Sunday, May 20, 2012

Walkie Talkie Guide (UHF CB Radios)

2019 Update - Real World Use
- Power matters less than you think!
- speaker mics are very practical
Been using the Uniden UH720sx-nb for awhile now. (note it is succeded by the UH820, which has USB charging)

Use indoors / small buildings / low density (eg country) areas.
0.1W is surprisingly more then adequate for alot of things.
eg. Distance ~400m on google maps (about 2.5 AFL pitches). Through (I counted)
5 to 6 brick walls. Some glass windows. two industrial warehouses.
I was able to communicate with clarity to my partner, sitting on a couch in a brick house.

Use on the slopes / snowboarding / skiing
0.5W (equiv to your cellphone's peak 3G power – 4G uses less.) is more than adequate at Mt Buller – The speaker-mic is extremely handy on the slopes as it clips to your ski jacket while your actual handset is in your inner pocket. The biggest issue on the slopes is not transmit power – it's TERRAIN... because physics (doesnt penetrate ground).
Real Life Suburban Environment: 
0.5W punched through about 17 houses and two large warehouses. (800m - labelled A)
2.0W punched thorough about 24 houses and two large warehouses. (920m - labelled B)

Realistically, it was difficult to determine when 2.0W really had an advantage over 0.5W.
In practice, both 0.5W and 2.0W sounded the same up to about 400m (the carpark in the picture)

Commercial 5W handsets - I think they are a great idea for convoys with external antennas, but I cannot justify having that much radiation (yes it's technically 'non ionizing') coming out from a device next to my face. The average cellphone uses about 0.1W during a call. Overkill for most people. Also note 5W translates to about a 1Amp drain on your batteries.

Original Article, 2012:

Once upon a time, I had a pair of really cheap 3xAAA walkie talkies. They were small and well built, but batteries died within three hours, and range was terribly limited. That was in 2006. Walkie Talkie tech has not progressed much since then (it's still all FM on an analog signal), but the quality and affordability of decent walkie talkies have improved.

There is a dearth of information on the internet regarding realistic Walkie Talkie / UHF CB practical range. Manufacturers often claim 22 to 36 mile ranges which is utterly inaccurate. Alot of people are also misled into purchasing small walkie talkies that are no more than kids toys.

This article covers UHF Citizen Band (CB) class licensed (public spectrum) radios. VHF is used in marine applications where range over unobstructed surfaces / water is more important. Ultra High Frequency (~477MHz in Australia) does have significant ability to penetrate objects and is better in built up environments. If you've used a cellphone, you've used a UHF radio so you already have some idea about how well it penetrates walls. Since cellphone towers are located at very strategic vantage points (hills / towers), cellphones get by with relatively low power output. GSM cellphones maxes out at 2W and averages less than 0.5W during a typical phone call. With a walkie talkie, both parties are the cellphone tower but located at ground level - a very big caveat as UHF does not penetrate ground/earth.

In this article:
  • Basic facts about walkie talkie range.
  • Buying Guide.
  • Nice accessories to have.