Unable to tune low Symbol Rate channels

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dodge4cover

Member
Hi.

Looked around a bit and think this is the correct place to post. Apologies if it's not.

I have the following problem: Can't tune SIC INTERNACIONAL, on Eutelsat W2(16°E) - 12735MHz/Vertical - SR 3703/FEC 7/8. That's it.

I have a fairly old 1.2m motorized dish/LNB, on a rooftop in the middle of Lisbon, Portugal, connected to a (very old) Humax NACI-5700 and then to a SkyStar2 PC-card. They are all working fine, except on very low symbol rate channels, of which SIC INT. (3703) is a good example. For instance, I'm able to tune NAT GEO MUSIC (same sat) with a symbol rate of just 5721, but anything bellow 4000 isn't detected at all.

My question: Is the LNB giving up on me? Had it installed 10+ years ago and on the "bang/buck" [cheapo...] side, that much I remember. Can it be cabling from the dish or the dish itself? Or is it that the STB and card's tuners aren't up to the task any more? (can't tune anything on 28°E that isn't directly "pointing" South, which means "can't tune anything worth tuning on 28°E", despite reports of success with similar, newer rigs)

That said, everything else works fine.

Thank you.


almost forgot: I used to tune SIC Int. with the same SR, before they switched frequency earlier this year (or was it late last year? I haven't been paying attention...)
 
Its an easy catch here with a 1m dish.

Try detuning the receiver slightly

12733 / 12731 / 13729 / 13727 / 12737 / 12739 / 12741 / 12743

May help if the local oscillator has drifted slightly.
 
dodge4cover said:
Is the LNB giving up on me? Had it installed 10+ years ago and on the "bang/buck" [cheapo...] side, that much I remember. Can it be cabling from the dish or the dish itself? Or is it that the STB and card's tuners aren't up to the task any more?
Click to expand...
If it is over 10 years old are you sure it is a universal LNB?

Also, try what Analoguesat says. Low symbol rates have narrower bandwidth and therefore require smaller steps.
 
Borrow another receiver and try it, it will narrow down the culprit.
 
Analoguesat said:
Its an easy catch here with a 1m dish.

Try detuning the receiver slightly

12733 / 12731 / 13729 / 13727 / 12737 / 12739 / 12741 / 12743

May help if the local oscillator has drifted slightly.
Click to expand...

Already tried 12730 through 12738, but will widen the range.


Huevos said:
If it is over 10 years old are you sure it is a universal LNB?
Click to expand...

Absolutely. Pretty sure it's a Samsung, no idea which model though. And I (the whole building in fact) have no direct access to the rooftop (missing tenant). That's why I'm hoping it's NOT the LNB.


Channel Hopper said:
Borrow another receiver and try it, it will narrow down the culprit.
Click to expand...

Tried with the Humax and the SkyStar2, which, truth be told, is rather weak. Will try to borrow a Kaon from a friend.


Thanks for the replies.
 
mmmh, it's working now. At a somewhat feeble but steady 50% signal strength.

Therefore, it stands to reason that "sunlight" disables satellite reception.

Or not... :confused:
 
Hi guys,

there are two problems trying to receive low symbol rate carriers. The first (mentioned above) is the fact that the badwidth is small. The frequency of the LNB drifts (unless you pay 1.500 euros for a professional single band LNB with 25KHz tolerance), the exact frequency of the IF can be found only by using a spectrum analyser.

The second problem is the strength of the signal. Let's say that we have a 36 MHz transponder. If the carrier is 27.500 then the bandwidth is almost 36MHz and the transmitted power is the one shown in the footprint. If the bandwidth is shared equally to two carriers then each carrier should 50% of the transmited power (-3dB). If the bandwidth of the carrier is 1/4 of the total bandwidth of the transponder then the power is 1/4 lower (-6dB) etc etc

The worst case scenario would be to have a narrow signal in a 72 MHz transponder.
 
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