Sudden, quick signal drops

[mkv7196]

I found a 10ft cband dish in the local classifieds last week and have it setup. It's working well 99% of the time but there is this one remaining thing I'm trying to solve.

A few times a day the signal quality (SNR) will drop to 0 for one or two seconds and then go back to normal. The signal strength (AGC) remains at 99% for the entire time. I don't think the issue is with the receiver since I've tried 2 different ones. I have a ~ 150ft RG6 run from the dish to the receiver. I tried swapping this with a new coax to no avail. I've tried a few satellites (107.3W, 105W) and this happens with all of them.

Any suggestions on what else I should try or ways to troubleshoot further?

 

[KE4EST]

What kind of feed is on the dish. Is it an LNBF(LNB and Feedhorn all in one)?
...or is it a feedhorn with servo- skew controller and separate LNB, or what?

If servo, I have saw those go crazy and twitch if you will and cause that.
You could also just have a failing LNB(F).

 

[. Raine]

Does it always happen at the same time of day, or is it just random times?

 

[mkv7196]

KE4EST, it's a LNBF.

Raine, seems to happen at random times, but I'm keeping a log now to see if there is any pattern. I'm logging the signal quality each second. So far today signals dropped for about a second at 1:23pm and 2:40pm. No drop since then (6:30pm here now in the Mountain zone).

 

[mkv7196]

Just as I was saying it hadn't dropped, it happened again 2 minutes later. Receiver 2 drops from 84% to 15% and Receiver 1 drops from 84% to 71%. Receiver 1 has more data points because it's faster in returning the signal info. I'm getting the signal data from the receiver and then sleeping for 0.5 seconds. I was looking at the video side by side on two tvs when this happened. Receiver 2 video cutoff for a second but Receiver 1 kept on going. More often than not, both receivers drop to somewhere in the 0-20% range for a second, but this time the first one didn't.

Receiver 1:
84 18:33:24
84 18:33:24
84 18:33:25
84 18:33:26
84 18:33:27
84 18:33:28
84 18:33:28
84 18:33:29
71 18:33:30
87 18:33:31
84 18:33:31
84 18:33:32
84 18:33:33
84 18:33:34
84 18:33:35
84 18:33:35
84 18:33:36
84 18:33:37

Receiver 2:
84 18:33:24
84 18:33:25
84 18:33:26
84 18:33:28
15 18:33:29
84 18:33:31
84 18:33:32
84 18:33:34
84 18:33:35
84 18:33:36
84 18:33:38

 

[. Raine]

Any tree limbs that could be swaying when there's wind and momemtarily blocking your LOS?

Check in the throat of the LNBF and make sure no bees are starting a nest in there, that could do it. When they're just starting a nest and there's only one or two of them, they don't block the signal all the time, but can block it for a few seconds here and there as they move around.

Is the LNBF and it's arm tight, so it can't move any when the wind blows? Or is there any slop in the polar mount that might be allowing the dish itself to move a little in the wind?

 

[mkv7196]

No trees in the way. The closest obstruction is the neighbours house, but that is far away and not blocking the signal. Checked the LNB for spiders, bees, etc and none there. LNB arm seems okay. I shook the dish and arm a bit for testing and the signal remained fairly steady (5-10% drop), so it wasn't like the 80-90% drops I'm getting.

With the last test data I posted yesterday, Receiver 1 wasn't showing a significant drop in signal. I was recording the output on both receivers and they both showed the video being cutoff at the same time, so it looks like Receiver 1 did actually drop along with Receiver 2 but the monitoring just didn't pick it up in time.

I'm going to try a shorter cable run for one of the receivers and see if that helps any.

 

[Titanium]

Does it happen with only one receiver connected? Try with only one receiver, then test with only the second receiver.

In addition to testing with these adjacent satellites, test again with a satellite on the other end of the arc. This might rule out or point to a terrestrial interference source.

 

[wvman]

It also sounds like the problem I was having on H&I, Decades and the others. The receiver wouldn't stay locked. I fixed that problem with a Freesat V7, but it created another problem with stuttering on Laff, Grit and another channel. May check it on another satellite and see if it's doing it on them. Just a suggestion.

 

[mkv7196]

Tested with one receiver only and then the other. Happens on both. Also tried different sats across the arc, same issue.

The dish came with a combo C/KU BSC621 LNBF. I borrowed a 2 output C2W-PLL LNBF to test simultaneously with 2 receivers.

I think I can probably rule out any issues with the 2 receivers at this point and look for something else. I was thinking maybe the LNB wasn't getting enough power so it momentarily lost signal and then jumped back up? How much power does the C2W need? I have a 3rd receiver that says 1000mA output on the LNB port. This should be more than enough to supply steady power? I'll try connecting this to see if maybe power supplied to the LNB is an issue.

 

[Titanium]

The recall the current draw of the C2W-PLL to be 130mA. As the signal level remains constant (LNBF amplification remains constant), but the signal quality drops, doubt that this is related to the power supply.

This spuds like terrestrial interference. A spectrum display might show the cause. If no spectrum analyzer is available, I would test by swapping out LNBFs.

 

[mkv7196]

Don't have access to a spectrum analyzer. Can terrestrial interference be blocked by putting large cardboard boxes covered with aluminum foil to the left and right side of the dish?

I can try another LNB, but I've tried 2 already.

 

[mkv7196]

I've reduced the polling time for the signal strength info from the receiver and now it returns results every 250ms. The order of the 3 numbers for each reading is SNR BER AGC. According to this the SNR dropped from 87 to 21 in about 250ms and then went back up to 87. I looked at the recording for when this occurred and there was a video drop at that time, so this small duration is enough to disrupt the video. Would passing airplanes be enough to cause quick outages like this? I don't have enough money to buy really expensive equipment like a spectrum analyzer that Titanium mentioned, but am thinking about bringing over a BUD from a friends house temporarily and then looking to see if that behaves the same way as mine at my location.

Thu Sep 8 04:36:55
87 0 99

Thu Sep 8 04:36:55
87 0 99

Thu Sep 8 04:36:55
87 0 99

Thu Sep 8 04:36:55
87 0 99

Thu Sep 8 04:36:56
21 0 99

Thu Sep 8 04:36:56
87 0 99

Thu Sep 8 04:36:56
87 0 99

Thu Sep 8 04:36:56
87 0 99

Thu Sep 8 04:36:57
87 0 99

 

[lost_mesa]

Just to be sure on everything you have swapped. You've tried 2 different receivers, 2 LNBFs, and new cable? No equipment was common in all the tests, such as a Vbox, short RG6 jumper cable, or switch?

What satellites have you tried and how many channels? Is there any channel this doesn't happen on? If you've tried two completely different sets of equipment, and it does it on both, it's probably interference.

 

[iBoston]

Good luck figuring it out. I can relate to your frustrations. I had a similar problem a year back because of my WiMax Internet connection. I ended up canceling my Wimax.

 

[mkv7196]

Yes, I've tried 3 receivers, 2 LNBFs, 2 RG6 cables. Only common equipment was the dish itself. I don't have any switches or other equipment like actuators, just a direct connection from the LNBF to receiver. I've tried various chans like NBC on 105, CTV on 107, NASA on 127, some shopping chans on 125, etc and sooner or later they all exhibit this quick video dropout.