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Circular Pol, Cross-Pol-Copol question

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Aug 9th, 2008 at 6:32pm  
Dear All,

I have iDirect 3100 connected on badr 6@26.2 E the service provider tell me that i need to migration to another sat in the same location of badr6 but request to change from linear to circuler and they said the uplink should be RHCP and downlink LHCP, my question is should i need a new option file to be loaded or this change in the polarizer not effect?

in case of not effect and no need for option file can you please give a details on the differences between Linear & circurler?

Thanks

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« Last Edit: Aug 11th, 2008 at 1:18pm by Admin1 »  
 
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Reply #1 - Aug 10th, 2008 at 1:58pm  
To save me some typing, here is some light reading (in PDF):

http://www.intelsat.com/_files/whitepaper/Polarization.pdf


I am nearly certain you will require a new options file as your freq plan will probably change on the spacecraft they are migrating you to.  Check with your ISP to ensure this is the case.
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Reply #2 - Aug 10th, 2008 at 8:35pm  
Thank you for reply,

can you please obsarve the differences between this below tow modem paramter


[MODEM_PARAMETERS]
     data_port = 0
     loopback = 0
     interface_type = 0
     rx_freq = 1021899999
     rx_acqrange = 1500000
     rx_bitrate = 3972409
     rx_mode = 2
     rx_modtype = 1
     rx_fecrate = 15
     rx_scram = 1
     rx_diff = 0
     rx_specinv = 1
     tx_freq = 1000000000
     tx_bitrate = 829156
     tx_mode = 0
     tx_modtype = 1
     tx_clksource = 0
     tx_fecrate = 5
     tx_scram = 1
     tx_diff = 0
     tx_specinv = 0
     tx_power_in_dbm = -13.000000
     rx_fsd = 43850

[ACQUISITION_PARAMETERS]
     fsd = 62334

[UCP]
     power_uplink_control_processing = 1
     max_power_level_in_db = -11.000000

[ODU]
     music_present = 0
     odu_rx_dc_power = 1
     odu_rx_10_MHz = 1
     odu_tx_dc_power = 1
     odu_tx_10_MHz = 1
     odu_disable_tx_pwm = 0

[TDMA]
     tx_watchdog_timeout_in_frames = 2

[TIMEPLAN]
     fec_blocks_per_outroute_frame = 125
     symbols_per_inroute_frame = 64212
     outroute_fec_block_len = 512
     inroute_fec_block_len = 128
     unique_word_len = 32
     symbols_per_outroute_frame = 256031
     num_acq_slots = 1
     aperture_traffic = 8
     aperture_acq = 1078
     num_traffic_slots = 113
     payload = 512
     skip_slots = 3

[LL]
     ll_open_active = 1
     ll_tx_window = 1024
     ll_rx_window_backoff = 102
     ll_rx_window = 1024
     ll_t1_timeout = 4000
     ll_t2_timeout = 1000
     ll_t3_timeout = 5000
     ll_t4_timeout = 1500
     ll_t1_retry_limit = 5

[SPOOF]
     spoof_debug_level = 0
     spoof_passthru = 0
     spoof_timeout = 100
     spoof_oos_buffer_size = 32120
     spoof_keepalive_timeout_ms = 6000
     spoof_fwd_ack_ms_timeout = 200
     spoof_fade_timeout = 9000000
     spoof_reap_timeout = 480000
     spoof_syn_timeout = 120000
     spoof_max_sessions = -1
     spoof_accel_connect = 1
     spoof_accel_port = 80
     spoof_retx_buffer_size = 32000
     spoof_peer_retx_buffer_size = 75317

[MODEM_INSTALLATION]
     hub_lat = 15.636028
     hub_long = 32.494028
     remote_lat = 15.465000
     remote_long = 32.660000
     spacecraft_long = 26.000000
     reflector_offset_angle = 0.000000

[FREQ_TRANS]
     down_translation = 5150.000000
     up_translation = 4900.000000      

2


[MODEM_PARAMETERS]
     data_port = 0
     loopback = 0
     interface_type = 0
     rx_freq = 1019300000
     rx_acqrange = 1500000
     rx_bitrate = 2538000
     rx_mode = 2
     rx_modtype = 1
     rx_fecrate = 15
     rx_scram = 1
     rx_diff = 0
     rx_specinv = 1
     tx_freq = 1000000000
     tx_bitrate = 528119
     tx_mode = 0
     tx_modtype = 1
     tx_clksource = 0
     tx_fecrate = 5
     tx_scram = 1
     tx_diff = 0
     tx_specinv = 0
     tx_power_in_dbm = -22.000000
     rx_fsd = 63508
     is_demod2_active = 0

[ACQUISITION_PARAMETERS]
     fsd = 62809

[UCP]
     power_uplink_control_processing = 1
     max_power_level_in_db = -19.000000

[ODU]
     music_present = 0
     odu_rx_dc_power = 1
     odu_rx_10_MHz = 0
     odu_tx_dc_power = 1
     odu_tx_10_MHz = 1
     odu_disable_tx_pwm = 0

[TDMA]
     tx_watchdog_timeout_in_frames = 2

[TIMEPLAN]
     fec_blocks_per_outroute_frame = 125
     symbols_per_inroute_frame = 64014
     outroute_fec_block_len = 512
     outroute_fec_type = 793
     inroute_fec_block_len = 128
     inroute_fec_type = 660
     unique_word_len = 32
     symbols_per_outroute_frame = 256031
     num_acq_slots = 1
     aperture_traffic = 8
     aperture_acq = 687
     num_traffic_slots = 113
     payload = 512
     skip_slots = 3

[LL]
     ll_open_active = 1
     ll_tx_window = 1024
     ll_rx_window_backoff = 102
     ll_rx_window = 1024
     ll_t1_timeout = 4000
     ll_t2_timeout = 1000
     ll_t3_timeout = 5000
     ll_t4_timeout = 1500
     ll_t1_retry_limit = 5

[SPOOF]
     spoof_debug_level = 0
     spoof_passthru = 0
     spoof_timeout = 100
     spoof_oos_buffer_size = 64240
     spoof_keepalive_timeout_ms = 6000
     spoof_fwd_ack_ms_timeout = 200
     spoof_fade_timeout = 120000
     spoof_reap_timeout = 480000
     spoof_syn_timeout = 120000
     spoof_max_sessions = -1
     spoof_accel_connect = 1
     spoof_accel_port = 80
     spoof_retx_buffer_size = 32000
     spoof_peer_retx_buffer_size = 43010
     spoof_merge_on = 0
     spoof_compression_on = 0

[MODEM_INSTALLATION]
     hub_lat = 15.636000
     hub_long = 32.494000
     remote_lat = 15.636000
     remote_long = 32.493000
     spacecraft_long = 26.000000
     reflector_offset_angle = 0.000000
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« Last Edit: Aug 13th, 2008 at 7:06am by N/A »  
 
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Reply #3 - Aug 10th, 2008 at 11:19pm  

Dear TDMAMike,

please verify the above because ISP send this new OP with this parmater and when I loaded to the modem I have lock with linear Feed when I attached the cir-pol with RHCP for Uplink & LHCP for the downlink I have no signal with iSite software & modem not locked but I have the signal with satfinder, I don't know what I doing wrong please I need your help.

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Reply #4 - Aug 10th, 2008 at 11:39pm  
Linear or circular has little to do with the options file.  

It has more to do with the RFT requirement needed radiate to specific spacecraft/transponder.   That said, the options file looks good.  However, the bit rate for the downstream carrier as well as the upstream carrier has been reduced.  

Not sure what your service plan looks like but if you are contracted for a certain throughput, you might want to check into that.   They also went from .66 to .793 coding (probably in an effort to save money on MHz). Dont blame them there...

Again, the options file looks good........but you need to realize that the options file is agnostic to the RFT requirement needed to radiate a certain xponder.  

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« Last Edit: Aug 11th, 2008 at 11:56am by N/A »  
 
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Reply #5 - Aug 11th, 2008 at 11:14am  
Dear Mike,

Thank you for your reply?

but how do I know the RFT requirement ar met ?

what this means

FREQ_TRANS]
     down_translation = 5150.000000
     up_translation = 4900.000000
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Reply #6 - Aug 11th, 2008 at 11:55am  
[FREQ_TRANS]
down_translation = 5150.000000
up_translation = 4900.000000

The above is translation (Local Oscillator) for your system.....specifically for C-Band use.

Where was the above text on the #2 options file you pasted in?  I see it for the first one, but not the second.  

Please include both.



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Reply #7 - Aug 11th, 2008 at 1:09pm  
Quote:
I have lock with linear Feed when I attached the cir-pol with RHCP for Uplink & LHCP for the downlink I have no signal with iSite software & modem not locked but I have the signal with satfinder, I don't know what I doing wrong please I need your help.


If you are trying to receive a C band circular polarisation signal and you have good lock with the feed in linear mode then your tuning config in the modem is OK.   You are lucky that there appears to be no cross pol carrier at your frequency.  Often if you attempt to receive a circular carrier with linear feed you will have the wanted carrier and some interfering carrier(s), both at same half power level, and no lock.

If you have good lock and then lose lock when you change the C band feed assembly from linear to circular then the problem is with the polariser.   The OMT (linear waveguides junction) polariser can be attached to the polariser in several rotary positions.  The two positions associated with circular polarisation are with the two lines of pins/vanes/cavities at 45 deg to the waveguide planes.  One way gives RHCP UP/LHCP DOWN and the other gives LHCP UP / RHCP down.  It sounds as though you have it wrong.  Undo the screws at the OMT/Polariser flange and turn the OMT by 90 deg and reattach.
...
...
...

While your SatFinder is in measuring power mode it will respond to carriers from any satellite and any polarisation.

If your SatFinder has been programmed to recognise a particular carrier frequency and symbol rate, then, once it has detected power and you have peaked up a bit it will lock up and say "XYZ Satellite Found" or something similar.

Best regards, Eric.


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Reply #8 - Aug 12th, 2008 at 7:52pm  
Thank you all for your help,

I have review my circular feed configured correct as Eric said but It seems that there are a wrong in some element,
Arabsat badr 6 announce that from 6 of Aug 2008 they will migrate from linear to circular.
Our local service provider starts change in their customer polarizer from Linear to Circular but some customer are running in linear till now without any shortage in the service.
The ISP transponder is C-22 –
Uplink RHCP: 6,247MHz-6,383
DownLink LHCP: 4,122MHz- 4,158 MHz

Badr 6 frequency Band
uplink 5.925-6.425 GHz
Downlink 3.700-4.200 GHz.

Is it possible that I had an error in the frequencies and how I now this is correct frequencies should I transmit and received on it.

Also what does that mean the transponder have 36 MHz?

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Reply #9 - Aug 12th, 2008 at 8:12pm  
This is a confi on OPF please Observe

[MODEM_PARAMETERS]
     data_port = 0
     loopback = 0
     interface_type = 0
     rx_freq = 1021899999
     rx_acqrange = 1500000
     rx_bitrate = 3972409
     rx_mode = 2
     rx_modtype = 1
     rx_fecrate = 15
     rx_scram = 1
     rx_diff = 0
     rx_specinv = 1
     tx_freq = 1000000000
     tx_bitrate = 829156
     tx_mode = 0
     tx_modtype = 1
     tx_clksource = 0
     tx_fecrate = 5
     tx_scram = 1
     tx_diff = 0
     tx_specinv = 0
     tx_power_in_dbm = -13.000000
     rx_fsd = 43850

[ACQUISITION_PARAMETERS]
     fsd = 62334
[FREQ_TRANS]
     down_translation = 5150.000000
     up_translation = 4900.000000
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Reply #10 - Aug 12th, 2008 at 11:00pm  
When you put the MODEM_PARAMETERS above and say please observe, I wonder if you should perhaps send this to the hub and say "Does this match your hub?.  If not, please send correct parameters."

The ISP seems to be leasing some bandwidth in this 36 MHz transponder:
6.247 - 6.383 up         4.122 - 4.158 down
Lots of C band satellites have 36 MHz wide transponders.   The ISP may lease 5 MHz and put several carriers, for example: a 4 Mbit/s outlink and two 500 kbit/s TDMA return links.

Then they need to tell you the actual carrier frequencies and bit rates to use.  They will have one big outlink carrier and you will be assigned to one of the smaller TDMA return links.   These carriers must have centre frequencies and bandwidths so they fit within the fractional leased portion of the transponder.

Using your figures:

RX
-1,021.899,999 MHz (L band in cable)
+5,150 MHz (LNB LO)
=4,128.100,001   (from Satellite) < probable

TX
1,000.000,000 MHz (L band in cable)
+4,900 MHz (BUC LO)
=5,900.000,000 MHz  (to Satellite)

The RX frequency is within the transponder  bandwidth.

The TX frequency looks improbable but it may be some kind of starting point reference from which the TDMA frequency is dynamically set by the hub once your site is commissioned.

You need to talk to your hub and obtain clear instructions as to what outlink carrier you are to tune to. The first priority is to get you receiving OK.  When you swing the dish you should get a lock on the outlink carrier.

Best regards, Eric.
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Reply #11 - Aug 13th, 2008 at 1:21am  
Eric, you are correct in the TX Freq merely being a starting point....until the the modem gets its timeplan.
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