On Mon, 26 Jun 2017, DK7FC wrote:
Is there any improvement of the Neo-7M over the Neo-6M? [...]
the neo-6m can generate up to 999Hz on the timepulse output. this is good
for a 1pps timing source for vlfrx-tools (just shorten the timepulse to
1ms, it's 100ms by default)
the neo-7m can generate up to 24MHz on the timepulse output, but this is a
NCO with 48MHz clock, so for clean output pick frequencies which are
48MHz/N where N is integer. this is a good reference for transmit
applications (of course it can do 1pps too).
the other difference is that while the chiniese boards with both neo-6m
and neo-7m often have an eeprom on board, only the the neo-6m will read it
upon startup. or at least i haven't been able to make the neo-7m start
with my settings after powerup.
to solve this i use a simple C program to talk UBX protocol to the gps to
set the required parameters. in my case this is 57600 baud, disable SBAS,
set 20kHz timepulse on lock, and set 4Hz refresh rate. i use the nmea
output to set time via ntpd, and the 20kHz signal as a reference to
ebsynth (right now i use it for sending stable carriers, but eventually
will do ebnaut too). i can post the program in case anyone is interested.
another fun fact: these are really cheap gps-es with not-so-stable clocks.
you can break the gps lock by changing the temperature quickly, even by
blowing compressed air at it. use a lot of thermal isolation.
VY 73
Jacek / SQ5BPF
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