Topics

TCXO Behaviour


Andy G4JNT
 

I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.



Robin Szemeti - G1YFG
 

I'd be interested to see what you find from those TCXOs and the frac-n chips, which give better performance.   I was looking for a cheap source of the 26MHz ones for a 13cms transverter I hope to complete soon ... just need to complete a bit of the switching logic and the various enable/pwrdn bits.   Should do 0.5 watt out and uses the SAW filters from Golledge ...  the extra SMA is a feed of rx if to feed to a SDR dongle

image.png


On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.




--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
T: +44 (0) 1299 405028
M: +44 (0) 7971 883371

CONFIDENTIALITY NOTICE
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error
and must not distribute or copy it.
Please accept the sender's apologies, notify the sender immediately
by return e-mail and delete this communication.

Thank you.


Ed G3VPF
 

Andy

Two effects happen when you turn on an OCXO. The first is getting the oven up to temperature, which can be quite quick, the other is the ‘ageing’ of the crystal. A quartz crystal will continually age with time which manifests as a small change in frequency. From switch on the rate of change steadily reduces with time but is still measurable after a year.

Some (many!) years ago I worked in the quartz crystal division of Marconi’s when they were supplying the frequency references for the satellite tracking dishes. The prototype sat in the corner running continuously and after two years the change was down to around 1 part in 10^11/year.

Ed G3VPF




From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Robin Szemeti - G1YFG <robin@...>
Sent: Friday, June 12, 2020 12:25:32 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] TCXO Behaviour
 
I'd be interested to see what you find from those TCXOs and the frac-n chips, which give better performance.   I was looking for a cheap source of the 26MHz ones for a 13cms transverter I hope to complete soon ... just need to complete a bit of the switching logic and the various enable/pwrdn bits.   Should do 0.5 watt out and uses the SAW filters from Golledge ...  the extra SMA is a feed of rx if to feed to a SDR dongle

image.png


On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.




--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
T: +44 (0) 1299 405028
M: +44 (0) 7971 883371

CONFIDENTIALITY NOTICE
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error
and must not distribute or copy it.
Please accept the sender's apologies, notify the sender immediately
by return e-mail and delete this communication.

Thank you.


Andy G4JNT
 

OCXOs yes, but TCXOs shouldn't have a warm-up  They should be on frequency instantly, hence my query about a [warm-up] drift each time they're turned on..  

The frequency of a TCXO is controlled via a forward correction loop, either from a simple bit of analogue circuitry including a thermistor in the older ones, or a digital look-up table.    Not sure what these use, but I suspect the digital route is cheaper.


 


On Fri, 12 Jun 2020 at 16:14, Ed G3VPF <g3vpf@...> wrote:
Andy

Two effects happen when you turn on an OCXO. The first is getting the oven up to temperature, which can be quite quick, the other is the ‘ageing’ of the crystal. A quartz crystal will continually age with time which manifests as a small change in frequency. From switch on the rate of change steadily reduces with time but is still measurable after a year.

Some (many!) years ago I worked in the quartz crystal division of Marconi’s when they were supplying the frequency references for the satellite tracking dishes. The prototype sat in the corner running continuously and after two years the change was down to around 1 part in 10^11/year.

Ed G3VPF




From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Robin Szemeti - G1YFG <robin@...>
Sent: Friday, June 12, 2020 12:25:32 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] TCXO Behaviour
 
I'd be interested to see what you find from those TCXOs and the frac-n chips, which give better performance.   I was looking for a cheap source of the 26MHz ones for a 13cms transverter I hope to complete soon ... just need to complete a bit of the switching logic and the various enable/pwrdn bits.   Should do 0.5 watt out and uses the SAW filters from Golledge ...  the extra SMA is a feed of rx if to feed to a SDR dongle

image.png


On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.




--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
T: +44 (0) 1299 405028
M: +44 (0) 7971 883371

CONFIDENTIALITY NOTICE
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error
and must not distribute or copy it.
Please accept the sender's apologies, notify the sender immediately
by return e-mail and delete this communication.

Thank you.


Andy G4JNT
 

Made up these two test modules for 40MHz and 26MHz TCXOs from Farnell (different makes of module, chosen more-or-less at random) 
http://www.g4jnt.com/DropF/tcxos.jpg  (spot the PCBs from the other thread) 

I did a quick frequency test of the 40MHz one first of all, and over a 10 minute period (after it had been on for about 5 minutes already while I was adjusting the frequency).  The drift was about 3Hz - it may have been less.

The 26MHz one has now been on for several hours. on a frequency counter while I've been out for a walk.  Came back to find it just 0.8Hz off where I'd left it.   However, opened the window to cool the shack down a bit, and teh frequency immediately dropped by 1.3Hz.

All well within spec, but for use in a microwave transverter you do want to keep them away from sudden temperature changes like drafts of wind.
It'll be a while before I connect them up to a synth to check what teh short term multiplied performance is like 

For anything above 5.76GHz I'd use an OCXO without question, if the LO is not going to be used locked to an external reference.  There are some quite nice small ones doing the rounds at quite reasonable prices (and they're NOT chinese)

But these TCXOs do seem to offer a remarkably good performance for a few quid each.

One trouble with adjusting these is that all my 10-turn presets, being wirewound, adjust in steps.   At the moment I just stick the whole preset across the 3.3V rail.  To get really fine adjustment, the tuning voltage range from the preset needs to be more restricted by additional R top and bottom.



On Fri, 12 Jun 2020 at 12:25, Robin Szemeti - G1YFG <robin@...> wrote:
I'd be interested to see what you find from those TCXOs and the frac-n chips, which give better performance.   I was looking for a cheap source of the 26MHz ones for a 13cms transverter I hope to complete soon ... just need to complete a bit of the switching logic and the various enable/pwrdn bits.   Should do 0.5 watt out and uses the SAW filters from Golledge ...  the extra SMA is a feed of rx if to feed to a SDR dongle

image.png


On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.




--
Best regards,

Robin Szemeti

Redpoint Consulting Limited

E: robin@...
T: +44 (0) 1299 405028
M: +44 (0) 7971 883371

CONFIDENTIALITY NOTICE
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error
and must not distribute or copy it.
Please accept the sender's apologies, notify the sender immediately
by return e-mail and delete this communication.

Thank you.


Ian White
 

The ageing is a long-term effect, but Andy is asking about changes on shorter timescales of minutes to a few hours.

This takes us back to the dark art of temperature compensated VFOs, and I believe the frequency changes happen for the same reason. The three main frequency-determining elements - the crystal, the transistors (which are the main source of internal heating) and the temperature compensating components (usually NTC capacitors)  - do not occupy a single point in space. Either internal or external temperature changes arrive at those three elements at different times, so even if the temperature compensation could be perfect over the longer term, there will still be shorter-term frequency excursions.

73 from Ian GM3SEK



On 12/06/2020 16:14, Ed G3VPF wrote:
Andy

Two effects happen when you turn on an OCXO. The first is getting the oven up to temperature, which can be quite quick, the other is the ‘ageing’ of the crystal. A quartz crystal will continually age with time which manifests as a small change in frequency. From switch on the rate of change steadily reduces with time but is still measurable after a year.

Some (many!) years ago I worked in the quartz crystal division of Marconi’s when they were supplying the frequency references for the satellite tracking dishes. The prototype sat in the corner running continuously and after two years the change was down to around 1 part in 10^11/year.

Ed G3VPF




From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Robin Szemeti - G1YFG <robin@...>
Sent: Friday, June 12, 2020 12:25:32 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] TCXO Behaviour
 
I'd be interested to see what you find from those TCXOs and the frac-n chips, which give better performance.   I was looking for a cheap source of the 26MHz ones for a 13cms transverter I hope to complete soon ... just need to complete a bit of the switching logic and the various enable/pwrdn bits.   Should do 0.5 watt out and uses the SAW filters from Golledge ...  the extra SMA is a feed of rx if to feed to a SDR dongle

image.png


On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.




--
Best regards,

Robin Szemeti

Redpoint Consulting Limited 

E: robin@... 
T: +44 (0) 1299 405028 
M: +44 (0) 7971 883371 

CONFIDENTIALITY NOTICE 
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error 
and must not distribute or copy it. 
Please accept the sender's apologies, notify the sender immediately 
by return e-mail and delete this communication. 

Thank you. 


Andy G4JNT
 

Even that argument doesn't really apply here.   The whole TCXO module is about 2.5 x 2mm, weighs less than a gram, and consumes just 2mA at 3V supply,  so I can't believe differential heating between components over that time scale is remotely feasible..

I can only assume it's imperfect temperature compensation.     It is within spec, but still a bit unexpected. The TCXO really ought to be renamed PTCXO;  Partially Temperature Compensated XO.
 


On Fri, 12 Jun 2020 at 21:09, Ian White <gm3sek@...> wrote:

The ageing is a long-term effect, but Andy is asking about changes on shorter timescales of minutes to a few hours.

This takes us back to the dark art of temperature compensated VFOs, and I believe the frequency changes happen for the same reason. The three main frequency-determining elements - the crystal, the transistors (which are the main source of internal heating) and the temperature compensating components (usually NTC capacitors)  - do not occupy a single point in space. Either internal or external temperature changes arrive at those three elements at different times, so even if the temperature compensation could be perfect over the longer term, there will still be shorter-term frequency excursions.

73 from Ian GM3SEK



On 12/06/2020 16:14, Ed G3VPF wrote:
Andy

Two effects happen when you turn on an OCXO. The first is getting the oven up to temperature, which can be quite quick, the other is the ‘ageing’ of the crystal. A quartz crystal will continually age with time which manifests as a small change in frequency. From switch on the rate of change steadily reduces with time but is still measurable after a year.

Some (many!) years ago I worked in the quartz crystal division of Marconi’s when they were supplying the frequency references for the satellite tracking dishes. The prototype sat in the corner running continuously and after two years the change was down to around 1 part in 10^11/year.

Ed G3VPF




From: UKMicrowaves@groups.io <UKMicrowaves@groups.io> on behalf of Robin Szemeti - G1YFG <robin@...>
Sent: Friday, June 12, 2020 12:25:32 PM
To: UKMicrowaves@groups.io <UKMicrowaves@groups.io>
Subject: Re: [UKMicrowaves] TCXO Behaviour
 
I'd be interested to see what you find from those TCXOs and the frac-n chips, which give better performance.   I was looking for a cheap source of the 26MHz ones for a 13cms transverter I hope to complete soon ... just need to complete a bit of the switching logic and the various enable/pwrdn bits.   Should do 0.5 watt out and uses the SAW filters from Golledge ...  the extra SMA is a feed of rx if to feed to a SDR dongle

image.png


On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.




--
Best regards,

Robin Szemeti

Redpoint Consulting Limited 

E: robin@... 
T: +44 (0) 1299 405028 
M: +44 (0) 7971 883371 

CONFIDENTIALITY NOTICE 
The information contained in this e-mail is intended only for the
confidential use of the above named recipient. If you are not the
intended recipient or person responsible for delivering it to the
intended recipient, you have received this communication in error 
and must not distribute or copy it. 
Please accept the sender's apologies, notify the sender immediately 
by return e-mail and delete this communication. 

Thank you. 


Robin Szemeti - G1YFG
 

Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.



--
Robin Szemeti - G1YFG


Colin Ranson
 

Hi Robin and others,   just for info I’m using a series of these in various applications.  (e-bay number 132652769518) The 25mhz one I’m using (via an LC filter) to stabilise my QO-100 LNB, it is 10hz (as measured by G4DDK) out but very stable so 10Hz x 390 means my RX is 3.9KHz out..... but hey-ho, beggars and all that.

Also use a 101MHz example to lock my 70cm ICENI (The xtal I used is not particularly good) and a 116MHz example in my ongoing 2m transverter project.

 

BTW I run the 25MHz ref and the 595MHz osc in my QO-100 downconverter 24/7/365.

 

Enjoy this lovely sunny Sunday, my missus says I have to put the soldering iron down and take her out !

 

Regards

 

Colin G8LBS. 

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 06 September 2020 00:35
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] TCXO Behaviour

 

Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:

I'm using this TCXO 

Part No  

RoHS1

449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm

 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

 

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

 

Guess I'm expecting too much :-)

 

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.

 


Andy

 


--
Robin Szemeti - G1YFG

 


Robin Szemeti - G1YFG
 

Interesting ... I have an almost identical device in my 817 as a "high precision" reference.  It is the second one I have had as the first died after a couple of years. I can't say the one in the 817 is particularly stable. Would you say yours is significantly better in terms of freq stability than a standard crystal?


On Sun, 6 Sep 2020 at 10:46, Colin Ranson <g8lbs@...> wrote:

Hi Robin and others,   just for info I’m using a series of these in various applications.  (e-bay number 132652769518) The 25mhz one I’m using (via an LC filter) to stabilise my QO-100 LNB, it is 10hz (as measured by G4DDK) out but very stable so 10Hz x 390 means my RX is 3.9KHz out..... but hey-ho, beggars and all that.

Also use a 101MHz example to lock my 70cm ICENI (The xtal I used is not particularly good) and a 116MHz example in my ongoing 2m transverter project.

 

BTW I run the 25MHz ref and the 595MHz osc in my QO-100 downconverter 24/7/365.

 

Enjoy this lovely sunny Sunday, my missus says I have to put the soldering iron down and take her out !

 

Regards

 

Colin G8LBS. 

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 06 September 2020 00:35
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] TCXO Behaviour

 

Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:

I'm using this TCXO 

Part No  

RoHS1

449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm

 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

 

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

 

Guess I'm expecting too much :-)

 

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.

 


Andy

 


--
Robin Szemeti - G1YFG

 


--
Robin Szemeti - G1YFG


Colin Ranson
 

Hi Robin,

 

Just on my way out.........   yes, the 101MHz example has better stability and accuracy than the cheap Czech xtal in the transverter which is a bit touchy getting onto frequency and I can’t fault the 25MHz one for stability.

 

 

Regards

 

Colin.

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 06 September 2020 11:38
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] TCXO Behaviour

 

Interesting ... I have an almost identical device in my 817 as a "high precision" reference.  It is the second one I have had as the first died after a couple of years. I can't say the one in the 817 is particularly stable. Would you say yours is significantly better in terms of freq stability than a standard crystal?

 

 

On Sun, 6 Sep 2020 at 10:46, Colin Ranson <g8lbs@...> wrote:

Hi Robin and others,   just for info I’m using a series of these in various applications.  (e-bay number 132652769518) The 25mhz one I’m using (via an LC filter) to stabilise my QO-100 LNB, it is 10hz (as measured by G4DDK) out but very stable so 10Hz x 390 means my RX is 3.9KHz out..... but hey-ho, beggars and all that.

Also use a 101MHz example to lock my 70cm ICENI (The xtal I used is not particularly good) and a 116MHz example in my ongoing 2m transverter project.

 

BTW I run the 25MHz ref and the 595MHz osc in my QO-100 downconverter 24/7/365.

 

Enjoy this lovely sunny Sunday, my missus says I have to put the soldering iron down and take her out !

 

Regards

 

Colin G8LBS. 

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 06 September 2020 00:35
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] TCXO Behaviour

 

Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:

I'm using this TCXO 

Part No  

RoHS1

449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm

 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

 

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

 

Guess I'm expecting too much :-)

 

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.

 


Andy

 


--
Robin Szemeti - G1YFG

 


--
Robin Szemeti - G1YFG

 


Robin Szemeti - G1YFG
 

Fair enough, that looks like the easy option then. 

Pity the output is on tag strip and not an SMA, but, cheap enough, can't complain I guess!

Thanks for the recommendation, I'll get one ordered!


On Sun, 6 Sep 2020 at 12:06, Colin Ranson <g8lbs@...> wrote:

Hi Robin,

 

Just on my way out.........   yes, the 101MHz example has better stability and accuracy than the cheap Czech xtal in the transverter which is a bit touchy getting onto frequency and I can’t fault the 25MHz one for stability.

 

 

Regards

 

Colin.

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 06 September 2020 11:38
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] TCXO Behaviour

 

Interesting ... I have an almost identical device in my 817 as a "high precision" reference.  It is the second one I have had as the first died after a couple of years. I can't say the one in the 817 is particularly stable. Would you say yours is significantly better in terms of freq stability than a standard crystal?

 

 

On Sun, 6 Sep 2020 at 10:46, Colin Ranson <g8lbs@...> wrote:

Hi Robin and others,   just for info I’m using a series of these in various applications.  (e-bay number 132652769518) The 25mhz one I’m using (via an LC filter) to stabilise my QO-100 LNB, it is 10hz (as measured by G4DDK) out but very stable so 10Hz x 390 means my RX is 3.9KHz out..... but hey-ho, beggars and all that.

Also use a 101MHz example to lock my 70cm ICENI (The xtal I used is not particularly good) and a 116MHz example in my ongoing 2m transverter project.

 

BTW I run the 25MHz ref and the 595MHz osc in my QO-100 downconverter 24/7/365.

 

Enjoy this lovely sunny Sunday, my missus says I have to put the soldering iron down and take her out !

 

Regards

 

Colin G8LBS. 

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 06 September 2020 00:35
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] TCXO Behaviour

 

Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:

I'm using this TCXO 

Part No  

RoHS1

449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm

 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

 

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

 

Guess I'm expecting too much :-)

 

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.

 


Andy

 


--
Robin Szemeti - G1YFG

 


--
Robin Szemeti - G1YFG

 


--
Robin Szemeti - G1YFG


Andy G4JNT
 

I only did a quick test on each.    All seem to hold their frequency quite well to a fraction of a PPM, far better then a straight crystal would.  But some seem to have a long time constant in their compensation.  If you  waft  air over them  the frequency changes rapidly, only by a fraction of a PPM, but sudile (at uWaves) , enough to be annoying.  So if using for  GHz, they do need to be inside a closed container in still air - and definitely away from any cooling fans.

BTW, I encountered one, once that was a frequency hopper.   Sounded like JT4 when multiplied up - those are designed / touted to overcome EMC regs by spreading interference.    Or it may have been digital temperature compensation that was applied via a 4 bit D/A and PRN mod.   If that was the case, it would have been a pretty clever bit of design.



On Sun, 6 Sep 2020 at 00:35, Robin Szemeti - G1YFG <robin@...> wrote:
Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.



--
Robin Szemeti - G1YFG


Robin Szemeti - G1YFG
 

Noted, thanks for the update. Just need something to tame this very wobbly crystal in the PLL ... I suspect it may be made from cheese.  I'll try one with a block of "something" around it to shield it ... polystyrene or similar.

On Sun, 6 Sep 2020 at 12:44, Andy G4JNT <andy.g4jnt@...> wrote:
I only did a quick test on each.    All seem to hold their frequency quite well to a fraction of a PPM, far better then a straight crystal would.  But some seem to have a long time constant in their compensation.  If you  waft  air over them  the frequency changes rapidly, only by a fraction of a PPM, but sudile (at uWaves) , enough to be annoying.  So if using for  GHz, they do need to be inside a closed container in still air - and definitely away from any cooling fans.

BTW, I encountered one, once that was a frequency hopper.   Sounded like JT4 when multiplied up - those are designed / touted to overcome EMC regs by spreading interference.    Or it may have been digital temperature compensation that was applied via a 4 bit D/A and PRN mod.   If that was the case, it would have been a pretty clever bit of design.



On Sun, 6 Sep 2020 at 00:35, Robin Szemeti - G1YFG <robin@...> wrote:
Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.



--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


Robin Szemeti - G1YFG
 

And as an update, I fitted the "golden" TCXO to the 13cm transverter and it is indeed very stable as described, can't fault it.   I tuned in the Telford beacon when the shed was nice and warm one evening left it running.  It was still the same tone the next morning when the shed was somewhat cooler.  It appears to be excellent, blowing some warm air over it has minimal effect, certainly for SSB purposes, it is more than adequate.

image.png


On Sun, 6 Sep 2020 at 16:10, Robin Szemeti - G1YFG via groups.io <robin=redpoint.org.uk@groups.io> wrote:
Noted, thanks for the update. Just need something to tame this very wobbly crystal in the PLL ... I suspect it may be made from cheese.  I'll try one with a block of "something" around it to shield it ... polystyrene or similar.

On Sun, 6 Sep 2020 at 12:44, Andy G4JNT <andy.g4jnt@...> wrote:
I only did a quick test on each.    All seem to hold their frequency quite well to a fraction of a PPM, far better then a straight crystal would.  But some seem to have a long time constant in their compensation.  If you  waft  air over them  the frequency changes rapidly, only by a fraction of a PPM, but sudile (at uWaves) , enough to be annoying.  So if using for  GHz, they do need to be inside a closed container in still air - and definitely away from any cooling fans.

BTW, I encountered one, once that was a frequency hopper.   Sounded like JT4 when multiplied up - those are designed / touted to overcome EMC regs by spreading interference.    Or it may have been digital temperature compensation that was applied via a 4 bit D/A and PRN mod.   If that was the case, it would have been a pretty clever bit of design.



On Sun, 6 Sep 2020 at 00:35, Robin Szemeti - G1YFG <robin@...> wrote:
Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:
I'm using this TCXO 
Part No  
RoHS1
449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm
 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

Guess I'm expecting too much :-)

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.



--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


Colin Ranson
 

Robin,

 

Pleased you are happy with your ‘Golden’ TCXO, as I said before, can’t fault them for the price.    I run my 101MHz (70cm) and 25MHz (QO-100) examples 24/7/365 as is the 116MHz one that will run in an eventual 2m transverter.   I would like them to ‘cut’ me a 25.788++++++++++MHz for QO-100 432MHz IF from an LNB but I dare not ask the price for a ‘one off’   !!

 

Good luck

 

Regards

 

 

Colin de G8LBS.

 

 

 

Sent from Mail for Windows 10

 

From: Robin Szemeti - G1YFG
Sent: 26 September 2020 00:33
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] TCXO Behaviour

 

And as an update, I fitted the "golden" TCXO to the 13cm transverter and it is indeed very stable as described, can't fault it.   I tuned in the Telford beacon when the shed was nice and warm one evening left it running.  It was still the same tone the next morning when the shed was somewhat cooler.  It appears to be excellent, blowing some warm air over it has minimal effect, certainly for SSB purposes, it is more than adequate.

 

 

On Sun, 6 Sep 2020 at 16:10, Robin Szemeti - G1YFG via groups.io <robin=redpoint.org.uk@groups.io> wrote:

Noted, thanks for the update. Just need something to tame this very wobbly crystal in the PLL ... I suspect it may be made from cheese.  I'll try one with a block of "something" around it to shield it ... polystyrene or similar.

 

On Sun, 6 Sep 2020 at 12:44, Andy G4JNT <andy.g4jnt@...> wrote:

I only did a quick test on each.    All seem to hold their frequency quite well to a fraction of a PPM, far better then a straight crystal would.  But some seem to have a long time constant in their compensation.  If you  waft  air over them  the frequency changes rapidly, only by a fraction of a PPM, but sudile (at uWaves) , enough to be annoying.  So if using for  GHz, they do need to be inside a closed container in still air - and definitely away from any cooling fans.

 

BTW, I encountered one, once that was a frequency hopper.   Sounded like JT4 when multiplied up - those are designed / touted to overcome EMC regs by spreading interference.    Or it may have been digital temperature compensation that was applied via a 4 bit D/A and PRN mod.   If that was the case, it would have been a pretty clever bit of design.

 

Andy

 

 

 

On Sun, 6 Sep 2020 at 00:35, Robin Szemeti - G1YFG <robin@...> wrote:

Out of curiosity, did you test the higher frequency TCXOs and come to any conclusions? 

 

On Fri, 12 Jun 2020 at 11:48, Andy G4JNT <andy.g4jnt@...> wrote:

I'm using this TCXO 

Part No  

RoHS1

449-LFTVXO075802CUTT     Type  LFTVXO075802Cutt     TCXO  10.0MHz .28ppm

 in my 3.4GHz transverter and for a relative low cost frequency source, it's excellent.  But I can't work out why there is a steady frequency drift from turn-on.  It's only about 0.1ppm so is within spec, and occurs over the first 20 - 30 minutes of operation.

 

Isn't the whole point of a TCXO that it's temperature compensated ?   Perhaps it's just compensation loop-gain is too low. 

 

Guess I'm expecting too much :-)

 

I've just bought a batch of each of the low cost TCXOs that Farnell & RS have available in several different frequencies, 19.2, 26 and 40MHz and will investigate their performance as references.    As modern Fract-N synths prefer a higher Fref than 10MHz,  wondering if these will do, and they can always be locked to 10MHz separately.

 


Andy

 


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG


--
Robin Szemeti - G1YFG