The TinyPFA forum provides significant and important information .
One important process that is documented is the requirement to determine the noise floor of the TinyPFA.
It is suggested that indication of noise floor may be determined by the application of a common RF source to ports 0 and 1 of the TinyPFA.
I conducted this experiment using a 10 MHz OCXO (~ -5 dBm amplitude) RF signal applied to the TinyPFA over a 12 hour test period (RED coded data)
I repeated the experiment with the TinyPFA enclosed in a faraday shield, with all other factors remaining as close to identical as possible. (Blue coded data).
I was a bit suprized with the results, and thus repeated the experiments multiple times and results were similar from all experiments.
I am unclear if my test evironment setup has high levels of external RF noise, however I believe this is somewhat unlikely.
I would suggest these tests illustrate that the TinyPFA is sensitive to external / internal RF signals that perturb the system.
I paln to enhance the faraday shield system and fabricate a improved thermal stability beyond the normal ambient temperature control.
I would appreciate comments / suggestions / critique of this data.
Don
some intial observations of TinyPFA noise floor
some intial observations of TinyPFA noise floor
- Attachments
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- OCXO applied to TinyPFA ports Allan Dev.
- Allan_Deviation.png (97.5 KiB) Viewed 137 times
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- OCXO applied to TinyPFA ports Phase display
- Phase_Difference.png (57.4 KiB) Viewed 137 times
Re: some intial observations of TinyPFA noise floor
Was the ocxo also inside the faraday shield?
Where the coax cables connecting ocxo and tinyPFA, when outside the shield, double shielded.
Where there any coax cables connected to still active clock sources with some meters distance?
Extra shielding will help as the shielding of the tinyPFA is limited.
The largest difference between the red and blue ADEV lines could be caused by the second order curve of the red phase . The blue trace is more straight.
Thermal effects normally are the biggest cause. Always remove at least the first 30 minutes of measurement after switching on or handling as touching does cause temperature changes.
The fast pfase variations could be due to draft. Always protect the tinyPFA against draft using at least a towel
Where the coax cables connecting ocxo and tinyPFA, when outside the shield, double shielded.
Where there any coax cables connected to still active clock sources with some meters distance?
Extra shielding will help as the shielding of the tinyPFA is limited.
The largest difference between the red and blue ADEV lines could be caused by the second order curve of the red phase . The blue trace is more straight.
Thermal effects normally are the biggest cause. Always remove at least the first 30 minutes of measurement after switching on or handling as touching does cause temperature changes.
The fast pfase variations could be due to draft. Always protect the tinyPFA against draft using at least a towel
Re: some intial observations of TinyPFA noise floor
Erik
thank you for your questions.
my response is as follows:
Was the ocxo also inside the faraday shield? YES
Where the coax cables connecting ocxo and tinyPFA, when outside the shield, double shielded. YES
Where there any coax cables connected to still active clock sources with some meters distance? NO
As you have indicated, thermal effects are a major perturbation onTinyPFA measurements.
I am testing some alternate configurations in an attempt to find a optimum layout and minimize thermal, RF and other environmental effects.
to be clear, the TinyPFA provides extraordinary measurements and I am very impressed with his instrumentation.
I find this area of study very interesting and provides a significant oppurtunity for experimentation and learning.
best regards
Don VE6HQ
thank you for your questions.
my response is as follows:
Was the ocxo also inside the faraday shield? YES
Where the coax cables connecting ocxo and tinyPFA, when outside the shield, double shielded. YES
Where there any coax cables connected to still active clock sources with some meters distance? NO
As you have indicated, thermal effects are a major perturbation onTinyPFA measurements.
I am testing some alternate configurations in an attempt to find a optimum layout and minimize thermal, RF and other environmental effects.
to be clear, the TinyPFA provides extraordinary measurements and I am very impressed with his instrumentation.
I find this area of study very interesting and provides a significant oppurtunity for experimentation and learning.
best regards
Don VE6HQ
Re: some intial observations of TinyPFA noise floor
For absolute best long term performance you should use the side channel feature of the tinyPFA.
See the wiki
See the wiki