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
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