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QRP Labs Si5351A Operating Manual

Vfo/signal generator
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1. Introduction
This is the operation manual for the VFO/Signal Generator kit. Please read it in conjunction with the
assembly manuals for building the kit:
 VFO/Signal generator assembly manual (the controller PCB, rotary encoder, buttons and LCD)
 Si5351A Synth assembly manual, or OCXO/Si5351A assembly manual if you use the OCXO
 QLG1 GPS assembly manual, if using the QRP Labs QLG1 GPS to discipline the oscillator
Note that the output of the Si5351A are squarewaves at 3.3V peak-peak. Please read the Si5351A
datasheet, linked from
could fit a QRP Labs Low Pass Filter kit
the squarewave harmonics. This would be effective over only a limited band of frequencies but may
suit your application.
The LCD may be configured to show not just VFO frequency, but also your callsign or other text, and
if you have a GPS connected (for disciplining the oscillator) you may display GPS parameters such
as date, time, latitude, longitude, altitude, satellite reception status, and Maidenhead locator.

2. Operating instructions

When you have just built the kit and have not yet configured it, upon power-up the kit will enter
"Diagnostic Mode". If you can see this message on the screen, all is well. Press the Left button to
continue. If you do not see this message or any writing on the LCD, please refer to the
troubleshooting web page.
On power up (and after leaving the diagnostic mode, if any), the LCD displays the firmware name and
version number for a few seconds, then loads Preset 0, and enters VFO tuning mode.
2.1 Modes of operation
There are four modes of operation. The usual running mode is the VFO tuning mode, in which the
Clk0 frequency is displayed on the screen, and the rotary encoder tunes it.
 VFO tuning mode (default at start up)
 Select preset mode
 Select tuning rate mode
 Configuration menu editing mode
Si5351A VFO/Signal Generator
http://www.qrp-labs.com/synth
http://www.qrp-labs.com/lpfkit
s1.02
. If you require a sinewave output, then you
to the main PCB, to filter away
1

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Summary of Contents for QRP Labs Si5351A

  • Page 1: Operating Instructions

     Si5351A Synth assembly manual, or OCXO/Si5351A assembly manual if you use the OCXO  QLG1 GPS assembly manual, if using the QRP Labs QLG1 GPS to discipline the oscillator Note that the output of the Si5351A are squarewaves at 3.3V peak-peak. Please read the Si5351A datasheet, linked from http://www.qrp-labs.com/synth...
  • Page 2 In the above example the frequency is 14.060050MHz and the tuning step is 100Hz. Note that the lower frequency limit of the Si5351A synthesiser chip when using the supplied 27MHz reference crystal, is 3.515kHz. The upper frequency limit has been found to be approximately 292MHz.
  • Page 3 2.4 Select tuning rate mode 14,060,050 Use the rotary encoder to move the cursor underlining the tuned digit, to the left and right. The select tuning rate mode is active only while pressing the right button. Remember that the internal button in the rotary encode is in parallel with the right button.
  • Page 4 The menu is a list of items and the rotary encoder is used to scroll through this list. When you see the item which you want to edit, press the LEFT button to start editing it. To return to the VFO Tuning mode, press the RIGHT button.
  • Page 5 Clk 1 009,002,000 The Clk 1 parameter allows you to set up the Si5351A Synth on a frequency of your choice, on its Clk1 output. Clk1 may be set anywhere in the permissible frequency range of the Si5351A. Here it is shown set to 9.002MHz for example.
  • Page 6 Note that the resulting Clk0 frequency must still satisfy the range requirements of the Si5351A. In the case of a frequency error, an error flag is set. This causes an “E” to be displayed at the top right of the display, in the default display configuration. It is cleared by tuning to a valid frequency that is within the Si5351A’s range.
  • Page 7 1pps gate is used to implement a frequency counter that measures the ¼ reference oscillator value. The measured value is fed into the computation of the register values to achieve the desired output frequency. The GPS discipline mechanism uses a two-stage process to achieve an accurate output frequency quickly but with minimum “jitter”...
  • Page 8 Clk0 or Clk1 outputs. The error can be cleared by tuning to a valid within- range frequency. The range of the Si5351A output is approximately 3.5kHz to 292MHz. The default setting for Lines 2..4 is just blank. You can edit it for your own fixed display or include valid #tags as described below, to dynamically update display data with GPS information such as time, date etc.
  • Page 9 Note 2: The VFO kit does not contain a real time clock of its own. The clock display functionality is only available if a GPS receiver is connected with decodable data and has a satellite lock. Note 3: The table also indicates the behaviour when no GPS data has been received yet, or when the GPS data validity flag is set to “V”...
  • Page 10 Local Offset +0,120 This setting specifies the offset of local time to UT. The time displayed by the #HH, #MM tags is always UT (straight from the GPS, if connected). The #LH, #LM, #H2 tags display local time, offset by the number of minutes in this setting.

  • Page 11: Factory Reset

    LCD Rows This kit can be used with any similar HD47780-compatible display having 2 or 4 rows. The supplied LCD has 2 rows and this is the default for this parameter. If you wish to use a larger display, you can edit this parameter to access rows 3 and 4.

  • Page 12: Version History

    4. Resources Please see the kit page http://www.qrp-labs.com/vfo for information on latest updates and issues. Please join the Yahoo group http://groups.yahoo.com/group/qrplabs/ for new kit announcements, to discuss any problems with the kit, enhancements you’ve made, or just to tell everyone how much fun you’re having.
  • Page 13  Bug fix: memory corruption when editing Line1 and Line2 could cause unexpected behaviour  Bug fix: It was impossible to edit display configuration lines e.g. “Line 1” parameter when they overflowed the 16 char display area 11-Nov-2016  Added example and further detail on the use of the negative IF offset, which had caused some confusion.