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Re: Expected noise results with Drake converter (no satellite.)




A semi-simple method is to use the fact that at the input to your RX, the
total noise power (with a matched input impedance presented to the
LNA/Converter/whatever input) will be
Pn=(FG+Frx)kTB
Where
	F and G are from all things in front of the receiver--preamps, converters,
coax loss
	Frx is the NF of the receiver itself
	kTB=-174dBm/Hz at room temperature
So it's apparent that if FG>>Frx you should hear something when you "Flip
The Switch", even with no signal source.

It is important to note the "Matched Input Impedance" part above--the LNA
or converter needs to either be connected to a good (50 ohm) antenna or a
50 ohm termination/dummy load.


At 04:52 PM 5/19/01 -0400, Al Lawler wrote:
>
>  Configuration:
>
>  Ft736r -> 25' rg6 -> Drake(With "easy mods" -> 24dbi bbq antenna
>(and no satellite in view)
>
>
>   What should I expect to hear with the above configuration
>when I power up the converter?  
>
>I'm not attempting to recieve any  satellites yet, 
>and understand the importance of a preamp when I do, 
>but for the purposes of debugging what I have built so 
>far,  should I expect to hear a change in the
>"white noise" on the 2m reciever (tuned to 144.050 or so)
>when I power up the converter?  Are there any "birdies"
>generated by the converter which I might be able to 
>tune to to verify whether the converter is working or not?
>
>
>  Thanks,
>
>  -al
>----
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>To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>
------------
Scott Townley		
nx7u@arrl.net
Gilbert, AZ  DM43
     
HF/VHF/UHF/Satellite MOBILE station
http://www.primenet.com/~nx7u

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