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R: L-Band Sanity - was "being heard over LEILA siren"



Hi Tony AA2TX,

If you radiate 1.5 kW  EIRP at 1269 MHz the power density in W/square meters
at 60,000 km is the same if you radiate the same 1.5 kW EIRP at 435 MHz

The path loss at 1269 MHz is about 10 dB greater (9.299 dB) only because
the path attenuation is referred to a receiving isotropic antenna wich
capture area A is:

             /  2
           / \
A= -------------           [square meters]
         4 x Pi

At 1269 MHz the isotropic capture area is A1 =0.00444  square meters
At   435 MHz the isotropic capture area is A2 =0.0378   square meters

And so 0.00444/0.0378 = 0.1175 or  -9.299 dB

Radiating 1.5 kW EIRP to collect  the full power concentrated in
1 square meter in 1269 MHz at any distance you need
1/0.00444 = 224.84 isotropic antennas in phase.

Radiating 1.5 kW EIRP to collect the full power concentrated in
1 square meter at 435 MHz at any distance you need
1/0.0378 =26.42 isotropic antennas in phase.

Again 26.42/224.84= 0.1175 or  -9.29 dB

To collect the full power concentrated in 1 square meter at 435 MHz
you need an antenna with isotropic gain G=26.42  or 14.21 dBi

To collect the full power concentrated in 1 square meter at 1269 MHz
you need an antenna with isotropic gain G= 224.84 or  23.51 dB

If the gain of your receiving antennas is 14.21 dBi at 435 MHz and
23.51 dBi at 1269 MHz than you collect the same amount of power
provided the EIRP is the same at 435 MHz and 1269 MHz

And this is the case on AO40 (about)

In conclusion your assumption that radiating 1.5 kW EIRP at 1269 MHz is
like running  150 watt EIRP at 435 MHz is incorrect otherwise my question
is:

Where the -10 dB of losted power is dissipated ? ?

73" de

i8CVS Domenico


----- Original Message -----
From: Anthony Monteiro <aa2tx@comcast.net>
To: Emily Clarke <w0eec@AMSAT.Org>; AMSAT <amsat-bb@AMSAT.Org>
Sent: Friday, August 22, 2003 11:21 PM
Subject: [amsat-bb] L-Band Sanity - was "being heard over LEILA siren"


> Dear Friends,
>
> As suggested by Emily, let's look at some numbers:
>
>
> 1. A 1.8m (6') dish has around 27 dB gain at 1269MHz
>
> 2. Let's assume around 2 dB for the cable loss
>     (i.e. 70' of LMR-600 has about 2.1 dB loss)
>
> 3. A 5 watt transmitter into this antenna system
>     puts out a little over 1.5 kilowatts EIRP.
>
> This might sound like a lot but...
>
> *** the path loss at 1269 is 10dB greater than at 435 MHz ***
>
> So this is like running 150 watts EIRP on U-band which is
> in the right ballpark and is more than 10 dB below the beacon
> at 60,000 Km.
>
> The exact levels will depend upon a number of factors such
> as the actual cable loss, the dish efficiency, the distance
> and squint from AO-40 etc.
>
> Ok, now an opinion; I think you could easily hear this station
> over the LEILA siren since there is no notch. You can often hear
> U-band stations over LEILA as well even with the notch.
>
> Comments are welcome!
>
> 73,
>
> Tony AA2TX
>
> ---
>
>
> At 01:22 PM 8/22/03 -0700, Emily Clarke wrote:
>
>
> >Oh please yes!  :-)
> >
> >Seriously I wouldn't want to have a war break out but a good discussion
> >would be nice.  I just started working on AO-40 and hearing some good
pros
> >and cons would be helpful.
> >
> >73
> >
> >Emily
>
> ----
> Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> Not an AMSAT member? Join now to support the amateur satellite program!
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----
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