GPS-Stabilized 10 MHz Oscillator

Due to the always increasing accuracy requirements, a GPS frequency standard was developed based on inexpensive components, which meet these requirements.

Many users are familiar with the HP Z3801 and his double-heated oven oscillator which can be found in the Surplus. This equipment should always be running, but requires a constant power of 30 - 40 W at 50 V supply voltage! Therefore, attempts were made in a new development to reach the accuracy specifications for the HP-Z3801 and to simultaneously undercut the power consumption as far as possible.

The difficulty is to find a very good oscillator (OCXO) that meets the development requirements in all desired parameters which is available for a decent price on the market. That is why different oscillator types were tested, which all can be used depending on the market situation. The manufacturers of the used OCXO's we are using, are TeleQuarz, Isotemp and OFC (same as ISOTEMP 134), just to name a few. The layout was specially designed for these mentioned types. They are OCXO's, which are very well insulated and do not have to be installed in styrofoam additionally.

For a GPS receiver a 16 channel receiver from the company U-Blox is used. The 1 kHz reference is connected via a very slow loop with the 10 MHz OCXO. Via the GPS receiver, the active external antenna is supplied with a supply voltage of 5V. Caution: In case of short circuit in the antenna cable, the GPS module can be damaged.

LEDs on the front panel show the following states:

1.

OCXO has reached its operating temperature

2.

the GPS module provides accurate data

3.

the PLL has locked.

Beside these LED status indicators, there is a display with 2 lines x 16 characters. This display can be switched in accordance with the "info button". Here are some examples:

After Power_On:
Searching GPS-satellites

GPS-Data OK
11 satellites visible, 9 „being tracked“

Longitude and Latitude

LOCATOR including "smallest field" calculated from longitude and latitude

Date and Time in UTC

All data supplied with the NMEA record coming from the GPS module can be picked up at the RS-232 interface (9600 Baud, No parity, 8 Bits , 1 Stoppbit) at the rear panel. You can find a lot of programs for this purpose on the Internet.

Since there is a shortwave beacon project with 18 beacons in a fixed time frame, the possibility was created to display the respective beacon with the appropriate frequency at the current time. Here are two examples:

Technical Data:

10 MHz output jacks:

4 BNC-jacks

Output voltage:

about 2 Vss at 50 Ohm (typ. +9 ... +10 dBm)

GPS-Antenna:

SMA-jack (including 5V-power supply for active antenna)

Power supply:

11.5 to 13.5 V DC with DC plug

Current consumption during heating phase:

ca. 800mA

Current consumption while operating:

ca. 400 ... 450mA (depending on OCXO)

Duration of heating phase:

about 5 min

Ready for operating:

after about 10 min, depending on GPS data

Phase noise OCXO:

@10 Hz - 105 dBc
@100 Hz - 125 dBc
@1 kHz - 140 dBc

stability:

averaged according to the measurement time > 1x10E-10 ... 1x10E-11

Housing dimensions:

175 x 175 x 55 mm (without protruding jacks)

If the GPS signal fails, the device will automatically switch to the "free-running" OCXO. The adjusting of the exact frequency is done by a potentiometer inside the unit, which is supplied from the internal reference OCXO. Before shipping, the frequency has been adjusted exactly. Due to aging of the OCXO in the course of time, the frequency may vary from the nominal value and can be corrected by the user.

Prices:

GPS-Stabilized 10 MHz Oscillator (complete):

€ 468,00

Active GPS-antenna with SMA-jack:

€ 28,00

Plug-in AC Adapter 12V / 1A with 12V-Plug for Oscillator:

€ 12,00

Customers who want the GPS frequency standard with a new OCXO, please ask for price and delivery time.

If you require a written offer, please ask..