Update 21-05-14:

Bugfixes: Starting before 10h failed due to time format without leading zero, last symbol was about one second too short.

Update 21-05-11:

Fractional Hz frequencies (e.g. 8270.0025 Hz) are now also supported. Note that the fractional part of the frequency is approximated by phase stepping every second, so it should be small to avoid excessive spurs. 

Absolute phase is maintained according to the time of day.

Included is also a simple version for sending phase-coherent DFCW. It uses a symbol list "dfcw.txt" containing 0, 1 and 2, as shown in the example for the message "DF6NM".

Update 21-03-21:

To avoid unwanted time-slips within a sequence (e.g. due to heavy CPU load), the script "send_ebnaut_ublox" now explicitly calculates the transmit time for each symbol, and compares it to the PC clock. If we are too early we will wait longer before the next symbol, if we are late we will skip over a few symbols. This also allows to start transmitting slightly late, even after the nominal starttime has already passed by.

Some variables need to be edited before use, as explained at the beginning of the script.

73, Markus

2019-12-13 (DF6NM)

A while ago I had posted a way to send EbNaut directly from a u-blox GPS device without further hardware, using multiple concatenated batch scripts: 
https://klubnl.pl/rsgb_lf_group-archives/html/rsgb_lf_group/2019-02/msg00052.html
Now I have simplified the method a bit, so only a single short batch file (attached here as txt) is needed.

Download setubx2.exe software from the specified URL, and generate your desired sequence using Paul Nicholsons ebnaut-tx and "Save Rows" (i.e with one symbol per line) as "pskln.txt". You can configure transmit parameters by editing the first lines in the script:
 startminutes=30: start time on multiple of number minutes (e.g on the next half hour),
 sym=3: symbol duration in integer seconds (1 to 60),
 freq=137536.000: frequency in Hz (may contain fractional part),
 comport=com5: the virtual serial port where the u-blox device is connected.

Non-integer frequencies can be generated using phase-stepping at the symbol rate, but the deviation from the nearest Hz should not be large. Note that frequencies which are either near integer divisors of 48 MHz (e.g. 137536 Hz), or just above integer multiples of 48 MHz/2^17=366.215 Hz, seem to be sweet spots in terms of low spurious sidebands.

The "setubx2 0" line can disable the output after the sequence has been completed. For a repeating beacon (e.g. every half hour), you can enable the "@goto loop" line by removing double colons. Finally save the script as a .bat and start it by double-clicking or from a console. 

Note that  while the script is running you should avoid mouse clicks or key entries into the console window, as these would destroy timing by inhibiting or prematurely aborting the timeout commands.