DXpatrol GPSDO 2.0 User Manual

: June 6, 2024
: DXpatrol

Table of Contents

Features:
Operating
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10 000 000Hz GPSDO 2.0 Reference from DXPatrol

fig 1: front panel

This is our new issue, a low-cost GPSDO developed for the most rigorous and demanding microwave enthusiasts.
The DXpatrol GPSDO uses an internal GPS reference original U-Blox 7N controlling a 10Mhz CTI – OCXO 0,05ppb * Square wave Oscillator

Features:

New Oled Display data presentation
Ultra-High accurate UTC Clock
Local GPS coordinates the presentation
Number of satellites in range
Wait/Lock indication.
GPS, Galileo, Glonass receiver
4 ( 3+1) Outputs 10MHz 1.5vpp
3 Sine Wave outputs A+B+C ~ 7dBm
1 Square Wave output sqr
Duty cycle 50%
Phase Noise @ 1Hz -80dBc/Hz
Phase Noise @ 10Hz -120dBc/Hz
Phase Noise @ 1KHz -145dBc/Hz
Phase Noise @ 10KHz – 150dBc/Hz
Second harmonic < 51dBs
Third harmonic < 56dBs
Turn ON time ~ 5 minutes
Working Temperature range 0ºC to 75ºC
Operating Temperature ~50º C (OCXO)
Supply voltage 8V to 14V
Current 600mA first minute, 270mA after lock
Dimensions metal case : 84mm/71mm/25mm

fig 2: back panel.

Fig 3: Sin Wave outputs ABC

fig 4: Square Wave output

How it works.
New version 2.0 Dxpatrol GPSDO has an internal ATMega microprocessor programmed to communicate with the Ublox module and present several GPS-NMEA pieces of information on an Oled display.
Useful information as your local geographic coordinates, UTC high precision time
Clock and the number of satellites in range.

The U-Blox GPS receiver is instructed by Atmega to generate a 1000PPS frequency on its output.
( Due to the very high Jitter these modules produce, the signal sharpness was highly improved with a Schmitt Trigger to get a clean 1kHz square wave.)
The OCXO 10Mhz passes through a chain of dividers so we had a 1000Hz to compare on a Phase Lock loop CD4046.

Fig 5: starting ON, no GPS received or no antenna connected.

Fig 6: UTC time clock detected, waiting for more satellites.

Fig 7: 6 satellites in range, clock and coordinates detected. OCXO warming up.

Fig 8 : Lock complete, ready to use

Fig 9 schematic

Operating

This GPSDO is programmed in Hotstart mode. This means, even without an antenna or any GPS signal received, the GPSDO will yet have a fair and accurate 10Mhz signal on its outputs.
However, as we are using an internal OCXO, Oven Controlled Oscillator, the internal heater will take about 5 minutes to achieve the operating temperature – 50ºC ( this means you will feel the box a bit warm. That is normal )
After connecting the supply, the display will show the logo Dxpatrol for 2 seconds.
If any satellite is detected, UTC time will be shown, usually after 5 seconds.
Acquiring position will be displayed until valid coordination is received from GPS.
OCXO Oven Oscillator will be in warming period for a few minutes and Wait to flash will be shown.
After a few minutes, a Lock indication will take place and GPSDO is ready to use.

Fig 10: SA signal reading @ 100Khz span.

Fig 11 Second harmonic -43dBm

Fig 12 Third harmonic -49dBm

Fig 13 Frequency accurate

FIG 13 ON0EME reception using Dxpatrol GPSDO as reference.

António Matias
www.dxpatrol.pt technical mails ct1ffu@gmail.com or commercial sales@dxpatrol.pt