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C-Band Satellite reception "burps"

Z

zach_morton

Guest
I have a weird problem that I can't figure out. My dish (an older 3 meter mesh dish) is receiving programming from ABC and Premiere on three separate recievers. Each receiver is fed using a Pico-Macom satellite da, and is getting a signal of approx 12.1db. Several times throughout the day, the signal will just "burp"...in other words, losing audio and signal for approx 6 to 10 seconds, then comes back. It happens to all receivers, and I am having a heck of a time figuring out why. We are located in Peoria, IL...so I should be able to get a higher signal level in the first place...up to 14.1db.

Any suggestions, ideas...etc?!?
 
Sounds like solar flare / sunspot activity to me.

Anyone else think the same?

R
 
I had originally thought this, except that it happens at random times throughout the day and night. Another possibility that has crossed my mind is aircraft radar. We are within 5 miles of an airport here...and large planes and military planes fly in and out all the time.
 
What is the AG level on your starguides? should be around 115. I actually had to attenuate the inputs on ours, as they were being overloaded, raising the noise floor in the receiver, causing just what you described.

dave


zach_morton said:
I have a weird problem that I can't figure out. My dish (an older 3 meter mesh dish) is receiving programming from ABC and Premiere on three separate recievers. Each receiver is fed using a Pico-Macom satellite da, and is getting a signal of approx 12.1db. Several times throughout the day, the signal will just "burp"...in other words, losing audio and signal for approx 6 to 10 seconds, then comes back. It happens to all receivers, and I am having a heck of a time figuring out why. We are located in Peoria, IL...so I should be able to get a higher signal level in the first place...up to 14.1db.

Any suggestions, ideas...etc?!?
Click to expand...
 
I doubt sunspots and solar flares are the problem. If the antenna is not 2-degree spacing compliant, you may be getting adjacent satellite interference. Certain aircraft radars will cause grief because they are next door to C band. One station I work for had random dropouts that turned out to be a wren flying into the feedhorn opening. I shoved a styrofoam coffee cup in it to fix the problem. If you have access to a spectrum analyzer you can identify the interference. Good luck.
 
Signal attenuation...padded down the recievers and things appear to be better now. Plus whomever wired this system apparently doesn't understand the importance of vertical and horizontal polarity...it was all screwed up. I'll let you know how it holds out!
 
zach_morton said:
Signal attenuation...padded down the recievers and things appear to be better now. Plus whomever wired this system apparently doesn't understand the importance of vertical and horizontal polarity...it was all screwed up. I'll let you know how it holds out!
Click to expand...

Oh damn, sorry about that Zach! I was on a caffeine rush during the installation. ;D

Good luck, and keep us posted!

R
 
Still had one drop out over the past few hours, but only on one reciever...ag signal level is a bit lower than the others...plus the dish may need to be aimed a bit better. Hard to do by yourself without a meter.
 
Don't know if this will help, but a few years ago we had a power supply going bad in a Sat receiver. It would cause chirping in the audio at times, or would just temporarily die.

R
 
I would try using a different receiver to power the LNB 1st. I agree about the power supply.

The radar thing could possibily be it (why the signal attenuation is helping). A friend of mine this past year put in a new control room (TV) and was having satellite problems b/c of the radar (intermittent).

Good luck.
 
I had a similar problem years ago with a roof-top mounted ABC dish. It was installed in the spring and worked fine until the colder weather came along when it started to glitch every 30-60 minutes. We looked for interference with a spectrum analyzer and there wasn't any. Seemed every time we would go up on the roof the problem would go away. I finally discovered the problem: about 25' in front of the dish was a Carrier HVAC unit with a pizo electric ignitor system. Whenever the thermostat called for heat the pizo would click on and off about a half dozen times to light the gas burner so in essence we had a wide band spark gap transmitter practically on axis with the very sensitive receive dish. Remember this was ABC and the station was in New England so the look angle was only about 9 degrees from horizontal so the dish was looking right at the unit. The reason why the problem seemed to go away whenever I went on the roof to troubleshoot was because I picked the warmer days to up, days when heat was being called for less frequently than usual! The fix was to replace the auto ignitor with a continuous pilot. I had another station with their dish pointing at a nearby state highway and whenever a motorcycle went by with a noisy ignition the sat signal would glitch. Take a look to see if there are any sources of electrical noise in front of your dish such as neon signs, welding shops, HV lines, electric fences and the like.

As stated previously there are military radars which operate on or near both the downlink and the IF (C-band) frequency. AWACS aircraft can be particularly problematic I'm told. Several companies make filters for this kind of interference.
 
I'm not an engineer, but I heard of an owl flying in and out of the feedhorn area at a setup a few years ago causing signal interruptions.
 
We found the ignition system on our standby genset - Ford powered Onan in a grounded steel enclosure - which is located about fifteen feet behind the dish was wiping out the satellite reception. New set of wires, and it has not been a problem since.

I'll note, I've had the same problem with this engine - Ford's 300CID six - in trucks as well. For some reason, they eat spark plug wires every couple of years. We now have the maintenance schedule set to simply replece them when we replace the cranking battery at 30 month intervals.
 
Didn't ANYONE see Independance day?

It's aliens using our satellites against us.

We had a problem with burps to Charles River's C Band Clasical feed a few years ago.

Microwave Filter Company supplied a filter for the lnb that fixed things. This was taken off when the station changed format and switched sats.
 
ChiefEngineer said:
Didn't ANYONE see Independance day?

It's aliens using our satellites against us.
Click to expand...

:eek:

Run fer ya life, Ethel!

R
 
The virtex receivers DO NOT like a high signal level into the front end of the receiver. Keep in mind that as the AG number goes lower, the signal is getting HIGHER. When you put a 6db attenuator between the virtex and the receiver, you have improved your S/N ratio. You can turn an EB: 15.3 and AG: 61 into an EB: 13.1 and AG: 121. Virtex prefers for the EB to be 120 or more.

Other items to consider: Is the earth station tuned for maximum signal when the bird is in the "Middle Of The Box"? Is the dish 2 degree compliant? PLL LNB?

Just suggestions..... I have found that an EB of 10-14 and an AG of 80-120 has worked well for my operations.

8)
 
rcs said:
I had a similar problem years ago with a roof-top mounted ABC dish. It was installed in the spring and worked fine until the colder weather came along when it started to glitch every 30-60 minutes. We looked for interference with a spectrum analyzer and there wasn't any. Seemed every time we would go up on the roof the problem would go away. I finally discovered the problem: about 25' in front of the dish was a Carrier HVAC unit with a pizo electric ignitor system. Whenever the thermostat called for heat the pizo would click on and off about a half dozen times to light the gas burner so in essence we had a wide band spark gap transmitter practically on axis with the very sensitive receive dish. Remember this was ABC and the station was in New England so the look angle was only about 9 degrees from horizontal so the dish was looking right at the unit. The reason why the problem seemed to go away whenever I went on the roof to troubleshoot was because I picked the warmer days to up, days when heat was being called for less frequently than usual! The fix was to replace the auto ignitor with a continuous pilot. I had another station with their dish pointing at a nearby state highway and whenever a motorcycle went by with a noisy ignition the sat signal would glitch. Take a look to see if there are any sources of electrical noise in front of your dish such as neon signs, welding shops, HV lines, electric fences and the like.

As stated previously there are military radars which operate on or near both the downlink and the IF (C-band) frequency. AWACS aircraft can be particularly problematic I'm told. Several companies make filters for this kind of interference.
Click to expand...

When I replaced my boiler about 8 years ago, I had to fight like mad to get a standing pilot light like the old one had.

I lived in a 2-flat for 5 years with a piezo-ign system, and with the landlord's blessing, I put shielded coax on the thermostat lines, liberal caps and filtering, enclosed AC wiring to the control with a 2-section line filter, multiple grounding experiments....nothing could keep the zap from getting into my AM, SW, pirate and amateur listening. If I happened to be enjoying a weak but clean signal at a high volume, the ignition cycle was deafening and distressing, sending me racing to the volume control.

Today, in my own house where such emf events do not occur, I can tell when a neighbor is lighting their stove.
 
I agree with ChiefEngineer. 93.9 Indy had the same problem years ago with a C-dish on the studio high-rise roof that was aiming in the direction of the airport to the SW.

It took a spectrum analyzer to find an intermittent signal just outside the C-band that was overloading the input. With further investigation I determined it to be aircraft landing approach radar that mostly showed up during peak flight times on a particular approach. A Microwave Filter band-pass filter between the feedhorn and the LNA took care of the problem (after much grief).

I'm not sure if the airlines are still using that frequency range but it would be worth checking out. It doesn't take much power to overload the input when you have an air-mobile source tracking within the focal point of the dish. The spectrum looked like a comb generator with REALLY hot spikes.
 
Remember that if you do analyzer measurements, to put the analyzer in peak hold mode!
Some radarbursts ( ground stations especially ) are transmitted with incredible high power.
Groundstations go up to 20Megawatts ( in 100nS bursts or so ). Mobile stations, like planes should be lower rated, but still very high power ( assume more then 1KW EIRP ).
A good wavguide bandpass filter will solve these issues.
If i put one of my 10ghz (2KW EIRP ) STL's close to my television reception dish, i loose the tv reception completely! TV reception is at 12Ghz. Most LNB's are quitte broadband amplifiers, that's in most cases the problem.

Regards,

Evert
 
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