As previously discussed, the BK4819 simplex FM transceiver chip with specified coverage of 18-660 and 840 to 1300 MHz covers a lot of Region 2 amateur radio bands with generally accepted FM operation: 10 m, 6 m, 2 m, 1.25 m, 70 cm, 33 cm, and 23 cm. The most popular models of amateur-oriented HTs using the chip generally only cover the popular VHF/UHF split with 2m and 70cm (and wide enough filters to support nearby business/public safety bands). How this is implemented varies in cost, complexity, and potential for effective modification. Of course, it's not really a modification if it's an actual product, but more on that further in.
The Quansheng UV-K5 ( product page archive ) handheld transceiver has been notable in cheap amateur radios of 2023 by using both a wideband FM chip BK4819 ( product page archive ). With support of 18-620 and 840-1200 MHz half-duplex with 6.25/12.5/20/25 kHz channel spacing, this puts the chip in the range of five ITU Region 2 amateur bands (10m, 6m, 2m, 1.25m, 70cm, 33 cm) and spitting distance from a sixth (23 cm). Presumably hitting 4m and the rare 8m would be within reason as well. The easily hackable firmware indicates at least nominal receive capability up to 1300 MHz, though!
After reading the W1GHZ GaAsFET LNA Bias entry, I wanted to see what the performance of these exposed-base optocouplers are. The concept comes from the IEEE Microwave Journal Application Notes: Photovoltaic Bias for Depletion-Mode Devices in Low-Noise Amplifier Applications (DOI 10.1109/MMM.2022.3226635). It's not open access, so I figured some publicly available characterization data would be cool to share. I have access to a dual-channel precision SMU (source-measure unit, Wikipedia ) and that's exactly what we need to characterize the photovoltaic behavior of optocouplers! Keysight B2902B SMU front panel during a 20 mA input, open circuit output measurement