Re: [softrock40] My Si570 is 4,6 kHz wrong
- On Fri, Mar 13, 2009 at 9:40 PM, petergouweleeuw <peter@...> wrote:
Hi group members.
Today I have finished my local oscillator part of the Lite V9.0 kit.
While performing the tests I saw that the frequency was 4,6 kHz wrong.
I have full control of the Si570 with Rocky.
I had to enter 7050600 Hz to get 28.184 MHz output.
I am new to this and I wonder if this is something to worry about.
The frequency is tested with the help of my spectrum analyser a Tektronix 2710 with precision build in counter. The level seems to be right too.
I would like to get some advise.
I couldn't find any advise about this on the terrific WB5RVZ pages.
73, Peter PA2VPeter,There is an external calibration tool that writes calibration values into EEPROM of the AVR:1. Start USB_SYNTH application,2. Reset the AVR (power-off, power-on). Make sure green LED appears.This will set si570 with default register values, required for calculating the internal crystal freq.Do not change frequency in meantime as it overwrites the default register values.3. In setup menu, press calibrate button. Check, if calibration succeeds by looking at status line.Now the si570 is calibrated against the factory setting, for more accuracy optionally you maypress tune up/down buttons to calibrate the si570 output to an external frequency standard.According this method, I am able to calibrate si570 within a few Hz (nice for e.g. QRSS).PowerSDR toghether in combation with a SDR1USB.DLL use the very accurate frequency calculationin the firmware. Be aware that for some other solutions might also introduce small frequency calculationerrors.73 GuidoPE1NNZ