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RE: antenna for low elevation vs. high elevation



Hmm...

So at 60.675N lattitude I should just throw all my satellite equipment into
the dumpster, right?  Well, I checked the next AO-40 pass and I get a max
elevation of 29 degrees a little after perigee [2.5 hour pass].  Track
AO-40 at apogee...forget it.  At the current inclination I'll never see the
bird at apogee.

So I can only hope that a more favorable antenna orientation will be
obtained thru magnetorquing, so that perigee passes are accessible.  Looks
like big antennas for the arctic!  That 8-foot dish may be needed afterall.
 Maybe I can borrow Jodrell Bank!  ;-)

Ed

>From: Tony Langdon <tlangdon@atctraining.com.au>
>Hmm, just reading through the posts here.  I'm not disputing potential
>problems at low elevations, but questioning some of the assumptions...
>
>I'm at 37 degrees S, so it's not a dissimilar position to the station at
>42N, as far as the current AO-40 orbit goes.
>
>Tony Langdon. 
>Systems Development and Support. 
>ATC Training Australasia.  Level 2 321 Exhibition St Melbourne  3000. 
>Phone:  1300 13 1983     WWW:  http://www.atctraining.com.au 
>
>> Using a 54 inch dish and 3.5 turn helix did not in my memory 
>> cause close
>> to the horizon problems .   Again it was AO-13.    Arsene 
>> QSO's were all
>> higher elevation and in country.   In fact I know of no EU  
>> QSO's being
>> made on that bird by anybody.  
>
>If it's ionospheric in cause, I suspect it's more likely to affect the lower
>frequencies (but don't quote me on this :) ).
>
>> =========================
>> On Thu, 15 Mar 2001 11:14:44 -0600 Estes Wayne-W10191
>> <W10191@motorola.com> writes:
>> > Jon Ogden wrote:
>> > 
>> > You get the CP and on S-band when AO-40 is 3 axis stabilized, you 
>> > probably won't need to shift the polarization sense.  Sure, perhaps 
>> > it could happen if you are close to the horizon, but will the 
>> > microwave bands really work there anyhow?
>> > 
>> > Wayne replies:
>> > 
>> > I'm curious what elevation you mean by "close to the horizon".
>> > 
>> > Whatever S-band antenna I use (I'm going to try linear polarization 
>> > first), I NEED it to work at low elevations.  At my 
>> latitude of 42.2 
>> > degrees North, AO40 will be below 20 degrees most of the time, and 
>> > will always be close to the horizon for the interesting DX 
>> windows.  
>
>Hmm, I have done numerous predictions of both the planned and current AO-40
>orbits.  The planned orbit, with its high inclination managed to peak around
>20 degrees elevation on good DX passes (though perigee passes at high
>elevation would have been a regular occurance, but with our isolation, it's
>hard to get outside the VK/ZL area at perigee).  The current orbit fares
>much better on this side of the world.  The highest elevation I have seen is
>48 degrees, and AO-40 spends a fair bit of its visible time above 30
>degrees.
>
>For the record, I'm at 37.83 S, almost the "mirror image" of the 42N
>position mentioned above.  Not sure how much difference the 4 1/2 degrees or
>so makes, but suspect there's still a lot of good pass opportunities going
>up there.
>
>Well, we'll see how the bird goes in due course. :)
>
>Now I'll have to put up some antennas, hopefully a 50-60cm dish (with a CP
>feed) on 2.4 GHz and a helix on 1.2.  Might investigate the possibility of
>setting up for U/S as an interim measure, while I get the 1.2 GHz uplink
>sorted out.  With our peso, oops, dollar the way it is these days, the power
>amp for 1.2 GHz is going to be an expensive proposition, and will take time
>to get it all running.  The satellite gear will also share a lot with my new
>ATV station, which is hitching an opportunistic ride to operational status,
>so even if AO-40 got trashed by a bit of space junk, there will be some good
>returns on my investment in time and hardware. :)
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