[amsat-bb] Re: Azimuth question

Edward Cole kl7uw at acsalaska.net
Sat Jan 9 19:02:16 PST 2010

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
>                 dguimon1 at san.rr.com
>                     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 dubususa at hotmail.com

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