Dual Frequency Question

[johnyboy88888]

Perhaps someone can explain this situation for me in my steep learning curve

I was looking for signals on 20W and found a few but not the one I wanted. I phoned a friend who is more experienced at finding feeds and he told me my channel was on 11128 and another channel was on 11131. When I scanned these freqencies, I found nothing on 11131 but a different channel altogether on 11128 (the one he said was on 11131). He did say that his Nokia machine could separate channels if they were on the same transponder and it was likely that my Skystar was only capable of reading the strongest. Now, I'm not absolutely certain what he means so it would be great if someone could explain it to me. Thanks.

[Derrick]

Hi,

 

your friend could be wrong.. How close together 2 channels can be on the frequency scale depends on the bandwidth. The bandwith is a function of the symbol rate. Imho there's only one carrier in your example, unless the SRs are very small. Though it is true that if one carrier out of 2 carriers spaced closely together is much stronger, the tuner will lock on the stronger signal. Tuning in the direction away from the stronger signal (a couple of mhz) could help.. ..and keep in mind, that the tuned frequency isn't the exact frequency cos lnbs suffer from frequency drift with temperature and can have an offset of some 2-3 mhz.

 

ps.

these channels are on the same transponder. The bandwidth of a satellite transponder is in the order of tens of mhz (e.g astra 27, eutelsat 36) With scpc it is possible to have several different carriers on one transponder.

[johnyboy88888]

Thanks for that Derrick. As I said, its a steep learning curve and if you can suggest any good books that will put me in the picture, that would be great.

The good news is that my new system with a slightly larger dish,dual LNB and dual motor is working very well.........other than not finding the signal today that I wanted. Thankfully this situation doesnt seem to arise that often.