The broken lines in Figure 1 show compliance distances for vertical VHF quarter-wave monopoles—ground-planes and mobile whips. I find this article somewhat misleading. I’ve enjoyed playing with varing Output Power, coax cable and band and noticing the changes in EIRP or Ant. However, the actual range you can get from your Ham radio in the real world can vary substantially from this estimate. With knowledge a handheld could get up to a hundred miles and a DMR radio with a hotspot could be worldwide. Eqs 2-4 are estimates of the worst case compliance distance—the farthest point from an antenna where the RF field strength is in compliance. 2. However, the resulting extra-conservative estimate might be useful when the free-space gain is unknown. Members of the general public can not be expected to take precautions to avoid exposure, so the safety standards are more conservative. Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields, OET Bulletin 65b (1997). As we’ll see, however, this “theoretical horizon” distance is just that: theoretical. For some commonly used antennas there is a general purpose formula for calculating compliance distances [1]. Using these limits in Eq 2 gives the formulas for the occupational/ controlled compliance distance (DO) and public/ uncontrolled distance (DP): DO = 0.143 * SQRT (P * G)     [m]                     (3), DP = 0.319 * SQRT (P * G)     [m]                     (4). The AM band is sometimes referred to as MW or medium wave. That being said, the majority of Ham radio operators stick to VHF and UHF frequencies. This group includes amateur radio operators. The general purpose formula has also been validated for use with Yagi arrays [1,5]. DO NOT USE this software to determine whether an antenna is emitting an unsafe or hazardous level of energy.". So, choosing the right frequency for your communications will have a major impact on your range. Table 3 in the OET Bulletin converts gain in dBi to numeric gain G [1]. Distances are measured from the part of the antenna closest to the point of exposure. But, if you’ve recently purchased a Ham radio (especially a handheld unit), the manufacturer might claim that you can get substantially more range than 2-18 miles. The main benefit of VHF is that it has longer wavelengths than UHF. Radio signals aren’t very good at traveling through solid objects, such as mountains and buildings. Like anything Ham radio-related, the answer to how far you can communicate with your radio isn’t as simple as it might seem. The EZNEC program displays a disclaimer with all near field calculations [8]: "ATTENTION: This software CANNOT BE USED TO tell whether (1) the amount of electromagnetic energy being emitted from an antenna I unsafe to anyone; (2) an antenna subjects anyone to potentially hazardous electromagnetic exposure. Here’s what you need to know about how choosing to use either VHF and UHF affects your range: VHF, or “very high frequency” radio bands are between 30-300MHz. LICENSOR DISCLAIMS ANY AND ALL WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. The height of an antenna has a major impact on the amount of range that you can get with your Ham radio. Thanks! So, when you buy a radio unit and it claims to have a range of 36 miles, remember that this is a theoretical range in ideal conditions and not the norm. More Ham Radio Links, Calculate safety distance from your antenna. 1 for half-wave dipoles. In some countries other guidelines are used. You can choose compliance distances by using the references listed below, or consult an expert. 3. I do not accept responsibility for claims that result from the use of this information. 1. So, if you live in a rural area with lots of open space, you’ll likely get better range with VHF. While commercial stations will broadcast between 50,000 – 100,000 watts, handheld radios usually have just 0.5-5 watts of power. Both the FCC and the ICNIRP distinguish between two types of exposed populations or areas around an antenna. In the US, standards are set by the Federal Communications Commission (FCC) [1]. By variating any of these values a different Safety Distance is calculated. Figure 2. We rebooted the controller and the repeaters and things have returned to normal. There are three resources for using this formula: (1) the Paul Evans VP9KF online calculator [5];  (2) the ARRL General Purpose Tables [1,4];  or (3) the formula directly, as demonstrated in the Formulas section below. The free space gain comes from far field antenna patterns generated with no ground in the antenna model. You can realistically get about 2-18 miles of range with a handheld Ham radio unless you have a particularly powerful base station with a large antenna, in which case your range can be hundreds of miles. The ICNIRPcalc is a MS windows application of aprox 900Kb, I’ve tested under Windows XP (running on a virtual machine under my MacOS) and is Multilingual too, having an English German and French translated interface. Some J-Poles That I Have Known, L.B. I will never SPAM you. Higher gain vertical antennas for base stations and mobile use have a longer, coil-loaded vertical element. The power used in these calculations is average power. So, a 5 watt Ham radio is going to be able to transmit further than a 2 watt Ham radio with the same antenna height and in the same terrain. However, the disadvantage of VHF is that it’s not as effective in areas with buildings or other tall obstacles. The NEC tables give horizontal compliance distances at various heights for an antenna at a specified height. By entering your e-mail you consent to subscribe to my newsletter. Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range 3 kHz to 300 GHz, Health Canada Safety Code 6 (2015). Notify me of follow-up comments by email. In fact, depending on the band that you use, you can talk with your friends on the other side of town or communicate with people across the world. Required fields are marked *. A person with a handheld radio and zero knowledge could expect 2-18 miles distance transmission and receive. The estimated gain of a VHF/UHF discone antenna example in Ref. I am a licensed operator and have made contacts to every part of the world, Your email address will not be published. P. Evans, VP9KF, Amateur Radio RF Safety Calculator. In reality, the range of your Ham radio depends on the frequency you’re using, the height of your antenna, the obstacles and terrain around you, and the wattage of your radio, among other factors. For the 5-element Yagi example, the NEC tables show that even at 400 watts, exposure is in compliance with occupational limits at every point more than 2.4 m (8 ft) below the antenna. UHF is more commonly used for cell phones, GPS, Wi-Fi, Bluetooth, and walkie talkies. 1. So, someone using a handheld radio that’s positioned at 5’ off the ground would have a theoretical horizon of 3.16 miles. A modeling error can lead to NEC compliance distances that are too close to the antenna. In fact, there are a whole lot of “ifs, ands, or buts” involved with giving estimates for the range of any radio and Ham is no exception. Within the United States, Ham radio operators can use 26 different “bands” or groups of frequencies with their radios. Compliance distances vs average power for half-wave dipoles (solid lines) and vertical quarter-wave monopoles (broken lines) from 30 MHz to 300 MHz., Peter DeNeef, AE7PD, is an Extra Class amateur radio operator in the U.S. Standards developed by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) are used in the UK and many other counties [2]. This means that they have shorter wavelengths and more energy than their VHF siblings. Pretty much, we updated the article to make the distinction, though. SAR can be calculated using a specialized simulation program or from measurements of the 3D electric field distribution inside a phantom containing a liquid electrolyte. This site use cookies to ensure you the best experience in navigation. Figure 2 shows compliance distances for a 5-element horizontal VHF Yagi array with a free-space gain of 8.71 (9.4 dBi) [4]. The general purpose formula does not include the effect of nearby metal objects that can reflect a significant amount of power and create dangerous hot spots. 4. If your main goal for your radio is to transmit as far as possible, you might be saying, great, sign me up for VHF! FCC/ICNIRP compliance distances vs average power for a 5-element horizontal VHF Yagi array (30 - 300 MHz). Some examples are in Safety Compliance Distances for Amateur Radio Antennas in Canada. For example, it underestimates safety distances for small loops [5] and end-fed inverted-L antennas [7]. The manufacturer specifications usually quote a far-field gain that includes ground reflections, which is higher than the free space gain used in Eqs 3 & 4. The FCC-recommended factor 2.56 is an estimate of the increase in power density around an antenna due to ground reflections. It is 2 W/m^2 in public/ uncontrolled areas. Safety Compliance Distances for Three Multi-Band, End Fed Inverted-L Antennas, P. DeNeef, AE7PD, QEX Nov-Dec, 2017. Signal strength is measured in watts, and there’s a big difference in strength between a handheld unit and a typical commercial radio station. Accessible at this ICNIRP site (pdf). 6. UPDATE 29-Sep-2020 Two items: (1) the Internet at the Rose Hill site is down; thus no Echolink, etc. Conversely, UHF is less effective over long distances, especially in mountainous areas. Safety Compliance Distances for Amateur Radio Antennas in Canada. In fact, to maximize the range of your radio, you need to operate on a frequency that’s appropriate for your location. The solid lines in Figure 1 show FCC/ICNIRP compliance distances vs average power for horizontal or vertical VHF half-wave dipoles. The FCC guidelines were reviewed in 2005 with no change. Higher gain vertical antennas for base stations and mobile use have a longer, coil-loaded vertical element. Calculations are done by considering many depending factors, like your Antenna characteristics, Band, Gain, Power Output, Coax Line, additional attenuation and many more. NEC antenna simulations at the ARRL Lab verified that the formula gives conservative estimates for a number of dipole, ground-plane, and Yagi antennas [4]. Current ICNIRP and FCC standards for the VHF bands are the same, so you can use VP9KF’s online calculator, FCC and ARRL tables, or the general purpose formula to find FCC and ICNIRP compliance distances for some VHF antennas. For example in 2015, Health Canada adopted somewhat more restrictive exposure limits than the FCC and ICNIRP guidelines [3]. Solving Eq 1 for D, D = 0.45 * SQRT (P * G / SMAX )     [m]                (2). So it is well below 3 Mhz, not HF. The FCC and ICNIRP maximum permitted power density exposure is independent of frequency in the VHF range, 30 - 300 MHz: 10 W/m^2 in occupational/ controlled areas [1,2]. The world of Ham radio is notorious for being a bit confusing to newcomers, so learning the basics, like how far you can talk with your radio, can easily seem like an insurmountable task. To demystify the concept of Ham radio ranges, up next, I’ll walk you through everything you need to know about what affects your transmitting distance so you can better understand what to expect from your own radio. When compared to VHF, UHF has the added benefit of being more reliable in areas with lots of buildings or tree cover. You can directly downoload the software from here or by visiting the IARU Page where the software is hosted under the EMC section. In general, the FCC and ICNIRP guidelines for dosimetry (maximum permitted exposures) differ, but they are in agreement for the frequency range that includes VHF, 30 - 300 MHz. ICNIRP Guidelines for Limiting Exposure to Electromagnetic Fields, Health Physics 118(5) 2020 pp 483-524. The ARRL Lab verified that the general purpose formula gives conservative estimates for a number of dipole, ground-plane, and Yagi antennas. According to the National Association for Amateur Radio, this includes everything above 1.8 Megahertz to 275 Gigahertz. But keep an eye out and report the issue to Don W7OXR if it happens again. This website has no ads or conflicts of interest.Email:  HamRadioAndVision *at* gmail *dot* com.

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