GPS-9700 Locked Frequency Source

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GPS-9700 KIT Description:

The GPS-9700 is a GPS Locked signal source that was designed for the Icom IC-9700 Transceiver to stabilize frequency when using narrow band weak signal modes. The basic EME197 module board could also be used with other Transceivers that use a frequency reference in the 30 to 50MHz frequency range, providing they have easy access to the frequency reference oscillator. The design incorporates a 0.28ppm low phase noise 49.152MHz Voltage Controlled Temperature Controlled Crystal Oscillator ( VCTCXO ) reference. The frequency is amplified and applied to the IC-9700’s internal 49.152MHz frequency reference using a small coupler PC board to mode lock the frequency. Tests indicate that when applying +5 to 8dBm into the coupler board, the IC- 9700 is easily able to be pulled onto frequency. The GPS-9700 module can be used with or without GPS locking, and is much more stable on its own compared to the IC- 9700 due to it being separated from temperature changes within the Transceiver. For high frequency stability narrow band weak signal modes, a high quality low phase noise external 10MHz GPS source is required.

The use of this product does require removal of the Icom IC-9700 bottom cover and replacement of a cable and soldering of the small coupler PC board. This should not affect Icom warantee as No modifictions are required to the Transceiver that could damage it. This also means that when the GPS-9700 is not used, the Transceiver will still function the same as from the factory and be locked to its internal TCXO. The use of the GPS-9700 however will not allow the automatic 10MHz calibration to work as the SMA to IPX cable is replaced and used with the coupler board, but this should not be an issue as manual calibration is still available.

Kit Constructors Alert:

Do Not construct this Kit unless you are very experienced with surface mount construction as the cost to repair could be very high.

1/ There are no current changes to this Kit.

GPS-9700 Kit Notes:

The pictures below are a final revision so should be carefully followed in construction. Probably the only really difficult part is the fitting of the AD9835. It is very important that the Kit construction notes are followed very carefully with regards to initial testing of the 5v regulator before increasing the voltage to the board. BUY THIS PRODUCT

Top View of the Mini-Kits GPS-9700 locked signal source
Top view of the GPS-9700 module board with optional SMA connectors showing the Arduino Nano board and most of the RF circuitry

 

Top View of the Mini-Kits GPS-9700 locked signal source
Bottom view of the GPS-9700 module board showing the DDS and VCTCXO circuitry

 

EME196 Coupler Board for IC-9700:

The pictures below show the coupler board with components fitted to suit the IC-9700. Care should be taken when fitting the small IPX connector as it has to be mounted so that the centre pins connection on the underside of the connector is soldered to the PC board strip line track. When fitting the board to the IC-9700, care should be taken when dismantling the transceivers bottom cover and soldering the board into place. The SMA connector cable on the rear of the Transceiver is removed carefully replaced with a longer cable which is connected to the coupler board instead of the Transceivers main board. This means that the automatic 10MHz calibration will no longer work but it is not required when using the GPS-9700.

Top View of the Mini-Kits IC-9700 Coupler Board
Top view of the EME196 Coupler board showing the IPX connector on the left side. The board is mounted on top of the IC-9700 TCXO shield with a single solder joint through the large plated hole in the coupler board.

 

Bottom View of the Mini-Kits IC-9700 Coupler Board
Bottom view of the EME196 Coupler board showing the 100nH inductor that is used to couple the 49.152MHz signal into the IC-9700 TCXO

 

Icom IC-9700 49.152MHz TCXO shieded can
Picture shows the TCXO shielded can inside the Icom IC-9700 where the small EME196 coupler board is mounted.

 

49.152MHz coupler soldered to the IC-9700 shieled TCXO can
Picture shows the EME196 Coupler board soldered through the plated via hole to the shielded can. Note how the ipx to SMA connector cable on the left is routed towards the rear of the transceiver

 

LZ2WSG ARDUINO SOFTWARE:

This open source Arduino software has been written by LZ2WSG to program a AD9835 DDS to a single frequency.

Although no problems have been found with the current Software version, Mini-Kits takes no responsibility for faults and minor glitches with the Software.

Software Description.

The Programming LZ2WSG software can be used to program the Arduino Nano for a single frequency for the AD9835.

GPS-9700 Performance Tests:

GPS9700-Phase-Noise
The above plot is the phase noise measured from the IC-9700 49.152MHz reference oscillator via a coupler board.
GPS9700-with Trimble
The above plot is the phase noise generated by the GPS-9700 when a 10MHz Trimble GPS reference is used.
NEO7M-Phase-Noise
The above plot shows the poor phase noise from a low cost Chinese NEO 7M Ublox GPS module at 10MHz.
GPS-9700 with NEO7M
The above plot is the phase noise generated by the GPS-9700 when a NEO 7M Ublox GPS module is used as a reference.
GPS-9700 50MHz Low Pass Filter
GPS-9700 50MHz lowpass filter Plot
GPS-9700 Blank
Plot showing the harmonic output from the GPS-9700 after the lowpass filter.

Mounting into a Hammond 1455C Enclosure:

The module board is designed to be fitted into a Hammond 1455C extruded aluminium enclosure. The enclosure helps to stabilize the freerunning frequency of the VCTCXO by protecting it from environmental temperature changes. Assembly is quite straight forward but you will require another SMA washer to be fitted onto the RF OUT connector as a spacer before the front panel is fitted. The LED should also be fitted after the front panel has been fitted as it makes it much easier to bent the leads to fit the board before soldering into place.

1455C-ENC-1
Front view of the completed GPS-9700 in the Hammond 1455C enclosure
1455C-ENC-2
Rear view of the completed GPS-9700 in the Hammond 1455c enclosure

Kit Changes and Repairs:

GPS-9700

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