[time-nuts] Designing and building an OCXO and GPSDO
SAIDJACK at aol.com
SAIDJACK at aol.com
Wed Aug 13 16:24:46 UTC 2008
Thanks Bruce,
it would be interesting to see how the different topologies affect phase
noise and stability etc, and what kind of performance can be achieved.
bye,
Said
In a message dated 8/12/2008 20:19:03 Pacific Daylight Time, SAIDJACK@
aol.com writes:
Hi Bruce,
do you have any phase noise/stability measurements for these circuits?
thanks,
Said
In a message dated 8/12/2008 18:53:38 Pacific Daylight Time,
bruce.griffiths at xtra.co.nz writes:
Attached schematic is for a variant of the Wenzel circuit using a JFET
high input impedance buffer to drive a cascaded pair of CB stages.
L104 is approximately resonant with C111 at 3MHz so that either an RF
choke and series resistor or a relative;y low value resistor (10K) can
be used to set the JFET gate voltage.
The impedance of C104 at 3MHz is about 530 ohms so a 1mA crystal current
will result in about 530 mV rms across C104.
An additional inductor can be used in series with the crystal to
resonate out the input capacitance of the oscillator stage if required,
this will allow a greater tuning range to be achieved.
Inductor L104 needs to have a reasonably high Q ( > 100 @ 3MHz) to
avoid degrading the loaded Q significantly.
The drain current of JFET Q103 is determined by the collector current of
Q104 this minimises the effect of JFET parameter variations from part to
part on its drain current.
The RF voltage at the source of Q103 can be amplified (a widebandwidth
opamp could be used) and used to drive a detector diode for AGC purposes.
Alternatively a common base stage connected to the other end of the
secondary of T101 could be used an RF current source to drive a full
wave diode detector with a low load resistance.
This will largely eliminate the effect of the detector diode forward
voltage drops on the detected output. This detector dc load current can
than be compared with a reference current and the dc collector current
of Q101 adjusted to regulate the crystal current.
Bruce
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Read reviews on AOL Autos.
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7 )
Hi Bruce,
do you have any phase noise/stability measurements for these circuits?
thanks,
Said
In a message dated 8/12/2008 18:53:38 Pacific Daylight Time,
bruce.griffiths at xtra.co.nz writes:
Attached schematic is for a variant of the Wenzel circuit using a
JFET
high input impedance buffer to drive a cascaded pair of CB stages.
L104 is approximately resonant with C111 at 3MHz so that either an
RF
choke and series resistor or a relative;y low value resistor (10K)
can
be used to set the JFET gate voltage.
The impedance of C104 at 3MHz is about 530 ohms so a 1mA crystal
current
will result in about 530 mV rms across C104.
An additional inductor can be used in series with the crystal to
resonate out the input capacitance of the oscillator stage if
required,
this will allow a greater tuning range to be achieved.
Inductor L104 needs to have a reasonably high Q ( > 100 @ 3MHz) to
avoid degrading the loaded Q significantly.
The drain current of JFET Q103 is determined by the collector
current of
Q104 this minimises the effect of JFET parameter variations from
part to
part on its drain current.
The RF voltage at the source of Q103 can be amplified (a
widebandwidth
opamp could be used) and used to drive a detector diode for AGC
purposes.
Alternatively a common base stage connected to the other end of the
secondary of T101 could be used an RF current source to drive a full
wave diode detector with a low load resistance.
This will largely eliminate the effect of the detector diode forward
voltage drops on the detected output. This detector dc load current
can
than be compared with a reference current and the dc collector
current
of Q101 adjusted to regulate the crystal current.
Bruce
[cid:X.MA1.1218597403 at aol.com]
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__________________________________________________________________
Looking for a car that's sporty, fun and fits in your budget? [1]Read
reviews on AOL Autos.
References
1.
http://autos.aol.com/cars-BMW-128-2008/expert-review?ncid=aolaut00050000000017
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
**************Looking for a car that's sporty, fun and fits in your budget?
Read reviews on AOL Autos.
(http://autos.aol.com/cars-BMW-128-2008/expert-review?ncid=aolaut00050000000017 )
-------------- next part --------------
Thanks Bruce,
it would be interesting to see how the different topologies affect
phase noise and stability etc, and what kind of performance can be
achieved.
bye,
Said
In a message dated 8/12/2008 20:19:03 Pacific Daylight Time,
SAIDJACK at aol.com writes:
Hi Bruce,
do you have any phase noise/stability measurements for these
circuits?
thanks,
Said
In a message dated 8/12/2008 18:53:38 Pacific Daylight Time,
bruce.griffiths at xtra.co.nz writes:
Attached schematic is for a variant of the Wenzel circuit using a
JFET
high input impedance buffer to drive a cascaded pair of CB stages.
L104 is approximately resonant with C111 at 3MHz so that either an
RF
choke and series resistor or a relative;y low value resistor (10K)
can
be used to set the JFET gate voltage.
The impedance of C104 at 3MHz is about 530 ohms so a 1mA crystal
current
will result in about 530 mV rms across C104.
An additional inductor can be used in series with the crystal to
resonate out the input capacitance of the oscillator stage if
required,
this will allow a greater tuning range to be achieved.
Inductor L104 needs to have a reasonably high Q ( > 100 @ 3MHz) to
avoid degrading the loaded Q significantly.
The drain current of JFET Q103 is determined by the collector
current of
Q104 this minimises the effect of JFET parameter variations from
part to
part on its drain current.
The RF voltage at the source of Q103 can be amplified (a
widebandwidth
opamp could be used) and used to drive a detector diode for AGC
purposes.
Alternatively a common base stage connected to the other end of the
secondary of T101 could be used an RF current source to drive a
full
wave diode detector with a low load resistance.
This will largely eliminate the effect of the detector diode
forward
voltage drops on the detected output. This detector dc load current
can
than be compared with a reference current and the dc collector
current
of Q101 adjusted to regulate the crystal current.
Bruce
_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
**************Looking for a car that's sporty, fun and fits in your
budget?
Read reviews on AOL Autos.
(http://autos.aol.com/cars-BMW-128-2008/expert-review?ncid=aolaut000
50000000017 )
Hi Bruce,
do you have any phase noise/stability measurements for these
circuits?
thanks,
Said
In a message dated 8/12/2008 18:53:38 Pacific Daylight Time,
bruce.griffiths at xtra.co.nz writes:
Attached schematic is for a variant of the Wenzel circuit using
a
JFET
high input impedance buffer to drive a cascaded pair of CB
stages.
L104 is approximately resonant with C111 at 3MHz so that either
an
RF
choke and series resistor or a relative;y low value resistor
(10K)
can
be used to set the JFET gate voltage.
The impedance of C104 at 3MHz is about 530 ohms so a 1mA
crystal
current
will result in about 530 mV rms across C104.
An additional inductor can be used in series with the crystal
to
resonate out the input capacitance of the oscillator stage if
required,
this will allow a greater tuning range to be achieved.
Inductor L104 needs to have a reasonably high Q ( > 100 @
3MHz) to
avoid degrading the loaded Q significantly.
The drain current of JFET Q103 is determined by the collector
current of
Q104 this minimises the effect of JFET parameter variations
from
part to
part on its drain current.
The RF voltage at the source of Q103 can be amplified (a
widebandwidth
opamp could be used) and used to drive a detector diode for AGC
purposes.
Alternatively a common base stage connected to the other end of
the
secondary of T101 could be used an RF current source to drive a
full
wave diode detector with a low load resistance.
This will largely eliminate the effect of the detector diode
forward
voltage drops on the detected output. This detector dc load
current
can
than be compared with a reference current and the dc collector
current
of Q101 adjusted to regulate the crystal current.
Bruce
[cid:X.MA1.1218597403 at aol.com]
_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
__________________________________________________________________
Looking for a car that's sporty, fun and fits in your budget?
[1]Read
reviews on AOL Autos.
References
1.
http://autos.aol.com/cars-BMW-128-2008/expert-review?ncid=aolaut0005
0000000017
[cid:X.MA1.1218644679 at aol.com]
_______________________________________________
time-nuts mailing list -- time-nuts at febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
__________________________________________________________________
Looking for a car that's sporty, fun and fits in your budget? [1]Read
reviews on AOL Autos.
References
1. http://autos.aol.com/cars-BMW-128-2008/expert-review?ncid=aolaut00050000000017
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