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.
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
One of my objectives for the good weather in Maine during my holiday travel was to get out to the convenient and interesting parks in the area. As highlighted by W1DED 's map documenting POTA MAINE , there are a couple of Midcoast Maine parks that had no activations ever by 2022: both the Durham State Forest and Ducktrap River Wildlife Management Area. The reason? They're poorly documented locations with no convenient drive-up-and-know-you're-there place. The WMA even overlaps the local Ducktrap Preserve, but you'd have to figure out what that meant and where to hike. And the forest, well, the forest barely even seems to exist on the internet by that name! No official state information and just lots of OpenStreetMap references. I looked to take on the forest to understand where it was, what the access looked like, and then get out there and put the park on the air.
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