so this has been driving me nuts for about two weeks now. im running an older Kenwood TM-D710A with the built in TNC and i've been watching my position on aprs.fi and it keeps placing me about 3 miles northwest of where i actually am. at first i thought it was just a propagation thing or maybe a digi was doing something weird but it's consistently wrong, like every packet shows up in the same wrong spot.

the GPS unit i'm using is one of those little external pucks i bought off amazon a few years back, works fine for other stuff. i did double check the NMEA sentences coming out of it and they look right to me but honestly im not great at reading raw NMEA so maybe im missing something. the radio itself is set to internal TNC mode and beacon interval is at 5 minutes. i haven't changed any of the position settings manually so it shouldn't be overriding the GPS.

anyone run into this before? is there a setting in the D710 that could cause it to cache an old position or something? or could the GPS just be feeding bad data even though the coordinates look reasonable to me?

yeah the D710 absolutely can get stuck on a manually entered position if you ever punched in coordinates at some point — there's a setting in the menu where it prioritizes the internal stored position over the GPS feed. dig into the APRS menu and look for the position input method setting, make sure its set to GPS and not manual. i've seen this trip people up more than once, the radio just happily beaconing wrong coords for months before anyone notices.

also worth checking if the GPS puck has a good sky view. 3 miles off sounds like more than just weak signal drift though, that sounds like it might actually be a datum issue or the radio is pulling stale data. what does the GPS indicator on the display show, is it solid or flashing?

not sure if this is related but i had a similar thing happen with a cheap GPS puck and it turned out it was outputting GGA sentences with a weird datum that wasn't WGS84. aprs.fi expects WGS84 and if your puck is for some reason spitting out something else the position offset can look exactly like what you're describing. probably a long shot but worth checking if the puck has any config utility.