C-Band Performance Tuning - New System. Help!

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bmcglynn

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Active SatelliteGuys Member
Jun 29, 2009
18
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Ottawa, ON
Hello,

I recently installed a 10' mesh Channel Master antenna at my residence in Ottawa, Canada (45N, 76W) and would like to tap into the experience base here around performance tuning before I start trimming branches and looking for a 15' dish.

After installing the dish on a 10' pole, I aligned the polar axis and declination, then installed and rotated the LNBF for maximum S/N ratio using my First Strike FS1 signal meter. Following this, I aligned the dish using ths push, pull, and rotate method to track true south and implement the correct polar axis, declination, and heading.

I then installed the GBox (from Sadoun) connected to my AzBox programming in all of the birds from 135W to 87W. After signal testing, and many hours of verification, the dish tracks the arc nicely.

After setting up the receiver system, I was able to scan in signals on most of the birds, although the main issue I am seeing is a picture stability issue. Even on satellites like 91W where I get 85% - 90% quality, the signal breaks apart every 5 or 10 seconds.

Strangely enough, on lower birds like 135W where the signal has 10dB less S/N, I see the same behaviour. In both cases, the signal breaks up every 5-10 seconds while the signal on the FS1 stays relatively constant.

I don't know if this is a gain or spurious noise issue. There seems to be enough signal on the higher birds and quality is much higher than I ever saw on my Ku setup. On the Ku side, I could watch a signal reliably at 40% quality while at 80% quality on the C band with the same encoding mechanism, I see the breakups mentioned before.

This issue is prevalent on my AzBox, as well as the the DSR-920 where the signal breaks up consistently on the birds at 133, 125, and 99W. On the DSR-920, the signal strength remains constant while the quality number dips every few seconds from 99 to 0 and back.

My thoughts are that the problem could be related to spurious noise. I tried two LNBF's: The DSC621 and the DMX741 - both displaying similar behaviour.

Here are my questions:

  • Is there a known AzBox sensitivity, or error correction issue?
  • What sort of performance enhancement could I get with a more heavy duty feedhorn/lnb setup?
  • Is there something obvious I can try to improve the performance?
One more observarion: The vertical transponders on many of the western arc satellites (133, 135) are consistently stronger than horizontal in S/N (3-5 dB better noise figures).

Thanks for any insights.

Brian
 
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Lak7

SatelliteGuys Master
Pub Member / Supporter
Feb 28, 2008
5,451
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Near Chicago, Illinois
What Firmware are you using on the AZbox?

Connect the Sat Meter to the AZBox Loop Out, how is the signal?
 
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bmcglynn

Thread Starter
Active SatelliteGuys Member
Jun 29, 2009
18
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Ottawa, ON
Thanks. I do have an airport nearby - less than 5 km away. They only have helicopter and small prop planes for traffic, although I can assume that this could be a source of intermittent interferrence.

With respect to the direction of the airport, most of the time the dish is facing between 180 and 90 degrees away. Additionally, there is litterally a forest of trees between the dish and the airport radar; however I assum there could be some scatter that the LNBF picks up.

In looking at a filter, I would asume that I would need to go with a Chapparal or similar type of Feedhorn/LNBF combination. In going that route, how do you adapt to 13/18v polarity switching when these units often have mechanically controlled polarity.

As for my AzBox firmware - it is 4980 (the latest update).
 
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Lak7

SatelliteGuys Master
Pub Member / Supporter
Feb 28, 2008
5,451
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Near Chicago, Illinois
When using a LNBF with the DSR 920, in the LNB setup Menu, you should have "LNBF" and "Rotate 90" selected.
 
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bmcglynn

Thread Starter
Active SatelliteGuys Member
Jun 29, 2009
18
0
Ottawa, ON
When using a LNBF with the DSR 920, in the LNB setup Menu, you should have "LNBF" and "Rotate 90" selected.

Thanks. I figured that out the hard way. Had to physcially turn the LNBF to make it work with the AzBox after installing it with the 4DTV first.
 
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Lak7

SatelliteGuys Master
Pub Member / Supporter
Feb 28, 2008
5,451
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Near Chicago, Illinois
Had to physcially turn the LNBF to make it work with the AzBox after installing it with the 4DTV first.
You did turn it back? :)

Is there a definite pattern to the Quality drops?

Did you try Ku yet?
If so, same results?
 
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bmcglynn

Thread Starter
Active SatelliteGuys Member
Jun 29, 2009
18
0
Ottawa, ON
You did turn it back? :)

Is there a definite pattern to the Quality drops?

Did you try Ku yet?
If so, same results?

I did turn it back :) The AzBox and DSR 920 are both happy now.

I haven't timed the interferrence for a pattern with a clock yet. As it stands now, it does seem to vary with some degree of frequency. At first, I thought it could be leaves blowing, although the branches are now gone that partially obstructed the view.

Also, the Vertical transponders seem stronger as well compared to Horizontal.

Brian
 
Hermitman

Hermitman

SatelliteGuys Pro
Jul 2, 2006
420
0
Limestone, Mi
If you've tried different lnb's, if you've tried different receivers, if it happens on all satellites, if it happens no matter which direction you're pointing, then look towards what's left. Have you taken a receiver and monitor to the dish and used a short cable to the lnb to eliminate the coax? Good luck.
 
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bmcglynn

Thread Starter
Active SatelliteGuys Member
Jun 29, 2009
18
0
Ottawa, ON
RESOLVED - High Speed Internet Issue

After looking at the post around airport RADAR, I got to thinking about what else could be on 3.5 GHz. Out in the country, we are serviced by an Internet broadband provider that uses microwave links to the home. I just happened to remember the installer talking about using a 3.5 GHz unit on our rooftop which points close to where the C Band dish is located.

Just for fun, I turned off the Internet radio unit and suddenly everything cleared up on the C Band set. My guess is that the 3.5 GHz Internet link was scattering through some trees, and the RF was overloading the front end of the LNBF.

Thanks for the suggestions. That helped me find this issue. This weekend, they are coming to install a 2.4 GHz unit.
 
B.J.

B.J.

SatelliteGuys Pro
Oct 15, 2008
2,029
1
Western Maine
After looking at the post around airport RADAR, I got to thinking about what else could be on 3.5 GHz. Out in the country, we are serviced by an Internet broadband provider that uses microwave links to the home. I just happened to remember the installer talking about using a 3.5 GHz unit on our rooftop which points close to where the C Band dish is located.

Just for fun, I turned off the Internet radio unit and suddenly everything cleared up on the C Band set. My guess is that the 3.5 GHz Internet link was scattering through some trees, and the RF was overloading the front end of the LNBF.

Thanks for the suggestions. That helped me find this issue. This weekend, they are coming to install a 2.4 GHz unit.

Neat. That got me thinking about a couple of my problem satellites. One of my dishes has always had a hard time on AMC21, which just happens to be aiming very close to the top of my garage where I have both a WildBlue dish AND an RF weather station. I had assumed that the KA band Wild blue wouldn't be an issue, but I had forgotten about the weather station, I forget what freq it transmits on, I'll have to look that up. Perhaps it's putting out harmonics that are messing up the Ku band.
Anyway, I mentioned in another thread that my house is full of devices putting out RF, and I often forget that I have some things running. I had completely forgotten that this weather station was even RF, mainly because it connects to a computer via an RS232 serial cable, but that's connected to a receiver module, not to the station itself. The weather station is solar powered, backed up at night by a neat SUPER CAPACITOR, and transmits to a desktop monitor that has a serial cable going to a computer in the other end of the house that then uplinks the data to the internet. So if you ever want to know what the weather is like on the roof of my garage, go to Current Weather Conditions at <!--StationCity-->, <!--StationState--> :)
 
eurosport

eurosport

In Dave Grohl We Trust!
Supporting Founder
Mar 31, 2008
6,862
309
North Florida
After looking at the post around airport RADAR, I got to thinking about what else could be on 3.5 GHz. Out in the country, we are serviced by an Internet broadband provider that uses microwave links to the home. I just happened to remember the installer talking about using a 3.5 GHz unit on our rooftop which points close to where the C Band dish is located.

Just for fun, I turned off the Internet radio unit and suddenly everything cleared up on the C Band set. My guess is that the 3.5 GHz Internet link was scattering through some trees, and the RF was overloading the front end of the LNBF.

Thanks for the suggestions. That helped me find this issue. This weekend, they are coming to install a 2.4 GHz unit.
Wow...different source, same frequency. Glad you got it figured out! :)
 
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