As I mentioned in a previous article, I am making many kinds of antennas for fun and profit, but mostly for setting up neighborhood networks or small community networks that I will not be involved in. I have made many antennas, and over the last decade, I have programmed countless radios in my area, as a free service to my neighbors and friends. I have many extra radios and antennas that can be put into the right hands if it serves the community. I would rather invest in these, than fancy and expensive transceivers. I have a pile of such equipment for this purpose.
Background
I am not a professional radioman, but only another self-taught amateur who became seriously interested just a little over a decade ago. In decades past, my experience working with professionals in the emergency services and disaster preparedness communications sector in another life, has helped. I grew up with a grandfather who was a pioneer in radio and telephone, and who, with his team of engineers, made the first intranet connection that connected the early IBM to Hewlett Packard computers. He was an influence in my life. It does seem as if I missed another calling, because radio and telephone communications are in my blood. My apologies if I bore you. I am attempting to help someone else get started. I am certain that there is another potential radio nut like myself out there somewhere. We need as many nuts as we can get. I still agree with John Moore who believes that the two skills sets that will be in the most demand, yet in the shortest supply, will be medical personnel, and radio technicians. (Nuts like me!).
Unlicensed Radio Communications for a Community
Why all the antennas and radios? Different radio services can be used in a future and tiered communications plan. For example, FRS/GMRS, and CB can serve a neighborhood, while MURS could serve a security operation, and 2 Meters, the broader community. A dedicated medical team would have an exclusive service on frequencies that can not be used by others, so that they can avoid being interfered with by requests for help. If there can be a transportation unit, then they also should have a dedicated set of frequencies, and more powerful mobile transceivers.
In my part of the country, and over the last decade, the number of folks getting started with the Technician’s license has been encouraging. Interest in radio is growing, and a few local Hams have been programming radios for newcomers in a semi-standard way, so that MURS and GMRS frequencies are installed alongside Amateur frequencies on many new handhelds. We also have a plethora of new repeaters from 70cm to 6 meters, two new 2-Meter digitals, and two for GMRS. Our region is ‘wired’ for radio. Yet, given their dependence on grid power, I would avoid reliance on repeaters.
Bringing People Together
Because radio communications is underappreciated at this time, this effort is surely needed. And because of my past involvement in county-wide operations, I know how this can work. Telephone and radio communications of any kind, is the backbone of any group of people, small or large. It brings people together.
My focus is on the small community, that should already have a sense of community. Because of decades of experience coordinating volunteer groups as large as 150 members, I have an appreciation for how a small community can come together and use radios effectively. Every set of eyes with a radio can contribute to the security of the net in some way, or offer their help organically, even if only loosely-organized. As word travels to those with whom I have no contact learn of the existence of the net, they might naturally participate. If possible, those who are tactically significant location — with a view of a significant roadway intersection, or point of ingress miles from my location, are of particular value. So they may receive the necessary equipment.
If we can promote and enable a community network, then we have many eyes and ears looking for potential threats. Those who might contribute in some other way to the community would then have the opportunity to participate. If it is necessary to provide the necessary equipment and instruction, it is enlightened self-interest to do so. I will not control the net, but only coordinate and maintain it, if possible or necessary. If all I can do is listen to this net, then it is a success. They need not even know that I exist, and I’d rather that they did not. Yet because I would have the ability to monitor and used every radio service, it might be necessary to serve as a relay station, or a dispatch center. Because I cannot be available 24/7, the burden can be shared by rotating the duty among friends.
GMRS and MURS
Antennas are important to low-powered networks that could, to a limited extent, replace a telephone system. A low-powered radio net would be akin to the bygone party line that once existed in my lifetime. While the focus is on GMRS, most of what applies to GMRS, can be applied to MURS. The focus is on GMRS, because MURS transceivers are not ubiquitous. GMRS is fast becoming the new CB. Here are some instructive videos available on YouTube:
- GMRS Basics – Everything You Need To Know To Be A GMRS Expert AKA GMRS 101 or GMRS For Dummies
- Top 5 Reasons why MURS Might be the Best for Survival
- External antennas for MURS radios. (Mobile range test)
- New to the market, a MURS mobile: Introduction to the Wouxun KG-1000M Mobile MURS Radio.
We might be able to successfully speak to others located further away, yet a neighbor who is located much closer, might not be able to talk to us unless we have an external antenna to hear them with. This would more often be the case if there is a dense forest of pine trees in the path. In some situations, one might have to use a high gain directional antenna. UHF frequencies only travel about half as far through undulating terrain covered with pine trees, than VHF. MURS frequencies are in the VHF spectrum. With only 2 watts of power, MURS can cut through the forest roughly twice as well as GMRS, when using the same power output of 2 watts. GMRS uses UHF frequencies. GMRS/FRS in less densely-forested and flatter terrain, or in cities, can do surprisingly well, often better than VHF. The terrain dictates line-of-sight effectiveness.
In general, UHF is not as suitable for rural terrain, yet there can be exceptions. Get to know what your radios can do in your terrain, and adapt and innovate to come up with a solution to overcome the limitation of your equipment. A better radiator of available power, namely an efficient antenna, is important, but more so is the height of that radiator (antenna). In the Amateur Radio world, the saying that ‘height is might’, is a golden rule for good reason. This and other factors do greatly improve the performance of any transceiver, regardless of the frequency used. What radio service we acquire and use first? In my opinion, GMRS/FRS. Here is why:
CB was once king, yet now GMRS/FRS radios are nearly ubiquitous. Some, or many neighbors in lightly populated and remote regions will need to improve their ability to hear their neighbor’s very low-powered FRS/GMRS radios (transceivers to us). Much like standardizing with .223 and .308 ammunition, this is the most likely transceiver to be used, because it is the only transceiver present in large quantity. Therefore, any community network of small or larger size, should have a low-powered base station, be it only a Baofeng on an external antenna, that is tuned for GMRS frequencies, namely, 462 to 463Mhz at minimum, or better yet, 462 Mhz to 468 Mhz. Baofeng now makes a FCC part 95 compliant model for GMRS that can accept an external antenna. Btech has a good selection as well. And there are still open banded Baofeng UV5Rs available, yet the supply is dwindling. Reportedly, Part 95 compliant Baofengs can be reset to be open-banded as they originally designed to be. However, until I have performed to the procedure and found it to be successful, I cannot promise that it actually works.
To Hear Better, Antennas for GMRS
While Midland and others produced excellent high power mobiles to transmit with up to 50 watts of power, the reason I focus on antennas is because these ubiquitous GMRS/FRS handhelds are typically 2 watts or less, and we’ll need good antennas to hear these radios, as well as to transmit to them.
If commercially available antennas might no longer be obtainable, a Slim Jim, a cousin of the J-pole, constructed of 1/2 copper pipe, has the necessary broader bandwidth to cover 462 to 468 Mhz, that include the 5Mhz step up for GMRS repeaters. (BTW, the tone most often used by GMRS repeaters is 141.7). I also avoid reliance on commercial antennas given their prices, and because they are not as reliable or rugged as my homemade variety. They do often boast that they provide additional gain, but if true, they often use transistors as a part of their design to achieve their gain rating, and I have found that these transistors are a failure point, as well as the flimsy plastic parts used.
I prefer to use 3/4 inch copper pipe to build a J-pole for these frequencies, because the larger in diameter that a radiator is relative to the frequency, the broader will be it’s bandwidth. We could also build a 1/4 wave antenna, if that is within our repertoire, and appropriate materials are at hand. Building and using a directional antenna for GMRS could also be a good choice. I prefer the Moxon (5.75 gain), or 6 element OWA yagi antenna (10.5Dbi gain) designed by L.B. Celib, because of their broadband with that can span up 10 megahertz. Omni-directional 1/4 wave antennas, have a broad bandwidth. Tpically, that is 10 megahertz, yet they offer no gain. A Jungle Antenna is a good 1/4 wave antenna, but I prefer something that is more durable. The J-pole provides only 5 megahertz of bandwidth, and around 2 Dbi of gain. And the Slim Jim, 8 megahertz, and up to 3-6 Dbi of gain. The Slim Jim is the best choice here. Estimates of the gain are disputed, and might be from 1.8 Dbi to 6 Dbi. Regardless, from years of experience building and using this antenna, I am sold on its ability to propagate and receive, and its almost indestructible construction when made with copper pipe.
For GMRS, if there is enough material available, I would prefer the Slim Jim over the 1/4 wave, or the J-pole. This is because of its durable design and construction if properly made, and because it offers a possible increase in gain, if properly constructed and installed. I do have a broad-banded J-pole design that breaks the rules, but for most home builders, the calculators are accurate and handy. The Slim Jim is more vulnerable to damage and failure, however, it has worthwhile attributes if a broader bandwidth is needed. To get the most out of it, the Slim Jim is best mounted at least 20 feet high to realize the full potential gain. This minimum height is necessary if the station is not on top of a hill. It is also a better receiver of very weak signals, because of the very low noise floor when copper or aluminum pipe is used in its construction. Full quieting is likely. I can hit repeaters located at 6000 feet, as far away as 80 miles away with only 4 watts. This can be done using either a 70cm or 2 Meters. However, there is often a trade-off: This is is that the Slim Jim might be a bit deaf to signals if the station is on a tall mountain with a steep grade, and the incoming signal is coming from below. In these locations, a 1/4-wave antenna is best.
Most, but not all, antennas will work better for RX/TX when installed as high as possible. The additional height easily compensates for the additional length of coaxial cable used to attain that height, and despite the high line loss that occurs at a greater rate when higher frequencies are used. GMRS is approximately 3 times higher in frequency than MURS. Use very low loss LMR 400 cable if possible. I recommend using stainless steel hose clamps to attach the coaxial cable over any other means as this connection is more reliable and durable. Soldering cable ends to the pipe and clamping, and using other strain relief methods to protect the connection, ensures near bomb-proof reliability.
Do use an air choke of at least 4 turns of cable. The coil cable should be approximately 4 to 5 inches in diameter and cable ties to secure its shape can be used. If the SWR needle moves when the cable is swung, there exists a noticeable amount of common-mode voltage on the outer shield. This commonly used ‘air choke’ should be used on most antennas including the Moxon. Construction methods and tips could be a whole other article. There is plenty of information on them available on the Internet.
(To be continued tomorrow, in Part 2.)