C-Band on a 1.0m - 1.2m dish? - Yes!

[glen4cindy]

I just finished reading a back issue of Tele-Satellite International magazine where they were experimenting with picking up C-Band on a 1.2 meter dish and a 1.0 meter dish as well. This was the 0603 issue and is no longer available on the website but I would be glad to try to copy the text of the .pdf file I have and post it for anyone interested.

They used a C-Band LNB with a modified mounting bracket fixed to a FortecStar dish with a cone shaped sclar ring. The picked up a few dozen channels of various satellites including AMC 15 and I 805. They were located in Canada and were picking up Atlantic birds.

I for one would like to experiment with this some day soon, but, I will have to upgrade my 80cm dish first.

Has anyone tried this? I know this subject has been addressed here before and the smaller dish size and why it won't work has also been dealt with, but, if Tele-Satellite can make it work in Canada on Atlantic birds, it would seem like the same thing may be possible here in CONUS.

Any ideas?

[rainman]

I think pmb1010 is using a 1.2 meter dish with a bsc621 lnbf to get some c band channels. the main problem with using a c band dish this small is when you get in to the area where the sats are only 2 degrees apart you get to much interfierence from the adjacent sat.

[elgemcdlf]

People are so funny sometimes. There is the group trying their best to get C Band on as small a dish as they possibly can. And then the others who want a bigger dish. I would be curious as to their results versus available channels and the quality of those channels. I would have a tendancy to think that it would be only the ones with higher FEC and then I would think the least little thing would cause a loss of signal.

Still waiting for the day these "little" 8.5' dishes get replaced with 12' or better

[wejones]

Originally Posted by elgemcdlf

People are so funny sometimes. There is the group trying their best to get C Band on as small a dish as they possibly can. And then the others who want a bigger dish. I would be curious as to their results versus available channels and the quality of those channels. I would have a tendancy to think that it would be only the ones with higher FEC and then I would think the least little thing would cause a loss of signal.

Still waiting for the day these "little" 8.5' dishes get replaced with 12' or better

? Higher FEC would make it harder for you to lock a signal, because not as many errors would be corrected.

However I have a theory too. My theory is that it would be the narrow bandwidth channels that they'd receive, ie the low SR signals. (m guessing this even though it's contrary to my experience. Ie I've generally had an easier time locking wide transponders, but I think that's because of my drifting lnbfs.

Reason I'm guessing this, is because I've looked at a couple sats that had wide and narrow signals side by side with about the same actual signal strength. THe wide signal had just average quality and yet the narrow signal gave near perfect quality. Ie it seems to be possible to pull a narrow signal out of the noise. This is somewhat analogous to amateur radio, where to receive weak signals, you typically use narrow bandwidth, however the ham analogy is also a case where the bandwidth of the receiver is narrow too, thus filtering out noise outside the bandwidth of the signal, however it is my assumption that consumer FTA receivers don't change the bandwidth filtering of the receiver to receive narrow signals, which would allow lots of noise in. However I'm thinking that it's that there will be less interferrence from the noise with a low SR signal, whereas a high SR signal will experience interferrence from a wider spectrum.

Anyway, I'd be interested in what the SR values were for the signals received by the small dishes.

[Iceberg]

I remember reading that article. They mainly used C-Band satellites over the Atlantic where they are more than 2 degrees apart

I know I have been able to use a Primestar dish (40x30) to get C-band. The very strong stuff. I could get ASN on AnikF1 and a couple feeds on G4 (the 4:2:2 ones) but at the time I could not lock on the nets.

As for the higher FEC, nope. I can't lock the Equity muc on G3 with my 6 footer without pixelation and the meter is at 60 (Pansat's threshold is 30) . The nets on G4 come in just fine

[elgemcdlf]

I would have thought the smaller dish = less signal trap = less room for error correction = need as much of the trapped signal to be actual good signal.

[glen4cindy]

The article did not address the sats being 2 degrees apart, but, it did indicate that the users achieved fairly high signal strength and qualtiy readings with very watchabel pictures.

I'm not going to run out and replace my 80cm with a 120 just to toy with this, but, I have seen and replied to posts regarding C-Band on a small dish and found this article interesting.

[wejones]

Originally Posted by elgemcdlf

I would have thought the smaller dish = less signal trap = less room for error correction = need as much of the trapped signal to be actual good signal.

I don't think I understand what you are trying to say here.
But the way I look at it, for you to be able to lock a weak transponder, you have to have a certain quality level, which one way or another will relate to your signal AFTER error correction has occurred. Ie, you can have lots of errors in the signal, but if they are corrected, you can still view the video. When you have a weak signal, due to a small dish, or a signal with interferrance from adjacent sats, you will have a lot of errors. When you have a high FEC ratio, like 7/8, then your receiver isn't able to correct all these errors, and your odds of being able to lock the transponder will be decreased. But if you have a low FEC ratio, like 1/2, then more of the signal is devoted to error correction, and your odds of being able to lock the transponder and have viewable video are improved. At least that's my understanding. Hard to prove it one way or another from examples, because it's hard to eliminate other parameters like interferrance from adjacent sats, differences in signal strength, bandwidth, etc.

[vj9999]

Originally Posted by glen4cindy

The article did not address the sats being 2 degrees apart, but, it did indicate that the users achieved fairly high signal strength and qualtiy readings with very watchabel pictures.

I'm not going to run out and replace my 80cm with a 120 just to toy with this, but, I have seen and replied to posts regarding C-Band on a small dish and found this article interesting.

Alot of us here have toyed with it. It's a fun hobby project. Not worth it if you want a reliable source for c-band, but if you like to play around and get some extra channels it can be fun to try.

SR is not a problem. I had equal success with high and low SR. Atlantic sats are alot easier and you will get 100s of channels because sats are spaced more apart.

On 120cm dish I believe beamwidth on c-band is something like 5 degrees. If you are aiming to US sats, you better hope that it has a strong transponder and that there are no sats on either side of it that have signal on similar frequency (doesn't have to be same frequency since a transponder with high SR on adjacent sat can over flood bunch of frequencies with smaller SR on sat yuou are pointing too).

Some transponders are so strong that you can be pointing 2-3 degrees away from that sat and still get the signal in because beamwidth is so wide.

[wejones]

Originally Posted by vj9999

.....

SR is not a problem. I had equal success with high and low SR. Atlantic sats are alot easier and you will get 100s of channels because sats are spaced more apart.

On 120cm dish I believe beamwidth on c-band is something like 5 degrees. If you are aiming to US sats, you better hope that it has a strong transponder and that there are no sats on either side of it that have signal on similar frequency (doesn't have to be same frequency since a transponder with high SR on adjacent sat can over flood bunch of frequencies with smaller SR on sat yuou are pointing too).

Some transponders are so strong that you can be pointing 2-3 degrees away from that sat and still get the signal in because beamwidth is so wide.

Hi VJ...
Thanks re SR not important thing. What you say after that may have been related to why I thought SR might be a factor though. Ie recently I was scanning G10r, and scanned in a narrow transponder from IA13. The one narrow transponder was the only channel from the adjacent sat that scanned in, ie I didn't scan in ANY of the high SR transponders. I did a spectrum scan of IA13, and the narrow channel wasn't really stronger than the other transponders on the sat. I'm guessing that when aiming in an area with 2 deg spacing, that the odds of seeing a weak signal without interferrence is better when that signal is narrow, and a high SR transponder is much more likely to see interferrence and get wiped out.

However over the atlantic, where there isn't as much likelihood of adjacent sat interferrence, perhaps it doesn't matter whether the signal is wide or narrow.

Interesting.

[elgemcdlf]

Originally Posted by wejones

I don't think I understand what you are trying to say here.
But the way I look at it, for you to be able to lock a weak transponder, you have to have a certain quality level, which one way or another will relate to your signal AFTER error correction has occurred. Ie, you can have lots of errors in the signal, but if they are corrected, you can still view the video. When you have a weak signal, due to a small dish, or a signal with interferrance from adjacent sats, you will have a lot of errors. When you have a high FEC ratio, like 7/8, then your receiver isn't able to correct all these errors, and your odds of being able to lock the transponder will be decreased. But if you have a low FEC ratio, like 1/2, then more of the signal is devoted to error correction, and your odds of being able to lock the transponder and have viewable video are improved. At least that's my understanding. Hard to prove it one way or another from examples, because it's hard to eliminate other parameters like interferrance from adjacent sats, differences in signal strength, bandwidth, etc.

No my thinking is at the dish and as you stated receiver corrects. So you need to trap enough signal first before you can do anything. If that signal contains primarily clean data and less error correction then the bulk of your signal coming in would be actual signal. Thinking of signal like a container of water. The 8.5' dish catches 3 cups of water and the 1 meter dish catches 1. Let's pretend I only need to drink 3/4 a cup of water to survive. On the 8.5' dish I can afford to give up 2 1/4 cups of volumn for water purification but on the 1 meter I can only afford to give up 1/4 cup for purification.

In any case that was my line of thought. Right or wrong it was my line of thought.

[wejones]

Originally Posted by elgemcdlf

No my thinking is at the dish and as you stated receiver corrects. So you need to trap enough signal first before you can do anything. If that signal contains primarily clean data and less error correction then the bulk of your signal coming in would be actual signal. Thinking of signal like a container of water. The 8.5' dish catches 3 cups of water and the 1 meter dish catches 1. Let's pretend I only need to drink 3/4 a cup of water to survive. On the 8.5' dish I can afford to give up 2 1/4 cups of volumn for water purification but on the 1 meter I can only afford to give up 1/4 cup for purification.

In any case that was my line of thought. Right or wrong it was my line of thought.

However, using this unusual analogy, I think the thing is, that regardless of whether your signal has high FEC or low FEC ratio, they are still sending the same cup of water. It's just that with the low FEC ratio, they are sending extra water in case you lose some of that water, so with low FEC, you have a better chance of getting your 3/4 cup needed to survive. Ie don't get stuck in a desert with a high FEC canteen.

The reason they use high FEC is to be able to squeeze that cup of water into a smaller canteen, ie with no need to include the extra water (ie signals intended for commercial dishes don't have to worry about so many errors).

[boroda1]

I've seen on russian forums, they receive C - band even with 90cm dish from Express-AM1, 40E, TP6: EIRP value from this TP is 43(48)dBW for European part of country: hxxp://www.rscc.ru/ru/satellite/zones/zone13.html, first pic from the left.
Also there is no adjacent sats, Paksat1 at 38E has a beam for Pakistan only, and on the East, next sat is at 49E:
hxxp://www.lyngsat.com/eam1.html
Here is a picture of this dish:
hxxp://www.album.alyno.ru/coppermine_alyno/albums/userpics/10001/M_40_53_60_001.jpg

Some more pics, with calculations for 53E Ku and 60E Ku, too:
hxxp://www.alyno.ru/old-forum/viewtopic.php?t=125&start=0

So, signal should be strong enough, and should be no interference from neighboring sats, in order to use small dish for C-band

[wejones]

Originally Posted by boroda1

I've seen on russian forums, they receive C - band even with 90cm dish from Express-AM1, 40E, TP6: EIRP value from this TP is 43(48)dBW for European part of country: ....

Well that's interesting re my "theory" about SR. That TP-6 is a pretty high SR, however, that transponder has the 48 contour, and that's VERY strong, compared to say an IA6 which has a 39 dBW contour around most of the US, so it's not surprising that you could receive that on a small dish, provided that there aren't any adjacent interferring sats. The other transponders that have the 43 contour are narrow, low SR channels.

I really enjoyed the pictures of the apparently home-made feed horns and wave guides.