Analog Oldtimer turns Digital Newbee - Question

[paulvr]

Dear folks,
I just found this forum, and hope that perhaps anyone here might be able to help me with the following question:

I own a 10 ft Unimesh dish on an AJAK H/H mount, and living in Europe this means that there are many satellites which lack power for a perfect picture on C-Band. In the 80's and 90's this was no problem, with the necessary audio and video band filters even the weakest signals could be viewed, most notably the Intelsat international news feeds on 4166,5 and 4188,5 MHz.

Digital TV made all of this equipment useless. For a long time I left C-Band for what it was and concentrated purely on Ku-Band improvements on other dishes like my Gregorian 120 cm and a noname 190 cm solid prime focus dish on an EGIS dual motor positioner.

A few years ago I wanted to pick up the bobby of C-Band again and purchased something which appeared to be a total desaster: an MSI C/Ku band LNBF for digital use. It was a desaster in more than one way: first of all it never allowed an equally well reception of opposing linearities: one could optimise RHCP reception but then there was no LHCP reception on C-Band possible, one could optimise for vertical Ku Band reception but then no horizontal channels could be seen, not even on the strongest satellites. In addition the indicated noise figure were an illusion: My Gerdiner 25 degree K LNB which was bought in analog times was at least as sensitive as this one which claimed to be 17 K.

What shocked me most was the shabby construction of the scalar rings. Being used to very sturdy and solid Seavey and Chapparal feeds I now got something that looked as if it was made out of a used tuna fish can. Pure rubbish from a quality point of view.

The funny thing was that I kept reading articles in which it was claimed that for digital reception specially made C-Band digital LNB's are needed because of their improved stability. This one experience at least contradicted this.

Now I am faced with the question how to go on. My basic issues are:

1. I receive a numger of C-Band satellites that are right at the brink of reception/non reception. Most of these, BUT NOT ALL, are in circular polarization. I won't use my dish for Ku-Band reception so no need for compromises on that part. I see that there is a Norsat LNB of 15 degrees K that is offered for prices between $50 and $ 80 but buying that one would force me to go on with an analog sat receiver as intermediary in order to adjust the polarization between horiz-RHCP-vert-LHCP.

2. Obviously a specialized C-Band only LNBF of very good quality would be much easier to use because you would only have to move the dish separately but all other functions would be carried out by the sat receiver.

3. However, somehow I can't imagine how to control such a system if it existed because the average digital sat receiver only knows 2 polarities. I am testing an AZ Box Premium HD+ receiver with experimental Enigma 2 software which appears to list separate settings for these 4 polarities but they are not (yet) functional.

4. My questions:

what should I do, which options do exist if I want an optimal sensitivity reception on C-Band? Get the Norsat 8515 LNB and attach it to a simple 20 year old Chapparal C-Band feedhorn using the skewing function of an analog receiver to switch polarities? Or is the stability of an Norsat LNB exaggerated and might one just as well buy a cheaper one?

or is it possible to get a complete C-Band LNBF of excellent quality in terms of reception which can be controlled by a normal sat receiver? I find so far the receivers of Clarke-Tech/MaxDigital to be the best in terms of sensitivity and blind scan results but they don't allow installation of 4 polarities. Funny enough on one satellite only (40 East) a blind scan gave the indication RHCP in spite of the fact that manually one can only select between V and H. I never found an explanation for that anomaly, other circular polarized signals were always indicated as V or H.

I'd be most grateful for any suggestion!
kindest wishes,
Paul.

 

[Lak7]

Most C Band LNBS are for Linear Signals.
Was the a small Block of Plastic that came with the MSI LNBF? If so, the gets inserted in the the Feedhorn to convert Circular into Linear so the LNB can tune.

 

[truckracer]

norsat 8515 is an excellent choice. i run two 8515's on a dual chap feed.
Be sure the inside of your feedhorn is clean and free of corrosion. if not you can clean it out with some steel wool. thats how i cleaned mine.

the plastic puck inserted into the new lnbs will get you left and right polarity signals.
looking at lyngsat its amazing how in europe almost everything is ku band.

 

[paulvr]

Most C Band LNBS are for Linear Signals.
Was the a small Block of Plastic that came with the MSI LNBF? If so, the gets inserted in the the Feedhorn to convert Circular into Linear so the LNB can tune.

Hi,
Thanks for your reply, but... I did mention I was an analog oldtimer.... My first teflon slab to change from linear to circular I placed into a feedhorn about 32 years ago. How else do you think I received the ultra weak Intelsat newsfeeds I mentioned?

No, my problem is NOT that I don't know how to receive circular polarized transponders, but to know if there is a way or a specific combination of LNBF and receiver that offer the selection of all 4 polarities.

thanks anyway,

Paul.

 

[paulvr]

Hi,

Thanks for your response. But to be frank, I have no idea what's a chap. Dual feeds I know, I once even had a triple feed (S-band/C-band/Ku band) but what to do with a dual feed on just one band I don't really understand where it's good for. Could you please explain?
As to the enormous quantity of Ku Band satellites in Europe, that can be explained easily. We have no history of C-Band like the US and the USSR had. The first European satellites where ECS on 13 East, Intelsat for Britain on 27.5 West and Intelsat on 60 east for Germany in the mid-eighties. I was one of the first satellite pioneers in my country so I remember it quite well.
And once you start on Ku-Band it makes no sense then to add C-Band as that requires much larger dishes. Dishes that cannot be placed in most densely populated urban areas. In fact I don't understand very well why C-Band is still alive in the rest of the world. For me the only advantage other than being able to see African and South American tv stations lays in the fact that the wider opening angles allow for a more stable reception in stormy weather. But where as C-Band gives me a very limited number of stations, perhaps around 100 or so, on Ku Band I cannot even count the total number of receivable stations. Perhaps somewhere between 3000 and 5000 in total.

 

[paulvr]

btw: I mentioned 40 east but that was a typo, the signals from that one are very forceful. I meant to say 49 degrees (Yamal).

 

[FaT Air]

a specific combination of LNBF and receiver that offer the selection of all 4 polarities.

The only way I see to have it so you can select linear and circular(all 4 polarities) is to have 2 feeds on the dish. One set up for linear and the other for circular. Selected via a diseqc switch and receiver programming. Pendragon's thread may clear it up.
http://www.satelliteguys.us/c-band-...63-c-band-linear-circular-orthomode-feed.html
btw: i think: chap feed = Chapparal

 

[linuxman]

4. My questions:

what should I do, which options do exist if I want an optimal sensitivity reception on C-Band? Get the Norsat 8515 LNB and attach it to a simple 20 year old Chapparal C-Band feedhorn using the skewing function of an analog receiver to switch polarities? Or is the stability of an Norsat LNB exaggerated and might one just as well buy a cheaper one?

or is it possible to get a complete C-Band LNBF of excellent quality in terms of reception which can be controlled by a normal sat receiver? I find so far the receivers of Clarke-Tech/MaxDigital to be the best in terms of sensitivity and blind scan results but they don't allow installation of 4 polarities. Funny enough on one satellite only (40 East) a blind scan gave the indication RHCP in spite of the fact that manually one can only select between V and H. I never found an explanation for that anomaly, other circular polarized signals were always indicated as V or H.

I'll try and help answer your questions.

The best method for receiving both H/V and R/L signals with one feed-horn would be a Chaparral C-Band only orthomode with two of the Norsat LNBs that you listed above. The price is reasonable here in the US, but I don't know what they would cost to have them shipped to Europe.

Most modern receivers only have H/V listed in the settings, but if you use those settings, the RHCP will come in on a V setting, and LHCP will come in on the H setting. You might have to adjust the Local Oscillating Frequency setup in the receiver for satellites in Europe, but you should be able to receive all 4 polarities with this setup provided you have the dialectric plate installed. You would also need a 3x4 multi-switch, or a 4x4 multi-switch to combine the polarities into one coax run and a power inserter installed to raise the R/V voltage output to the required 18V. Most modern receivers only output 18V on H/L and 13V on R/V.

The second best alternative is to use a GesosatPro C-2, C-band only LNBF which is a combination feed-horn and LNB built into one unit with dual outputs. You would only need to use one of the outputs for a single receiver. The functionality should be the same, but no multiswitches would be required with this setup. I have had good success with this unit, but if your signals are extremely weak, the Chaparral C-Band only orthomode feed-horn above would be your best option.

Hope that helps you, and if I have made any mistakes, I am sure someone will correct me.

 

[paulvr]

The only way I see to have it so you can select linear and circular(all 4 polarities) is to have 2 feeds on the dish. One set up for linear and the other for circular. Selected via a diseqc switch and receiver programming. Pendragon's thread may clear it up.
http://www.satelliteguys.us/c-band-...63-c-band-linear-circular-orthomode-feed.html
btw: i think: chap feed = Chapparal

Hi chap (I thought of it as just another word for guy, haha, now I know better!)

Somehow the idea of 2 feeds doesn't seem like much of an advantage to me. Sure, you resolve the polarity issue that way but then you traded external polarity switching for switching between feedhorns. And in addition it means working with a compromise as in reality there is just one perfect focal point and last but not least you end up with two close but nevertheless different physical positions in case you use a positioner with accurate degree readouts.

That seems a lot of drawbacks, I think using my old Echostar 50 manual tuner for H/V and skew for R/L would be a better option as just using an external skew control makes any further cost and compromises unnecessary that way.

But thanks for the interesting information and link!

Paul.

 

[paulvr]

Thanks very much for your advice. Indeed on Ebay this LNB costs 49 dollars ( see Norsat 8515 C-Band DRO LNB **New** 500KHz Stability | eBay ) but only the shipping costs are rather exaggerated I'm afraid. I hope it's the correct LNB, the numbers seem Ok but the picture differs somewhat from one I saw on other places. And strangely enough on the Norsat site I couldn't even find a 15 degree K LNB at all.
The advantage of the second best alternative you mention for me is not just price. When I use a manually adjusted Chapparal feed the biggest problem for me is that when doing a blind scan the receiver often sees a transponder twice due to cross polarization of the dish. Using a single dedicated LNBF like the second option you mentioned makes manual adjustments unnecessary and therefore causes a blind scan to give simple correct results.
But then of course I don't know if the difference is marginal or significant. From my "golden analog days" I remember quite well how on weaker satellites that were especially close to the horizon very precize skewing was of the essence in order to obtain the best possible reception. And although signals have changed from analog to digital, I cannot really imagine that that aspect would have changed along with it. Or am I wrong in this respect?

 

[linuxman]

And although signals have changed from analog to digital, I cannot really imagine that that aspect would have changed along with it. Or am I wrong in this respect?

Precise skewing is essential to receiving signal with the most efficiency, but with these new voltage controlled LNBFs, and with the orthomode feeds, skew is set on you True South Satellite, and the polar mount as it swings across the arc adjusts the skew accordingly.

The result is that you get what you get.

 

[paulvr]

Thanks very much for your advice. Indeed on Ebay this LNB costs 49 dollars ( see Norsat 8515 C-Band DRO LNB **New** 500KHz Stability | eBay ) but only the shipping costs are rather exaggerated I'm afraid.

Well, this guy wants more than $ 33,00 extra just for the fact that sometimes he has to wait in line in the Post Office. Crazy situation, sot of like a shopkeeper charging extra money for the fact that sometimes he has to wait for customers.

Anyhow: is there any of you who know someone selling this LNB for a similar price but with only the REAL shipping costs? my email address is paulvr20@ tele2.nl I'd greatly appreciate your help!