|
Stability in 1 x 10x |
Stability in ppm |
Stability in % |
Stability @ fc = 10 MHz |
Stability @ fc = 100MHz |
Stability @ fc = 1GHz |
Stability @ fc = 10GHz |
|
1 x 10-2 |
10000 |
1 |
100 KHz |
1000 KHz |
10 MHz |
100 MHz |
|
1 x 10-3 |
1000 |
0.1 |
10 KHz |
100 KHz |
1 MHz |
10 MHz |
|
1 x 10-4 |
100 |
0.01 |
1 KHz |
10 KHz |
100 KHz |
1000 KHz |
|
1 x 10-5 |
10 |
0.001 |
100 Hz |
1 KHz |
10 KHz |
100 KHz |
|
1 x 10-6 |
1 |
0.0001 |
10 Hz |
100 Hz |
1 KHz |
10 KHz |
|
1 x 10-7 |
0.1 |
0.00001 |
1 Hz |
10 Hz |
100 Hz |
1 KHz |
|
1 x 10-8 |
0.01 |
0.000001 |
0.1 Hz |
1 Hz |
10 Hz |
100 Hz |
|
1 x 10-9 |
0.001 |
0.0000001 |
0.01 Hz |
0.1 Hz |
1 Hz |
10 Hz |
|
1 x 10-10 |
0.0001 |
0.00000001 |
0.001 Hz |
0.01 Hz |
0.1 Hz |
1 Hz |
|
1 x 10-11 |
0.00001 |
0.000000001 |
0.0001 Hz |
0.001 Hz |
0.01 Hz |
.1 Hz |
|
1 x 10-12 |
0.000001 |
0.0000000001 |
0.00001 Hz |
0.0001 Hz |
0.001 Hz |
.01 Hz |
|
1 x 10-5 |
RED = TAPR Supplied Epson 10 Mhz XTAL Stability
The 10 MHz crystal supplied with the TAPR kit should be an Epson CA-301 Type (DK SE3420). The Epson crystal data from the Data Sheet is ± 30ppm or a ± 300 hz at the 10MHZ frequency used in the DSP-10. With careful setting of variable cap C110 it is possible you can achieve 1 x 10-6 for short periods of time. But due to temperature variations and other component instability it can't hold that for long periods of time.
Click here for a Data Sheet (Epson CA-301 spec. pdf)
There is information about how Bob W7PUA selected the Epson crystal on his DSP-10 web pages. Look way down the page under 10 MHZ CRYSTAL. This crystal is provided to make short term portable operation possible, but the DSP-10 needs a extremely STABLE 10MHz source to operate successfully in long term weak signal modes.
|
1 x 10-7 |
This is the long time accuracy of the HP 10811 on a yearly basis.
|
1 x 10-9 |
Mode = 3
BLUE = The Shera controller in Mode = 3, the the random variation in frequency is a few parts in 10^10 (10 to the tenth power).
In a Quote from Bob W7PUA, "This is better than the phase modulation on most interesting propagation paths and so frequency stability will not be the limiting factor in weak-signal communication. Using Shera Controller in Mode = 3 provides the minimum stability for needed PUA43 and other high frequency stability modes. Use whatever you can get a hold of, but holding your frequency to a part in 1 x 10-9 or better, really enhances the weak-signal capabilities. It also allows you to see a lot about propagation paths to see what is happening."
|
1 x 10-10 |
Mode = 4
MAGENTA = Where W7CQ Frequency Standard is in terms of stability with Shera board in Mode = 4 and the HP 10811A. My unit will operate stable in Mode = 4 for months at a time.
|
1 x 10-11 |
Mode = 5 (It is just fun to be real accurate)
For short periods of time in Mode = 5 which get you into the area of 1 x 10-11, Nice to be here, but not necessary for maximum use of the DSP=10. (It is just fun to be real accurate)
MODES of the Brooks Shera GPS Frequency Standard
Each time you increase your MODE = X by one unit you double your accuracy by increasing the time averaging by two. ( after you leave Mode = 1)
Mode = 1 30 second time averaging
Mode = 2 1500 second time averaging = 25 minutes
Mode = 3 3000 second time averaging = 50 minutes
Mode = 4 6000 second time averaging = 100 minutes = 1 2/3 hours
Mode = 5 12000 second time averaging = 200 minutes = 3 1/3 hours
Mode = 6 24000 second time averaging = 400 minutes = 6 2/3 hours
Mode = 7 48000 second time averaging = 800 minutes = 13 1/3 hours (over half a day)
Quote from Bob Larkin on the Shera Controller:
"Note that when you use the Shera controller, your frequency will, on the average, be exact (the same as NIST). The Frequency errors are both plus and minus from this "correct" value. This is what "phase lock" does for you.
I like the GPS-locked oscillator as it is self checking. A Rb oscillator is very adequate for weak signal use, but if something goes wrong and there is an error, it doesn't tell you about it. You still need the external checking capability to be sure (GPS, WWVB, LORAN-C).
Use whatever you can get a hold of, but holding your frequency to a part in 10^9, or better really enhances the weak-signal capabilities. It also allows you to see a lot about propagation paths to see what is happening."