Dave, If you are technically correct or give a rough answer you get nit picked form on side or the other. Near by magnetic objects can cause serious errors using the Sun or Moon for alignment solves all problems for both azimuth and elevation. For near DC 70cm and longer wavelengths a pointing error of less than 10 degrees is insignificant. 13cm and shorter accuracy becomes more important. Art
-----Original Message----- From: Edward Cole [mailto:[email protected]] Sent: Saturday, January 09, 2010 7:02 PM To: Dave Guimont; [email protected] Cc: [email protected] Subject: Re: [amsat-bb] Re: Azimuth question
At 04:11 PM 1/9/2010, Dave Guimont wrote:
Dave, A fraction of a degree per year, and at least once in the history of the Earth the North and South magnetic poles reversed.
Art
Yes, I'm aware of that, it also rotates about 1° about true north, the earth wobbles a bit to change the AZ, but how many ham antennas in the world need that accuracy?
And I doubt that the average ham can orient within more than 2° by eyeball!
73, Dave, WB6LLO [email protected] Disagree: I learn.... Pulling for P3E...
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For 144 & 432 that is probably adequate. On 2400 the beamwidth of my 33-inch dish is 10.6 deg. (24.9 dBi) so keeping a signal within 1dB, probably requires 3 deg beamwidth and knowing true north with an accuracy of 10% of that results in 0.3 deg accuracy.
Of course if you are doing something like eme on 1296 with a 16-foot dish the beamwidth is 3.38 deg. (34.9 dBi). For eme it is desirable to track within 1db of maximum gain which may is something like 1-deg. and 10% accuracy is 0.1 deg. How would you set up a dish azimuth so that it is that accurate to true north? For eme it usually requires comparison with tracking sw for location of the Sun or Moon. At these freq. and dish sizes one can detect solar and lunar noise to peak onto, then adjust az and el calib. to match tracking sw az and el.
As it turns out my dish digital az-el readout has 0.1 deg. resolution so that is best I can read. On the Yaesu B5400, one is lucky to determine direction within 7.5 deg. for azimuth and 3.75 deg. for elevation. Manually tracking AO-40 with the B5400 was very touchy, as fine adjustment is near impossible. But I did refine my azimuth positioning using solar noise on 2400.
For 144 or 432 probably the most accurate method for calib of azimuth is using a repeater many miles away (knowing both its Lat-Lon and your Lat-Lon with bearing sw that produces a great-circle bearing).
73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com 500-KHz/CW, 144-MHz EME, 1296-MHz EME DUBUS Magazine USA Rep [email protected] ======================================
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