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troubles with idirect am1

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Ex Member
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Jul 4th, 2007 at 11:49pm  
Hi,

Last few days (from friday), i'm experiencing troubles with RX signal from Express AM1.

SNR highly varies between 10.5 (night) to 3.5-4 (sometimes even RX shows "unlocked"). Also i got a lot delta_scpc_errors,when SNR was low.

Provider tells me to check antenna pointing, but i think - troubles in another place.

Highest SNR i got only night, lowest - evening from 6PM to 8-9PM (GMT+4).

So, i have two questions - anybody experiencing the same troubles from Express AM1 (40East) IDirect ? or i have trouble with LNB/cables/modem ? or something else ?

For me - it's very strage "timesheet" troubles, i don't know to think about it...

PS. Thanks in advance, and sorry for bad english.
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Eric Johnston
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Reply #1 - Jul 5th, 2007 at 1:04am  
What is the frequency, symbol rate and nominal polarisation of your downlink carrier ?

You may be able to find it on the spectrum analyser if the beam includes the UK.  https://www.satsig.net/spectrums/satellite-spectrum.htm
wxw
Try finding the satellite around 785 on the position encoder.

Best regards, Eric.
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Reply #2 - Jul 5th, 2007 at 7:14pm  
I've put the images together.  The top one came first.
...
The spectrums look the same to me, which suggests that the downlink from the satellite is stable.  Unfortunately my dish is very small and may not be well pointed so measurement accuracy is poor.  The actual signal here is about the same level as the noise level and the composite shows up as a 3 dB high hump.   Although the two images appear the same, the signals may differ by a dB or so.

Is your dish pointed OK.  If the signal goes up and down during the day it can be due to the satellite being on the side of the beam and the normal slight dialiy movement of the satellite (-/- 0.1 deg) will cause significant level changes.

Please say what is your symbol rate and polarisation ?
The carrier on the right of the screen is about 2 MHz wide and with a similar symbol rate.  I am set to horizontal polarisation now.

There is a similar carrier on the vertical polarisation, slightly offset in frequency.

Displayed frequency may be in error by up to 1 MHz due to DRO type LNB here.

Best regards, Eric.
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Reply #3 - Jul 5th, 2007 at 10:34pm  
symrate: 1936428
polarization: (as i know - horizontal)

Btw, we have very warm weather, can this "broke" LNB or something else (modem works in room with air conditioner)?
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Eric Johnston
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Reply #4 - Jul 6th, 2007 at 9:17am  
If you are using a DRO type LNB, then temperature extremes will produce maximum frequency errors.  These can be up to 1 MHz, depending on the LNB specification.   Since your carrier is only about 1.9 MHz wide this will give the modem a problem.

Is there any readout from the iDirect that displays "Receive carrier frequency error or offset".   If so, observe it at different times of day and temperature.

You could try different modem receive tuning frequencies, say plus/minus 300 kHz and see if makes any difference to the Eb/No displayed.  Aim to reduce the average frequency error.

Most DVB-S outlink carriers are about 27.5 MHz wide and an LNB frequency error of 1 MHz is relatively small and not a problem.   When the carrier is narrow, like 2 MHz, an error of 1 MHz probably makes it difficult or impossible for the receiver to lock on.  Many cheap DVB-S demods are not specified for use below 2 Mbit/s.
 
Best regards, Eric.
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Reply #5 - Jul 17th, 2007 at 4:34pm  
Hi Eric,

First of all: thanks for your help.

I don't get any "Receive carrier frequency error or offset" errors and similar there is problem not in carrier offset.

I made small stats with rmtstat command:

hour before dead link:

Remote Status: t:000846442442 SNR=5.85 TxPower=-18.50 dBm RxPower=-34.77 dBm DigitalRxPower=24.27 Temp=54.9 COF=  -8738 TDM_Lost=0 FllDac=2089 delta_scpc_errors=3374
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000846462443 SNR=5.65 TxPower=-18.50 dBm RxPower=-34.87 dBm DigitalRxPower=24.65 Temp=54.9 COF=  -7329 TDM_Lost=0 FllDac=2089 delta_scpc_errors=850
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000846482444 SNR=5.67 TxPower=-18.50 dBm RxPower=-34.87 dBm DigitalRxPower=24.27 Temp=54.4 COF=  -5748 TDM_Lost=0 FllDac=2089 delta_scpc_errors=540
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000846502444 SNR=5.79 TxPower=-18.50 dBm RxPower=-34.77 dBm DigitalRxPower=24.46 Temp=54.8 COF=  -5229 TDM_Lost=0 FllDac=2089 delta_scpc_errors=377
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0

as we can see COF is small, but there is begin delta_scpc_errors and SNR low.

now dead link stats:
Remote Status: t:000849922444 SNR=4.29 TxPower=-18.50 dBm RxPower=-34.87 dBm DigitalRxPower=25.21 Temp=55.6 COF=   4716 TDM_Lost=0 FllDac=2088 delta_scpc_errors=66480
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000849942444 SNR=4.22 TxPower=-18.50 dBm RxPower=-34.87 dBm DigitalRxPower=25.03 Temp=55.6 COF=   3769 TDM_Lost=0 FllDac=2088 delta_scpc_errors=31823
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000849962444 SNR=4.12 TxPower=-18.50 dBm RxPower=-34.87 dBm DigitalRxPower=25.40 Temp=55.0 COF=   3540 TDM_Lost=0 FllDac=2088 delta_scpc_errors=36283
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000849982443 SNR=4.29 TxPower=-18.50 dBm RxPower=-34.77 dBm DigitalRxPower=25.03 Temp=55.0 COF=   4365 TDM_Lost=0 FllDac=2088 delta_scpc_errors=53830

Low SNR, A lot of delta_scpc_errors, COF still small.

few hours after (link now alive):
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000007962435 SNR=5.52 TxPower=-18.50 dBm RxPower=-34.66 dBm DigitalRxPower=24.65 Temp=54.2 COF=   1445 TDM_Lost=0 FllDac=2086 delta_scpc_errors=359
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000007982435 SNR=5.52 TxPower=-18.50 dBm RxPower=-34.66 dBm DigitalRxPower=24.84 Temp=54.4 COF=   1626 TDM_Lost=0 FllDac=2086 delta_scpc_errors=260
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000008002434 SNR=5.59 TxPower=-18.50 dBm RxPower=-34.66 dBm DigitalRxPower=24.27 Temp=53.6 COF=   1506 TDM_Lost=0 FllDac=2086 delta_scpc_errors=534
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000008022438 SNR=5.69 TxPower=-18.50 dBm RxPower=-34.77 dBm DigitalRxPower=24.46 Temp=53.8 COF=   1361 TDM_Lost=0 FllDac=2086 delta_scpc_errors=208

Small amount of delta_scpc_errors, Low SNR, small COF.
1.5 hours after last stats:
Remote Status: t:000008502443 SNR=5.88 TxPower=-18.50 dBm RxPower=-34.66 dBm DigitalRxPower=24.65 Temp=54.1 COF=  -1161 TDM_Lost=0 FllDac=2087 delta_scpc_errors=8
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000008522443 SNR=5.96 TxPower=-18.50 dBm RxPower=-34.66 dBm DigitalRxPower=24.46 Temp=54.4 COF=  -1357 TDM_Lost=0 FllDac=2087 delta_scpc_errors=38
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000008542443 SNR=6.21 TxPower=-18.50 dBm RxPower=-34.55 dBm DigitalRxPower=24.27 Temp=54.0 COF=  -1399 TDM_Lost=0 FllDac=2088 delta_scpc_errors=2
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000008562446 SNR=5.96 TxPower=-18.50 dBm RxPower=-34.66 dBm DigitalRxPower=24.46 Temp=54.2 COF=  -1545 TDM_Lost=0 FllDac=2088 delta_scpc_errors=47

SNR higher, but still low, COF small, almost no delta_scpc_errors.

and now best SNR (late night):
Remote Status: t:000022102444 SNR=8.79 TxPower=-18.50 dBm RxPower=-34.45 dBm DigitalRxPower=23.14 Temp=55.2 COF=    112 TDM_Lost=0 FllDac=2086 delta_scpc_errors=0
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000022122444 SNR=8.96 TxPower=-18.50 dBm RxPower=-34.45 dBm DigitalRxPower=22.77 Temp=54.9 COF=     77 TDM_Lost=0 FllDac=2086 delta_scpc_errors=0
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000022142444 SNR=8.82 TxPower=-18.50 dBm RxPower=-34.45 dBm DigitalRxPower=22.77 Temp=55.6 COF=    291 TDM_Lost=0 FllDac=2086 delta_scpc_errors=0
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0
Remote Status: t:000022162445 SNR=8.80 TxPower=-18.50 dBm RxPower=-34.45 dBm DigitalRxPower=22.77 Temp=55.5 COF=    794 TDM_Lost=0 FllDac=2086 delta_scpc_errors=0
LAN Port: 100 Mbps Full Duplex(AutoNegotiation: Complete) on phy 0

SNR acceptable, COF still small, delta_scpc_errors = 0.


I don't know what it can be, but i've already bought new LNB Eurostar ES-38 Ku-band, lo 10Ghz, 0.5dB (was NJR2784H: Ku-band, lo 10Ghz, 0.7dB.),
when we will try repoint antenna (this spring SNR was almost 13), first we change all cables/connectors - test it, then change LNB - test it and then will accurately repoint antenna to get max SNR, i hope it helps.

PS. Sorry for bad english.
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ahmedmaher30
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Reply #6 - Jul 17th, 2007 at 11:30pm  
Sir,

TRY to change the cross pole first and align the antenna at at free area

then try to ask the provider to change the Sat. if possible so that they will change the transponder

and please send me a snapshot from the result
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Reply #7 - Jul 20th, 2007 at 8:27pm  
Okay, what we have.

We changed cables/lnb/turned off buc/re-pointed antenna/tried another frequencies: Space TV  (we have used usual tv tuner, there is signal troubles too)/ - anything.
Signal still low and looks like "wave" (night - good SNR, day,morning - middle SNR, evening - lowest SNR).

Any suggestions ?
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Oasis Networks
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Reply #8 - Jul 21st, 2007 at 10:50am  
where is the site?
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www.oasisnetworks.net - Oasis Networks - Online with you!
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Reply #9 - Jul 22nd, 2007 at 5:37pm  
Uzbekistan
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ahmedmaher30
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Reply #10 - Jul 23rd, 2007 at 11:02pm  


Sir,

Can you please state to me what kind of LNB you use for that system

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Reply #11 - Jul 24th, 2007 at 2:57pm  
Dear Ahmed,

If you readed my messages earlier, you can find that i tried different LNBs.
Original:
NJR2784H (Ku-band, 10Ghz LO, 0.7dB)
and tried another LNB:
Eurostar ES-38 with the almost same parameters (Ku-band, 10Ghz LO, 0.5dB).

Troubles can't be in type of LNB (PLL/DRO), 'coz i don't get "huge" carrier offsets (as i know it's main problem of DRO LNB's).
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ahmedmaher30
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Reply #12 - Sep 2nd, 2007 at 11:34pm  
OK Sir,

Try to use LNB NJR2184HH, this kind is very stable more than njr2784HH, its error +/- 0.1 instead of the other one it was +/- 0.9 db

Make sure that you are using iSite Software and also confirm with me the Down SNR from the iSite software. it should be more than 16 on the iSite monitor for pointing

Make sure that the antenna located at free Area, if all the same  you have external obligation called "Change the Satellite"

with higher foot print and totally compitable with your hardware, confirm with your Service Provider and the NOC

UP Date me ASAP.
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ahmedmaher30
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Reply #13 - Sep 2nd, 2007 at 11:40pm  
Sir, you are 100% sure that you use AM1.

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