Satellite Station 4.0 Part 8 – GPSDO Frequency Locking

Remote Gateway Rack with Satellite Additions

Frequency accuracy and stability become more challenging for transceivers that operate at 400 Mhz and above. Our 4.0 Satellite Stations operate at frequencies approaching 1.3 GHz and we want to be sure that their operating frequencies are accurate and stable. Our Flex-6700 SDR includes a GPS Disciplined Oscillator (GPSDO) so the radio and all of the transverters associated with the radio use the radio’s GPS disciplined 10 MHz output for frequency synchronization.

Portable Satellite Station 4.1

We wanted to add GPSDO frequency control to the Icom IC-9700 Transceiver in our Portable Satellite Station 4.1 station. Icom just released a version 1.11 firmware update for the IC-9700 which makes this possible.

Leo Bodnar GPSDO Kit

We choose a GPSDO from Leo Bodnar. The unit is compact, USB powered, and comes in a nice case which includes a GPS antenna and a USB cable. The unit has two GPS disciplined frequency outputs which can be configured for a wide range of frequencies and levels via a Windows application.

GPSDO Connected to an IC-9700

The GPSDO is connected to the 10 MHz reference input on the back of the IC-9700 with a BNC to SMA cable and the GPSDO is powered via a USB connection to our iMac. We configured the GPSDO output frequency to 10 Mhz and for an output level of +7.7dBm (drive setting 8mA). We also added a 20 dB pad in line with the GPSDO output to better match the drive level requirements of the IC-9700’s 10 MHz input.

Locked GPSDO

The GPSDO will lock in a very short period of time (less than 1 minute) once GPS antenna and power connections are made the unite t. The unit has a red LED on each of its outputs and the unit is GPS locked when the LEDs are on and not flashing.

Configured and 10 MHz Input Locked IC-9700

The last step in the setup process is to configure the IC-9700 to sync its reference frequency to the 10 MHz input. This is easily done in the IC-9700’s Set/Function Menu.

It was pretty easy to add GPSDO locking to the IC-9700 and the arrangement described here works well. While this upgrade is not essential for satellite operation, it’s nice to know that our satellite transceiver frequencies are accurate and stable.

You can find other articles about our Satellite Station 4.0 project here:

Fred, AB1OC

 

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