Amateur Radio

Change broken relay Rot2Prog

The Rot2Prog rotor controller from AlfaSpid has four simple relays that several users has reported to be broken. This has also happened to me – I have a relay that has not function very well for several years. So I decided to try to replaced it.

These releay are very cheap and I found replacement at TME:

l:12VDC;16A/250VAC;16A/24VDC ROHS
Przekaźnik:elektromagnetyczny;SPDT;Ucewki :12VDC;16A/250VAC
Mfr: RELPOL Original part number:



Unmount the board

First remove the top cover by removing the four screws at the side of the chassi. Then remove the two screws holding the board, see image below:

The board is built nice, with ferrite on the input and output cable to prevent RF-noice. If needed to change the board, this can be easy done.

Remove relay

Then desolder the faulty relay. For me, it was one of the azimut direction relay, the one to the left:

It was a pain in the *** to desolder and remove this relay! I was close to give up and nearly destroyed the board. But finally, after two hours, I did managed to remove it. I can not understand why AlfaSpid did not mount a relay socket for easy change…

Solder the new relay

This was an easy task, just solder the 8 legs:

Function test

Now connect all the cables and try it. Hopefully it will now work again!

Good luck!

Amateur Radio

LNA and antenna switch with ESP8266

This is my first ESP8266 project, for control of my LNAs and antenna relays via a web interface. More info and code at my Github:

Amateur Radio

Simple full duplex relay switch

My setup for amateur radio satellites is SDR for receiving (RX) and Icom IC-705 for transmitting (TX). To my antennas I have two separate coax feedlines. Before, when switching band between RX and TX I was forced to manually change the coax feedlines connectors between SDR and IC-705.

I started to plan a simple relay switch to be able to switch fast and easy between TX/RX and UHF/VHF antenna – I call this a ”Simple full duplex relay switch”. The plan was this:

  • When no power to the relays the SDR is connected to the UHF antennas and IC-705 connected to the VHF antennas.
  • When 12V power to the relays the SDR is connected to the VHF antennas and IC-705 connected to the UHF antennas.

The relay used was this mini SMA relay by OK1CDJ. It can handle 10 watts (up to 20 watts according to hamshop.cz). The short coax between the relays are RG-405.
I have done SWR and loss measurements and it is very low. The original design and measurements can be found here:

This is the result, it works very good. Todo: put the relays in a nice box.

Amateur Radio

IC-705 WLAN doppler with OmniRig PstRotator

I got the PstRotator to work with OmniRig and IC-705 over WLAN. I’m using ”Icom Remote Utility” on Windows to set up the virtual COM-port. And I’m setting up OmniRig like this:

I had several problem getting the OmniRig to communicate with IC-705 via WLAN, but after re-installing to the OmniRig supplied with PstRotator (v1.18) I got it working OK. It is also working from SDR-Console V3.

So now it is possible to do doppler control of the IC-705 without any cables for true portable operations! See short video below:

Amateur Radio

FT8 20 meter 2021-03-28

My signal heard on almost all continents. 8 watt with IC-705, antenna EFHW. Band: 20 meter, 2021-03-28 daytime UTC. IC-705 connected to PC/WSJT-X via Wifi.

Amateur Radio

AX.25 APRS with UISS and IC-705

This is a very fast guide to set up the IC-705 with UISS for sending AX.25 packets and APRS.

  1. Download and install UISS. During installation, install the Soundmodem software TNC.
  2. Download the file ptt-dll.zip from Soundmodem webpage. Unzip and copy the files to your UISS folder.
  3. Download the CAT dll file v 1.21 that includes IC-705 setting and replace CAT.DLL from the file above.
  4. Set the radio to FM-D (Data) and select the frq for APRS (in Sweden 144.800 MHz).
  5. Start UISS
  6. Setup UISS with your callsign and your location:

  7. In Soundmodem, set the Sound Card device to your IC-705 USB audio card.

  8. In Soundmodem, set the PTT Port to CAT and radio IC-705. The COM-port should be the one that IC-705 uses for CI-V.

  9. Now you should be able to see traffic

  10. Now send your first APRS Position. Use digipeater if you like.
    The IC-705 now sends your APRS location.

  11. If everything is OK you should be seen on aprs.fi
Amateur Radio

Rot2Prog powered with Dell 19.5V adapter

Important update!
When using automatic control from PC then both the elevation and azimut is controlled (moved) at the same time. It seems that the Dell power adapter can not handle the current amp spike and turns off (overload protection I guess).

I have now return to using my 13.5 volt power supply.

I have been powering my Rot2Prog rotor controller for my RAS rotor with 13.5 volt. This means that the rotor turns slow. My 13.5 volt power supply also has a very high idle consumption of 10 watts.

I changed the power supply to a standard Dell power adapter – LA130PM121 19.5V 6.7A PA-1131-28D1 130W. It can be found very cheap. I just cut off the power plug and connected the wires from the Dell adapter to the Rot2Prog controller wires.

Now the turning goes MUCH faster! The Dell adapter also has a very low idle consumption – under 0.5 watt. So it can be connected all the time. What I can see there is no interference from the adapter on VHF and UHF.

I highly recommend using the Rot2Prog controller with an old computer adapter. Below is a short video of how fast it is turning.