[amsat-bb] Re: Galileo interference on L band
John B. Stephensen
kd6ozh at comcast.net
Wed Sep 20 13:13:28 PDT 2006
The article predicts that there may be limitations on the amateur service.
The biggest problem is sidelobes from the antenna that can be of either
polarization sense. A 16 kW EIRP uplink can easily generate 500 W EIRP
sidelobes (15 dB down) within the Galileo receiver passband and, replicating
the calculations outlined in the article, they can cause interference from
42 km away.
----- Original Message -----
From: "Marc Franco" <lu6dw at yahoo.com>
To: <amsat-bb at amsat.org>
Sent: Wednesday, September 20, 2006 19:03 UTC
Subject: [amsat-bb] Galileo interference on L band
> Galileo is circularly polarized, so using the opposite
> polarization sense will help.
> An excellent paper on Galileo interference was written
> by Peter Blair, G3LTF, a well known moonbounce
> authority and outstanding engineer. The paper can be
> found following this link:
> 73, Marc N2UO
> --- "John B. Stephensen" <kd6ozh at comcast.net> wrote:
>> Unfortunately, the Gaileo downlink covers 1258-1299
>> MHz, the first satellite
>> has been lanched and the satellites in the
>> constellation will be on over the
>> entire world. Our uplink antennas have sidelobes
>> that are 10-20 dB down, so
>> a 1 kW EIRP SSB uplink results in 10-100 W radiated
>> towards terrestrial
>> receivers. A 256 kbps uplink would require 16 kW
>> EIRP and be 0.5-1 MHz wide.
>> P3E has a second L receiver tuned to a null in the
>> Galileo signal (there is
>> only one null in the 1260-1270 MHz band) but no one
>> knows if this will help.
>> SSB users can move to the U uplink if L is a
>> problem. However, this only
>> works for narrowband signals. A wideband uplink
>> won't fit in the null and
>> can't move down in frequency.
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