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R: Recommended ERPs ?



Hallo Richard,

Following a report  received from  Rene', DJ1KM using his panoramic receiver
on day December 12/01 with AO40 at very low squint angle for me about
3 to 4 degrees,i was 3 dB above the beacon using my 23 cm uplink.

My power was about 40 W in to a 4 x 23 elements yagi horizontally polarized
array.

Since the gain of this array is about 23 dBi = 200 time in power,my EIRP
at that time was 40 x 200 = 8000 W

If i liked to stay 10 dB belove the beacon at that time i had to reduce my
power by 13 dB or  20 time and so 40/20= 2 W

2 W in to my 23 dBi gain antenna make 2 x 200 = 400 W EIRP and this power
match very well with the nominal EIRP required for the L/S operation.

If the squint angle is very high like it is now days around 25 degrees or
more for me,the above 8000 W EIRP has not the capability to override the
beacon level by 3 dB but my signal is more than 10 dB belove the beacon
level.

Unfortunately,using 23 cm uplink it is very easy to override the beacon
because LEILA do not operate with the same level for uplink signals as in
the U band 435 MHz

In conclusion,the necessary EIRP using 23 cm uplink  changes from 400 W EIRP
...........and up depending on satellite Squint angle and Range

About the necessary EIRP using 70 cm uplink my antennas are 2 x 21 elements
yagi horizontally polarized and the gain is about 20 dBi or 100 time in
power.

When the Squint angle is very low,in the same order of 2 to 3 degrees,my
power must be 50  W or less at the antennas in order do not disturbe LEILA

In any case,when the Squint angle is around 25 to 30 degrees like it is at
some MA now days,i must use 300 W at the antennas or 3000 W EIRP to
be barely audible in to the S passband with a very havy QSB

Even in this conditions it is possible to get LEILA using 70 cm because the
uplink signal is very strong in to the U band satellite receiver input but
it is very weak in to the S dowlink receiver on the ground because of the
AO40 very high off-point.

I hope this help.

73 de i8CVS Domenico


----- Original Message -----
From: Reinhard Richter <dj1km@dj1km.de>
To: (Richard W L Limebear) <Richard@g3rwl.demon.co.uk>
Cc: <amsat-bb@AMSAT.Org>
Sent: Saturday, January 05, 2002 9:34 PM
Subject: Re: [amsat-bb] Recommended ERPs ?


> Hallo Richard,
>
> Saturday, January 05, 2002, 3:48:03 PM, you wrote:
>
> RWLL> Has anyone yet defined just how much power (ERP) it takes for
satisfactory
> RWLL> comms via AO 40 yet ?  Both on 70cm (until LEILA takes an interest)
and on
> RWLL> 23cm (to achieve a signal 10db below the strength of the beacon).
>
> I think it's not defined, but when talking with people I learned that with
> 2 kW ERP on mode L you're on the safe side, while on U-uplink 500 W ERP is
> more than sufficient. I think, that Domenico, I8CVS will know that much
> better.
>
> 73,
>  Reinhard
>  DJ1KM
>
> ----
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