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Preparing the Red Pitaya's STEMlab 122.88-16 SDR

The Red Pitaya SDR runs a specific Linux image which contains software written by Pavel Demin that let it communicate with SDR software via the ethernet using the HPSDR protocol.

There will be 2 SDR instances available, so you will be able to run 2 CW Skimmer Servers.

Please follow the following to prepare an microSD card and then have it to communicate with the 2 CW Skimmer Server instances.

1 - Prepare the microSD card with Pavel Demin's Linux image

  • Use Windows Disk Manager (diskmgmt.msc) to delete all the partitions on the microSD card, then create a new partition and format it as FAT32 (FAT won't work).
  • Download Pavel Demin's Alpine Linux image in zip format from
  • Unzip the above zip file and copy its content to the microSD card.
  • Copy the file from the zip file's folder "apps/sdr_receiver_hpsdr_122_88" to the microSD card root directory.
  • Insert the SD card in STEMlab SDR and connect the power.

    More information at:

    If everything is ok, you will have green LED lit alone on the receiver initially for a while until it gets an IP address from the DHCP server, at which point the blue LED will come on to tell you it uis ready to go

    At this point you must check on your router which IP address was assigned to the SDR and try to ping it and/or access it on your web browser.

    Note: the SDR_Receiver_HPSDR script starts *two* (2) independent 8-slice SDRs, and the board will end up with two IP addresses and two MAC addresses on your LAN. So you can start two independent versions of Skimmer Server, each referencing a different MAC address by renaming the HermesIntf.dll as described below. You can control which bands will get which antenna ports.

2 - Running CW Skimmer Server

  • Install CW Skimmer Server.

  • Copy HermesIntf.dll to the CW Skimmer Server program directory (C:\Program Files (x86)\Afreet\SkimSrv).

  • In the SkimSrv directory, rename HermesIntf.dll to HermestIntf_XXXX.dll where XXXX are the last four digits of the MAC address of the STEMlab SDR (you can find the MAC address on the sticker on the RJ45 ethernet port).

  • Make a copy of the SkimSrv directory and rename the copy to SkimSrv2.

  • In the SkimSrv2 directory, rename SkimSrv.exe to SkimSrv2.exe and rename HermestIntf_XXXX.dll to HermestIntf_FFXX.dll, where XX are the last two digits of the MAC address

  • Start SkimSrv.exe and SkimSrv2.exe, configure frequencies and your call sign.

  • Install Reverse Beacon Network Aggregator

  • Start Reverse Beacon Network Aggregator.

Thanks to Pavel Demin, N4ZR, N6TV