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Fri Jan 29 12:04:30 UTC 2016

receive. From those, if the geometry is appropriate (I know the VORs =
positions from a database) I can calculate a =
position.<o:p></o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal>The software then just round-robin tunes the VORs in =
range and continually tries to calculate positions. If too many drop =
out, it returns to the initial scan mode.<o:p></o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal>Not being able to receive this VOR or that VOR is not =
generally a problem, but obviously, the more the better. With extra VORs =
I have better options for choosing the closest ones or the ones with the =
best geometry.<o:p></o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal>This is actually quite difficult to test, because VORs =
can generally only be received line-of-sight -- which means in the air. =
I'm a private pilot but I found that flying and noodling with a laptop =
is too much trouble. From my office window, on a high floor in Oakland, =
CA, I can receive one VOR from the Oakland airport. And I have now =
discovered a ridge near my home with a scenic overlook from which I can =
receive two.<o:p></o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal>I've tested the software enough to know that the =
initial scan function seems to work, and the morse decoding kind of =
works, but I am not confident I'll get it to work very well. (One =
transmitter's dit looks a lot like another's dah.) The nav signal =
decoding is simple. (A 30 Hz AM modulated tone is phase compared with a =
30 Hz tone FM modulated at 9960 Hz. The phase obtained is the azimuth to =
the station.)<o:p></o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal>If I ever get this working, I looking forward to =
sharing it with the community. In the process of building this, I =
created a simple SDR toolkit of DSP functions. It's like Gnuradio in =
concept, but 16b fixed-point, and has no external dependencies, and C89, =
so is easier to build on weird and limited platforms. It also has perl =
bindings. Compared to GR, it looks like the work of a rank amateur just =
learning DSP, but I do like the concept of there being a GR-like library =
out there, lightweight and =
embedded-friendly.<o:p></o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal><o:p> </o:p></p></div><div><p =
class=3DMsoNormal>Regards,<o:p></o:p></p></div><div><p =
class=3DMsoNormal>Dave J<o:p></o:p></p></div><div><div><div><p =
class=3DMsoNormal =
style=3D'margin-bottom:12.0pt'><o:p> </o:p></p><div><p =
class=3DMsoNormal>On Tue, Oct 22, 2013 at 3:06 AM, jdow <<a =
href=3D"mailto:jdow at" =
target=3D"_blank">jdow at</a>> wrote:<o:p></o:p></p><p =
class=3DMsoNormal>He sent me two frequencies in private email. These =
were in the FM<br>broadcast band (in the US). He probably needs to notch =
them out<br>in order to get adequate response.<br><br>As for wanting =
narrow bandwidth - I am not quite sure why he thinks<br>that is a =
benefit. I use a large FFT (about 10 Hz per bin) and use<br>the zoom =
control to see fine detail. (Different FFT settings suite<br>different =
uses. This one seems to be a good compromise with my two<br>needs. I'm =
too lazy to change it.)<br><br>{^_^}<o:p></o:p></p><div><div><p =
class=3DMsoNormal><br><br><br>On 2013/10/22 02:08, Sylvain Munaut =
wrote:<o:p></o:p></p><blockquote style=3D'border:none;border-left:solid =
#CCCCCC 1.0pt;padding:0cm 0cm 0cm =
6.0pt;margin-left:4.8pt;margin-right:0cm'><p class=3DMsoNormal>Effective =
filtering must occur between antenna and receiver. All the<br>problems =
that a saturated preamp and ADC cause can’t be repaired =
by<br>software. Never.<o:p></o:p></p></blockquote><p class=3DMsoNormal =
style=3D'margin-bottom:12.0pt'><br>But his original problem is not with =
saturated preamps or ADC ... it's<br>aliasing ... and that can be solved =
in the digital domain provided<br>fast enough =
ADC.<br><br>Cheers,<br><br>    =
Sylvain<br><br><o:p></o:p></p></div></div></div><p =
class=3DMsoNormal><o:p> </o:p></p></div></div></div></div></div><p =
class=3DMsoNormal><o:p> </o:p></p></div></div></div></body></html>

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