Re: INMARSAT C-Band Channels

Paul Gulliver

One thing I forgot, and this is just a shot in the dark, it's possible the signal polarity may be different between the series 3 and series 4 birds - try reversing the polarity on the LNB either by voltage or changing the slab orientation in the LNB itself


On 21/03/2020 at 10:08, Paul Gulliver via Groups.Io <paulg1953@...> wrote:
Hi Fred,

Good to hear you are receiving C band data from 4F3,

Unfortunately I don't know of any continuous c-band signals on 3F5 - that would make life too easy, the 2 most active frequencies for me are 1533.81 and 1534.36 both 10500bps burst. There are other frequencies that have 10500bps burst but the data is infrequent so I tend not to bother monitoring them.
The laptop I use is not very powerful, if I try to monitor too many frequencies it tends to crash.

Remember these frequencies are approximate, exact values depending on your LNB oscillator frequency - with temperature drift these frequencies can change up to 30KHz during the day especially if we have a chilly night followed by a warm day - I think my LNB must be particularly bad for temperature drift.

If all else fails, make a small helix along theses lines  and swap it for the LNB and align the dish with L band signals (aero on 1545.0 to 1545.3MHz for 3F5) theses are fairly strong and continuous so it makes alignment easier

Hope this info helps


On 20/03/2020 at 22:00, Fred Albertson <albertso@...> wrote:
Hi Paul,

I wrote a while ago that I was going to put together a C-band system. 
You provided a lot of valuable info that I considered as I developed
my setup.

It took a while, but I'm "on-the-air" with a 120cm Prime Focus dish
and C1W-PLL LNB.

I have no problems getting data from the 4F3 satellite, but I can't find
the signals from the 3F5 bird.

Do you have a solid ACARS downlink frequency from 3F5 that I can search for
as I position the antenna?

Here are some frequencies I have found on the 4F3. All are listed as the translated

1531.125 - 1200 data

1534.975 - 10500 burst - Good ACARS data

1535.200 - 10500 burst

1535.800 to 820 - 1200 burst



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