Re: Reception of C band - Problem #aero

Paul Gulliver
 

Hi Patrick,

Just re-reading your original post, did you align your dish with your L band antenna, this is what I do, I fix my L band helix in place of the LNB and carry out basic alignment and then put the LNB back in place.
I usually have to tweak the alignment to maximise the C-band signal. I take my receiving laptop outside and have it next to my dish and watch the signal strength as I tweaking.

Regarding precision, yes with a 1.1m dish the signal is weak at best so you do have to be accurate, I find just 2 or 3 degrees off can make a big difference - I also notice on my off set dish, the indicator scale on the dish has no relation to reality, it's showing around 30  deg elevation when it's actually pointing around 10 degrees - by looks alone the dish appears to be pointing into the ground but this is a feature of being "off set".

I can't help you with the testing of the LNB but the increase in noise level when you apply power must be a good sign, I get the same effect

Hope you have better luck today, as I write this I have around 50 aircraft showing on my Plane Plotter map - all from my own data.

Cheers

Paul


On 26/12/2018 at 21:50, Patrick Lindecker <f6cte@...> wrote:

Hello Paul,

 

TKS for the advice.

Yes I tried to reverse polarity, but there was no effect ( I tried also to remove the dielectric without any effect).

 

I tried this afternoon. But I received the L band transmissions so I suppose that I could have received the C band.

 

I wonder if my LNB works. But it is difficult to test it because 3.6 GHz sources are rare.

 

>as you have the dish aligned correctly.

I have a compass for azimuth and a setting at about 10 ° of elevation is not a big problem (there is a raw indicator of the dish). My alignment was perhaps at +/-5 ° maximum, in azimuth and elevation, but I don’t think it needs to be extremely precise (in general I get a first signal and then try to adjust elevation and azimuth so to have the maximum signal). But here I had no signal at all.

 

73

Patrick

 

De : multipsk@groups.io [mailto:multipsk@groups.io] De la part de Paul Gulliver
Envoyé : mercredi 26 décembre 2018 21:57
À : multipsk@groups.io
Objet : Re: [multipsk] Reception of C band - Problem #AERO

 

Hi Patrick,

 I've been receiving 3F5 all day so I can confirm there is no problem with the satellite.

Have you tried reversing the polarity, applying 12 volts instead of 18. I notice if the dielectric is in the wrong slots within the lnb this has the same effect as changing the voltage. Ie reversing the polarity. 

 I can't think of anything else that could cause the problem as you have the dish aligned correctly.

What time of day did you try? I always find the strongest signal is when the satellite is above the equator, at the moment between 06.00 and 12.00 gmt 

 

Cheers

 

Paul

 

On Wed, 26 Dec 2018, 17:05 Patrick Lindecker <f6cte@... wrote:

Hello to all,

 

Today, I tried to receive C band from 3F5, with a 1.1 m diameter dish, applying the diagram (for a possible “Easy” document), below.

I received absolutely no signal on the expected C band frequencies (tested with SDR# and Multipsk). I checked that I could receive L band signals from this satellite (with the same RTL/SDR receiver, a LNA and a patch antenna) and this works well.

I checked the voltage on the LNBF which was correct (about 18 V but it’s true that I did not checked the quality of the filtering). If you have ideas of possible causes of problem, don’t hesitate.

 

Note: when I switched on the LNBF with the 18 V, the level on the SDR# waterfall increases of about 10 dB (which is reassuring).

 

73

Patrick

 

 

 


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