C band LNB on Fibo 120?

[Captain Jack]

Bloody hell! As most European C band sats are circular, why are there no ready-made circular C band LNBs? Seems very odd.... is there a reason why C band uses circular vs linear polarity?

 

[doktorofsat]

Captain 1st of all you should know that russians ,africans and arabs usually works with circular (L/R) polarizations .asians and americans with linear (H/V) polar.


2nd : the dielectric plate made the separation f the polarities , this is da reason why is so important to have a good plate.There is NO PLATE what works fine for all da 3.6-4.2GHz!!!Don't bother , this is da "funny" sidethe plates works fine on certain freq. .My plate works fine for 3.6-3.9GHz ,but there are other plate for the 4-4.2GHz or 3.7-4GHz .There is a cross sign design plate for the upper freq 4-4,2GHz that I test right now ,and others in testing .

 

[Captain Jack]

Thanks DOS. I didn't realise that there's a difference between plate designs depending on a frequency range.

 

[Trust]

agree 100% Rima

Trust1 try the dielectric plate that i presented a few years ago here on the board

My goal is to receive circ and lin polarisation without chancing the dielectric plate .
Its already working on 5º west (circ.) and 3ºEast (lin.)
Next thing to do : drill a hole in the back of the lnb and put a Black Ultra Ku lnb behind .
See what happens

 

[Captain Jack]

I received the (massive) scalar ring today and I am thinking of trying the LNB on my ... Penta.. just for kicks. Are the C band signals from 5W and 3E the strongest ones around? Won't be at my parents' till Sunday so won't be able to play with the Fibo until then. And even that depends on the weather.

 

[aceb]

I think most of us cut our teeth on 5W but either one is pretty strong. I used 5W as it was easy to confirm on Ku. I'll take some relative signal strengths later and let you know which is the strongest transponder.

 

[Trust]

Arabsat 20 E is also very strong , receive 35 channels from there .

 

[Captain Jack]

Thanks both! Looking forward to testing it out.

 

[Captain Jack]

Welp, got the LNB on the Penta but not received anything yet. I stuck a depolariser plate inside, that came with it for circular stuff but can someone let me have the strongest transponders please? Also would prefer linear ones on 3E...if they are strong enough.

 

[Trust]

TP 3764H is the strongest here . try without the plate .
At circ. TP's the most succesfull place for the plate , for me , was just in the frontside of the lnb .
On the back of the lnb is a mark "0" . I noticed that at some brands this mark must be at 9 O'clock and other brands at 6 O'clock

 

[aceb]

I've still got my plate in but on 3e the strongest signal I get is 3920H at -23dBm. On 5w it's 4153R.

 

[Captain Jack]

Whoohoo! Got it! Blind scanned it - looks like I need to rotate my dish 90 degrees, like you say. So there you go, 85cm Penta is enough for C band!

 

[Trust]

Congratulations !!!

 

[Captain Jack]

Welp, other than 3E, I haven't managed anything on 5W. Not sure if it's the plate or position of the plate or just that the dish is far too small... Need to try it properly on the Fibo at some point.

 

[Trust]

You can put the plate in 2 positions in the lnb 90º changed

 

[nelson_b]

very good -- i,m pleased you got something -- must admit i was doubt- full -- with 85cm Penta
but you never know until you try ----

regards nelson.b.

 

[Captain Jack]

Good weather forecast for tomorrow and the weekend, so will play around with the C band on Fibo with different combinations.

 

[pride21]

nice one CJ be interesting to see what you can pick up this weekend.

 

[Captain Jack]

OK, the day has been sunny but bluddy cold! Did as much as I wanted to and here is the report.

First I tried simply replacing the Ku band LNB on the Fibo with the C band one using Trust's holder *without the feedhorn* and I got a decent signal (9d on the Arabic channels on 3E in linear. This I could get on my 85cm dish. Then I swung the dish to 5W and stuck the depolariser plate that came with the LNB (looks like a thick piece of circuit board with the circuit on it). Managed to get some channels mainly in the higher band with ORTB being the strongest.

Next I tried placing the LNB *with* the feedhorn at an offset angle, next to the sub-reflector but got very, very poor results. The focal point of the LNB is a lot further than the sub-reflector and I think one of the LNB support arms was in the way. Either way, I couldn't get more than around 5dB on 3E so I abandoned that idea.

Next, I tried placing the LNB back where it was but this time with the feedhorn and, surprisingly, I got a better signal with it than without, despite me thinking that the huge feedhorn would be blocking some of the signal heading towards the sub-reflector.



I was now getting around 10.6dB on 3E channels without the depolariser plate and around 8dB with. So far so good. Made a few adjustments and a crappy and a very temporary holder, which I intend on replacing tomorrow with something studier.

Went scanning around the arc and have received the following satellites:

3E, 5W, 11W, 22W, 27.5W and 20E.



Had signal but no lock on 10E, 1W and a bunch of others.



I expected to receive 37.5W and 17E but got nothing at all from either of these satellites.

I cannot really see beyond 45E so couldn't test any of the more interesting (to me) channels.

My next step, I guess, is to fabricate my own depolariser plate to squeeze more out of circular channels but I need to read on it since I don't really know where to start! Unless someone can send me a few of their own to try?

I also wonder how a 1.2m Channel Master will perform relative to the Fibo as Fibo isn't really designed for C band.....

 

[Captain Jack]

By the way, I couldn't lock Star Times on 5W. I know it's a crappy TP with 8PSK and 5/6 FEC but has anyone locked it on a 1.2m dish?