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Mode-S: can't be easier!



Hi Folks,
after setting up my portable AO-40 receiving station my feeling
concerning the S-downlink is even better than earlier: it just couldn't
be easier!

The system here describes as follows:
                               approx. cost (USD)
60 cm (2ft) dish               20
G3RUH patch feed               140
DB6NT preamp                   120 
old Mode-S Downconverter       100
 (buyed used in AO-13 times!)  
FT-290 (used)                  220
camera tripod                  10
battery, cables, etc..         20

sum:                           630 USD

ok, this might seem expensive at first look, but remember:
- this is the complete downlink, including receiver!
- you get a very sensitive RX system (DB6NT preamp: 0.6dB NF!)
- some guys spend more money on a FM mobile for their car..

Actually, the 60cm dish with the G3RUH feed and the DB6NT preamp gives
you excellent performance! Thanks to
James,G3RUH/Fred,ON6UG/Michael,DB6NT !

After screwing it all together (the only measuring device I needed was a
multimeter for the power supply/battery!) I calculated AZ/EL and thought
about difficulties setting up 3 parameters: azimuth, elevation and
frequency.. this proved to be wasted time! A coarse setting of direction
is sufficient as the dish has an opening angle of around 13 degrees..
and the signals today from 1138ut to 1200ut (Jan 12th, 2002) were just
booming in. A summary of heard stations:

W5UAQ   Eldon
OK2AQK  Mirek
I7LIT   ?
LZ1JH   ?
F6BKI   Jacques
ON4DY   ?
OE6WMD  Wolfgang
DJ1KM   Reinhard
G3WDG   Charlie
HB9DRD  Jonathan (?)

range: 20000 km, Squint 25 degrees!

After 22 minutes, I got cold and went inside again.. so another system
item will be a heater and some hot coffee (here in Zuerich/HB9 we are
around the freezing point..).

I couldn't judge sun noise and transponder noise (which should be
detectable with this system) because my S-meter was at it's limit (too
much gain in the RX stages.. an attenuator is my next item to build..
easy to do, because 2m IF.

As soon as I can make some digital photos of the system, I am going to
set up a web page demonstrating that Mode-S (even portable!) is not
complicated or even magic..

to-do list:
20dB attenuator for the IF
thermobottle with some coffee
I need some portable TX system.. which could be more difficult to build 
;-)


73s Achim, HB9/DH2VA

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