SatSig topic:

Linkstar S2 led is blinking/fast blinking/on/off

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Feb 1^st, 2009 at 10:31am

Please help with my issue. I am activating a new S2 modem, when I turn it on the sat led starts to blink slowly, qpskber is like 0.000008, after several seconds the sat led starts to blink fast and qpskber is higher: 0.0002, and goes higher and higher 0.019 and sat gets active.. after 10-20 seconds sat goes off... ber is -1.0000 or 0.02. when rebooted no sat is blinking with the 0.02 ber... if turn off for 1 minute or more and turn on again it starts the abouve again with perfect ber.. There is an existing S1 modem using the same dish, lnb, buc, on the same satellite (just modem upgrade to S2) and works fine with stable ber: 0.000007... please help with resolving the issue. thank you,
Parviz

Feb 1^st, 2009 at 1:28pm

It appear that when you transmit it causes your receive BER to deteriorate.

Three ideas:

There is a poor connection somewhere with four F type connectors. The effect is due to the increased BUC DC supply current (when your transmit burst is on) causing voltage changes on the LNB DC supply. e.g. return DC path from BUC is coming back via the LNB outer sheath.

The output L band power from your modem to the BUC is excessive and is overdriving the BUC. The BUC output is then splattered all over the spectrum and interferes with the LNB receive input. There is also risk of permanent BUC damage. Reduce the modem transmit output power by several dB.

The transmit reject filter is missing. Just before the LNB there should be a transmit reject filter in the waveguide between the OMT joint and the LNB. This is typically a length of waveguide about 2 inches long at Ku band with slots, cavities, vanes or pins inside. It allows the receive band to pass (10.7 -12.75 GHz) but stops (reflects back) any energy in the transmit band (14-14.5 GHz).

Best regards, Eric.

Feb 1^st, 2009 at 1:42pm

thank you Eric, the dish, lnb, buc is ok and in use with S1 modem with the same provide at the same satellite, it is just a modem change. S1 works great without any problems.
Currently I have value -22 on tx power. what power do you suggest me to test? thank you for your attention..

Feb 1^st, 2009 at 4:09pm

all connectors are ok for sure, as there is existing S1 system works fine; waveguide also exist and functioning... the only issue left to check is BUC power adjustment, please assist what power to enter ...

Feb 1^st, 2009 at 4:59pm

Read out the current modem transmit output power using dbpr bootconf
Write it down.

The modem output power may be adjusted from -30 to -5 dBm.
The BUC needs a maximum of -20 dBm at its input.
The modem output power setting depends on the cable length and the level needed to get the correct level signal into the teleport hub.

The adjustment is applied using command save -t -60 for example.
Each save adjustment step make 0.5 dB difference.

Talk to your hub and get them to help you.

If you set the level by save -t -30 you will set the output level from the modem to -15 dBm.

If you set the level to the minimum save -t -60 you may find you can't connect to the hub. Increase in 2 unit steps (1 dB at a time) until you start to connect successfully, then maybe go up a further 4 dB with approval from your hub. Your hub can make measurements of your carrier and increase your modem output in steps while watching the level at their end. Once your actual BUC output level (on the satellite) stops increasing in 1 dB steps they know they have gone too far and need to record the -1dB compression value, when your signal starts to be distorted by overloading; this value should never be exceeded. Now they need to back off your carrier by typically 3 to 10 dB, to set the correct level into the hub.

Best regards, Eric.

Feb 2^nd, 2009 at 2:45pm

still trying to get it active... tx adjustments didn't help, still the same thing. Today activated this modem on S1 link, works perfect, just doesn't want to get on with S2. any ideas?

Apr 4^th, 2009 at 1:24pm

Hi,
I had a similar problem but mine was on C_band platform.

The modem will slow blink on reset or recycle then fast blink for awhile afterward no sat lock

The "LOCKED" changes to "!LOCKED"
meaning not LOCKed to point satellite

As at that time I noticed that the dVb mode changes from "DVBS2" to "DVBS1"

I explained this to ISP. What they did was just to enable the modem (MAC) as if its commissioned. wala. everything became ok. modem is till up and running for 4 months now.

My ISP said maybe the modem does not retain S2 parameters

tell your provider to enble the modem for a while then they can do power test and then xpol.

the modem sud function accordingly

Regards

Green A. O
Nigeria

Jun 10^th, 2010 at 9:58am

i have the problem similiar too

the rx power start good -43 and the status locked but in a moment rx power lower to -58 and the status !locked, and the modem will restart

output power form tx port modem = 20vdc
output power form rx port modem = 18vdc

the cable is not shoot

any one know why?