4m 2020/June/01

After missing the big 2m ES last friday i had some luck on 4m today. Among others i worked GM4VVX, EA6FB, OH1KH, PA3FMP, GW8ASA, GU6EFB, EI8IQ and OY1OF.

reception reports on pskreporter.info for 4m on June 1st 2020 for DH5YM. map by openstreetmap contributors.

New 23cm transverter and DUR contest

Last weekend i tried to put my new 23cm transverter with 28MHz IF and the 100W PE1RKI PA together. The picture shows my ugly “transverter in a box” construction.

23cm transverter ugly test construction

I used this setup in the March 23cm DUR contest. My ODX was HA5YA via aircraft scatter about 550km distance. I also worked DL3IAE and OM5CM, both >400km.

OM Raachermaa

This is an traditional figure from the Erzgebirge. OM seems to do VHF contesting which is also popular there ;) But maybe not only the OM is smoking but the transceiver as Wellness eventually. Merry Christmas to all of you!

OM Raachermaa

Searching for some FreeDV QSO partner on VHF

Since i use Quisk for my HiQSDR i found it interesting to experiment with FreeDV again. Quisk can directly support using the FreeDV API and work in this digital mode without building lots of cables. Since i wanted to try the latest mode 700C i had to compile the library from the scratch and add the mode to the configuration of quisk. Below you can find recordings of my CQ call in the modes 1600 and 700C which were made loopback.
Now i search for a QSO partner preferably on 2m somewhere in the area around JO61. I can work relatively well direction southeast. So east OK might be good.

Mode 1600

Mode 700C

Please remember the 700C mode uses only 1kHz of bandwidth.
If you are interested in some tests just send me a email to dh5ym@darc.de

GPS 10MHz reference

Since some time i own a DF9NP GPSDO. Currently i only use it to lock my signal generator but i also want to use it for my microwave transverter OCXOs. When connecting a SMIQ signal generator and checking the signal output at 6GHz i noticed some +-50Hz jitter under the poor reception conditions at thelocation of this signal generator. So i want to look a bit closer into that topic. In China i ordered a Neo-M8N module that can be configured to provide a 10MHz clock at its timepulse output. I tried to compare it with the GPSDO and the OCXO of my SMY-02 signal generator.
Of cause the digital clock has significant jitter because it is generated by a CPU (specified with +-10ns).

Neo-M8N clock output at 10MHz

The picture of the timepulse at 10MHz shows, that it seems that comparing the clock to a stable oscillator over a relatively short period could be sufficient for adjusting the frequency of this oscillator to the GPS.


The screenshot shows the oscilloscope triggered to the GPSDO (green). The output of the M8N module (yellow) shows the jitter and the adjustment range within 60 seconds (yellow shadow). The third (blue) trace comes from my SMY-02 which was locked to the GPSDO. The SMY signal shows some slight jitter compared to the reference. To me it is not clear if the cause is the reference or the locking in the generator. The clock from the M8N module shows significant adjustment of the clock frequency within the 60 seconds shown compared to the GPSDO which has a TCXO that is slowly compensated by the GPS inside the reference.
Looking to the signal in frequency domain shows this picture:

Neo M8N spectrum

There are rather close sidebands that require narrow band adjustment of a oscillator eventually locked to this GPS clock. Wideband the spectrum is noisy as well.

M8N phasenoise at 10MHz

Finally i took a short video showing the the scope triggered to the 10MHz OCXO reference of the SMY and comparing the GPSDO and the M8N output. The OCXO is slightly off 10MHz and therefore the picture is moving all the time. You can also see that the M8N is slowly adjusting compared to the GPSDO output.

GPS 10MHz GPSDO vs Neo-M8N and 10MHz OCXO

Watch this video on YouTube.

Tiny Sequence control unit (WIP)


Thats a simple sequence control unit for transverters etc. ON a double layer PCB. The design was eine with the open source tool KiCAD. Its made around a attiny2313 and features a highside switch, a lowside switch as well as a uln2003 driver. In addition further sensors can be connected via I2C or SPI. The software is not finished. More information will follow.