Bob,
I intended nothing aiming for "perfect".
My initial proposal was actually for a 1 pole low-pass and then a block
at 30 MHz for third overtone, but I never put that in mail-form.
Cheers,
Magnus
On 07/17/2015 02:57 PM, Bob Camp wrote:
Hi
But your 3 pole will not be as good as my 5 pole. My 5 pole will not be as good
as the next poster’s
13 pole. My 5 added traps will not do as much as the next poster’s 13 traps.
What *will* happen as all of these parts are added:
1) It becomes a real mess to properly lay out and align
2) Even with good equipment, you will need ever more accurate parts to
implement it
3) The sensitivity of the result to minor parts variation will keep going up.
(I get -180 dbc here and “only” -120 dbc 1% away).
4) The odds of anybody actually building one go down probably as the square of
the number of parts involved.
The simple filter topology posted earlier by Charles is indeed quite adequate.
You can get -60 dbc harmonics without
going very crazy on the design. Part values can either be calculated from formulas
that have existed for > 80 years
or you can play with simulation.
Bob
On Jul 17, 2015, at 4:07 AM, Magnus Danielson <mag...@rubidium.dyndns.org>
wrote:
I was thinking along these lines.
Cooking up a 3-pole filter in the form of a Pi-filter should be a good start,
and then add traps for third and possibly fifth overtones that will not get
much damping initially can be done if you need it pretty clean.
Cheers,
Magnus
On 07/17/2015 04:07 AM, Graham / KE9H wrote:
All you need is a 10 MHz low pass filter.
How far down do you need the harmonics/spurious to be?
If 40 dB suppression of the 2nd and 3rd harmonics is adequate,
(you can't see the distortion with the eye on an oscilloscope)
you can make your own for about $2 in parts, not including a PC board or
housing.
Feel free to copy the low pass filter (L1, C9, C10) from here:
http://openhpsdr.org/wiki/index.php?title=EXCALIBUR
Or for about $35, you could get the same performance from an inline BNC
filter from Minicircuits.
http://www.minicircuits.com/pdfs/BLP-10.7+.pdf
If you need more harmonic suppression, buy two and put them in series.
--- Graham
==
--- Graham
==
On Thu, Jul 16, 2015 at 12:49 PM, skipp Isaham via time-nuts <
time-nuts@febo.com> wrote:
re: 10MHz Square to Sine Wave Conversion
The GPSDO I recently acquired outputs a 10 MHz square wave. I'd like
to convert it to a sine wave and I am looking for suggestions and info re
any reasonable pre-made circuits and/or boards. No sense reinventing the
wheel if I can avoid it.
Otherwise I will start from scratch and make a new wheel....
Thank you in advance for your replies.
Regards,
skipp
skipp025 at yahoo dot com
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
