Re: [time-nuts] Si5351A harmonics question

[Bo Hansen]

Harmonics from a Si5351A is not a problem. As pointed out a LPF will do what it 
takes to get the fundamental frequency "extracted". The Si5351A is designed to 
clock/feed other digital circuits so that shouldn't be a problem in this 
particular case either.

In the digital clock domain spurs are, in most of the cases, not important. But 
in the RF domain things are VERY different. Unfortunately there seems to be a 
trend that only harmonics are important when in fact the in-band spurs are the 
important ones and what disturbs other stations and own receivers too.


In the RFzero  that also uses a 
Si5351A great attention has been devoted to keeping spurs and especially 
in-band down.
Bo

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Re: [time-nuts] AD9912 DDS frequency resolution measurement?

[Bo Hansen]

Hi

I have experience with the AD9912 in this H/W and S/W implementation: 


But I must admit that I personally haven't measured the minimum frequency step 
size. Poul-Henning Kamp, among others, is using one of the AD9912 DDS units and 
observed a similar error, I think, that he has solved in this S/W: 


Whatever applies list the FTW values and calculate back to the real frequency 
and see if the frequency change is correct.

A friend of mine has a x96 multiplier from 108 MHz to 10 GHz but we don't have 
access to any counters capable if measuring the difference.

Bo

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Re: [time-nuts] Looking for a reference oscillator called XRef-VS made by VK3HZ for TS-2000

[Bo Hansen]

Hi Wayne

I am not 100% sure but can you use the this AutoPLL: 


Availability: 

Bo, OZ2M

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Re: [time-nuts] Setting Time on WSPR Radio Transmitter

[Bo Hansen]

Hello Brooke

I do have some experience with beacon solutions that can also be used for WSPR 
among all the different modes available:

The Next Generation Beacons platform:  also 
used by some REAL time nuts :-)

PI4ino:  OK not WSPR but PI4 but the 
principle is the same.

But I can't find much information about the technical capabilities of the 
WSPRLite in respect to what you need to know, e.g. what is the accuracy of the 
MCU clock, how does it perform vs temperature, is there an on-board external 
sync?

As pointed out by others the WSPR decoder accepts some time offset. But even if 
you start your WSPRLite at the correct second for how long will it stay inside 
the time capture window of WSPR before the above mentioned factors make it 
useless?

For another application I have built a GPS simulator that sends out NMEA frame. 
But after some time it has to be reset because the MCU ceramic resonator clock 
has drifted to much. I have made this last a bit longer by adjusting the 1 s 
interrupt controlling value but it still drifts.

For a remote operation I would not recommend a non synced device. As far as I 
can see there is no such possibility in the WSPRLite so a GNS controlled 
on/off-switch may be the way forward to make the WSPRLite start at the correct 
time over time. Far from elegant I must admit.

Bo, OZ2M


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