UHF might actually be a better choice out on the range. In Montana, there are trees and mountains, or hills to help contain a signal.
Well my new NV showed up. Time to open that box!
Re: Important detail
The cross band repeater at the house, that would use a standard dual band antenna, or better yet one such is the Tram 1181 that can transmit on a broad range frequencies would be the best match for this application as it is so versatile and it is also not the best radiator, so range is some what limited, an advantage if the ranch is less than 10 miles wide or long. Mounted just outside, or up on the roof, this or any external antenna would hear or receive the weak signal from the Harbor Freight sensor much better than the small rubber duck antenna on most hand held radios.
Thanks for the ideas…I am just getting into various radio types…very interesting…the harbor freight sensor transmits on 433 Mhz…sensor and alarm both are only $15. I am wanting to put the sensor as much as 2 miles out on the road (private road).
As a senior citizen living in rural North Idaho, Dakota Alert has been a security staple around here for years. It is easy to use and set up. The ONLY problem is the sensors pick up the deer, moose and elk, especially in the driveway. They have a 4000 series sensor for driveways that detect metal that is on my wish list. One side note that was learned is that the Dakota Alert is on a MURS channel and if I am out on the property away from the base unit, then I just set the portable Baefeng radio to the MURS channel and it will tell me if anyone is in my driveway. Of course, a gate is the best driveway security. The Dakota Alert is set up near the gate to see if there are any looky loos lurking around. 🙂 Great detail in the article.
Hi Sheepdog,
The 4000 series is the best for picking up vehicles and in all weather conditions, especially when it is cold out. Southern Prepper 1 does a great job at explaining the different ways of using this model, and even, with a metal driveway gate.
https://www.youtube.com/watch?v=UuJ0nZIeFoQ&t=322s
Here is one possible solution to your wild life problem. For security reasons we have today, and for security reasons in the future, it is good SOP (standard operation procedure) to always have the gate closed. Anyone coming down your road may not be able to see the house, or if your vehicles are present or not. They would never know if you were home or not. And they would be denied the opportunity to become familiar in any way with your property. If this is good SOP for you, then placing the sensor on the inside of the gate, so that it sees only on the inside, or across the drive way, and is limited in range by an object on the far side of the gate, would greatly reduce the false alarms due to wildlife. However if UPS opens the unlocked gate, or it is left open, so that UPS can drive through, you’ll be more confident that is not a false alarm, and that someone is that is hopefully UPS, or those expected, are approaching.
Hi Tunnel Rabbit:
I’ve looked at the spec on the 4000 series and it said that if you place the probe in the driveway it should be 50 feet away from a main road. In my case, that would be problematic and since I don’t want to pick up any additional traffic on it it may or may not work. The people at Dakota Alert are amazing and I’ve worked with them for years on repairs etc. so I will call and relate the distance issue with them to see if this would work. It’s funny that you mentioned the gate being closed because it is always closed and locked. Yep. That way no one knows whether we are are home or not. UPS/FED EX always call at the gate for package pickup. It actually works out quite well because it keeps them off of a gravel driveway and since their job is time sensitive they don’t go speeding up or down it. 🙂
Tunnel Rabbit,
You seem to be an expert on all things for communications! This is my one really weak spot, I have a lot of gear for all types of alarms and communications, I’ve taken classes, read books, etc., and I still don’t get it! This remains my one area of complete failure. I tried to find an “Elmer”, even made the drive to Austin on several occasions to join a ham group, I just can’t seem to find anyone who is willing to be helpful! I wish I lived close to someone with your knowledge!
Hi TXnurse,
I would not consider myself an expert on anything, and certainly not on this topic. It does seem that I do have something to share, so I will do the best I can to fill the gaping gap that is proving to wider than heretofore imagined. Watt is obvious to one person, is not to another. Some are naturally tune in to the topic of radio and take to it like a fish does to water, others not, so much. I was a fish out of water until about 5 years ago.
Don’t feel all alone, knowledge about radio in general is dying off, and there are fewer real world learning opportunities, and modern distractions. Although the survivalist community has sparked new interest in the topic, it appears to be shallow. I’ve learn much about most topics via the internet. Please do not bore me with formal instruction! Learning anything takes time, but goes faster if an individual’s method of learning can be hands on, as well as academic. Once the missing pieces of the puzzle are discovered, then acquiring more knowledge about any topic is picked up faster and faster. It is hard to know watt you need most at this time. However, most of the time, it is a certain level of interest that must be present. Getting out there and using the radio, tends to be more interesting, than boring talk. Just like shooting guns. It’s lot more interesting when you are pulling the trigger. Learning by doing is best for myself. I prefer the Viking Method, of sink or swim. Seems to work every time! Get your Tech License, and jump right on in! However, if you are not a fish or a Viking, there is another method.
Perhaps the best on line ‘Elmer’ (Amateur radio mentor) is David Cassler. He teaches radio for radio’s sake, and perhaps in greater depth than most can immediately handle. This is the opposite of the Viking Method. He does not teach to the test as most do. He would like to make radio operators that than then get a license. It is tough to find the perfect teacher who speaks your language, but this is free and accessible, and may help to break the ice in some way. The water could be too chilly for the Viking Method for some. Give him and others a listen. Cassler is a fine example of what the best Elmer, or teacher of radio, could be, but some one else on line might have what you need at this time. Cassler is a retired engineer who could be too ‘brainy’, or too technically oriented for some. Find a simpler presentation that make sense to you if this is the case. If you have specific question, or something about radio that is particularly a challenge for yourself, I will try to point you in the direction of a possible answer from an on line source. Otherwise, start here and give David Cassler a try:
https://www.youtube.com/watch?v=N6aFXH_SQUo&list=PL07A7D1C9D7BF7F48
If a person already has a MURS capable receiver, is there any reason to buy the Dakota receiver?
Nope. Just use your MURS walkie-talkie, set to the corect frequency. That also gives you Push To Talk.
Tunnel Rabbit
Thanks for the info.
Re: Other reasons to own and operate a Murs Dakota Alert Sensor.
I’ll be setting up a Dakota Alert today to catch a Grizzily in action or before they go into action. We still have a Grizzily sow with cubs knocking over chicken coups, and was recently believed to be nearby. And they do more than just knock over chicken coups. To say the least, I am loaded for bear, and I am out of bear spray… The plywood with screws will keep her off the front door, but grizzlies don’t care if you have a door! She has cubs to feed, and they have acquired a taste for chicken. Just the scent of chicken likely makes them drool in anticipation of a easy to get meal. I may also set up pepper spray on a trip wire.
We can afford to loose some chickens, but the sow will utterly destroy the coup. The MURS sensor would alert me soon enough that a shotgun blast or two, might scare them away. I will allow her to destroy the coup rather than harm them, so early warning and prevention is the best SOP for this. We really need more old plywood with screws to slow down the process, or as a second choice, or in addition, an electric fence with wired smeared with something smelly so that the bear’s nose is attracted to the hot wire. And perhaps they’ll go for taste! Unfortunately, the chicken house operator does not like electricity, and to be effective on thick fur coats, the electric fence should be as high powered as possible. It is hard to stop a hungry grizzly, especially if they have cubs to feed and defend.
Do not mess with momma bear! I should also consider making a 12 ga shot shell for a low powered rubber slug, or rubber shot for the shot gun. I would want to have plenty distance, and a place to run if it did not scare them away. I would not want to get between momma or a cub either. These sensors are truly multi purpose.
Hi Tunnel Rabbit:
The portability of Dakota Alerts works for detecting destructive wildlife. We had “something” in our fenced garden eating all the plums. We moved one of the Alerts into the garden and at 2132 that night, we dispatched a bunch of raccoons. It works. Plums saved. Happy owner.
Thanks Tunnel Rabbit, we have also used the Dakota Alert system for years. We had the Dakota Alert DCPA 4000 system (with the buried device) on the driveway for years but found that the signal would not reach the base unit very far, and we had to locate the unit too close to the house. Perhaps, this is where one of the extended antennae would work? On those extended antennae you discussed, are they located on the remote unit? Or have you modified the base unit?
We ended up going to the Dakota DCHT-2500, that uses the rubber hose, like the old gas stations, you roll over and send the signal to the device which transmits it to the base station. Very reliable, no false alarms and great range (over 300 yards). But we get very little snow this far south, so it may not work for all, in the winter. Combined with a motion sensor it may work for you. We have been experimenting with Spypoint link, a game camera that uses cell tower technology to send pictures to your phone in real time (takes about a minute after the event for you to get it). I have been using it on the driveway to test. It has had a few false events with wind, and rain. Definitely still picks up game and dogs, etc. We keep our gate locked at most times as many of the other do. I was looking for a visual, on a remote location, when the sensor when off. This may work.
https://www.spypoint.com/en