FCC/ICNIRP compliance distances vs average power for a 5-element horizontal VHF Yagi array (30 - 300 MHz). With that in mind, your distance to the horizon (in miles) is calculated at: where D is the distance in miles and H is the height of your antenna in feet. 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.
radio + cable + antenna need to be in harmony and everything has to be thoroughly calculated. The ARRL Lab verified that the general purpose formula gives conservative estimates for a number of dipole, ground-plane, and Yagi antennas. A modeling error can lead to NEC compliance distances that are too close to the antenna. The formulas include a field multiplication factor of 1.6 for the effect of ground currents near the antenna, so using a "real-world gain with ground reflections" includes ground effects twice. You can choose compliance distances by using the references listed below, or consult an expert. The AM band is sometimes referred to as MW or medium wave. The article is reprinted here. 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.
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. 5. In an urban area, however, your range will generally be better if you opt for UHF instead.
This Blog is mainly dedicated to Amateur Radio (Ham radio) and contains external articles and personal esperiences. The online calculator includes this option . Guidelines for Human Exposure to Radiofrequency Electromagnetic Fields, OET Bulletin 65b (1997). The free space gain comes from far field antenna patterns generated with no ground in the antenna model.
Members of the general public can not be expected to take precautions to avoid exposure, so the safety standards are more conservative.
LICENSOR DISCLAIMS ANY AND ALL WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Another option for calculating compliance distances, antenna simulation with an NEC-based computer program, is discussed below. My Yaesu FT817ND is small and highly portable and using 2 1/2 watts I’ve talked from Oregon to Florida on 20 and 40 meters using a Silver Bullet 102 inch vertical whip antenna. There are three resources for using this formula: (1) the Paul Evans VP9KF online calculator ; (2) the ARRL General Purpose Tables [1,4]; or (3) the formula directly, as demonstrated in the Formulas section below. It is 2 W/m^2 in public/ uncontrolled areas. Increasing the height of your antenna is one of the easiest ways to extend your range.
In fact, many 2-way radio units claim as much as 36 miles of range. The general purpose formula has also been validated for use with Yagi arrays [1,5].
If you continue to use this site it is assumed that you are happy with it. But keep an eye out and report the issue to Don W7OXR if it happens again. Safety Compliance Distances for Amateur Radio Antennas in Canada. 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. UHF, or “ultra high frequency” radio bands are between 300MHz and 3GHz, so they’re one step up in the frequency ladder from VHF. ICNIRP Guidelines for Limiting Exposure to Electromagnetic Fields, Health Physics 118(5) 2020 pp 483-524. Accessible at this archive. ... That's not bad at all — compared to the average ham's setup, ... my entire system, i.e. P. Evans, VP9KF, Amateur Radio RF Safety Calculator. The US AM radio band is roughly 0.5 Mhz to 1.7 Mhz.
Your email address will not be published. 1 (general purpose formula). Figure 2 shows compliance distances for a 5-element horizontal VHF Yagi array with a free-space gain of 8.71 (9.4 dBi) . However, the resulting extra-conservative estimate might be useful when the free-space gain is unknown.
Additionally, it’s important to understand the limitations that your surrounding terrain has on your potential communication range.  The formula is not accurate for all types of antennas. The numerical gain in free space used in the calculations is G = 1.64 (2.15 dBi) .
This group includes amateur radio operators. Calculations are done by considering many depending factors, like your Antenna characteristics, Band, Gain, Power Output, Coax Line, additional attenuation and many more. I do not accept responsibility for claims that result from the use of this information. Higher gain vertical antennas for base stations and mobile use have a longer, coil-loaded vertical element. So, what gives? The general purpose formula is not valid when your body is very close to the antenna. and (2) the amplitude of the signal from the 2m VHF repeater has suddenly decreased dramatically (in the order of 50%). Ask Question Asked 4 years, 1 month ago. So, someone using a handheld radio that’s positioned at 5’ off the ground would have a theoretical horizon of 3.16 miles. Both the FCC and the ICNIRP distinguish between two types of exposed populations or areas around an antenna. Pretty much, we updated the article to make the distinction, though. We rebooted the controller and the repeaters and things have returned to normal. Measuring near field strengths accurately is not trivial. 5 shows typical free space gains from some antennas. Your e-mail is 100% safe.
Higher gain vertical antennas for base stations and mobile use have a longer, coil-loaded vertical element. There are also laws about the signal strength of amateur radios, and Ham radios can generally have up to just 5 watts of power.
Some examples are in Safety Compliance Distances for Amateur Radio Antennas in Canada. If your main goal for your radio is to transmit as far as possible, you might be saying, great, sign me up for VHF! This is why we almost never communicate as far as our maximum theoretical range says we should be able to.
For example, the ARRL table for a 2-meter-band quarter-wave ground-plane at 100 watts,146 MHz, and 6 ft (1.8 m) above ground shows the controlled and uncontrolled compliance distances are 1.2 m and 2.9 m, respectively, compared to 1.6 m and 3.6 m in Fig.
DO NOT USE this software to determine whether an antenna is emitting an unsafe or hazardous level of energy.".
7. Therefore, VHF is best for use in long-distance communications in outdoor areas where the receiving radio is more or less within the line of sight of the transmitting radio. I’ve enjoyed playing with varing Output Power, coax cable and band and noticing the changes in EIRP or Ant. This means that the question of maximum Ham radio range isn’t easy to answer because there are a whole lot of different factors that affect how far you can communicate with a radio. In the US, standards are set by the Federal Communications Commission (FCC) . However, the actual range you can get from your Ham radio in the real world can vary substantially from this estimate. The estimated gain of a VHF/UHF discone antenna example in Ref. You said, “It’s also used for FM radio broadcasting (AM radio actually uses HF or “high frequency,” which is 3-30 Mhz).”. You can directly downoload the software from here or by visiting the IARU Page where the software is hosted under the EMC section. Within the United States, Ham radio operators can use 26 different “bands” or groups of frequencies with their radios. As I’ve mentioned, UHF frequencies are better at travelling through buildings and other objects in urban environments because of their higher energy wavelengths. Solving Eq 1 for D, D = 0.45 * SQRT (P * G / SMAX ) [m] (2). 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. For some commonly used antennas there is a general purpose formula for calculating compliance distances .
Copyright © 2011 - 2020, AE7PD. I can talk over 200 miles vhf. The solid lines in Figure 1 show FCC/ICNIRP compliance distances vs average power for horizontal or vertical VHF half-wave dipoles. Also, the public includes individuals of varying health status and may include particularly susceptible individuals. The power used in these calculations is average power. Distance between antenna and radio. The EZNEC program displays a disclaimer with all near field calculations : "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. According to the National Association for Amateur Radio, this includes everything above 1.8 Megahertz to 275 Gigahertz. I used the general purpose formula for the VHF examples in this article. Not published at this time, but the entire book is available as a 56 MB pdf download from the ARRL web site, and membership in the ARRL is not required: arrl.org/rf-exposure. Accessible at this FCC site (pdf).
Figure 2. A person with a handheld radio and zero knowledge could expect 2-18 miles distance transmission and receive. Table 5.7 in Ref. Manufacturers are required to limit the specific absorption rate (SAR) for RF devices that are used close to the human body. 6. Other disclaimers apply. 8. Figure 1.
The FCC guidelines were reviewed in 2005 with no change. In fact, to maximize the range of your radio, you need to operate on a frequency that’s appropriate for your location. R. Lewallen, W7EL, EZNEC Software and User Manual. This website has no ads or conflicts of interest.Email: HamRadioAndVision *at* gmail *dot* com. There are many variations on the J-pole design for which you might not know the gain. However, your communication range is limited not only by the height of your antenna, but the height of the antenna that’s receiving your transmissions. Thanks! Distances are measured from the part of the antenna closest to the point of exposure. UHF is more commonly used for cell phones, GPS, Wi-Fi, Bluetooth, and walkie talkies. Required fields are marked *.
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