Monday, May 25, 2015

Phase Locking the G8ACE MKII Ovened Oscillator

I decided I needed to build a new 1296MHz Transverter that would be a single unit and have enough output to drive my 350W amplifier. I had a spare G4DDK2004 Transverter module but this requires drive at 96MHz for the local Oscillator. I could have built another DFS96 but that would occupy a lot of real estate. Similarily an RDDS is too large.  In my parts collection I found some G8ACE mkII oscillators, in boxes with the PLL lock boards. One was already on 106.5MHz for my EME 10368/144 xverter so I could put another on 96MHz. I ordered a 96MHz crystal cut for 60C via G4HUP. Putting it in the unit and running the Calibration produced the following:-


The TP1 Volts was set to 6.0V for optimum performance

Thoughts then turned to the lock board. I had no idea which software the EPM3064-4 FPGA had, so I decided it was best to reload the chip.  Originally I had used a parallel port programmer running MAXIIplus+ software for programming the chip but I no longer had a parallel Port. Some time ago I bought a USBBlaster clone from China so this was found.  I downloaded and installed the QuartusII 13.0sp1 Programmer software from the Altera web site and attempted to load . Nothing useful happened. I discovered that unlike my PIC programmer the USBBlaster does not power the target, It has to have its own power. Once that was supplied the software told me it could see the correct chip and the ref_e1_64_4.pof file was succesfully loaded to the FPGA. 
After making the connections between the boards I connected a Voltmeter to the monitor point. After applying the 10MHz reference this Voltage slowly oscillated before finally settling down at a fixed Value with the Rubidium locked Frequency counter showing exactly 96MHz

Spurred on by this success I found I had a temperature calibrated 123.75MHz crystal in the third oscillator/lock board (for 24192/432MHz). I loaded the FPGA with mwref_ww2r_3064-4.pof , set conf=101 and it locked to 123.75MHz . All I need to do now is order a 123.25MHz crystal for 24048/144

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