In a variety of activities, including photography when you are not doing it alone, it makes sense to have good communications. We are pretty lucky here in Europe that there is a part of the frequency spectrum open to unlicenced use for anyone who can afford a €20 set of ”walkie-talkies” can access this. This means anyone can use these radios without any licencing or fees and it sure beats mobile phones when it comes to the cost of the calls.
The channel spacing is 12.5 kHz just like some other older PMR (Personal Mobile Radio) systems earlier. The modulation type is FM (F3J) and with the low power they have pretty good battery times as well, I can carry one unit for a full day without needing to recharge it.
|Geocaching and Geohashing is using this frequency
The output power is limited to 500 mW ERP (Effective Radiated Power) and the antenna is only allowed to be the fixed built-in antenna that was tested with the device for compliance. This output power gives you a coverage radius of a few hundred meters in a cityscape and a few kilometers in a flat country side.
Several manufacturers are printing ”5 km coverage” and similar numbers on their boxes. You can also see the same manufacturer claiming 5 km, 6 km and even 8 km coverage on similar devices and although they charge much more for the 8 km version there is very little proof that it is actually better than the 5 km verstion. The reason for this is that the output power is fixed to be a maximum of 500 mW radiated.
The most variance you will find is on the receivers and not the transmitters really so there may be some differences depending on how sensitive the receiver is in your particular unit.
Many of these radios also employs a kind of squelch system called CTCSS (Continuous Tone-Coded Squelch System) which is used when several users are using the same frequency. If you set your radio to the ”sub channel 5” using the CTCSS system then you will not hear people as they talk unless they transmit this code. The code is automatically transmitted when the push-to-talk button is engaged. This avoids random conversation disturbing you.
It does still not allow people to talk simultaneously on the same frequency and it is not a privacy function since any radio can turn off the feature and then hear all conversations that are carried on the frequency. Most radios can also be set to scan the whole frequency band and therefore find any ongoing conversation quite easily.