FE 5680A "new version" - Filtering the 10 MHz
Hi all,
As noted somewhere on the list, the 10 MHz output of the newer version
units is less filtered than before.
The output at the internal RF connector is even worse (there is some
more filtering going on inside the DB9 itself).
I'm looking for ways to clean up that 10 MHz output, preferrably that
would fit inside the unit itself (like a small PCB, adding an external
SMA output).
Any suggestion ?
BTW, does any one know what kind of connector are the small ones
inside ? I tought maybe mini-ufl but my pigtail don't seem to fit.
Cheers,
Sylvain
Hi,
One "off the shelf" or more likely out of the junk box option is to use the filter components from a 10Mb/s ethernet card. They work quite well but might introduce some temperature related phase shifts.
Robert G8RPI.
From: Sylvain Munaut 246tnt@gmail.com
To: time-nuts@febo.com
Sent: Tuesday, 15 November 2011, 9:46
Subject: [time-nuts] FE 5680A "new version" - Filtering the 10 MHz
Hi all,
As noted somewhere on the list, the 10 MHz output of the newer version
units is less filtered than before.
The output at the internal RF connector is even worse (there is some
more filtering going on inside the DB9 itself).
I'm looking for ways to clean up that 10 MHz output, preferrably that
would fit inside the unit itself (like a small PCB, adding an external
SMA output).
Any suggestion ?
BTW, does any one know what kind of connector are the small ones
inside ? I tought maybe mini-ufl but my pigtail don't seem to fit.
Cheers,
Sylvain
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.
Robert wrote:
One "off the shelf" or more likely out of the junk box option is to
use the filter components from a 10Mb/s ethernet card. They work
quite well but might introduce some temperature related phase shifts.
As others have pointed out here in the past, to minimize phase and
amplitude shifts with temperature changes, you would like the phase
and amplitude responses to be changing as gradually as possible in
the vicinity of the oscillator frequency. However, this is not the
case with a bandbass filter centered on the oscillator frequency or a
low-pass filter with a cutoff near the oscillator frequency.
If the undesired output components are harmonics, you can reduce the
first few with traps (i.e., notch filters). This may be all you need
(for example, if the harmonics were generated by a buffer amp with
simple nonlinearities). Even if there is an extended harmonic
series, as may be the case with the 5680A, it will allow you to
filter the higher harmonics using a low-pass filter with relaxed
specifications (higher cutoff frequency, fewer poles, and/or better
damping), thus preserving gentle phase and amplitude response at the
oscillator frequency.
Best regards,
Charles
I am trying to understand the problem with harmonics on the 10 MHz output.
If you use it to drive the external input of another instrument, it won't be a problem, more likely it will probably help since the instrument will convert that signal to a square wave more appropriate to driving digital logic anyway.
If you use it to drive a mixer, mixers are highly non-linear devices that will generate their own harmonics, and most mixers actually show improved performance (like reduced conversion loss) when driven with a square wave.
So what is the problem?
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: "Charles P. Steinmetz" charles_steinmetz@lavabit.com
Sender: time-nuts-bounces@febo.com
Date: Tue, 15 Nov 2011 16:15:37
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] FE 5680A "new version" - Filtering the 10 MHz
Robert wrote:
One "off the shelf" or more likely out of the junk box option is to
use the filter components from a 10Mb/s ethernet card. They work
quite well but might introduce some temperature related phase shifts.
As others have pointed out here in the past, to minimize phase and
amplitude shifts with temperature changes, you would like the phase
and amplitude responses to be changing as gradually as possible in
the vicinity of the oscillator frequency. However, this is not the
case with a bandbass filter centered on the oscillator frequency or a
low-pass filter with a cutoff near the oscillator frequency.
If the undesired output components are harmonics, you can reduce the
first few with traps (i.e., notch filters). This may be all you need
(for example, if the harmonics were generated by a buffer amp with
simple nonlinearities). Even if there is an extended harmonic
series, as may be the case with the 5680A, it will allow you to
filter the higher harmonics using a low-pass filter with relaxed
specifications (higher cutoff frequency, fewer poles, and/or better
damping), thus preserving gentle phase and amplitude response at the
oscillator frequency.
Best regards,
Charles
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.
Hi
I think that the issue is not so much harmonics, as spurious signals on the
output (signals not equal to N times 10 MHz). Harmonics by themselves are
not a big deal.
Bob
-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of shalimr9@gmail.com
Sent: Tuesday, November 15, 2011 11:12 PM
To: Time-Nuts
Subject: Re: [time-nuts] FE 5680A "new version" - Filtering the 10 MHz
I am trying to understand the problem with harmonics on the 10 MHz output.
If you use it to drive the external input of another instrument, it won't be
a problem, more likely it will probably help since the instrument will
convert that signal to a square wave more appropriate to driving digital
logic anyway.
If you use it to drive a mixer, mixers are highly non-linear devices that
will generate their own harmonics, and most mixers actually show improved
performance (like reduced conversion loss) when driven with a square wave.
So what is the problem?
Didier KO4BB
Sent from my BlackBerry Wireless thingy while I do other things...
-----Original Message-----
From: "Charles P. Steinmetz" charles_steinmetz@lavabit.com
Sender: time-nuts-bounces@febo.com
Date: Tue, 15 Nov 2011 16:15:37
To: Discussion of precise time and frequency measurementtime-nuts@febo.com
Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
Subject: Re: [time-nuts] FE 5680A "new version" - Filtering the 10 MHz
Robert wrote:
One "off the shelf" or more likely out of the junk box option is to
use the filter components from a 10Mb/s ethernet card. They work
quite well but might introduce some temperature related phase shifts.
As others have pointed out here in the past, to minimize phase and
amplitude shifts with temperature changes, you would like the phase
and amplitude responses to be changing as gradually as possible in
the vicinity of the oscillator frequency. However, this is not the
case with a bandbass filter centered on the oscillator frequency or a
low-pass filter with a cutoff near the oscillator frequency.
If the undesired output components are harmonics, you can reduce the
first few with traps (i.e., notch filters). This may be all you need
(for example, if the harmonics were generated by a buffer amp with
simple nonlinearities). Even if there is an extended harmonic
series, as may be the case with the 5680A, it will allow you to
filter the higher harmonics using a low-pass filter with relaxed
specifications (higher cutoff frequency, fewer poles, and/or better
damping), thus preserving gentle phase and amplitude response at the
oscillator frequency.
Best regards,
Charles
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To unsubscribe, go to
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time-nuts mailing list -- time-nuts@febo.com
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and follow the instructions there.