Base of the 10 MHz frequency standard is a compact modul with the appellation RS-GGO10M-TG. This modul is produces by Inwave AG under the label RF Suisse.
It is a GPS guided Oscillator (GGO), which works with a GPS receiver as Temperature Compensated Crystal Oscillator (TCXO).
Minimal only the power supply of 5 V and an active GPS antenna are to connect.
Within a few minutes a high-stable signal with 10 MHz is available.
Specifications of the RS-GGO10M-TG
- Output frequency: 10 MHz
- Stability: locked < 1 · 10-8 (±0,1 Hz)
typical < 5 · 10-9 (±0,05 Hz),
free running < 2.5 · 10-6 (±25 Hz)
- Output: 3.3 V CMOS
- Active antenna: 50 Ω, 3.3 V, < 35 mA, Connector U.FL
- Power supply: 5 V, < 65 mA,
typical 45 mA (without current for active antenna)
- Dimensions: 2,5 × 2,5 × 1 cm
- Weight: 7 g
- Source of supply: was Box 73, but now only RF Suisse
In order to recognize the status of the module, LEDs can be attached. In the simplest case a duo-color LED is enough. The different colors mark the status.
- red: no GPS signal available
- yellow: regulation actively
- green: 10 MHz signal OK
Since duo-color LED's do not assure to me optically, I use 3 separate LED's. The logical combination takes over 3 NAND-gates of the 74HCT132 (Schmitt trigger). Gate number 4 serves as buffer for the 10 MHz output. I use a regulator for 5 V to operate the frequency standard also with 12 V.
Printed circuit board
The printed circuit board is 5,6 × 9,9 cm largely and double-sided. It fits into an aluminum housing, which I buy at Reichelt Elektronik (order no. TEKO BC1). I have reduced the height of the housing to the here necessary measure. The top side of the board serves mainly as heat sink for the voltage regulator. Therefore also a one-sided board is usable. Only under the 74HCT132 is located a bridge. All conductor paths are arranged on the buttom side. Who does not want to develop the circuit on a universal board, who can also use my finished layout. For the design I used the program Sprint-Layout by Abacom, for which a free viewer is available.
As GPS antenna any active antenna is usable, which is designed for 50 Ω, works with 3,3 V and does not required a current greater than 35 mA. I use the antenna ATN-555 available at Sander Electronic. (Note: The antenna is not listed in the online shop. Send your request by email.) The ANT-555 possesses a SMA connection with a 5 m coaxial cable and a magnetic foot. Since the module RS-GGO10M-TG possesses only a very small U.FL plug, I recommend the 10 cm long adapter cable of SMA on U.FL.
In order to be able to use a 10 MHz signal as stable as possible, two things are to be considered. On the one hand the GPS antenna should be attached with a maximum possible free view to the sky. On the other hand the module should operate in a thermally isolation. To the fulfillment in the simplest case a thick isolation made with polystyrene sheets is sufficient. I use 10 mm thick sheets, which I cut to shape properly and join with glue. I inverted this cap over the module, under which likewise a sheet are located as isolation. The module is mounted on 10 mm high sockets strips.