Usually between 136mhz and 174mhz, with only software-based restrictions that are easily worked around. This applies for other bands as well (e.g. 70cm).
The transceiver ICs they usually use are designed for commercial radios and that is the frequency range that they typically cover. The ability to monitor other services is a useful feature.
I have a few monobanders by Yaesu & Icom, and all of them are able to ony only Rx but also Tx outside of the HAM freqs. Of course, I’d be very careful with them 😇
Note that there’s 25% of fractional bandwidth in there and many antennas won’t work everywhere in that range (and also other elements like power dividers, diplexers etc if part of circuit)
What do you mean? Can you elaborate?
If we consider groundplane antenna, which should be much better than anything that you can fit on a HT, it might be centered on 145MHz (region 2 band) and it’ll be good for 10MHz for 1:1.5 SWR (140-150) and 17MHz for 1:2 SWR (136.5-153.5) according to some random measurement, first that i found. Outside of these ranges SWR rises rapidly and if you tried to transmit on say 170MHz you might get SWR 1:5, perhaps 1:10 or worse if you’re unlucky. On receive this doesn’t matter too much because these nano- to microwatts of rx power would just bounce back harmlessly with the only effect being that apparent signal strength is lower. But if you tried to transmit then design currents or voltages would be exceeded and something will break, usually final stage of amplifier. This gets rarer than it used to be because some radios can measure SWR and will reduce power in such scenario. This also gets worse the higher transmitted power is
This happens because unlike on HF + 6m, on 2m and up ATUs are not a thing* and all antennas are expected to be matched. So you can use the same radio on GMRS or PMR or what have you and on 2m or 70cm band, but you have to change antennas between these uses. If you want to use all of these on one antenna, then there are special wideband designs like LPDA but this makes sense on a mast and not on handheld radio
* there are tuner designs that work on 2m and up, but you won’t find them in HT, there’s no point, they’re too big, too heavy and too expensive
Even if you tried and made it to work, there might be other incredible problems with things like harmonics or other spurious emissions because filters were not designed to work way out of these frequencies. For example you can try to force Quansheng UV-5K (?) to transmit on 60-ish MHz but most of the power goes out at 2nd and 3rd harmonic, because of the way filters were set up. Narrowband designs are much easier and this is what you’ll see all the time in amateur radio. Wideband and ultrawideband designs are constant source of job security for RF/microwave engineers
You can think of matching units and antennas (and to some degree even feedlines) as filters to some degree, because their bandwidth is not infinite
Thanks for the explaination!
The other day I was checking out the datasheet for my Yaesu monobander’s final amp, and I noticed that it is able to performs optimally up to its advertised 80w only between 144mhz and 148mhz, while outside of that it’s capped to 60w. I’m pretty sure this is related to what you just explained.
Overall, I feel like the 2m band is like a kiddie playground, while the grownups are hanging out with their big antennas on HF.
Could be. Amplifiers are a bit more complicated and there are many things that can limit bandwidth
They don’t come with the ability to transmit outside the ham bands from Yaesu or Icom. Somebody has modified them. It’s known as the MARS or CAP mod.
Perhaps it’s a regional thing. It is quite the wilde west where I’m from after all.
For the Yaesu FT-2900R, I indeed acquired this second hand, but I also got myself a new old stock FT-60R that seems to be able to transmit outside the HAM band for both 2m and 70cm out-of-box.
