Advice Needed Long Cable RG-11 Issue

Asoet

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Hi All,

I am new here and need some advice from all of user who might have an experience with my mine.

I build a Satellite TV reception with 4.2 m C-Band dishes (aligned to Palapa D and Telkom 1 satellite ) with 135 m cable length from dish to IRD (Decoder), currently I am using Belden 9292 RG-11 cable and now I am facing unstable reception.

Sometimes the IRD can't lock the signal for only several second and get back to normal, this is happen 4 - 6 times a day with random time. I am realize with the cable loss since the long cable used, therefore I put L-Band Amplifier in the middle distance between the dish and the IRD.

What I don't understand is my signal reception has a good enough quality and also i already measure the signal quality with below details for certain TV Channel :
a. Reception level input : - 43 dBm
b. Link Margin estimated : 6 dBm
c. C/N level : 10 - 12 dB

Some channels even has better quality than that but still sometimes the IRD shown demodulator unlock.

Maybe some user here has a same experience as mine and fix the issue please share.

FYI : Using fiber optic converter is the last option due to budget limitation.

Thanks,
 
A

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Hi All,

I am new here and need some advice from all of user who might have an experience with my mine.

I build a Satellite TV reception with 4.2 m C-Band dishes (aligned to Palapa D and Telkom 1 satellite ) with 135 m cable length from dish to IRD (Decoder), currently I am using Belden 9292 RG-11 cable and now I am facing unstable reception.

Sometimes the IRD can't lock the signal for only several second and get back to normal, this is happen 4 - 6 times a day with random time. I am realize with the cable loss since the long cable used, therefore I put L-Band Amplifier in the middle distance between the dish and the IRD.

What I don't understand is my signal reception has a good enough quality and also i already measure the signal quality with below details for certain TV Channel :
a. Reception level input : - 43 dBm
b. Link Margin estimated : 6 dBm
c. C/N level : 10 - 12 dB

Some channels even has better quality than that but still sometimes the IRD shown demodulator unlock.

Maybe some user here has a same experience as mine and fix the issue please share.

FYI : Using fiber optic converter is the last option due to budget limitation.

Thanks,
It's only qualified guessing, but I would suggest that the actual cable-length is not the problem per se.
Any signal power loss can be compensated by a proper line amplifier as you describe.

But it's not the signal strength that is the key factor: Quality is really the most important thing.
With a C/N level of 10-12 dB you should be fine for most situations.
I speculate that your problem is interference, or irradiation somewhere along the signal path.

I have personal experience of 100+ meter cable run with marginal reception, whre IRD indicates 0% strength, but 90% signal quality.
And continous picture.
I believe this is down to professional grade cable and connectors being used (it's at head-end of cable-operator).
The key is to avoid any degradation or noise-induction along the signal path.

Without knowing the specifics of your installation, I can first suggest checking things like:
  • Connectors: Are you using simple twist-on F-connectors, or RF-tight compression connectors throughout?
  • Cable proximity: does the coax cross power lines (even 220V) anywhere? Or (worse) run alongside at any length?
  • Household equipment proximity: is any of the signal path passing close to washing machines or boilers that could induce power surges into the coax cable?
  • Neighbours: if you live in a "multiple dwelling unit" (ie. apartment buliding or the like), then your neighbours may have a bad microwave or wireless phone which can cause interference. This can be very difficult to diagnose.
In my home, I have the problem of swithing on the light in the hallway will disrupt SAT-signal to bedroom for a few seconds.
This is undoubtably down to a high spike in harmonics being radiated from the electrical switch into the coax (which is over half a metre away in the roof). Most practical work-around is to fit electronic power switch that "fades" the 230V in rather than mechanical bouncing switch. Moving the cable will be much more expensive.

But this is all speculation.

If you really want to know what happens, you need to get a data-logger that captures signal strength and quality over a 24h period.
Apart from pro-grade equipment, I think you can achieve the same using a "linux receiver" and a suitable image. I think these can be set up to do datalogging of the reception parameters, so that you can see what happens to the strength and (more importantly) quality.
This should give you a better idea of what causes to look for.

Re fibre optics: This will only work if the problem is irradiation along the coax. Irradiation in the IRD connectors will not be solved by this.
Also, you can have coax cables that are better insulated (but they are also more expensive, and often require special connetors etc.)
 

Asoet

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It's only qualified guessing, but I would suggest that the actual cable-length is not the problem per se.
Any signal power loss can be compensated by a proper line amplifier as you describe.

But it's not the signal strength that is the key factor: Quality is really the most important thing.
With a C/N level of 10-12 dB you should be fine for most situations.
I speculate that your problem is interference, or irradiation somewhere along the signal path.

I have personal experience of 100+ meter cable run with marginal reception, whre IRD indicates 0% strength, but 90% signal quality.
And continous picture.
I believe this is down to professional grade cable and connectors being used (it's at head-end of cable-operator).
The key is to avoid any degradation or noise-induction along the signal path.

Without knowing the specifics of your installation, I can first suggest checking things like:
  • Connectors: Are you using simple twist-on F-connectors, or RF-tight compression connectors throughout?
  • Cable proximity: does the coax cross power lines (even 220V) anywhere? Or (worse) run alongside at any length?
  • Household equipment proximity: is any of the signal path passing close to washing machines or boilers that could induce power surges into the coax cable?
  • Neighbours: if you live in a "multiple dwelling unit" (ie. apartment buliding or the like), then your neighbours may have a bad microwave or wireless phone which can cause interference. This can be very difficult to diagnose.
In my home, I have the problem of swithing on the light in the hallway will disrupt SAT-signal to bedroom for a few seconds.
This is undoubtably down to a high spike in harmonics being radiated from the electrical switch into the coax (which is over half a metre away in the roof). Most practical work-around is to fit electronic power switch that "fades" the 230V in rather than mechanical bouncing switch. Moving the cable will be much more expensive.

But this is all speculation.

If you really want to know what happens, you need to get a data-logger that captures signal strength and quality over a 24h period.
Apart from pro-grade equipment, I think you can achieve the same using a "linux receiver" and a suitable image. I think these can be set up to do datalogging of the reception parameters, so that you can see what happens to the strength and (more importantly) quality.
This should give you a better idea of what causes to look for.

Re fibre optics: This will only work if the problem is irradiation along the coax. Irradiation in the IRD connectors will not be solved by this.
Also, you can have coax cables that are better insulated (but they are also more expensive, and often require special connetors etc.)

Thanks ST-1 for your suggestion, in fact yes this installation is for professional used. For your question what I can answer is following :

  • Connectors: Are you using simple twist-on F-connectors, or RF-tight compression connectors throughout? RF Tight Compression
  • Cable proximity: does the coax cross power lines (even 220V) anywhere? Or (worse) run alongside at any length? This one not sure, the cable was laying on the office building following cable shaft.
  • Household equipment proximity: is any of the signal path passing close to washing machines or boilers that could induce power surges into the coax cable? Need to check but I don't think so.
  • Neighbours: if you live in a "multiple dwelling unit" (ie. apartment buliding or the like), then your neighbours may have a bad microwave or wireless phone which can cause interference. This can be very difficult to diagnose.

I also suspect the interference is a problem but it's so hard to find where is the interference coming from. I have 2 dish both with dual polarity, once the problem comes it's happen to all of dish and both polarity in the same time and also i notice the down time is only 6 - 8 seconds. It's looks like some signal blasting for only several second between the dish and the cable.

This problem has been happened a month, I try to make simulation by using 6 feet dish with same setup in my office (same cable length, same IRD, same Amplifier and splitter).
In my simulation setup I also found same issue but less frequent (once or twice a days) maybe since I am only using small dish and reception quality is not so good (2 dB margin, 6 dB C/N).

I did some analyze even using professional spectrum analyzer since I though there is wimax interference and did following :

1. Trace Maximum signal recorded
2. Trace Minimum signal recorded

Put the analyzer until get demodulator unlock alarm but then when I see the trace signal recorder there was no signal drop at all or unwanted carrier/signal neither.
This result made more confuse to find out the interference source.

The only clue I have now is 6-8 seconds down time every problem happen and big C/N number without drop or unwanted signal interference.
I never have this kind of issue with this symptom before therefore I need an advise.

Note : I am using 8 way passive splitter in the end of the cable to split into 8 IRD (is there any effect)
 

Terryl

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OK at 135 meters of RG-11 you will have about 20 dB of signal loss at 1 GHz, at 1.1 ohms DC resistance on the center conductor and about 1.3 ohms DC resistance on the shield.

This would be about 3 tenths of a volt drop if your LNB takes 150 mA to run, his may not be a problem.

But it still could be a DC voltage problem at the LNB, is the in-line amp one that has a DC power path? (one way?) If not then your LNB could not be getting the power it needs.

And using a plane 8 way signal splitter may be your problem, to use 8 receivers you should use a switch that is capable of splitting the signal from the LNB to 8 receivers with out loss, your signal loss is too great through a simple 8 way splitter.

Take a look at an EMP switch, something like this one.

Code:
http://www.emp-centauri.cz/index.php?lang=en&page=prodview&id_kateg=1&id_pkateg=11&id=17
 

Asoet

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Hi Terry,

Thanks for your advice, just now I am try using Active Splitter from Quitech Electronic with smaller loss (1 - 2 db ) but I still get an alarm 2 hours ago.
Regarding with the DC power to LNB, currently DC power supplied by IRD with capabilities of 350mA, for the LNB I have been tried 2 brand 1 Norsat 3120 which is currently used (250 mA current) and Zinwell (100 mA) both has same result and yes the Line amplifier is powered from the same source as LNB which is IRD.

Now in simulation setup, I trying to put the LNB power supply next to the dish and monitoring it while the IRD still receive in the end of long cable. Will let you know the result.
 
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a33

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I'm not sure if I understand your setup right.
You have two dishes with two polarities, you wrote.
Do you have a multiswitch at the dishes and ONE cable of 130 meter? And then a passive 1/8 splitter (which receiver has control?)?


greetz,
A33
 

Terryl

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Hi Terry,

Thanks for your advice, just now I am try using Active Splitter from Quitech Electronic with smaller loss (1 - 2 db ) but I still get an alarm 2 hours ago.
Regarding with the DC power to LNB, currently DC power supplied by IRD with capabilities of 350mA, for the LNB I have been tried 2 brand 1 Norsat 3120 which is currently used (250 mA current) and Zinwell (100 mA) both has same result and yes the Line amplifier is powered from the same source as LNB which is IRD.

Now in simulation setup, I trying to put the LNB power supply next to the dish and monitoring it while the IRD still receive in the end of long cable. Will let you know the result.


That active splitter you mentioned is DC blocked at the outputs according to the spec's from the manufacture, this may be a problem.

Have you tried it with just one receiver attached at the far end with the splitter removed from the circuit?

The way that splitter works is it has a secondary power supply for the LNB(s), also most LNB's use a DC switching voltage to go between the horizontal and vertical transponders on the satellite, unless your only watching one channel on on transponder, otherwise with a splitter that has DC blocking there would be no way for the individual receivers to go between transponders.

Now for a possible problem, if your trying to have individual control of transponders for each IRD so each IRD will be able to channel surf, then that splitter will not work.

For individual control on each receiver you will need at least a two output LNB and a 2 in by 8 output switch, this would give each receiver (IRD) the ability to change to a different transponder and differant channels.

The switch I mentioned would be able to do this, however it would have to be located at the far end where the receivers are, also a second RG-11 coax would be needed to allow independent control at each receiver. (one coax for the Horizontal transponders and one coax for the Vertical transponders)

This way one receiver could be watching a channel on a horizontal transponder and another could be watching a differant channel on the vertical transponder.

This is a problem with most linear LNB's that use a DC voltage to switch between transponders.
 

Asoet

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I'm not sure if I understand your setup right.
You have two dishes with two polarities, you wrote.
Do you have a multiswitch at the dishes and ONE cable of 130 meter? And then a passive 1/8 splitter (which receiver has control?)?


greetz,
A33

Yes, I have 2 dish aligned to two satellite. Each dish has 2 LNB for each polarity and I am using professional LNB which is not DC voltage switching to choose the polarization.
Each LNB connected to coaxial cable with 130 m length and L-Band amplifier in the middle, in the end of coaxial cable I am using 8 way passive splitter to distribute the signal into 8 receiver (each receiver only looking into 1 channel all the time)

Hope this clear for you.
 

Asoet

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That active splitter you mentioned is DC blocked at the outputs according to the spec's from the manufacture, this may be a problem.

Have you tried it with just one receiver attached at the far end with the splitter removed from the circuit?

The way that splitter works is it has a secondary power supply for the LNB(s), also most LNB's use a DC switching voltage to go between the horizontal and vertical transponders on the satellite, unless your only watching one channel on on transponder, otherwise with a splitter that has DC blocking there would be no way for the individual receivers to go between transponders.

Now for a possible problem, if your trying to have individual control of transponders for each IRD so each IRD will be able to channel surf, then that splitter will not work.

For individual control on each receiver you will need at least a two output LNB and a 2 in by 8 output switch, this would give each receiver (IRD) the ability to change to a different transponder and differant channels.

The switch I mentioned would be able to do this, however it would have to be located at the far end where the receivers are, also a second RG-11 coax would be needed to allow independent control at each receiver. (one coax for the Horizontal transponders and one coax for the Vertical transponders)

This way one receiver could be watching a channel on a horizontal transponder and another could be watching a differant channel on the vertical transponder.

This is a problem with most linear LNB's that use a DC voltage to switch between transponders.

Hi Terry,

As I have mentioned in the post above I don't use LNB DC Voltage switching to change the polarity. Each Dish has 2 LNB for each polarity and both LNB connected to different coaxial cable, amplifier, splitter and receiver.

I do this setup since each receiver only looking into one channel all the time, and also the quintech active splitter which i use i equipped with DC Voltage to the LNB but DC Blocked to IRD.
 
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