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# Re: Communication thru P5-A

```Chris,

There was discussion about this a couple weeks back.  I wonder if you
remember what the paramters are for P5A?  What freq. will be used to link
with earth, transmitter power, antenna (gain).

With those facts we could calculate expected signal levels (i.e. path
loss).  I need to look up the distance of Mars, but to memory it is roughly
twice as far from the Sun, so would be on the order of 100 Million miles at
closest approach (which only occurs about every two years).

I have a spreadsheet that calculates the path-link for eme and it is around
280 dB path loss at 2400!
The formula of simple path loss is
L = 32.4 + 20Log(Freq. in MHz) + 20Log(Distance in km)
Lmars(min) = 32.4 + 20Log(2400) + 20Log(160,000,000)
Lmars(min) = 32.4 + 67.6 + 164
Lmars(min) = 264 dB

so that looks like a 16 dB stronger signal!

Now at 2304 eme stations run around 100w and a ten-foot (36 dBi) or larger
dish!  EiRP = 400,000w
How does this compare with the ERP of P5A?
Lets say 10w and 20 dBi; EiRP = 1,000w

That is 1/400 the signal (-26 dB!)....hmmm 10 dB bigger dish than ten-foot

Of course I'm going on assumptions, what are the real parameters?  Anyone?

Ed, AL7EB

At 11:10 PM 8/25/2002 -0400, CLVANCIL@aol.com wrote:
>Hi Everyone,
>
>At the Mars Society Convention Gary Synder (N7QAM) made a presentation on
EME
>as an analog for Deep Space Communication.  He said that moonbounce
>communications is about ten times as difficult as Communications with a
>spacecraft at Mars.  If this is true then anyone doing EME communication
>should be able to do P5-A communication.
>
>--Chris Vancil
>----
>Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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>

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