LVB [Tracker] Extender

I started using an LVB Tracker by G6LVB (also of FunCube Dongle fame) to control my Yeasu G400RC and KR-5400 rotators which have my directional antennas on them – The G400RC + homebrew jack-arm elevation was mainly for EME and the KR5400 was for satellite work.  I had to built an elevation feedback circuit, I chose a MXD5125 for this but I found I still lacked some of the features of more advanced rotators and with the LVB Tracker being controlled by serial using the GS-232 protocol I found this would be easy to remedy using a PIC.


The main features I wanted to add were the ability to input a wanted heading and then leave the rotator to goto that heading instead of having to hold any button down as the rotator can be slow and my attention span is short.  I wanted to have a button for ‘park’ to put the antenna in it’s ‘resting’ direction and an easy way to just rotate 45 degrees or 180 degrees (flip) at a time, I also added a button to toggle a relay which was used to switch the satellite antennas from RH to LH circular polarization and back again.

This shows how I interfaced the LVB extender (in yellow) with the LVB Tracker (in blue)…


In the end I used a PICAXE-28X1 chip as I needed a bit of program memory and lots of input pins.  The input buttons consist of UP, DOWN, CW & CCW plus LH/RH, Park, +45 degrees and +180 degrees.  The serial from both the LVB Tracker PIC and PICAXE-28X1 are TTL so I connected the serial to the LVB Tracker between the PIC and the MAX232 chip used for RS-232 level conversion.

Whenever UP, DOWN, CW, CCW, +45 degrees or +180 degrees button are pressed the first thing my LVB Extender has to do is read the current positions using the GS-232 “C2” command which prompt the LVB Tracker to output both current azimuth and elevation positions which I read and store. From these positions the code works out what needs done with them.  If it is UP, DOWN, CW or CCW then it runs a loop to increment or decrement the original position for the duration of the button being pressed with increasing speed over time.  It writes the value back to the LVB Tracker on every loop.  If the +45 degree or +180 degree buttons are pressed the LVB Extender again reads the current positions using a “C2” command and either adds 45 degrees or 180 degrees to the value and writes it back to the LVB Extender ensuring the write command has the originally read elevation value to this is not effected.  The Park button sends a stored position, from my old QTH in JO02ab the best heading for me was 127 degrees azimuth and 0 degrees elevation (best for monitoring 144.300 into Europe).  The Park heading is programmable only in the code, I made no provision to set it on the fly, main because I didn’t know how when I created this, I do now and will add it if requested.

The LH/RH button only toggles a relay to switch a voltage to the antennas.  If azimuth value reaches 360 degrees the code converts it to 0 degrees and if it reaches 0 degrees it converts to 360, both are able to be set if you like to go over the limits a little.  On elevation the counting is limited to between 0 and 90 degrees.

LVB_Extender_AND_LVB_Tracker LVB_Extender_Buttons

LVB_Extender_Fitted LVB_Extender_Boxed




240711 – Project posted to web.


  1. Bill

    Is it possible to get files in a high resolution download ? The circuit diagram is near impossible to read.

    1. m1bxf (Post author)

      Hi Bill, if you click on the schematic image it opens the original .png image in full resolution, and looks the same as the original document I uploaded (you can then download it if you like), this is the direct link if it helps:

  2. Bill

    The new functions make sense to me. I just completed my LVB tracker kit modified for a H-Switch output for single winding motors and will like to add your extender to the rig.


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