Re: [amsat-bb] Maximum squint for AO-40 to be usable

[Scott Townley <nx7u@xxxxxxxx>]

At 07:25 2003-09-13, Keith N6ORS wrote:
<snip>
 >uplink power. Depending on the orbit the sqnt may not be rising as
 >fast as the range is falling and this can permit you to use the
 >sat at high sqnts quite easily, it is also what makes the sat
 >useable to very low powers at low squints.

This is why I wrote my little standalone link budget calculator...it's very 
tedious to calculate single points in the orbit to determine their utility, 
so I do it all at once using the listing utility in Nova for Windows.  The 
output looks like this, for example:
   AO-40 position on Sunday, 14 September, 2003 (Local)  from 
NX7U 

time       az      elev    rng(kkm)sq      mode    MA      UpSNR PTx(W)
07:30:00    247     31     56.4     16.9   UL       84     8.8   20.0
07:40:00    248.5   29.6   57.1     16.2   UL       87     8.9   20.0
07:50:00    249.9   28.2   57.7     15.6   UL       89     8.9   20.0
08:00:00    251.4   26.8   58.3     15     UL       91     8.9   19.8
08:10:00    252.8   25.4   58.9     14.4   UL       93     8.9   19.5
08:20:00    254.2   23.9   59.4     13.8   UL       96     8.8   19.2
08:30:00    255.5   22.4   60.0     13.2   UL       98     8.8   18.9
08:40:00    256.8   20.9   60.5     12.6   UL       100    8.8   18.6

So we have increasing range and decreasing squint for example...but the 
overall conditions actually improve...that noted by the decrease in 
transmit power required (the far right column).  The inputs to the program 
include capping to your maximum transmit power (in this case, it was 
20W).  The overall link is capped at the "Leila detection level" as well.

The program makes it easy to stay in bed when I see this:
  AO-40 position on Thursday, 18 September, 2003 (Local)  from 
NX7U 

time       az      elev    rng(kkm)sq      mode    MA      UpSNR PTx(W)
03:10:00    198.1   48.5   31.9     39.6   UL       32     1.6   20.0
03:20:00    199.5   48.9   33.4     37.8   UL       35     2.8   20.0
03:30:00    201.2   49.1   34.8     36.2   UL       37     3.7   20.0

Those aren't too useful SNRs...




Scott Townley NX7U
Gilbert, AZ  DM43di
http://members.cox.net/nx7u

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