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Re: minimum setup for AO51 receiving



kf4fsw asks:
>does anybody know which are minimum requirements to receive AO51
>on different bands?  Satellite power on 70cm is 1 to 6 watt then 
>probably a quarter wave long vertical antenna is enough.

I've successfully received a *few* packets from AO-51 using a 
nineteen inch whip directly connected (no coax cable) to a 
DownEast Microwave 435-preamp feeding an old Pro-38 scanner.  

The preamp/whip sits on the center of the roof of my car 
(the roof acts as a groundplane).  I have tapped off 
the Pro-38 discriminator and it feeds a DSP soundcard 
modem that I'm writing.  

This is not a great receive setup. You would receive more packets 
with a directional setup, but I will get *some* packets with this on 
the higher elevation passes (over thirty degrees max elevation) 
even when the satellite is transmitting under a watt.

Remember, it's a SYSTEM.  Everything works together and
acts together.  It depends on the power output from the
spacecraft, the distance to the spacecraft at that time, 
the noise figure of your preamp, the gain from your antenna, 
receiver noise and gain, the performance of your modem, 
and other factors.  

Start with a good enough antenna and low noise preamp 
and you'll have more room for some compromises later in 
the receive chain.  But, if you start with a poor antenna 
and no preamp at all then and you'll never make up for 
their signal "losses" further down the receive chain. 

Douglas KA2UPW
Satellite/QRP/Mobile <--- all at the same time!
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