C Band Interference!

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KJ6EO

KJ6EO

SatelliteGuys Pro
Original poster
Apr 16, 2013
388
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118.3W 34.3N
Here is a short video clip of the C Band Interference I get on SATMEX 8 116.8 (3815/H/3600). It happens during the day starting at around noon and can last till 5:00pm. It does not happen at night. There is an interval of 3 minutes 30 seconds between the interference. If I take off my LNBF (ESX242) and put my Chaparral Horn on it never happens (but then I have no way of controlling polarity). The only thing that I know of operating in this area is the Channel 7 doppler radar (megawatt)(C Band) which is located on a hilltop 15 miles away at an elevation of 3700 feet.

?Any suggestions you might have would be appreciated.
 

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hello KJ6EO
What is the declination angle on your dish? I am in the riverside area, and my declination is set for 39.5 degrees and i do not have this problem. I gor this dish for free and it was close to where I live and I did not make any changes on the polar mount.
I have orthomode feed with norsat lnb's.
Regards.
Chewie
 
The polarotor and LNB's probably have better 'out of band' rejection.
1) Get in touch with the Channel 7 doppler radar operators. Have them, and you, run a test at some specific time for a minute or two. (Tell 'em it's a matter of national security or something [if they ask"what for?"]) They should be able to tell you 'when it's aimed at you'.
2) Time to break out the spectrum analyzer. Find out exactly 'what it is'. Maybe put a LNBF with a conical scalar, aimed at the horizon, on an antenna rotor, to get a bearing to the source. Power with a switchable 13/18v source to check on polarity. Should get fairly accurate bearing by looking for a null on either side of the source. (Source should be half way between) Spectrum analyzer detected freq, with accounting for the L.O., could be used at wireless2.fcc.gov/UlsApp/UlsSearch/searchLicense.jsp to see who the licensee is.
""interval of 3 minutes 30 seconds"" sounds like it could be the doppler radar. {One 360 degree scan} How long does the interference last per 'episode'?
 
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The 0:3:30 interval is curious, but probably a clue to your interference. Slow scan radar?? Are you pointed in the direction of the radar you mentioned? Can you post a picture of the dish and a closeup of the LNBF scalar and mount? Possibly you could experment with the position of the scalar ring but maintain the focal distance to the LNBF opening.

EDIT:

Sorry FAT, you posted just ahead of my reply.
 
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Radar seems a likely culprit. Determining the source specifically is the tough part. My first Uniden satellite receiver had a TI filter button that I thankfully never needed or used. There are cell phone and microwave relay towers everywhere you look, even in my area in farmer's fields.

It seems that today transmitters are everywhere. Your home may have a KWH meter for your power, your car may have a ezpass device for automated tolls or transmitting tire pressure sensors in the wheels. Most transmitting data at very low power for milliseconds and unlikely could cause any interference.

In the news locally in this area there have been many questions raised by concerned residents in a nearby town with new electronic water meters being installed for remote reading. Many are opposed to having these devices placed within their homes. Not many answers from the utilities about the power or duration of the transmissions. Sometimes referred to as wireless mesh networks on the news when describing some of the metering technologies in use.
 
Thanks for your comments and suggestions. Attached you'll find a picture of my WSI LNBF, and a picture of my Chapparal Horn with California Amplifier LNB's. Neither the LNBF or Chaparral Horn can fully illuminate my dish (Winegard Pinnacle F/D .278). However I think the Chaparral comes much closer to doing it than the LNBF. The Chapparal horn is set up per instructions from Chapparal. The front edge of the horn is .800" from the surface of the scalar ring. The Focal Distance is also set per Winegard recommendations to 33 1/16". Regarding the WSI LNBF (no information was supplied with the product, so I took a guess). I set the front edge of the LNBF to .800" from the surface of the scalar ring (just like the Chapparal). After sliding the button hook in and out to obtain maximum signal, the Focal Distance came out to be 32 5/8".

To answer your question, my BUD is pointed right at Oat Mountain where the Doppler is located. It's at 3700' and I'm on the other side of the valley in the foothills at an elevation of 1400'.

The duration of the interference is from 10 to 15 seconds. The hours of the interference are: 8:30 - 9:30am, Noon till around 1:30pm, 4:00pm - 5:30pm. I don't record in the evening so I don't know if the interference is there or not. I can say for sure that there is no interference between the hours of 11:30pm to 7:00am. There could be interference on other TP's but so far I've only noticed it on SATMEX 8 (3815/H/3600). I hope that some of this information has helped!
 

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  • Chapparal.jpg
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According to the info here: http://www.chaparral.net/troubleshooting/feedhorn-troubleshooting-guide/ .8" of the throat forward of the scalar equates to around a F/D ratio of .35. That would under illuminate the dish for sure.
According to the 'chart' on the page[half way down], for an F/D .278 looks like you'd want an inch and a quarter protruding. (If possible)
Sure sounds like it's that radar you're getting the interference from. Hours of it's operation, etc.
I can say for sure that there is no interference between the hours of 11:30pm to 7:00am.
Click to expand...
That may hold true till there's some bad weather incoming. Then it may be continuous until it passes.
I see only two choices. Use the LNBF and 'live with it' OR the Titanium Satellite ASC-1 Positioner / Controller, that's to come out soon, to operate the servo polarotor and move the dish.
The other option i don't recommend, an analog receiver, I abandoned a few years ago[and will never go back].
 
A few years back when I put the ortho on my Paraclipse, I developed a problem that drove me nuts for months,till I figured out what it was.I live about a mile from the main shipping channel of the St Lawrence Seaway.I finally realized that when interference was occurring,I could here the big diesels going by.There's a web site that shows the locations of the ships in the Seaway and I started checking that when I started seeing the interference.Sure enough whenever a ship was from about 4 miles away you could watch the radar antenna spin.It only bothers horizontal not vertical.I also notice it on the Winegard with the lnbf but not as bad.
There are filters that might fix it but they're kinda spendy so I just live with it.At least the seaway is closed in the winter so the problem goes away for a few months.
 
There are filters that might fix it
Click to expand...
All the filters I've seen were adaptable to WR229 waveguide *. Have yet to see a filter, or anything resembling, that would work with a LNBF anywhere. And yes, the costs seen have been astronomical, especially for a "hobby".
* But since the C band LNB/feedhorn combo isn't affected, no gain in implementation. Solution for the LNBF is required.
References:
https://www.avcomm.com.au/waveguide-filter-c-band-3-7-4-2ghz-detail or a DIY project - http://www.goulouev.com/connector/examples.htm
I just had a revelation as to a new product. And it's not a filter.
 
Thanks for your replies. Yes, I think I can get an inch and a quarter out of the LNBF. I'll readjust it and give it a try ... maybe over the weekend. Interestingly enough, I contacted Chaparral Tech Support and they said that my current Chaparral Horn (Dual Band) was incapable of fully illuminating the Pinnacle. The Winegard Manual suggests a Seavey Horn which would cost about $500.00 not including the LNB's of course.
 
FaT Air said:
I see only two choices. Use the LNBF and 'live with it' OR the Titanium Satellite ASC-1 Positioner / Controller, that's to come out soon, to operate the servo polarotor and move the dish.
Click to expand...

FaT ... that Positioner / Controller looks like it's gonna be extremely expensive. Even that PLL LNBF looks like it would be expensive. Guess we'll just have to wait and see what the actual price is.
 
No, no, no. The guy behind Titanium knows the market.
I expect the LNBF to be "inexpensive', and the controller "reasonable".
To make a guess: $20-50, and $80-125.
I just made up those numbers, and have no inside knowledge.
It's just doubtful that higher prices would entice customers. ;)
?We'll see in a few months.
 
Seems a little expensive for the job but somebody bought one an hour before I posted this message. You can buy a hacksaw for half of the cost and take a 1/4" off of the scalar ring's throat in 10 minutes.

Are the feeds of a Chaparral corotor and ortho the same diameter that the ring would fit both? That would be my concern about spending $25 on it.
 
FaT Air said:
According to the 'chart' on the page[half way down], for an F/D .278 looks like you'd want an inch and a quarter protruding. (If possible)
Click to expand...

FaT - I readjusted the LNBF as you suggested (1.250) from the scalar ring. I then slid the button hook in and out to maximize the signal strength. The button hook ended up to be in the same place (in/out) as the original Chaparral Horn. There was a noticable signal strength increase (about 5% on most TP's). So far, there hasn't been any interference this weekend. We'll see what happens tomorrow morning at 8:00am.
 
When I put my Pinnacle up I didn't even attempt to adjust the button hook,just ass umed that after 20? years out in the weather it wasn't gonna move anyway.Just threw the lnbf (bsc621) in,gave it a quicky peek job on c band and went about watching tv.The ku side doesn't work as good as it could but I'm more interested in the C on that dish.;)
 
Well, this morning (Monday), right at 8:30am the interference fired up. There are several other channels on the same TP, so tomorrow morning when the interference is happening, I'm gonna switch to another channel. It would be interesting to know if the interference is specific to that PID only. Backhaul, uplink problems maybe?
 
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