Home User Tutorial How to choose their own walkie-talkie – UHF CB Radios

How to choose their own walkie-talkie – UHF CB Radios

by retevis

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.

Basic Facts About Walkie Talkie Range

  • UHF’s range is limited by line of sight (through hills/earth)
    • the max theoretical range due to earth curvature is around 6km. A most basic 0.5 watt unit could transmit this distance over open air without obstructions.
    • All radios regardless of power will not work at all behind hills.
    • Signals will penetrate walls just like cellphone signals do.
  • UHF is attenuated by metal objects / trees / snow / walls
    Especially large metal objects (read: from inside a car). Hence despite having a range of a few miles (5km+) on open, line-of-sight, road, two cars on a road trip using 0.5W handhelds may have an effective range of less than 1km.
  • Realistic Range For UHF CB Walkie Talkies
    *range is a square root of power.Watts vs Relative Range

    • 0.5W = 0.71
    • 1.0W = 1.00
    • 2.0W = 1.41
    • 4.0W = 2.00
    • 5.0W = 2.24
    • 0.5W is more than adequate in an open area like a stadium. Poor penetration, ~200m in suburbia. Does not really work in buildings. Will be good enough for most supermarkets, and smaller cruise ships. Good for say conveying orders to the kitchen in a restaurant. Road trips with two cars close (visible) to one another. Use indoors in a typical two story house.
      • 0.1W ultra low power is convenient to have as it offers better privacy and will work in most houses that arent too big.
    • 1.0W has significantly better penetration, look to getting around 1km range in suburbia. ~10 floor buildings. Note there are two brands offering “tradie twin packs” in australia, and they are one watt units. Will work in most factories/warehouses/workplaces/offices. Will work on most cruise ships based on multiple amazon feedback of 1W 440MHz GMRS radios.
    • 2.0W improves penetration further. Look to getting a mile (2km+) of range even with both people in different cars (metal faraday cages!) on the open road. ~2km range in suburbia. ~20 floor buildings. Will cover 95% of areas on most cruise ships.
      • It’s worth noting that 2W is the peak power for GSM mobile phones, which typically consume only 0.2-0.4W during a phone call. Mobile phones benefit from having towers in high places, so even a small output power is enough and range is typically less than 1km in most urban areas.
      • Also note that most smaller commercial walkie talkies (eg. motorola CLP/RDX) max off at 2W.
    • 5.0W is the commercial standard for large walkie talkies. Will work in 30+ floor buildings. Will still be blocked by terrain/hills/earth though, but is powerful enough to provide coverage in almost any building. For most practical purposes, 5W does not provide much advantage to 2W as range will be limited by terrain / Line-Of-Sight more than anything. Many users lower power to 3 or 2W to conserve battery.

Guide To Choosing A Walkie Talkie

Never buy anything that uses AAA batteries. These will, inevitably, suck. For one they will not be powerful enough (usually under 1W), but more importantly, their size will be unfeasibly small. Size is important but having a half decent antenna is also important. They also tend to come with mediocre receiving circuitry and have really crappy unclear speakers. 0.5W on a bigger unit is very different from 0.5W on a small AAA walkie talkie. AAA batteries max out at around 700mAH. But radios are high drain and will drain batteries quicker than their mAH rating will suggest, especially in subpar environments (read: cold / ski slopes). Kids toys.

Strongly consider a AA unit. AA rechargeable batteries are inexpensive and high capacity (2200-2700mAH). Depending on your use, commercial (read: proprietary) lithium ion battery packs may be suitable, but for most prosumers and non-business people, these are also expensive to replace over the long run and the cost of a spare lithium proprietary battery is usually high. AA’s are so cheap that you could rely on your rechargeable cells and top them off with disposable alkaline cells for just about any prolonged trip without a second thought.

Consider the following functions before purchasing:

  • Scanning – useful for finding a free channel.
    • dual watch scanning: Automatically scan your priority channel every 1-2s while scanning other channels in the time between.
  • CTCSS – an analogue tone that is used to make your walkie talkies shut up (stay quiet) when other people are using the same public channel. Useful to have on any radio polluted environment such as a ski resort. Your receiver only turns on when the right CTCSS tone is transmitted. It does not give you any privacy at all – it just silences your unit when people from other groups are talking.
    DCS – Digitally Coded Squelch, a more advanced version of CTCSS. I havent found this documented anywhere, but in practice, DCS (on Uniden sets at least) also suppresses that annoying loud “TCH” scratchy sound you get whenever you release the PTT button. There are anecdotal reports that suggest DCS reduces sensitivity and decreases effective range (ie. occasionally, squelches fail to open the receiver circuitry)
  • Squelch sensitivity: Essentially, how loud a radio signal has to be before your unit’s speaker blares in your face. Many basic units do not come with this very handy feature, and it’s particularly useful for listening in on public channels, such as #40 used on highways. Set too high and you’ll get lots of screechy staticky broadcasts. Too low and you’ll hear nothing.
  • [ For Australian Consumers ] 80 channel (12.5khz spaced) capability is important. The older 40 channel (25khz spaced) sets will become illegal in 2017.
  • Use while charging: Convenient if you are using in a vehicle most of the time. Seldom documented anywhere and you may have to contact users directly on forums to answer this question for a particular model.
  • Room monitoring: Useful as a baby monitor. Not a replacement for parenting, of course. It disables the receiving circuit for more battery life and gives you a few sensitivity settings.

Nice Accessories to Have

  • Headset: Useful in noisy environments. Better ones let you choose between VOX and PTT.
    • Feeling like a security guard? Doing events all the time? Ask about an “air tube” “throat mic” set.
  • Car Charger
  • Desktop Charger: I sound picky, but having a well designed charger is quite essential. The very very cheap ones charge at low power continuously 24/7. The better ones know when to shut off the charging circuitry. The more advanced models allow your units to be on while charging.
  • Speaker Mic: Useful in a car as your unit will usually be mounted on the dash where the reception is a little better.

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