Picking a simplex portable radio frequency

June 20, 2019

It’s generally much better to use 440 MHz band instead of 144 MHz band for portable hand-held radios (walkie-talkies). The 440 MHz signal is able to pierce through openings in buildings better. The interference from computers, LED lights, phone chargers, etc. is generally 20 dB or more less on 440 MHz vs. 144 MHz.

Generally we use “wide” 25 kHz bandwidth, as the performance is about 4 dB better than “narrow” 12.5 kHz spacing due to the nature of FM analog “processing” gain from wider bandwidth. That is, in the absence of interference, 25 kHz wide modulation performs significantly better than 12.5 kHz narrow modulation. Most members have analog-only radios at this time, so we kept with analog FM.

In North America, hams generally should not use FM below 442 MHz, as there are other modes coordinated for that frequency range. Hams should first consider 445.975, 446.0, or 446.025 MHz for FM simplex to be “safe” in most of North America, to not interfere with data links or repeater backbone links.

With modern radios after about year 2000 or so, there isn’t a significant advantage of one PL tone over another. There is too much bursty interference to run carrier squelch (no PL).