Thank you, Richard, for your response.
Yes, a GPS is connected and the radio
shows the GPS position. And yes, I'm trying to poll
other vessels using the Auto POS Poll function. (The radio is also connected to an MFD which shows the position of vessels responding to a Position Request call.)
And yes, the manual suggests it should work.
The function is apparently designed to periodically poll up to 4 other vessels (presumably via a recurring DSC Position Request message) and then show a TEST ACK message as a response from the polled station is received. I do not see that when the function is set up to poll a nearby station.
I believe that the relative positions of the other vessels may also be displayed on a "radar-ring" display as the Position Report messages are received (although the manual does not specify). The periodicity of the poll is user selectable in the setup.
Nevertheless, while Position Request does work (and such transmissions and the receipt of a Position Report are routinely recorded in my DSC log), the Auto POS Poll does not seem to work (an no entries appear in the TX or RX logs).
So I'm wondering if anyone else with this radio has actually verified that the function works.
I should note that I also have a newer HX890 handheld, and its manual documents the Auto POS Poll function as well. But it does not work, either, in testing--possibly because the "Class H" HX890 does NOT support the DSC Position Request function. The earlier HX870 does support Position Request and I have confirmed that Auto POS Poll on the HX870 does work.