(Continued from Part 4. This concludes the article.)
Mobile Antennas Selection, and Mounts
The following list is very short list as most antennas on the market require the installer to tune the antenna with an SWR meter. Often this fact is omitted. Fortunately, both these antennas do not need to be tuned and are more than adequate. There is not much need to look further. Both of these antennas have NMO bases, and there is a variety of heavy to light magenetic mount with various cable lengths available that have MNO fittings. Magnetic mount bases are very popular, yet they are not the only way to mount antenna without drilling a hole. There are several different types. Be sure to shop and find a mount that has cable that is long enough for your installation.
Diamond Antenna SPM/NMO Magnet Mount Mobile Antenna (NMO Mount)
Diamond Antenna K515SNMO Luggage Rack Mount (NMO)
Diamond Antenna K400CNMO Trunk Lid / Hatchback Mount
UHF and VHF Mobile Antennas:
UHF, high gain antenna intended for the GMRS and UHF business band range of frequencies between 462 and 467 Mhz: Midland MicroMobile MXTA11 6db Gain Antenna https://www.buytwowayradios.com/midland-mxta11.html
For VHF and UHF
Multi-purpose wide band, and dual band antenna on a magnetic mount intended for all radio services on VHF and UHF:
Tram 1181 Dual Band NMO Mount Antenna (140-170/430-470 MHz) https://www.buytwowayradios.com/tram-1181.html
A BASE STATION ANTENNA: THE SLIM JIM
KB9VBR Slim Jim Antennas
There are many choices, and we good down many rabbit holes and lose sight of what I believe is one of the best choices in base station antenna out there for the prepper. KB9VBR, Micheal, has lots of information on his website, and many YouTube videos. I got my only store-bought slim jim from him over a decade ago. He takes care of his customers. As I now do, he makes j-poles and slim jims for all radio services.
For the transceivers discussed, purchase a high gain ‘slim jim’ antenna here:
UHF for GMRS and business band frequenices select 462 to 470mhz.
In the option boxes, select ‘N Female’ or PL259 connectors.
High gain ‘slim jim’ antenna , 150 to 160 mhz, that can be used for MURS radio, and for your scanner, if a MURS radio is not in use.
VHF Public Safety, MURS, Marine, & Scanner Slim Jim Antenna
$48.00 – $52.00
Use the directions on the website to properly install the antenna. Although not recommended by the manufacture, it is wiser to use an RF (radio frequency) air choke on these antennas, and it certainly necessary on J-pole antennas to get the best performance. Make an RF air choke with a coil of cable that is approximately 4 inches in diameter, and 5 coils of cable. Secure with wire ties or cordage. This decouples the antenna from the cable. We do not want the cable to be a part of the antenna and detune it. This is very important to the antenna’s performance in terms of SWR and bandwidth.
My Experience with Slim Jim Antennas
Slim Jim type antennas are my favorite antenna that I have made for many different frequencies, or radio services, and tested and tuned with precision, over and over. These feature rugged construction, high gain, and have more bandwidth and gain of J-poles, and a lower noise floor with full quieting, or low noise to signal ratio. It is superior to the J-pole, but only requires a bit more material and work. It is less expensive to buy this one than to make it if you do not already have the supplies, and the skills of a plumber to sweat copper joints, and cut copper pipe with precision. However, you will likely be successful if when make your own using this Slim Jim calculator: https://m0ukd.com/calculators/slim-jim-and-j-pole-calculator/american-version/ The wide bandwidth makes this antenna forgiving. You can off on your measurements, and still end up with a usable antenna.
This example demonstrates that indeed ‘height is might’, and what a low power transmitter can do on a slim jim antenna. I’ve used my homebrew slim jim to talk to a 70cm repeater at about 6,200 feet in elevation, that was 80 miles away with a 4 watt Baofeng. Understand however, that this example had no obstructions to navigate. It was a straight shot, clear line of sight situation to the repeater allowing a strong enough signal into the repeater that the repeater broadcasted a clear crisp (5×5), and intelligible voice communication, with little to no noise in the background. It was ‘full quieting’. This is ideal, or in this case, phenomenal performance, given the low quality and low power transceiver used, a junky old nasty and dirty-RF Baofeng. My ham buddy had it on his antenna analyzer during this contact and experiment. My Extra Class acquaintance, who builds repeaters and antennas for a living, was in disbelief after scoffing profusely at the Baofeng.
The General Class fellow was so impressed he bought a slim jim antenna from me. My builds feature a tune-able 1/4 wave stud that dials these antennae in. As just a ‘hick in the sticks’, I’ve been forced to learn what can be done with nothing, a Baofeng, and with low power. In light of our not-so-bright future, this skill and experience attained, could prove to be very useful. Anyone can just turn up the power to get it done. Embrace low power and learn what you can do with it. If the guy on the other end sounds weak, if you sound weak to him, that is exactly the maximum power needed for a high-threat situation. Getting it done on very lower power makes it very difficult to intercept you. And if you aren’t intercepted and identified as a “target of interest”, then they won’t DF you.
We might see that most cost-effective radio communications can be had with an inexpensive radio that is on the best antenna you can afford. I believe the Slim Jim is one of the best for a Baofeng, or a full power transceiver. The advertised bandwidth of this antenna, 462 to 470 Mhz is a conservative estimate of the kind of bandwidth I would expect. My UHF Slim Jim builds uses 3/4 inch copper pipe, in place of 1/2 inch pipe typically use in construction of these antennas. It has a surprising bandwidth of 420 to 470Mhz. This is partly due to the fine-tuning involved to make the most of its increased bandwidth. Larger diameter radiators produce wider bandwidths. My recent Slim Jim build for the High VHF band, is centered on 153.000Mhz, and tested in the current installation location to be lower than 2.0 to 1 between 143.000 and 163.000 Mhz. From my perspective, this is ideal. One transceiver on one antenna can do nearly the whole usable High VHF band if necessary. It is an efficient use of resources, and funds. It is also a good use of space in the antenna farm that is the crowded roof, and good use of space in the ‘Ham Shack’. There are therefore fewer antennas, and few cables, and less RF noise in the shack.
A 4-watt Baofeng on one of these antennas on a 20 foot run of SI600 (LMR400 is suitable as well) cable would have an ERP of 6.4 watts. Under conditions where pine forests are present, I would expect a range of no more than 1 to 4 miles. Pine tree needles are of the length and density that absorbs UHF frequencies. If one is attempting to practice secure radio communications, this limiting factor could work to your advantage. If transmitting ‘down’ or the length of a valley with a river and flat land, and hills on both sides, with pine trees on those hills, unlike VHF, most of the signal will stay in the valley. UHF has its advantages, and is better to use than VHF in many situations. Deciduous forests do not have the same extreme effect on UHF, especially after they lose their leaves in the fall.
Low Power Propagation
Estimating the range of radio and antenna combinations are difficult as there are so many variables to account for. Hopefully, my estimates are accurate representations of the performance that is possible or actual in your neighborhood. We can certainly use a low-power handheld that transmits with 1 to 5 watts as a base station if the station is above the average terrain. And we might avoid the expenditure of the expensive mobile, if we have the best antenna we can afford. Low power settings, or low power transceivers, transmit in the power range that provides the most secure communication circuit at the maximum ranges when ideal, or good antennas are used.
If you need only one mile of range, do a radio survey of the area using only 1 or 2 watts from your base station. If the range is not adequate, then perhaps it is time to use a better antenna, or change the antenna height, but no more than is necessary to complete the necessary communication circuit. Hams seek to speak to as many contacts as possible, as far away as possible. Situation dictating, for secure communication, we should seek to do the opposite. We should limit our range, and who can hear us. We can use our GMRS antenna, and a handheld to accomplish a more secure method of radio communications as handhelds typically have power settings that are much lower than what typical base station transceiver offer — no less than 5 watts. If one watt is all that is needed, then that is all we need. The high gain antenna might double that signal to two watts ERP, and it will hear the very weak signals from other handhelds only use their attached antenna they come. In a war zone, low power is your friend.
In the case of GMRS that is often used, we are best served with low power and good antennas. If later you can afford a mobile, then by all means get one to talk further out, but use it only if the hand held will not do the job. GMRS 40 watt mobiles can talk much further than 4-watt CBs, and the mobile provides the power to talk to ubiquitous GMRS handhelds at extended distances that a patrol carries and must use to provide early warning of an attack, and to coordinate a defense.
The Final Step, Verifying the Operation of an Antenna
Always after an antenna is installed, check the SWR of the antenna. We are not only testing the antenna, but the location of installation, the connectors used, and the cable itself. If a connector is loose, a bad SWR would result, and can easily be corrected. And we should periodically, or when suspect, we should have a VSWR meter to verify that the antenna is still good, and is not doing damage to the radio. There are much better SWR meters out there. For this price, it is must-have. There are a plethora of instructional videos available demonstrating the use of this meter. This is lowest cost and the easiest to use SWR meter I know of:
If further help is needed, feel free to ask, in the Comments to this article. If BuyTwoWayRadios.com cannot program a business radio for you, or you need a more personal approach other than e-mail exchanges, or if you need a Baofeng programmed, or other services not found here or elsewhere, then I would give Paul Strammer a call on the phone or send him an e-mail. He knows what preppers need, and will help with radio in a way few other can or will. He is a retired logger, a patriot, and General Class Ham living in Northwest Montana: Paul Strammer
I hope that you found the preceding helpful. – Tunnel Rabbit, out.
I hope that you found the preceding helpful. – Tunnel Rabbit, out.