16-12-2016, 04:22 PM
Over the last few days I have been working on getting some spectrum analyser shots of the transmit carrier from the IC910 comparing the factory optional internal high stability OCXO with the ProgRock board.
On the back panel near the earth screw i added a panelmount SMA socket and a small toggle switch. The switch turns on and off the dc to the internal OCXO. The SMA couples the external 30.2MHz from the ProgRock via a 680 ohm resistor to the junction of R515 and C515. Rex VK7MO came up with this mod and details can be found on the net.
The ProgRock is using a clean 1 Pulse per Second signal from the chinese GPSDO.
This shows the IC910h on transmit into a dummy load at full power through a microwave attenuator using the Internal OCXO
This shows the same setup with the external ProgRock connected and the internal IC910h OCXO turned off.
I cant see a difference.... (dont worry about the date and time on the speccy clock, i havent got around to setting it)
On the back panel near the earth screw i added a panelmount SMA socket and a small toggle switch. The switch turns on and off the dc to the internal OCXO. The SMA couples the external 30.2MHz from the ProgRock via a 680 ohm resistor to the junction of R515 and C515. Rex VK7MO came up with this mod and details can be found on the net.
The ProgRock is using a clean 1 Pulse per Second signal from the chinese GPSDO.
This shows the IC910h on transmit into a dummy load at full power through a microwave attenuator using the Internal OCXO
This shows the same setup with the external ProgRock connected and the internal IC910h OCXO turned off.
I cant see a difference.... (dont worry about the date and time on the speccy clock, i havent got around to setting it)