PA3FYM Sorry for the late answer......a lot of sun here the last days.......was up the mounains here in the southern part of bavaria......thanks a lot for your antenna design
Posts by DL5MGD
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PA3FYM Very interesting design. I want to build it the same way. Please can you give some advice on how to build your solution (e.g. some hand drawing with dimensions). Thanks a lot
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PA3FYM I think that at the beginning the vco voltage oscillates a few times around the setpoint until it reaches it. The oscillation is probably caused by the dimensioning and the resulting damping factor of the loopfilter. Seems really fine and good working; i will impelement it in my code. I will try the idea to sitch off the atmega 328p tonight - after work - to see if this reduces the hum and hiss in the si5351.
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PA3FYM Hi Remco, i calculated the loop filter by using this pdf file: http://www.k9ivb.net/GPSDO/fil…0GPSDO%20PLL_11092014.pdf .
You are right the jitter will disappeare by using a 22µF capacitor. Perhaps it would be better to recalculate the loopfilter for a smaller loop bandwith. But what really is bad is the SI5351. You can not use this device for producing a signal which can be fed into a lnb. The signal of the si5351 is awful. In the moment i take the 10MHz gpdso signal and use it as reference for a 27MHz pll described by df9np with an adf4001 and a VCTCXO with 27MHz
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Hello Frank,
great job!!!!!! Do you think we can get a sd card image for testing / using your solution. Would be fantastic.
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Wir (DJ5MHZ, DL5MGD) verwenden hier eine QFH und eine X30 Vertikalantenne, beide Unterdach montiert zum NOAA Empfang. Sind damit sehr zufrieden. http://www.db0tol.de/index.php?page=noaa-wx-sat
Mit nur einer Antenne wars bei weitem schlechter. Die Vertikal klappt gut bei niedrigen Überflügen, die QFH bei hohen (wie zu erwarten).
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Hello,
I'm new here. Thanks for the forum: Great opportunity to talk to each other.
73, Andreas DL5MGD
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Hi Remco,
there is some jitter. The jitter only disappears if you use even divider values, best in power of 2 (eg 2,4,8,16 and so on). Neo 6, 7 and 8 use a 48 MHz oscillator to generate the output frequencies at the 1pps pin. The pll loop together with the ocxo removes this jitter.
A version with 1pps will result in an extreme long pll filter constant. A pll would need to have a bandwidth considerably less than 1Hz, meaning that the loop would only lock up after many tens of minutes or hours. So the 1pps approach can not be used in a simple design like this. More information can be found eg here http://ve2zaz.net/GPS_Std/GPS_Std.htm or here http://www.ik0otg.net/index.ph…e&id=53&Itemid=59&lang=en
vy 73
DL5MGD
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Thanks for your replies. The second frequency (28,8MHz) for the sdr is only for fun or if one have no "good" sdr stick. My primarily goal was to disciplin the lnb frequency with off the shelf components and programming the gps receivers 1pps output to 1MHz for a faster and more easily to construct loopfilter.
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Good morning,
I am using here an Octagon Oslo Optima LNB and a sdr usb stick. As reference frequency source for both devices i made a small circuit from parts lying around which delivers 25MHz for the lnb and 28.8MHz for the sdr stick disciplined via gps. The arduino sketch is programmed in a very direct stile.....not very nice, but working. The sketch needs two libraries: https://github.com/mikalhart/TinyGPSPlus and https://github.com/etherkit/Si5351Arduino
vy73
DL5MGD