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1dB compression test values ?

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Apr 6th, 2009 at 1:13pm  
Hi All,

Ive done 1dB compression test and have been given a specific value for the initial and max tx power.

The issue is that whenever I used this value, the modem will never go up. But then, i did change the tx power to more than what the 1dB result, and the modem went up. For example the max value from 1dB is -9dB but by changing to -5dBm, the modem went up. And it is always operating at this max value! The uplink SNR was around 6.5dB.

Can some one suggest what went wrong? is 1dB test? or other RF issue?

Thanks in advance!
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« Last Edit: Aug 18th, 2011 at 3:39pm by Admin1 »  
 
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Reply #1 - Apr 6th, 2009 at 3:06pm  
iDirect's Network Uplink Control Parameters (UCP) set the upstream SNR for the entire network.  If the inroute value is set to 9dB (which is default) the NMS will send power offsets to the entire network mandating each remote to maintain 9dB (as TDMA nominal).  So, if your remote upstream SNR is at 6.5dB the NMS will give it power adjustments until it acheives 9dB.

1. Is the Hub earthstation or your location under weather?
2. Is your BUC capable of closing the upstreams you are using?  
3. Is there any change you may be pointed poorly?

Ruling our weather is Step 1.  Ensuring you have a capable BUC is step 2.  Step 3 is ensuring you are pointed properly.  

Are you a Hub Network Operator?  If so, what is the Rx_Power on your Rx (return) Line Cards supporting this inroute?  Also, what is your UCP set to (TDMA Nominal?)?

M
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Reply #2 - Apr 7th, 2009 at 7:00am  
Hi Mike, thanks for the reply.

1. Both locations are on clear weather. The 1dB done under clear weather as well.

2. Yes, the BUC is capable of closing the upstream. There are other few remotes using the same BUC.

3. We did the isolation twice with good result. More than 30dB achieved.

For the UCP, it was set to 7.5dB. And the Rx_power is -31.5dBm

Any ideas what went wrong?


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« Last Edit: Apr 7th, 2009 at 9:39am by N/A »  
 
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Reply #3 - Apr 7th, 2009 at 11:55am  
7.5 is low for TDMA Nominal.  Is there a reason why you are operating so low?

I recommend a value higher than 8.  What are your fine adjust margins set to?  1dB either side of 7.5?  In setting it to 7.5 dB, you do realize that your remotes will not have the fade margin as they would with say...9dB.  

If you know the skies are clear, the BUC is capable, and the system is pointed properly, I would take a look at the uplink (Tx) IF/RF chain.  

1. The Rx Power, where was queried from?  The line card stats, or the remote.  

2. Is the suspect remote staying around 6.5 dB of upstream SNR?  NMS able to get it to 7.5?

3. Are other remotes able to achieve the 7.5dB sweet spot you have configured for UCP?  

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Reply #4 - Apr 7th, 2009 at 12:53pm  
Hi Mike,

Yes, the adjust margins is set to 1dB either side of 7.5.

1. The Rx power was queried from the line card stats itself

2. Currently the suspect remote staying around 6.5 dB of upstream SNR and never goes up more than 7dB as per observation

3. The are other remotes in the same inroutes and i can say only 2 or at most 3 remotes can reach more than 8db while others are staying low than that.

The operating outbound is a big carrier which is around 15mbps.
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Reply #5 - Apr 7th, 2009 at 6:01pm  
With regards to the spot beam: How much EIRP variance is there between the suspect remote (operating at 6.5dB) and nodes that are operating at 8 dB?  
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Reply #6 - Apr 16th, 2009 at 3:42pm  
Hi Mike,

There is not much varience in the EIRP since all of the remotes are operating almost at the same area.

Can other remotes that operating with such high power  affect others in the same inbound group?
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Reply #7 - Apr 16th, 2009 at 7:19pm  
Any chance that this system has significantly more coax than the others? 

The system is obviously close to saturating if the NMS UCP is giving it power offsets and it is not responding to the offsets to achieve the 7.5 UCP sweet spot (you said this system is staying around 6.5).  Tell me, in the UCP tab for this remote, is it stating that the NMS is sending .5dB power offsets (pushing up power?)?

Also, what is this systems current operating power (tx) when it is nominal TDMA?  What is its maximum power setting based on the compression test? 

Additional Questions: Has this system been repeaked? My thoughts are that the system is either slightly off azimuth...or it doesnt have the BUC you think it has.
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