[Elecraft] K3S XREF GPSDO recommendation needed

Tue Jun 5 16:09:54 EDT 2018

Here is a copy/paste of the post I made on the VNWA Group for a summary 
of the two methods I've seen for setting 36MHz and 10 MHz just for the 
record:
Other combinations would require the use of the SilLabs software to 
calculate the parameters.... I have yet to figure out how to use it 
correctly.  But there are those who have and MAY be amenable to 
calculating them for you.
____________________________________________________

Here are TWO methods for setting 36MHZ and 10MHZ together:

Method #1: Output #1 = 10MHz; Output #2 = 36MHz  (Thank you, Jan!)

Start GPS Clock Configuration application

1. Set Outputs 1 & 2 (Hz) to 10000000 (10 MHz) AND "Output Drive 
Strength" to 8mA.

2. Make sure both output enable boxes are checked.

3. Press “Find”.  When complete, both outputs lock at 10000000 Hz.(10MHz)
4. Now, enter the following register values:
____________________________

10000000  = GPS Reference Hz

5         = N31

6         = N2_HS

450       = N2_LS

5         = N1_HS

108       = NC1_LS

30        = NC2_LS

0         = Phase shift degrees (unchanged)

15        = BW  (unchanged)
____________________________

5. Click "Update".  When finished, both will show 10000000 MHz, BUT wait!

7. Close the GPS Clock Configuration app.  Then restart the app.  The 
displays will update to reflect 10 MHz on Out #1 and 36MHz on Out #2.  
You can confirm this by measuring them with a frequency counter/meter.

DO NOT PRESS "Find"!  If you do, you will set both to 10MHz and have to 
start all over.

++++++++++++++++++++++++++++++++
++++++++++++++++++++++++++++++++

Method #2: Output #1 = 36MHz; Output #2 = 10MHz  (Thanks to Simon @ Bodnar)

Start GPS Clock Configuration application

1. Set Output 1 (Hz) to 36000000 (36 MHz) and "Output Drive Strength" to 
8mA.

2. Make sure both output enable boxes are checked.

3. Press “Find”.  When complete, both outputs lock at 36000000 Hz.(36MHz)
4. Now, enter the following register values:
____________________________

4800000  = GPS Reference Hz

11        = N31

11        = N2_HS

1350      = N2_LS

9         = N1_HS

20        = NC1_LS

72        = NC2_LS

0         = Phase shift degrees (unchanged)

15        = BW  (unchanged)
____________________________

5. Click "Update".  When finished, both MAY show 36000000 MHz, mine 
displays correctly about a third of the time.  BUT as before... wait!

7. Close the GPS Clock Configuration app.  Then restart the app.  The 
displays will update to reflect 36 MHz on Out #1 and 10 MHz on Out #2.  
You can confirm this by measuring them with a frequency counter/meter.

DO NOT PRESS "Find"!  If you do, you will set both to 10MHz and have to 
start all over.

Here is an image to illustrate the results:
http://www.montac.com/images/vnwa/36x10Mhz_Bodnar.jpg

================================

NOTE: You can tell the "Find" or "Update" process is complete when ALL 
three labels ("Find", "Update", and "Sleep") are NOT "greyed out.  Text 
is black.

I've not yet confirmed whether 8mA is sufficient drive current to feed 
10 MHz to my HP5335a or Elecraft K3s, et al. yet.  When I do, I will 
post back with results.

Hope y'all find this useful!

______________________
Clay Autery, KY5G
(318) 518-1389

On 06/05/18 12:48, David Box wrote:
>
>
> I have one of Bodnar's units and works well.  The software is clunky 
> but usable.  There is a way to set other frequencies than what the 
> pulldown menus offer.  You need to go to and download a copy of the 
> DSPLLsim utility in order to calculate the correct coefficients..
>
> Below is a set of steps that Jan Verduyn has published that allows 
> setting the two ports to other frequencies, in this case he was trying 
> to get 10Mhz and 36MHz but using DSPLLsim you can work out other 
> pairs. DSPLLsim is at 
> <https://www.silabs.com/products/development-tools/software/clock>
>
>
> If you only need one frequency then Bodnar also sells a smaller unit 
> <http://www.leobodnar.com/shop/index.php?main_page=product_info&cPath=107&products_id=301> 
> that is lower priced.  AirSpy also sells this unit.
>
> Dave K5MWR
>
>
> From Jan Verduyn instructions for tailoring frequencies.
>
> Setting of the GPSDO Output 1 to 10MHz and GPSDO Output 2 to 36.000 
> MHz as external clock for the VNWA is done as follows:
>
>
>
> Start the GPS clock application for the Leo Bodnar standard 2 port GPSDO.
>
>
>
> 1. Set output 1 and output 2 to 10000000 Hz    = (10 MHz)
>
> 2. Make sure both outputs are enabled
>
> 3. Press “Find” and both output should be locked and produce 10.000 MHz
>
> 4. Now change the register details as shown below by typing in the 
> following data:
>
>
>
> 10000000   = GPS Reference Hz
>
> 5                   = N31
>
> 6                   = N2_HS
>
> 450              = N2_LS
>
> 5                   = N1_HS
>
> 108              = NC1_LS
>
> 30                = NC2_LS
>
> 0                           = Phaseshift degrees (unchanged)
>
> 15                       = BW  unchanged
>
>
>
> 5. next press “Update” button and both outputs should show red – locked
>
> 6. If you measure with Frequency meter you will find that output 1 
> produces 10 MHz and Output 2 will produce 36 MHz.
>
>
>
> Note that the output 2 indication will continue to show 10 MHz, which 
> is wrong.  It should read 36MHz.
>
> These settings are stored when  you switch off the GPSDO, When you 
> apply power to GPSDO at a later date the same frequencies should be 
> produced.
>
> Remember however as soon as you press the “Find button”  the settings 
> will be lost and will need to be re-entered.
>
> If GPS Signals are lost then the output frequencies are derived from 
> the built-in TCXO  with the last correction factor applied before lock 
> was lost.
>
> The above register settings were obtained using DSPLLsim utility. Make 
> sure you select the SI5328 to obtain the correct settings.
>
>
>
> Attached is a screenshot of the GPS Clock Configuration screen.
>
> Good luck.
>
>
>
> Jan G5BBL SDR-Kits