Nice observations there, John. I too have noticed frequency drift of a similar magnitude to what you describe below. Just about every time I work a VO-52 pass I need to reset the frequency calibration on SatPC32 up or down a few hundred Hz.
One thing I thought was interesting from last night's overhead pass (3/27/2012 around 0320z) was that close to mid-pass, there seemed to suddenly be a very large amount of noise (almost sounding like hash from a microwave oven) coming through the passband. At the time, I was the only station on the sat, calling CQ with my 0.5 watts, and a very nice quiet clean downlink. When the noise came, it virtually drowned out my input signal, even going up to 5 watts. The noise lasted about 30 seconds and then faded out -- it seemed to occupy most of the passband. After the noise dissipated, I was surprised that I had to reset my SatPC32 calibration by about 200 Hz. I found this really interesting, the seeming coincidence between the noise and the frequency offset changing rather suddenly during a pass. The graphical plot of the sat path showed it starting the pass just barely touching the sun line, and ending with the footprint a good ways in -- maybe as the satellite entered more sun exposure its temp increased, causing the freq shift and possibly a bit of oscillation causing the noise?? Could just have been me, of course, but it would be interesting if anyone else has noticed these things.
Dave KB5WIA
On Tue, Mar 27, 2012 at 8:41 AM, John Papay [email protected] wrote:
There were three passes of VO-52 here this morning, 27March2012. I was able to copy the beacon on all three passes. Here are the results: 1200utc 145862.6 1335utc 145861.7 1510utc 145861.9
The frequencies are not exact. My CW offset is 850Hz. There is significant frequency drift and temperature is probably the cause. It would be interesting to hear from the control team regarding this.
HO-68 provides an excellent check of your doppler compensation in your tracking program. I find that the beacon is always very strong and the frequency is rock solid. You can save the frequency in your program and a month later find that it is right where it was the month before. If you can listen to the beacon with your CW filter on throughout the entire pass, you have everything set right, keps, computer clock etc. The doppler gets quite severe on a high pass and is a great way to make sure you have everything set right. Since HO-68 is on UHF, everything becomes more critical.
73, John K8YSE