Signal strength is measured in watts, and there’s a big difference in strength between a handheld unit and a typical commercial radio station. 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. 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.
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. Table 3 in the OET Bulletin converts gain in dBi to numeric gain G . The power used in these calculations is average power.
Therefore, you can think of this calculation as an indication of the maximum possible communication distance rather than what you should expect every time you use your Ham radio. 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. If your main goal for your radio is to transmit as far as possible, you might be saying, great, sign me up for VHF! Notify me of follow-up comments by email.
The free space gain is 1.26 (1.0 dBi) . DL9KCE released a new version of his ICNIRPcalc software that allows you to calculate safety distances for many know amateur radio antennas with respect to ICNIRP limits. 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. 1 for half-wave dipoles. Calculations are done by considering many depending factors, like your Antenna characteristics, Band, Gain, Power Output, Coax Line, additional attenuation and many more.
According to the National Association for Amateur Radio, this includes everything above 1.8 Megahertz to 275 Gigahertz. 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.
DO NOT USE this software to determine whether an antenna is emitting an unsafe or hazardous level of energy.". A modeling error can lead to NEC compliance distances that are too close to the antenna. Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range 3 kHz to 300 GHz, Health Canada Safety Code 6 (2015).
What this means for you, when it comes to Ham radio range is not that you should definitely choose VHF over UHF because VHF is better over longer distances. What’s more important is that you understand what affects the range of your Ham radio and what you can do to improve your range for better performance when SHTF. The AM band is sometimes referred to as MW or medium wave. This is a pretty wide range that technically covers HF, VHF, UHF, SHF, and EHF frequencies. This is why we almost never communicate as far as our maximum theoretical range says we should be able to. As I’ve mentioned, UHF frequencies are better at travelling through buildings and other objects in urban environments because of their higher energy wavelengths. Safety Compliance Distances for Three Multi-Band, End Fed Inverted-L Antennas, P. DeNeef, AE7PD, QEX Nov-Dec, 2017.
All rights reserved. Distance between antenna and radio. I find this article somewhat misleading.
Required fields are marked *. 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.
Input power… very interesting. 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. More Ham Radio Links, Calculate safety distance from your antenna.
1 is 2.0 dBi. In the US, standards are set by the Federal Communications Commission (FCC) . Meanwhile, a fixed station antenna that’s 20’ high would have a theoretical horizon of 6.33 miles. The broken lines in Figure 1 show compliance distances for vertical VHF quarter-wave monopoles—ground-planes and mobile whips.
However, the disadvantage of VHF is that it’s not as effective in areas with buildings or other tall obstacles.
The online calculator includes this option . 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. I can talk over 200 miles vhf. UHF, or “ultra high frequency” radio bands are between 300MHz and 3GHz, so they’re one step up in the frequency ladder from VHF. Some examples are in Safety Compliance Distances for Amateur Radio Antennas in Canada. Higher gain vertical antennas for base stations and mobile use have a longer, coil-loaded vertical element. The guidelines for maximum permitted RF exposure depend on the country where you operate. It is 2 W/m^2 in public/ uncontrolled areas. Therefore, instead of telling you that you can simply expect a range of 2-18 miles with your Ham radio and leaving the conversation at that, here are 4 key factors that affect your transmitting and receiving range.