What the... OK, this is stupid...

Captain Jack

Captain Jack

Retired human
My Satellite Setup
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OK, following my Penta installation on my balcony with a very short cable run to the receiver, I have been having problems with strong satellites, in that the signal reading was reading way below what it should have been. At the same time the weaker satellites have been stronger than they ever have been, so this rules out bad alignment... So, it looks like the strong satellites, combined with a short cable run is overloading the tuner.

To test the theory, I have tuned in to 19.2E NHK World transponder, which is breaking up(!) and the signal (SNR) jumps in and out of lock. However, after I put a wet cloth over the LNB, the signal jumps to 46% and the picture is stable.

How can I reduce the signal on the strongest satellites without affecting the weaker ones? Is there an attenuator of some sort I can use? I could use a 20m cable run I guess but I really want something more intelligent than this....

Help!
 

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The only way I can think of is to replace the LNB with one having a wider signal acceptance without overloading - although what that might be I have no idea!

Are you sure the weaker signals wouldn't disappear with an attenuator?

EDIT

Having had a ponder I seem to remember that Invacom LNBs have greater signal handling capabilities. But - *ouch* - the cost.
 
PaulR said:
The only way I can think of is to replace the LNB with one having a wider signal acceptance without overloading - although what that might be I have no idea!

Are you sure the weaker signals wouldn't disappear with an attenuator?
Click to expand...

I have a Titanium 0.1dB LNB lying around but I haven't tried it. All I know is that it was a worse performer than my Black Ultra.

I don't know what effect a signal attenuator would have on already weak signals. Really I'd want an equivalent of a zenner diode (from my distant college days)... if the signal is over x dB then attenuate it. If below x dB then don't touch it....
 
Perhaps, using lateral thinking, you need to go for a "deafer" LNB?

Zener diodes, eh? Unless you're going to to use the avalanche curve to control an active feedback of AGC in some manner they're just DC devices. Or were you just hypothesising...
 
I was just hypothesising :) Just need something to act as a "current" limiter. Actually, I did find a way to "increase" the signal and that's to move the dish out of alignment...!

I will try the deafer LNB and see what happens...
 
Wet flannel on a servo? :p
 
CJ, on my TD88 NHK comes in at 71% SNR. However, I have 28.2°E at focus on that dish, with a lot of channels at 99% SNR and they've never shown any sign of breaking up. Is the AGC on the Uno somehow disabled?
 
You could just try mis-aligning your dish, having it point a few degrees out, to weaken the signal, using your receiver to nudge it slightly.
 
Captain Jack said:
OK, following my Penta installation on my balcony with a very short cable run to the receiver, I have been having problems with strong satellites, in that the signal reading was reading way below what it should have been. At the same time the weaker satellites have been stronger than they ever have been, so this rules out bad alignment... So, it looks like the strong satellites, combined with a short cable run is overloading the tuner.

To test the theory, I have tuned in to 19.2E NHK World transponder, which is breaking up(!) and the signal (SNR) jumps in and out of lock. However, after I put a wet cloth over the LNB, the signal jumps to 46% and the picture is stable.

How can I reduce the signal on the strongest satellites without affecting the weaker ones? Is there an attenuator of some sort I can use? I could use a 20m cable run I guess but I really want something more intelligent than this....

Help!
Click to expand...

I had similar problems on 19.2E (and somewhat less on 1W), where the strong signals of 1KR/1L/1M were overloading the system when I was using an Inverto Black Ultra LNB, and literally destroying the signal of 1H, which is a low signal satellite in my region (actually the situation was worse than this, the problem was apparent across the spectrum, not only on 1H). I replaced the Inverto with a Smart Oxid and the problem disappeared...
 
Interesting. What's this LNB like compared to Black Ultra? Looks like it's not expensive so could give it a go.
 
Only slightly worse in sensitivity (something like 0.3dB worse SNR by my estimation), and yet not at all expensive! I seldom miss my Inverto...
 
Buy attenuator to put between LNB and box..
 
My DR.HD F15 acts as a great attenuator when it is off and feeding the TBS6925 from the loop through! Really, I'm not joking here... :)
 
strs65 said:
My DR.HD F15 acts as a great attenuator when it is off and feeding the TBS6925 from the loop through! Really, I'm not joking here... :)
Click to expand...

I would suggest a passive two way splitter in line with the existing cable run. It will add about 4dB to the loss, doesn't introduce (m)any nodes/harmonics/slope/noise and is easily removed.
 
CH definately has the best solution imo ..
..but its odd that the problem appears to be AGC related ..
Firmware issue in the receiver ??
perhaps it was inadvertantly modified or even disabled in a recent firmware edition..

rgds
VS
 
Vipersan said:
Firmware issue in the receiver ??
perhaps it was inadvertantly modified or even disabled in a recent firmware edition..
Click to expand...

I don't know which image CJ is using but I haven't seen any mention of the same problem on the VIX forum. I wonder if a reset and reloading the image would make any difference?
 
I do have another receiver (General Satellite 9300) to try this on, so will be good to see if that exhibits a similar problem.

Wonder if my receiver is just faulty...? The image I am using is the VIX 2.3 on the latest kernel (3.1?).
 
Hmm, this is interesting.
On my CM180 with a BUQ, I was worrying about the 2A and EB1/Eutelsat 28A strength being too much contrast for the original 2D signals.
But I never had any probs with overloading.
(I have used three different boxes, including FaxSat and Samsung low-cost box, but only the Foxsat sits directly on the output of the LNB - the others go through at least one F-coupler and a wallplate.)

I'd try your spare box just to see if it's the receiver.
 
Tried the spare box this morning and it was absolutely fine - so it looks like the Uno is the problem :( Going to investigate this before investing money in LNBs etc...
 
Just a thought to try might be a good idea to open the Uno and remove and reseat the Plug & Play tuner see if it improves any
 
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