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<div class="moz-cite-prefix">Hi,<br>
<br>
Well this 30-40Hz jumping is with the on-board 10MHz TCXO, someone
mentioned that this is coursed by<br>
the internal temp compensation.<br>
For me this is unacceptable, maybe there is one with better spec's
available, but looking at the spec's for these oscillators,<br>
I can not find much info about this behavior.<br>
So I wanted to use my external GPS controlled 10MHz standard, but
this gives me problems off not stable locking to the Hermes board.<br>
Changing the R141 from 100 to 50Ohm did help, but still a jump one
in a while.. <br>
Bert<br>
<br>
<br>
Op 18-5-2013 8:50, John Marvin schreef:<br>
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<div class="moz-cite-prefix">I think there is a misunderstanding
here. When I was referring to small jumps of 0.5 Hz (perhaps
larger in the 10/6m band) I was referring to the behavior of the
TCXO when it is enabled. If you have enabled the external clock
input then the TCXO is no longer involved in providing a 10 Mhz
reference to the fpga. If your GPSDO is not locking properly
then you are switching back and forth between your GPSDO
providing the 10 Mhz reference, and no 10 Mhz reference. When
there is no 10 Mhz reference then the 122.88 Mhz VCXO is just
free running, which can easily be 30 to 40 Hz off. Hopefully an
adjustment to your signal level will fix the locking problem.<br>
<br>
John<br>
AC0ZG<br>
<br>
On 5/17/2013 11:28 PM, H.A.Meijer wrote:<br>
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<div class="moz-cite-prefix">Hi,<br>
thanks for your thoughts about the freq jumps from the 10MHz
osc.<br>
You are talking about "just 0,5 Hz' but my Hermes is jumping
30 to 40 Hz when on 10/6 mtr and with transverters (MF=28MHz)
use.<br>
This is very annoying and for me not the so called "high
performance" I'm looking for.<br>
<br>
I did change the R141 and still see that is has some locking
problem to my external 10MHz, now and then.<br>
I will do some measurements at that circuit, maybe my 10MHz
level is to low..<br>
<br>
Bert<br>
<br>
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