| Two-way Radios for 4x4 Usage |
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| Member Articles - Technical Articles | |
| Written by Eric Skeen | |
| Saturday, 18 July 2009 11:18 | |
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I would like to present an “easy to follow” article on Two-Way Radios and Licensing procedure. In a short article such as this, one cannot present all, but hopefully enough to help clear some confusion. Some of this article has been culled from previous articles, I will try weed out the repetition as I go along.
WHAT TYPE, 29MHz AM or FM?
29MHz AM RADIOS:The virtues of 29MHz AM radios are many – they are relatively cheap and many Clubs and 4x4 drivers make use of them. They are priced at around R800 – R1100 excluding antenna & installation. Their reliable operating range is anything from about three to fifteen KM or thereabouts, but this varies greatly with weather conditions and time of day, as well as area of operation and motor vehicle suppression..
Antenna location is important with AM, a permanent mount is to be preferred over a magnetic mount, and ideally the antenna should be mounted in the middle of a large expanse of metal, such as the roof of a double-cab. This might not always be convenient, and mounting the antenna elsewhere could result in directional RF radiation. Usually, you could always expect up to 5Km useful coverage between two like units.
FM RADIOS:The most common FM radios operate on VHF, which is a range of frequencies within the 146-174MHz band. FM radios offer very good distances, anywhere from about 25-50Km between mobile units but once again dependent upon terrain! They are powered at 25W RF and are relatively immune to interference caused by atmospheric or electrical conditions. The radios are not freely available over the counter however, because of stringent ICASA licensing requirements. Upon receiving a Licence, you will not be granted a country-wide frequency, but one for your own private use and it will not necessarily be the same as that in use by any Club or other user. In fact, other than joining the local chapter of a 4x4 Club and making use of their allocated frequency, you might consider getting together with some local pals and forming your own 4x4 club, writing a constitution, and obtaining a licence in the name of your new club. More on this later.
The same rules for AM antennas apply to the FM antennas as well. However, there are two common types available:
Of the two types, I prefer the former for mountainous terrain, the latter for flat countryside.
KENWOOD TK7102 4-Channel VHF Radio
VERTEX VX2100 8-Channel VHF Radio
HANDHELDS:I am not discussing the 29MHz hand-held portable radios here as they are totally impractical for 4x4 usage and their long aerials are cumbersome. They have a very limited operating range and are no longer readily available. Licence FreeThe cheapest radios are the so-called “Licence Free” hand-held radios, which have very limited RF output stages, usually somewhere between 50mW & 500mW. Dump the 50mW, they are worthless. The 500mW radios offer an operating range of anywhere between 1 – 3Km, depending upon terrain, irrespective of what their Manufacturers might like to claim on the packaging. Line of sight provides the best range. They are powered by three or four penlight cells and are usually supplied with rechargeable Ni-Cad battery packs and a battery charger. Useful for short-range communication, not all that useful for communication between two or more vehicles except when within a few hundred metres from each other. HYT TC1688 “Licence-Free” 500mW Portable Radios
Pre-LicensedICASA (the SA Regulating Authority on Radio Communications equipment) have granted certain companies permission to sell portable handheld radios that have been pre-licensed, i.e. the fees for the first year are included in the radio’s selling price. These radios have a greater RF output than those mentioned above, being typically 2 Watt units. They are professional radios and are priced at three or four times the price of the licence-free radios. Typical operating range is from 3 – 5 KM, although longer ranges have been reported in good conditions. Again, line of sight works best. The radios are supplied with a Ni-Cad battery pack & a 220V charger, although the chargers can be modified for 12v charging with certain limitations.
[insert picture] Licence Required:VHF/FM Portable RadiosSimilar in price to a fully installed 29MHz radio and antenna system, these are proving immensely popular with many 4x4ers now, especially with many Clubs now being affiliated to the ORRA (Off Road Radio Association) and thereby allowing their paid-up members to make use of the ORRA frequency. Typically, these radios provide a nominal 5-watt RF output over a line-of-sight area, which can provide a successful operating range of anything from one to five kilometers, dependent upon intermediary terrain conditions. The radios are battery-powered and the batteries will typically last a full eight-hour period between re-charges, based on a cycle of 5% talk, 5% receive and 90% standby basis. Atmospheric conditions do not affect reception at all. These radios are rugged enough to withstand being operated in a normal 4x4 environment and technical service for them is generally available through selected Radio Dealers country-wide. Pricing and quality varies considerably but overall we have carefully selected radios that we feel are eminently suited to being used on Trails and for general 4x4 use. Typically, they feature 16-channels and can accommodate various accessories such as headsets, speaker/mics etc. They are small enough to be carried in a bush shirt’s top pocket or by means of the included belt clip, on your belt. Pictured below is the general-purpose Kirisun PT4200 VHF Portable Radio, which is ideally suited for our purposes and carries a good price.
HF/SSB RADIO:These high-power radios operate on low RF frequencies, typically between 1.8 ~ 30MHz, at RF levels of about 100W. They offer greatly extended operation, but they do have pitfalls. The operating range varies with a local ground-wave signal providing about 30Km radius, but this is in general not too reliable and nor is the radio designed for ground-wave communications. HF comes into its own with the reflected Sky-wave signal, which signal that is reflected off the Earth’s Ionosphere, which is constantly varying in height from above the Earth’s surface. The RF path can be compared to a tennis ball bouncing up and down as it is thrown hard into the ground.
KENWOOD TK90 HF/SSB Radio
VERTEX VX2100 HF/SSB Radio
LICENCING COMMUNICATION EQUIPMENT
ICASA LICENCING PROCEEDUREAll Two radio equipment has to be licensed. In the case of the so-called “Licence-Free” products, ICASA has already approved these short-range radios for use by the general public, School sports events, parking attendants, etc. As previously mentioned, some of the Clubs have already been allocated an operating licence for their members by ICASA, and should you wish to make use of their frequencies, you will have to contact the Club directly and apply for membership. They will allow you to use their frequencies subject to a small fee to cover their licencing costs. The Licence granted to the Clubs is exactly that: They will allow you to use this frequency as long as you are a member of the Club, but it is not transferable to you should you resign from the Club, and you may not operate any radio without an official licence (ICASA ruling). The fines are not small! You may also apply for a private radio communications licence, but there is little sense in that if no-one else is on the same frequency as you. It therefore makes sense to join a Club and use their allocated frequency. If you live in a remote area, you may by all means apply for a private communications frequency, or, as already mentioned, form a local Club with other 4x4ers and apply for a frequency in your new Club’s name. ICASA requests a Radio Communications Licence Application fee must first be paid to them before they will consider your Application. You are required to submit proof of payment along with your Application. They do not accept any form of payment directly at their premises. Currently, the Application Fees are R290 for 29MHz AM Radio, and R620 for VHF, and then if granted, an Annual Licence renewal fee of R42.00 per radio applies. Should you apply in the name of a Club, these Application costs can be shared amongst the members. In the case of a VHF frequency, you will receive a frequency which can be used within a 50Km radius of your home, or Base. You are not legally allowed to make use of the same frequency outside this area, unless you apply for a "Roving Frequency", which is the type of frequency that the larger Clubs would apply for. Roving frequencies require a minimum of 40 radios to be granted such a frequency, and the applicable annual licence fee becomes expensive for an individual. The following thread is separated as per the requirements on the ICASA Application Form one “reply” per page. There is a degree of repetition, but the Form can be confusing. I am trying to simplify it as far as I reasonably can. Members are invited to PM me for any additional help. OBTAINING THE RADIO COMMUNICATIONS APPLICATION FORMThe "Landmobile Application" form can be downloaded from the ICASA web site Scroll along until you find the application form entitled "Landmobile Application", and then download the PDF document, which will open in a new window. Print it out, it is six pages long. It is advisable to number the pages in the order they are printed so that they do not get muddled up, they are confusing enough! Please use BLACK INK to complete the form. The emphasis here is on a VHF FM frequency, but the procedure is much the same as for 29MHz AM, with a few small changes where applicable. Page 1: SECTION 1: RADIOCOMMUNICATION APPLICATION Page 2: APPENDIX A - DETAILS OF FIXED AND MOBILE TERRESTRIAL SERVICE.
PAGE 3: APPENDIX A: DETAILS OF FIXED & MOBILE TERRESTRIAL SERVICE
SITE A:
SECTION 3: CLIENT INFORMATION
SECTION 3: CLIENT INFORMATION
COSTSThe application fee for a VHF frequency is much more expensive than for a 29Mhz frequency. Here are the tables:
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| Last Updated on Monday, 03 August 2009 11:49 |
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