Troubleshooting signal loss at certain times of day - C/N margin (1 Viewer)

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Pete2k

New Member
May 17, 2021
3
1
TX
I'm located in central TX, fixed 12 foot dish locked on 125W. For a week or so now I've been losing signal around 11:30ish and/or around 2pm. When I'm able to check the receiver at the same time I notice that my C/N margin is fluctuating back and forth between 0 dB and 5 dB (where it normally sits). Because this seems to happen around the same time of day I'm wondering if this might have something to do with small fluctuations in the satellite arc and some limbs on one side or the other that interfere for a few mins a day. Logical explanation? If so, is it possible to isolate whether the north or south side is the offending party? This is still kind of magic to me, so any help is greatly appreciated...Thanks!
 
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Radioguy41

SatelliteGuys Pro
Aug 7, 2008
2,219
1,788
Lehighton, PA
No, it's not too early, this is exactly the right time although it can vary by location, click on the link I provided. You can have two different interferences for each satellite in the arc, one for your downlink and one for the uplink.

"Twice a year, in the spring and the fall, coincident with the spring and fall equinoxes (March 20/21 and September 20/21, i.e. when the seasons change), the sun passes across the equator where it crosses (passes) directly behind each satellite in the orbital belt. "
 
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Captain Midnight

SatelliteGuys Pro
Sep 16, 2019
447
297
Greers Ferry, Arkansas
I'm located in central TX, fixed 12 foot dish locked on 125W. For a week or so now I've been losing signal around 11:30ish and/or around 2pm. When I'm able to check the receiver at the same time I notice that my C/N margin is fluctuating back and forth between 0 dB and 5 dB (where it normally sits). Because this seems to happen around the same time of day I'm wondering if this might have something to do with small fluctuations in the satellite arc and some limbs on one side or the other that interfere for a few mins a day. Logical explanation? If so, is it possible to isolate whether the north or south side is the offending party? This is still kind of magic to me, so any help is greatly appreciated...Thanks!
Mind if I ask which transponder? I don't have any signals that weak on my 10ft mesh dish.
 

Martyn

SatelliteGuys Pro
Sep 25, 2005
614
246
Annandale, VA
This site gives you exact timing for solar outages: Sun Outage / Sun Interference Prediction for Geostationary Orbit Satellites - Jens T. Sætre - https://www.satellite-calculations.com

A rough location in central Texas and 125W reveals the sun will cause outages during the first week of October at around 2030 UTC daily, which I think is about 3:30pm. So this is unlikely to be solar-related.

If you can take those readings at the dish, I'd go out there next time and push the dish a bit back and forth to see if they disappear. That would indicate you're not quite perfectly aligned.

You're saying this happens twice a day, right? At 1130 and 1400, not between those times?

Is it on a particular transponder and only on 125W? Local interference is possible but I would expect it to also affect similarly powered transponders on the same satellite or adjacent ones. Could be temperature related, although that doesn't account for it coming and going.

Sorry, this isn't much help.
 
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Martyn

SatelliteGuys Pro
Sep 25, 2005
614
246
Annandale, VA
No, it's not too early, this is exactly the right time although it can vary by location, click on the link I provided. You can have two different interferences for each satellite in the arc, one for your downlink and one for the uplink.
Solar interference occurs at the spring and autumn equinox for locations on the equator. As you move north and south from that line, the dates shift a little. For most of the United States it's in about two weeks.
 

c-spand

SatelliteGuys Pro
Feb 25, 2019
1,139
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You can check when the sun is aligned with the sat your from your location. Try this www.satbeams.com it will show you when the sun is aligned with the sat creating more interference /loss of signal.
 

arlo

SatelliteGuys Pro
Dec 4, 2016
622
349
North Eastern
Call me crazy. I just looked at central TX. on DishPointer for where 125W's angle is. And tracked the sun angle for different times during the day.
I have the same thing in the summer. In the late morning 101W will obliterate for a period. So I jump to 103 or more west and signal is great. I lose 125 and 127 eventually. For a while.
Or jump to 89 to 55W. Signal is good.
Anyway.
Watching 103 when 101 is dead, as the sun moves it will die. Then down the arc through the afternoon to early evening.
Let's say around noon 101W is dead. At 1:30pm it starts coming back.
The sun apparently is reflecting off-angle on the dish through its arc. Something like my offset KU LNBF shoots 6 degrees east of anything on C-Band.
Yeah.....
 
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907TECH

SatelliteGuys Pro
Aug 29, 2018
382
381
Alaska
Solar interference occurs at the spring and autumn equinox for locations on the equator. As you move north and south from that line, the dates shift a little. For most of the United States it's in about two weeks.
Yes as I said, too early. I work at a C band teleport.
 

Pete2k

New Member
May 17, 2021
3
1
TX
Wow...thanks for all the help everyone. The dish is black mesh and with it happening at the same time daily it seems to be too much of a coincidence to not be sun related, even if it's not the equinox. I was able to confirm that the signal strength stays at the same level the whole time....just a lot of interference (if I'm understanding C/N ratio correctly)

Yesterday it started earlier at 11:05 central and went in and out for over an hour. Today it was completely fine despite being a completely cloudless day so I suppose the search continues





 

Titanium

AI6US
Lifetime Supporter
May 23, 2013
7,329
8,407
Meadow Vista, Northern California
Local interference from a well pump, a failing transformer, battery maintenance, generator, or ???

Many years ago, my mother's C-band went out every afternoon at the same time the return a few hours later. Used a spectrum.snslyzer to track down to a powerpole transformer that was failing. When the neighbor's milking parlor machines fired up, the transformer spewed out RFI and swapped the satellite signal. The power company replaced the transformer and the problem went away...
 

KE4EST

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Aug 9, 2004
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I agree, it sounds like local interference.
 
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