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Pages: 1

4 Port Feedhorn for 7.3 M Andrew

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Ex Member
Ex Member

Aug 28th, 2008 at 12:04pm  
Dear List.
A Friend of mine has a 7.3 M antenna with  four services running. Apparently one of the TX  is affecting the RX on opposite POL . any advise will be of much help

4CPNC-76-206  7.3 M andrew Antenna
Question: I have a  7.3 M antenna that has  4 ports. 2 Rx  and  2 TX

RX1 splitter A  locked on LHCP DVbs2  
RX1 Splitter B locked on LHCP SCPC-R
RX2 Locked on Idirect HUB RHCP carrier

TX2 Idirect HUB TX on LHCP 2.7 Mb

TX1  transmit Kills RX 1splitter lock on LHCP Dvbs2

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« Last Edit: Aug 28th, 2008 at 5:18pm by Eric Johnston »  
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Eric Johnston
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Posts: 2109
Reply #1 - Aug 28th, 2008 at 5:18pm  
Why does the DVB-S2 loose lock ?   Does the noise level increase ?  Is there interference ?  Does the noise floor or carrier level change ?  Does phase noise increase (increase in BER with no change in C/N) ?  Is there a problem with the  power supply to the DVB-S2 LNB or receiver ?

There must be some cause link from the TX1 to the DVB-S2 receiver.   Unfortunately there are many possibilities.  It could be very local, like the mains power for the TX1 is on the same mains supply at the DVB-S2 modem and the mains supply is not adequate when TX1 is powered on.  More likely, it is some IF or RF interference problem.

Is there any chance of measuring and recording spectrum analyser plots of:

If there are 6 GHz couplers or low level monitor points on the HPA TX outputs (3 - 7 GHz), plus expanded views of the transmitted carriers and any spurious transmissions.

With and without TX1 powered on:
LNB outputs (DC to 7 GHz) or LNA outputs (3 - 7 GHz), plus expanded views of the wanted carriers.  In the case of LNBs the range DC to 200kHz is of interest in case of switch mode PSUs causing phase noise.

If there are spare, exposed, ports on a splitter they should all be terminated with 50 or 75 ohm terminations.

Best regards, Eric.
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Ex Member
Ex Member

Reply #2 - Aug 29th, 2008 at 10:45pm  
Thank you for your suggestions

They  solved this issue.
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