I remember that you say that your dish was 2 m diameter pointing to 4F1 (so with a weak power similar as the 4AF4 satellite here) and the polarization of 4F1 was LHCP so RHCP at LNBF level.
However, I wonder if you tried to monitor the 4F3 satellite that you might be able to receive, no?
I cannot help but think that you are confusing some of the issues.
Let us take a step back and acknowledge that there are two completely different issues: Inmarsat L-Band AERO transmissions and Inmarsast C-Band transmissions.
I would strongly suggest that for the moment you forget about the C-Band, until you get the L-Band going properly.
· The L-Band does NOT require a dish
· You can use either a helix or a patch
· It would be useful to have an LNA for either the helix or the patch antenna
· The helix or patch needs to be properly polarised. I understand that in your case the
satellite transmits a LHCP (Left Hand Circularly Polarised) signal.
.· If your helix is the RFHam design eshailsat, it is most unlikely to include an LNA, as it is quoted at 300W transmit power. Therefore the question regarding the supply voltage is irrelevant.
· This helix is LHCP, so if you use it in a dish feed it will receive RHCP signals, which is not suitable for the satellite you are trying to receive signals from.
· The patch or helix does not require exact focusing on the satellite, however the more accurate your feed is “focused” on the satellite, the stronger your signal.
· You refer to “Bauds” . Strictly speaking the Baud unit is the number of times a signal in a communications channel changes state. In the case of the Inmarsat AERO transmissions we are dealing with signals in which x-number (e.g. 1200) zeros or ones are transmitted in one second and the correct terminology is bps (Bits Per Second).
· You state that 1500 baud seems to be out of your reach. I presume this is a typo and should read: “10500 baud (bps)”
· I am not sure why you wish to focus on 1200 bps signals On the L-Band most signals are
600bps or 10500bps. Both are easily decoded with a patch and on 4F1 there is only one 1200bps signal.
· Be aware that some channels will lock when you tune to them with Multipsk, but they do not necessarily transmit any ACARS data. Also some may only be “fill in” or “SU Sys Table” transmissions. Once you get the hang of tuning onto the signal you will find a channel that transmits ACRAS data.
· All transmissions on the L-Band are continuous – there are NO burst transmissions.
· For receiving C-Band signals you will need a device which down-converts the 3.6Ghz signals from the satellite to a frequency you receiver can handle (around 1.5GHz). Such a device is called an LNB (Low Noise Block).
· The Titanium C1-PLL Wide-Band LNB is intended for receiving TV signals and it is designed to respond to linearly polarised signals. The LNB can be used for circular polarisation by inserting a dielectric slab in the feed horn, which is usually supplied with the LNB. The polarisation is selected by changing the LNB feed voltage - 11.5 – 14V for Vertical or RHCP and 16 – 20V for Horizontal or LHCP.
· You will need a bias-tee to provide that voltage. I believe Mr. Gulliver has advised that your satellite is LHCP, so you will need to power the LNB with 18V
· Make sure you turn OFF the bias voltage supply in your radio (Funcube), as it may damage your SDR. Bothe the Funcube and the DVB T DAB FM TCXO dongle are perfect for receiving signals between 1.5 - 1.7 GHz.
· You can use the “splitter” provided in a satellite receiver to supply the correct LNB voltage. I do not know how much these satellite receivers cost, but if you do not have one you can either construct your own, if you have the facilities or you can buy a bias-tee on ebay for a few dollars. https://www.ebay.com/sch/i.html?_from=R40&_nkw=bias-tee&_sacat=0&rt=nc&LH_FS=1 If you buy a bias-tee you will still need a DC power supply to supply the required 18V.
· It DOES NOT MAKE SENSE to use an LNA between the receiver and LNB. All active devices generate unwanted noise and unless your coax feed cable >30 meters an additional LNA will probably do more harm than good, as it may overload the SDR input.
. The Titanium LNB has an output impedance of 75 Ohms, whereas the input impedance of the Funcube is 50 Ohms. I recommend that you use 75 Ohm low loss satellite cable right to the receiver. (the input impedance of the "dongle" is 75 Ohms).
· On the C-Band I suggest you start with decoding 10500 bps burst signals first, as they are easiest to decode. The 1200bps burst are a bit more tricky, because they are generally weaker and require more accurate tuning. Use a band-width od 15kHz on youe SDR for 1 0500bps burst signals and 3kHz for 1200bps burst channels.
The At 04:28 AM 17/12/2018, you wrote:
May I again ask for your advice, please ?
I wish to receive mainly 1200 Baud data - 1500 Baud seems to be out of my reach here in Germany as I lack the space for putting up the seemingly required 1.1 m to 1.8 m ? dish.
I am mainly interested in "catching" far-out aircraft position reports.- I already use VDL with its limited range.
My RX is the Funcube prof. plus dongle. Length of my coax cable abt. 15m. I plan to use also my existing 80cm dish either with the Dutch Helix or with the C1W pll C-band LNBF.
I have both - the RFhamdesign LHCP Helix dish feed tuned to 1545-1546 MHz
as well as the Titanium C1W-PLL Wideband C-band LNBF which requires a DC-voltage of 11 - 20 Vdc.
Unfortunately I do not know yet which voltage is required by the Dutch LHCP Helix dish feed, but I guess ist 11-20 Vdc as well ?
As my Funcube has an inbuilt Bias Tee turning out I think 5V only, I guess that this voltage is too weak meaning for me another piece of equipment,
namely a separate Bias T delivering a DC-voltage of between 11 to 20 Vdc. Is my assumption correct ?
If so - please advise which suitable Bias Tee YOU use - plus the name and email address of its supplier/s. An "economical" version would do for me
as I have already spent more than enough towards one day receiving AERO data.
I definitely would like to stick to my Funcube - as an alternative SDR I also have a DVB T DAB FM TCXO dongle.
In plain words - using the Funcube with its inbuilt Bias Tee de-activated, linking it to a suitable external DC-voltage source, ie a suitable Bias T
which injects the necessary 11-20Vdc voltage into my coax cable.
I should be most grateful for your kind suggestions.Thanks in advance,