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Problem with Nera Satlink Modem

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papayeya

Senior Member
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Posts: 53

Mar 25^th, 2008 at 12:16pm

Dear Eric, All,

I 've a nera modem installed and the Rx and the Tx is locked, but there is no intenret link.

I checked with my Provider "Telenor", and they said we are not able to see you perfectly, note that my values is almost perfect, not that only, i am able to logon and establish a two way link, then how come they can't read my values.

Also when i type the command to show us the Rx valus most of the times this line appears with different values each time:

Viterbi Error Rate: 1.668 E-5 and some times it is higher? can that be the problem ?

I changed the BUC and LNB and Cables, Network Cables, everything except the modem coz i don't have a spare modem.

Also there is a C-Band antenna 2 m far from the Ku Antenna, and no Walki Talki antenna and no GSM antenna.

I am confused if i am logged on and the two way link is established how come i am not able to receive internet?

My Satellite is Intelsat 1002 Spot 2 - Ku-Band
Find below my modem output:

# ip show
Interfaces
If IPAddress SubnetMask BroadCastAddr MTU Alias AdminStatus
1 10.7.4.97 255.255.255.224 10.7.4.127 1500 eth0 1
2 N/A N/A N/A 4074 air0 1
3 10.8.7.45 255.255.255.255 10.8.7.45 4074 dvb0 1
Interface Statistics
------------- Input ----------------- ------------- Output
----------------
If UCast NUCast    Disc    Octets UCast NUCast    Disc
Octets
1 123 119 11 25291    6 27    1
2948
2    0    0    0    0    0    0    0
0
3    0    0    0    0 123    0    0
10074
IP Receive Deliver Errors Discards Forward Request NoRoute
Discards
   452 97 108    6 123 30    0
0
Routing Table
DestMask RouteMask    NextHop If
   0.0.0.0    0.0.0.0 10.8.7.254 3
10.7.4.96 255.255.255.224    0.0.0.0 1
10.8.7.45 255.255.255.255    0.0.0.0 3

# dvb tx show

Satellite (DVB) TX Configuration
--------------------------------
Auto start    : Disabled
Population ID : 4
IDU output power : -12 dBm
Default CW Frequency: 14.379000 GHz
AAL5 Encapsulation : VC MUX

DVB Transmitter Status
----------------------
State       : On
IDU Output Power : -12.2 dBm
Eb/No       : 6.5 dB
delta T    : 248338 microseconds
Frequency Correction : -110 Hz

# dvb rx show

Satellite (DVB) RX Configuration
--------------------------------
Auto start    : Disabled
Frequency       : 11.606750 GHz
Symbol rate    : 13.356729 Msps

Satellite (DVB) RX Status
--------------------------------
Rx State : Forward link up
Frequency       : 11.609299 GHz
Symbol Rate    : 13.356700 Msps
FEC Code rate : 7/8
SNR       : 5.4 dB
Viterbi Error Rate : 3.2663 E-4

# odu show

Antenna Configuration
---------------------
Type    Channel Master Type 184 - 1.8m
Tx Gain at 14.25 GHz    47.0dB

Transmitter (BUC) Configuration
-------------------------------
Type    JRC NJT5017F (14.0-14.5 GHz)
Local oscillator    13.050000 GHz
24V DC supply       On

Receiver (LNB) Configuration
----------------------------
Type    Invacom SPV-1SM (10.70-12.75 GHz)
Local oscillator - High band    10.600000 GHz
Local oscillator - Low band    9.750000 GHz
Oscillator switching frequency 11.700000 GHz
LO Switching mode 22kHz
13/18V DC supply    13V

# sw show

SW versions
--------------------------------
Boot    : 7.5.3.5
Current : 9.1.5.66
Backup    : 9.1.5.66

Manual SW upgrade settings
--------------------------------
TFTP server IP addr : 10.11.112.194
File name       : 1.tgz

Automatic SW upgrade settings
--------------------------------
Activated       : No
PID       : 511
IP address    : 224.0.1.59
Port No. : 2001

Licenses for SW options
--------------------------------
None

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ICQ | YIM

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Eric Johnston

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Posts: 2109

Reply #1 - Mar 26^th, 2008 at 9:24am

I suggest you send all this information to Telenor and ask for their help.

Your receive performance is bad ( SNR �: 5.4 dB �Viterbi Error Rate �: 3.2663 E-4 ). �You should see �Viterbi Error Rate of more like E-8 in clear sky conditions.
Try adjusting the pointing. �Alter the azimuth and elevation in small steps, like 1/2 turn of a nut, then measure the BER again and see what is the difference. �You may have to make perhaps 10 such adjustments and measurements and it may take 30 minutes to complete this task and get the beam exact centre.

If pointing does not solve the problem, check the polarisation angle. �You need to calculate it and set it to 1 deg rotation accuracy. �If you have this wrong you may be receiving interference from the opposite polarisation which is degrading your signal. � If the interfering signal varies from time to time then your BER may vary also. �Many carriers are intermittent.

Also consider the assembly of the dish/feed/feed arms arrangement. � Possible problems are that the feed yoke is not attached at the correct holes in the feed arm, side struts not attached at correct place, so out of focus? �Does it look right compared with the documentation pictures ? �Dish surface distorted?. �Do the crossed fishing line test. � �If your dish has two short side struts at the rear, from the sides of the dish to the az.el head, �then they are there for a purpose - to prevent the sides of the dish being pulled forwards or pushed backwards by the weight of the BUC. �The inner end holes are elongated so you can tighten the nuts while a couple of other people pull on the sides of the dish. Adjust till the strings just touch.

You should be able to ping to IP addresses in the internet. �If you can do this but not access web sites by url name, then you have probably not set a valid DNS address in your PC.

Best regards, Eric.

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« Last Edit: Mar 26^th, 2008 at 4:08pm by Eric Johnston »

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papayeya

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Posts: 53

Reply #2 - Mar 28^th, 2008 at 2:14pm

Dear Eric,

The problem was from the NOC, they didn't activate my account, however am still worried about:

1- Signal: I tried with my digital meter to get the best and to eleminate the message: Viterbi Error Rate as i didn't see it before on any nera terminals, but i faild, however the signal is 7.5 db which is good as the maximum i guess is 8.5 db, so baiscly increasing the signal wont remove the Viterbi Error Rate Message.

So i tried the plorization, if i turned the BUC left or to the right the singal goes down, so it is in the best position, i don't know how to remove the error message.

2- Electricity: Today when i touched the tripod i felt a small current and i couldn't keep holding the tripod, i don't know from where the current is, can it be from the connectors ?