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Comment by landgenoot | Hacker News Reader

> 1 watt transmit can go miles yet sips your phone’s battery

How far can such a device reach in a typical urban environment with the longer antenna?

VHF is effectively line-of-sight, and no antenna size can change that (although it does improve efficiency for both sending and receiving), so for two handheld radios, you are limited to about 10 km.

The only thing that really helps extend the range is elevating the antenna, and repeaters allow you to do that even between two mobile stations.

VHF doesnt need line of sight, it has excellent ability to penetrate obstructions due to its long wavelength. For example, its not difficult to receive FM radio transmissions indoors, even from tens of km away. Some obstacles will effectively block any radio signal though, such as solid earth or concrete (esp rebar reinforced concrete).

You are right that handheld radios wont get more than about 10km, but that is due to the curvature of the earth. Mountain top to mountain top, you could easily do 50-100km

That's what I meant by "effectively": Reflections, diffraction, and (moderate, i.e. think doors and windows, not walls) light obstacle penetration make some indoor reception possible, but the radio horizon remains the strong limiting factor.

That's even true for the L- and S-band; otherwise you wouldn't be able to use a cell phone in a windowless room, for example. (Much of what's commonly attributed to "object penetration" is actually mostly due to reflections and diffraction around obstacles.)

I think there's other phenomena that people might be interested in such as E-skip and tropospheric ducting. Although you cant really rely on those.

Practical use, dense urban, flat, UHF is about 1km. VHF is worse.

Most radio amateurs would utilize a repeater to get over this limitation. Assuming there is a reliable repeater one is welcome to use nearby.

In dense urban environments, VHF (~144 MHz) actually performs better than UHF (~446 MHz) for a few reasons... Lower frequencies diffract better around obstacles. VHF diffracts more readily around and over buildings than UHF. VHF penetrates building materials better than UHF — lower frequency = longer wavelength = better penetration through walls. UHF suffers from higher path loss over distance compared to VHF.

You can extend the reach using repeaters. This free app is handy for that https://hearham.com/repeaters

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