Next Generation Beacons

GPSDO/GPS reference

Overview VCO-PLL DDS GPS reference Distribution amplifiers Service management Sequence PI4 Software


Emanuele, IW9GDC - "... I can really say that this hardware is actually the best ever made ..."


The Next Generation Beacons uses GPS to synchronize both frequency and time. This done by using a GPS disciplined oscillator (GPSDO). The GPS reference can be used both as a beacon site reference but also as a station clock and 10 MHz reference in your shack and lab. If used as a station clock an additional display board must be used to show time and date etc.

All timing outputs are galvanically isolated to protect against static discharges. If needed voltage to the GPS antenna can be supplied via the coaxial cable.

If you have a GPS reference already with 10 MHz and NMEA outputs you can most likely use it for your Next Generation Beacons.


The 10 MHz is made using an AXTAL AXIOM40 high stability and low noise ovenized oscillator (OCXO). The GPS receiver is a Jupiter TU30. The 10 MHz signal is available from two galvanically isolated ports. The 1 PPS signal is available on two TOSLINK optical transmitters. The GPS data is available on a TOSLINK optical transmitter. A PLL lock signal is also available on a TOSLINK optical transmitter.

The GPSDO is designed with an analog holdover functionality in case the GPS signal is lost.


If you want to use more than one DDS board, i.e. you want to have more than one beacon on the air, you will need a NMEA distribution board.

For lab and home use you will need a 10 MHz distribution amplifier board if you want to connect more than one instrument or transceiver.

Site interference

Empirical data show that GPS signals are not affected by the carriers even if many SHF carriers are on the air and close intermodulation wise to the GPS RF signal.


To use the GPSDO for a Next Generation Beacons unit it must be setup to only send the $GPRMC frame.


DC characteristics Unit Notes
Voltage 13,5 V to 15 V  
Current ~300 mA After warm-up. During warm-up ~600 mA
Power consumption <5 W After warm-up. During warm-up ~7 W
RF characteristics Unit Notes
10 MHz output 0 dBm Into 50 Ω
10 MHz accuracy 2 x 10-11 200 µHz at 10 MHz. 99% RMS accuracy after one hour warm-up
Phase noise See table
Frequency Phase noise [dBc/Hz]
10 Hz -120
100 Hz -140
1 kHz -145
10 kHz -150
GPS board ports Connector Notes
Supply 2 pin Molex  
RF connector SMA/BMB/MCX Depends upon GPS receiver used
10 MHz out 2 x BNC female Galvanically isolated
10 MHz lock TOSLINK  
Serial Out USB B, female  
GPS receiver 10 and 20 pin connector Designed for Rockwell Jupiter GPS receivers TU30 (included), TU40 and TU60 series
Display board interconnection, galvanic 3 optical transmitters NMEA, 1 PPS and 10 MHz lock
Display board interconnection, non-galvanic 6 pin header or optical NMEA, 1 PPS and 10 MHz lock
GPS board mechanical Unit Notes
Size 146 mm x 72 mm x 40 mm Fits into a standard tin plate box 148 mm x 74 mm x 50 mm
Weight 150 g  


The price for an assembled, tested and ready-to-use GPS disciplined oscillator is 2277 DKK* (~316 EUR).

Additional shipping and money transfer cost applies.

*: Prices are subject to change due to exchange rate fluctuations.


Operational troubleshooting

Here is a guide to troubleshoot an operational beacon including retrofits.

Further information

Please contact Bo, OZ2M, at my call sign @ this domain.


Bo, OZ2M, www.rudius.net/oz2m