(Continued from Part 3.)
The Quad Barreled Cannon, The Wouxun KG-UV980P, $310.00
The Wouxun KG-UV980P Quad Band Base/Mobile Two Way Radio is a quad band, with cross band repeat, a 50 watt transceiver, that transmits using FM only in these frequency ranges: 26 to 29 MHz, 50 to 54 MHz, 136 to 174 MHz, and 400 to 480 MHz. It can generally be described in terms of Amateur Radio as a 10 meter, 6 meter, 2 meter, and 70cm, yet this unit transmits outside of these Amateur bands, and is much more than simply a Ham radio. For example, it also transmits in FM in the CB range of frequencies, and is subsequently in a gray area where FCC regulations are not enforced, and likely not even monitored. For clarification, while it will transmit on the same frequencies, and other frequencies as does a CB, it cannot talk to CBs, because CB uses Amplitude modulation (AM), and not frequency modulation (FM) that this transceiver uses. It can, however, receive AM-mode CB traffic. Because of this deficit, it does not function as a CB per se, but it is a very capable radio in other regards. It just barely fits into the theme of this article, and the big price makes it a tighter squeeze. It is mentioned as with this class of radio for the benefit of Amateur Radio enthusiasts who naturally would see the advantages of this radio, that can work injunction with the Anytone Smart, and Anytone AT6666.
AMATEUR RADIO AND YOU
An amateur radio Technician (“Tech”) license could still be in your future. It allows you to legally key up on the Ham Bands, and does give one access to numerous well-maintained repeaters. However, I would not plan on using repeaters after a collapse, or necessarily even the Ham bands frequencies as these would be carefully monitored by those seeking to develop intelligence in a post-collapse society or possible civil war. When Hams use their call sign, we can look them up on a database and get their full name, physical or mailing address. And it is possible that one day, that a tyrannical government might use the FCC-granted licenses as a means to target Amateur Radio operators as they are typically a patriotic, and freedom-loving group who would be central to a command and control. During World War 2, all amateur radio activity was prohibited. With that warning said, the 2 Meter Amateur band will likely bring and hold a community together. We should at least have a scanner to monitor all the 2-meter repeaters and other popular Ham frequencies in your area. Fortunately, there are no test licenses for GMRS that give one comparable coverage to that of the 70cm Ham band should there be GMRS repeaters present. Without repeaters, the range of powerful 40-watt GMRS transceiver would be in many regions of the country, be adequate to cover a 20 to 30 mile in diameter area of AO (Area of Operation), your home turf.
GMRS provides most of what most people in this day and age require. To reiterate, the downside of GMRS for preppers is that the inexpensive GMRS handhelds are ubiquitous, and your transmissions will likely be monitored. It is one of the most unsecure means of radio communications. But because it is populated by mostly the average user, it could be an opportunity to hide in plain sight, and to talk to neighbors. Fortunately, the use of a Ham call sign that can be used to locate your address is not used with GMRS. We should also consider the low barrier to entry — just $35, and the whole family can join in and use the same license. We could then also install our own repeater. In the GMRS section of the article, all the basic components are listed to get one up and running. The GMRS transceivers come already programmed. The radios are relatively simple to operate. These are sort of like a modern CB, but with greater range. We should choose a radio service that can be used by the least skilled member. GMRS, Citizen Band transceiver, and the MURS handhelds fit into this category.
GMRS uses Ultra High Frequencies (UHF), that do not travel as well along the ground and through forests as well as the lower frequencies of MURS (151 to 154 Mhz), that is VHF, or the CB frequencies (27 Mhz). If we use UHF, we should work harder to get all the power we can from the radio to the antenna to best propagate a signal. Although the focus is on GMRS, the principles discussed apply to all radio communications, or transceivers and handhelds. If one must cut corners to save money by using inferior and less expensive cables and antennas to get the job done in your AO, then there is no need for the added expense, and effort. In the majority of cases, we need to work harder to get the most range out of UHF.
Looking at a few numbers we’ll discover why we should choose the more expensive components, and install antenna as high as we can. We can use a 15-foot to 20 -oot metal or wooden pole in the ground as that will do just fine most of the time. We’ll do the best we can without going ‘whole hog’ like a Ham would. However, if you are surrounded by hills, or a hill or building is between you and the local repeater, we’ll need to either need an antenna that is mounted higher, or we’ll need to move the antenna. In some cases, the expense of a tower could be justified. But before spending that kind of money, perform a survey of the intended coverage area.
BASE STATION ANTENNAS AND COAXIAL CABLE
Most or all of the components for your base station antenna can be used for a different radio service. All principles that make a good antenna apply no matter the frequency. A base station transceiver should have a rugged high-gain antenna that is mounted at least 15 to 50 feet in height, and above a roofline. The heaviest cable that can be installed should be used as UHF frequencies easily escapes from coaxial cable, and the power the radio makes is lost before it gets to the antenna. This is not as much a problem with lower frequencies such as those in the VHF spectrum that are in the 136 to 174 MHz range, and lower. For UHF, avoid using light cables such as RG58 and RG8X that are better suited to Low VHF such as CBs (27Mhz). Instead, choose RG213, RG8, RG11, LMR 240, or best yet, LMR400, LMR600, and SI600 if at all possible — especially when cable lengths are over 20 feet. Long runs for CBs should use RG213. Long runs for High VHF, such as MURS should use RG213 to LMR400, and long runs for GMRS or other UHF radios should use LMR400 or better yet, LMR600 or SI600. We’ll learn why shortly.
Using a coaxial cable loss calculator (https://www.qsl.net/co8tw/Coax_Calculator.htm), here are a few figures to demonstrate why. The sample lengths of the cable used are 20 and 50 feet. The power sent through the cable is 40 watts. This is the maximum output of the MXT400. 20 feet is the shortest conceivable and practical length for a base station antenna, and 50 feet is adequate for most good installations. When it comes to antennas, one should not underappreciate the fact that, when it comes to antennas, “height is might”. The minimum height should be 15 feet, and the ideal height would 50 feet. Heights over 50 feet are usually at the point of diminishing returns in terms of increases in range. Figure that 10 feet of cable will be used to get the cable outside. It is best to use cordage, or a stiff rope, or coaxial cable used for cable TV to estimate the amount of coaxial cable that is needed for this installation. Because the heaviest cables are not very flexible, allow for some additional length, as these cables do not bend well around tight corners. Using the heaviest LMR cable is almost comparable to running 1/2 inch Pex line use for home plumbing. Of course, we could use what we have on hand, or what we can afford, but consider the chart and link below before we buy.
Here is the link to a selection of coaxial cable for price comparison: https://www.buytwowayradios.com/accessories/coaxial-cable/bulk-cable.html
Amazon offers precut cable with connector ends, but Amazon is pricey and we may need more or less cable, and we should avoid adding line by using a barrel connector as that is potential future failure point. Wrap that kind of connection with vulcanizing weatherproof 3M electrical tape, the expensive stuff sold at hardware stores. It is better to have a bit more cable than needed, than just not quite enough.
(The following cable loss calculated based upon an input frequency 465.000 MHz)
ERP Chart #1: 20 Foot Cables
Estimated Radiated Power (ERP) of two different antennas when fed by 20 feet of various types of cable, when using a UHF transceiver (radio) that transmits 40 watts through the cable to two different types of antennas.
Cable Power delivered ERP of an ERP of 1/4 wave
Type with 20 feet antenna with wave antenna with
of cable 5.5dBi of gain. no gain.
RG58 25.0 watts 54 watts 25.0 watts
RG8x 26.5 watts 56 watts 26.5 watts
RG213 31.0 watts 67 watts 31.0 watts
RG11 34.0 watts 73 watts 34.0 watts
LMR240 31.0 watts 67 watts 31.0 watts
BR-400 35.0 watts 75 watts 35.0 watts
SI600 36.7 watts 79 watts 36.7 watts
ERP Chart #2: 50 Foot Cables
Estimated Radiated Power (ERP) of two different antennas when fed by 50 feet of various types of cable, when using a UHF transceiver (radio) that transmits 40 watts through the cable to two different types of antennas.
Cable Power delivered ERP of an ERP of 1/4 wave
Type with 50 feet antenna with wave antenna with
of cable 5.5dBi of gain. no gain.
RG58 13.5 watts 29 watts 13.5 watts
RG8x 14.6 watts 31 watts 14.6 watts
RG213 22.9 watts 49 watts 22.9 watts
RG11 27.1 watts 58 watts 27.1 watts
LMR240 20.9 watts 45 watts 20.9 watts
BR-400 28.6 watts 62 watts 28.6 watts
SI600 32.2 watts 70 watts 32.2 watts
In this example: A recommendation to use 50 feet of LMR600, or a modern equivalent that is SI600, and a Slim Jim antenna that is estimated to have a gain of 5.5dBi. LMR400 is close in performance, costs less, and is easier to work with, and therefore is likely the most practical choice for 50 foot runs, but we should be aware of SI600 as that could be the better choice if a 150 foot run to a tower is necessary. Use this coaxial cable loss calculator to determine the most appropriate cable type: https://www.qsl.net/co8tw/Coax_Calculator.htm
Coaxial Cable Selection
Looking at the chart, LMR600, and its equivalent, SI600, at typical home installation lengths of 50 feet, delivers twice the power as does RG8 does at 50 feet. And because the antenna is mounted much higher than if 20 feet of RG8 were used, the range the radio can talk will be disproportionately further than if it were compared on the basis of ERP only. Why? In the radio world, antenna ”height is might” as obstacles in the ‘radio line of sight’ can block even high power transmitters. This fact makes longer cable lengths and loss acceptable to attain greater height an acceptable trade-off.
The higher the antenna the less the loss in the cable matters. Because of the shorter wavelengths that typically do not travel as far as VHF frequencies, we should do all we can to compensate by using additional antenna height, heavy low loss cable, and high gain antennas that are available for UHF. These three factors should be used to offset as much of the difference in performance as possible between UHF and VHF, especially when used in rural environments.
Use antennas that claim to have a gain of 2.5 dBi, or higher, to increase the radiated strength of the power supplied to the antenna. But the most important factor that produces the longest ranges is antenna height. Again, to reiterate, use a long run of cable, if additional height can be achieved, and do not be concerned with cable loss especially if the additional length allows the installation height to be above nearby obstacles. And if we can minimize the loss of signal by using a heavier cable, we can increase the range, and just as important, improve the coverage within an AO. If you’ve noticed ‘dead’ spots in wifi or cell phone coverage, a higher radiated power out reduces these areas with no coverage in an area that is otherwise within range.
Buy the lowest loss cable as we can afford to attain the greatest antenna height we can construct. And we would use a high-gain antenna to magnify the signal supplied by that cable.
How antenna height, the gain of antenna, and the power delivered to it affects antenna performance, or propagation.
I could argue that if only RG8 were used to mount the Slim Jim with 5.Dbi gain, at 50 feet, that delivers 13.5 watts, a 5.5dBi antenna would compensate, that is, the use of a high gain antenna would offset the loss from the cable, because the high gain antenna magnifies the signal resulting in an ERP of 29 watts ERP, rather than only 13.5 watts ERP, if only the typical 1/4 wave antenna were used. The result in performance could hypothetically, and in my experience, have better range than if only 20 feet of the heaviest cable, SI600 that nets an ERP of 79 watts, were used. Again, height is might, but a high gain antenna is important if we can use on. For every doubling of the power out, or 3Dbd,or 5.5Dbi of power, there is only one ‘S’ unit out of 5, that is realized. 2 watts is twice as powerful as 1 watt, but does it does not travel twice as far, but only a fraction further. Increases in power out is not proportional to an increase in range. Increase in antenna height has strong correlation to increases in range. Power out does not. Power out correlates more strongly with the signal’s ability to penetrate, or travel around (deflect) or bounce off of obstructions in the ‘radio line of sight’.
Where the antenna is erected relative to nearby objects is critical and a higher antenna means fewer obstacles in the ‘radio line of sight’. We should place the antenna above all objects at the roof’s peak. Specifically, at least one 1/2 wavelength above, that is approximately 2 feet for UHF antennas, and 2 feet away from any metal object that is perpendicular or adjacent to the antenna. It should be at the highest point above the roofline, or much higher. This distance away from metal objects is needed to avoid ‘coupling’ that distorts and alters the antenna, and reflecting the signal when we wish to have an omni-directions antenna and low SWRs. Install a vertically polarized antenna as far away from vertically oriented metal as possible.
Hopefully, this discussion helped us better appreciate that ‘height is might’, and the importance using the appropriate coaxial cable. CB’s that we grew up with can use light cable, but GMRS is a different animal. GMRS can greatly exceed the range that CBs provide, if we install a good antenna system. We may need as much range as we can get to be able to access a distant repeater, or have enough power to cover an AO that might be 20 miles in diameter, comprised of hilly countryside, or covered in dense pine forests. The antenna and cable used is often as important, or even more important than the radio used. Spending the money on the antenna, and using a lower cost and less powerful radio can be a good combination, if money is tight.
The performance of a low power transmitter on a ‘good’ antenna as defined, can surprise us. Also, the other, and perhaps more important part is listening, or the ability to hear weak or distant signal from other low power stations such as hand held’s, or other GMRS stations with antennas that are less than optimal for GMRS. If we can hear a weak signal, we can talk to that station. If we cannot hear it, we cannot talk to it. The radio transmits better with high-gain antenna, and also hears better with high gain antennas. The use of less expensive and more secure low-power transceiver is optimized by the use of the best antenna we can construct. A radio circuit can be more secure if we can hear weak signals that an intercept station cannot. There is more than one reason to use a high gain antenna.
If necessary, it could be the best money spent, because as they used to say in the Army…. “Without Commo, you got nothin'”.
Here is a low cost tower:
Rohn 25G 30′ Tower No Base (Cement not included, but needed.)
(To be concluded tomorrow, in Part 5.)