RE2 - v2 GPSDO & 10 MHz Disciplined Frequency Reference


 

For better  quick  viewing of the design, download the Source file from the Material List  below , unzip it and drop the .sch or .pcb file onto kicanvas from a web browser.


Features & Improvements

  •     Provides up to 7 configurable user outputs,  master clock for HF transceiver or SDR    
  •     Implements Continuous Fractions algorithm for essentially perfect frequency accuracy
  •     Much improved close-to-carrier noise floor
  •     GNSS satellite or local  10 MHz frequency reference
  •     Flexible supply 7-30 VDC
  •     Typically better than .1 ppb, .00000001% accuracy and stability
  •     WiFi web Interface
  •     Common SDR and HF transceiver Frequency presets

  •  Connections:

    • SMA: GNSS Antenna
    • External 10 MHz reference
    • Seven SMA:User Selectable outputs  4 kHz to 225* MHz
    • 2.1mm power barrel connector
  • Four-layer,  through-hole plated, silk-screen printed PCBs
  • Aluminum enclosure

Example Web Interface





Material List

What you will need to build this hardware

Item Description

Provider

Source Code

Notes

Approximate Material Cost

(excludes setup fees and shipping)

Assembled RE2 PCB

Download RE2 Kit Files

Download RE2 Source Files

 *The SI5351 version C part is sanctioned in China so must be placed as part of final assembly  by the user US$55
Si5351C-B-GM

Mouser
This part will not have been assembled on the PCB because it is currently sanctioned in China and must be reflow soldered by the end user $6
IoT33 CPU

IoT33 CPU

US$26
2 x 15p CPU socket

eBay

US$2

38x88x100mm Clam Shell Enclosure

eBay


Other sources possible. Enclosure needs to accept 84mm wide PCB. US$12

38x88mm RE2 Front Panel

Download RE2 Front Panel Kit Files

Download RE2 Front Panel Source Files
US$1

38x88mm RE2 Rear Panel

Download RE2 Rear Panel Kit Files

Download RE2 Rear Panel Source Files
US$1

Firmware

Code you will need to program the CPU
Arduino Code

Download RE2 FW Binary

By Request

 after kit construction, send request along with output of [ipaddress]:8078/status


Final Assembly & Test


As of this time of writing, due to component sanctions in China, the RE2 Reference will not have had it's Si5351 version C assembled and soldered on the board. You will have to do this yourself as a separate reflow operation.  Using low temperature solder paste, add just a little extra solder to the pads on the PCB then after cooling and applying solder flux, carefully place the component with the Pin 1 marking matching the PCB silkscreen and reheat the assembly to reflow the paste.  This can be done with a hot plate while the PCB is resting on a small piece of aluminum directly under the Si5351 to restrict reflow to just that portion of the PCB.  Once cool, use alcohol or flux remover to allow close examination of each of the pins to verify that each is soldered and that there are no shorts.

After receiving assembled PCB from fabrication and before final assembly with the CPU & socket,  first verify with an ohmmeter that the power input line and the 5V and 3V regulator outputs are not shorted. Next connect a current limited or low power source of 7-16 VDC  power the board. Without CPU verify that there is only a few mA flowing. The raw PCBs have already been pretested but doing this makes sure nothing has gone wrong during component assembly or soldering. 

Next and before mounting onto the PCB, program the IoT33 using the Transverter Binary File as described.  With no PCB it will complain via its USB serial port about not finding resources and devices. This is normal but indicates correctly running FW.

Final assembly and soldering of the CPU header and socket is next.  Put the long pins of the header into the socket and the shorter ones into the IoT33, then mount everything on the PCB squarely. Solder corner pins on the CPU, and socket making sure everything is flush and squarely aligned. Once the position is good solder all the rest of the pin connections on both the PCB and the CPU.

At this point again apply DC power and verify that there is 3.3V on the LDO output and that the IoT33 comes alive as it did after programming. This time, watching the serial/programming port as you did before, initialization should complete with no complaints other than lack of WiFi connection and GNSS lock.

Modify the SSID:PASS values to match your local WiFi access point and network, type 'A' to save these in the IoT33's NVRAM and cycle DC power or type 'X' to reboot. This time the TRansverter should indicate that it connected to your AP and was supplied with a web address for you to point a web browser at.

You can now slide the PCB into the clam shell enclosure and attach the end panels but leave the top clam shell off until later.

From here on you can use the Web page interface to set the DAC via the utility page so that the on-board XO is approximately correct as verified in a receiver or spectrum analyzer known to be fairly accurately calibrated. This can be done by connecting to and tuning to the frequency of the User Clock output on the rear panel.

Provide either a GNSS antenna or else a 10 MHz  reference and verify that when the corresponding disciplined mode is selected that the unit shows LOCK when when using the Utility web page for reporting.

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