rnx2rtkp error : no nav data, convbin doesn't create .nav file

Question

I have U-Blox ZED-F9P receiver and antenna U-Blox ANN-MB-00-00. I'm trying to create precise GNSS tracks.

I never had such experience, so maybe I'm doing something wrong.

For recording, I use Armbian 22.02.1 with gpsd v3.22. For post-processing, I use Devuan 5 "daedalus" (based on Debian testing) with rtklib v2.4.3.b34.

Preparations:

export UBXOPTS='-P 27.12 -f /dev/ttyACM0'
ubxtool -e RAWX
ubxtool | fgrep RAWX

gives

UBX-RXM-RAWX:
UBX-RXM-RAWX:

Then I started to record a raw data (~570 KB for 11 minutes):

gpspipe -x 700 --raw > rover_700s_raw.ubx

In parallel, I downloaded a correction information from the nearest station (~750 kB for 15 minutes):

str2str -in 'ntrip://[email protected]:[email protected]:2101/Rychtal' -out /tmp/base_Rychtal.rtcm3

Then I convert them into .obs:

 $ convbin rover_700s_raw.ubx
input file  : rover_700s_raw.ubx (u-blox UBX)
->rinex obs : rover_700s_raw.obs
->rinex nav : rover_700s_raw.nav
->sbas log  : rover_700s_raw.sbs

scanning: 2022/05/07 22:16:30 GREC
2022/05/07 22:04:52-05/07 22:16:30: O=699

 $ convbin base_Rychtal.rtcm3
input file  : base_Rychtal.rtcm3 (RTCM 3)
->rinex obs : base_Rychtal.obs
->rinex nav : base_Rychtal.nav
->sbas log  : base_Rychtal.sbs

scanning: 2022/05/07 22:17:59 GREC
2022/05/07 22:02:50-05/07 22:17:59: O=910

 $ ls -l
total 4364
-rw-r--r-- 1 user user 2515356 May 14 11:15 base_Rychtal.obs
-rw-r--r-- 1 user user  756077 May  8 00:17 base_Rychtal.rtcm3
-rw-r--r-- 1 user user  607734 May 14 11:17 rover_700s_raw.obs
-rw-r--r-- 1 user user  577720 May  8 00:16 rover_700s_raw.ubx

Then I tried to create NMEA with correction:

 $ rnx2rtkp -n rover_700s_raw.obs base_Rychtal.obs
error : no nav data

So I found I have no .nav file after convbin conversion…

I've tried different options for convbin, but anyway it woun't create anything else except of .obs file.

What I'm doing wrong? How should I create a track with correction?