My dongles drift about 8ppm from cold start to warm up after around 40 minutes.
And converter will drift also.
Kalibrate, or kal, can scan for GSM base stations in a given frequency band and can use those GSM base stations to calculate the local oscillator frequency offset.
Download it from here:
See the list of options below.
(I have the ‘Kalibrate’ files on my D: drive in the folder named ‘Kalibrate’)
(The commands below are what are in my shortcuts. If you want to run from a DOS window, just enter everything after the ‘C:\Windows\System32\cmd.exe /k’)
Use this command to find a GSM850 signal in your area.
C:\Windows\System32\cmd.exe /k “D:\Kalibrate\kal.exe” -g 42 -e 22 -s 850
Then, once you have identified a GSM signal in your area, run calibrate using the command below.
C:\Windows\System32\cmd.exe /k “D:\Kalibrate\kal.exe” -e 41 -c 234 -v
For the above command:
GSM Channel 234 (-c 234)
-e is roughly the error rate expected. ’41’ in this case. (not real critical) (-e 41)
That will give you the:
‘Frequency correction (ppm)
Where options are:
-s band to scan (GSM850, GSM900, EGSM, DCS, PCS)
-f frequency of nearby GSM base station
-c channel of nearby GSM base station
-b band indicator (GSM850, GSM900, EGSM, DCS, PCS)
-R side A (0) or B (1), defaults to B
-A antenna TX/RX (0) or RX2 (1), defaults to RX2
-g gain as % of range, defaults to 45%
-F FPGA master clock frequency, defaults to 52MHz
-D enable debug messages
Then, if you are using a converter, you need to set ‘Shift’ or ‘Offset’ for it.
I don’t use a converter so I can’t help with that part.
If you have ‘Snap to grid’ selected, SDRSharp will land on an exact multiple of your selected step size.
Using channel 136, the ‘Frequency correction offset’ rounds up to 38ppm. (SDRSharp accepts whole numbers only)
Source : Extracted from forums.radioreference.com
Lots of readers are into toying around with RF and ham radios. One thing that is always of concern is tuning the antenna. New equipment is never cheap, so whenever another option comes along that uses existing test gear it gets our attention. [Alan Wolke] aka [w2aew] covers a process he uses to tune his HF antenna using a signal generator and oscilloscope.
The process is more of a teaching aid than a practical replacement for commercial equipment mostly because proper signal generators and oscilloscopes are large items and sometimes not available or affordable. That said, if you do have such test gear you only need build a simple breakout board containing a form of wheatstone bridge where the unknown Rx is the antenna. Two oscilloscope probes are connected across the bridge balance nodes. Some special care needs to be taken matching probe cable length and 50 ohm input impedance to the oscilloscope. A couple of 1K probe coupling resistors are also needed to prevent affecting the impendence at the hookup points. Once the selected signal is injected you can adjust an antenna tuner until the two voltage waveforms match on the oscilloscope indicating your antenna network is tuned to 50 ohm impedance with no reactance.
Being able to tune your antenna visually can really help you understand what is going on in the turning process; matching not only input impedance but also phase shift indicating inductive or capacitive reactance. Join us after the break to see the video and for information on what’s presented in the second part of [Alan’s] presentation.
The lesson ends at 8:50 but continues ten seconds later with a part 2 presentation “Estimating the complex impedance of the antenna”.
Via : hackaday.com