Over the past few months there has been a renewed interest in AllStarLink FM simplex nodes among our members. These low power devices allow users to connect to remote VoIP nodes and repeater systems using an internet connection and an HT. Most opt to buy or build a device on 70cm.
A couple years ago, during the initial DMR hotspot craze, SBARC expert consultant Matt W6XC identified a few frequencies around 431 MHz that were useful for digital hotspots like the OpenSpot and ZumSpot. HOWEVER, these frequencies are NOT appropriate for analog FM nodes. We must use a different part of the 70cm band for FM emissions.
Matt suggests the following options for low-power, analog FM usage:
440.000/445.000; 446.860/441.860; 446.880/441.880 may be used as pairs for a low-power duplex node or as separate simplex node frequencies. Please listen to these frequencies with low squelch settings and no CTCSS for a few days before permanently parking your node here to see if and how these frequencies are used. FM simplex nodes are best PL/CTCSS protected, especially if they are left connected to a system like K6TZ or WIN System.
Definitely avoid 446.000 altogether. This is the National Calling Frequency for 70cm. 446.500 and 446.520 are “General Simplex” frequencies. Others many want to use these for simplex QSOs or other itinerant purposes so please don’t park your node on any of these three frequencies. Also note that 432.000-439.999 MHz is allocated to weak signal, Amateur Television and digital emissions only. 440 is tough given the lack of simplex allocations. It’s a truly stuffed band!
Perhaps just as important as which frequency you choose for your node is setting the PL/CTCSS tones. In Santa Barbara and Ventura counties, DO NOT use 131.8 or 88.5 127.9 or 131.8 Hz as a tone for your node. Picking almost anything else will ensure that you don’t inadvertently open the receiver of a repeater on the same or nearby frequency.
If you are interested in these FM VoIP nodes, consider the ClearNode and SHARI projects.