Oscilating signal

[magnigyro]

What will cause the signal swing and is not maintained fixed in some tp´s?

Sometimes variation goes from 10 to 55%.... Others tp´s of bird are OK.

 

[CommCtr]

My guess is that you are looking at a spot beam transponder frequency and that you are not covered by a spot using that frequency but, are between spots. You will get that kind of signal strength swing because you are really getting some signal from two different spots and they are interfering with each other. Sometimes, the signal from one spot beam is enough for the strength to be 55% and at other times the strengths interfere with each other so much that you get 10%.

If you are not having any problem with channel reception, then I wouldn't worry.

 

[rv1pop]

My guess is that you are looking at a spot beam transponder frequency and that you are not covered by a spot using that frequency but, are between spots. You will get that kind of signal strength swing because you are really getting some signal from two different spots and they are interfering with each other. Sometimes, the signal from one spot beam is enough for the strength to be 55% and at other times the strengths interfere with each other so much that you get 10%.

If you are not having any problem with channel reception, then I wouldn't worry.

Can you move the dish to change location in the beam, and if so, how far would you have to move it? This may seem to be a dumb question, but I changed dishes on G25, moving about 50 feet and went from 20 to 60. I credited the dish, but could it have been the location? AMC4 comes in fine at the orignial location, but have not been able to get it as the second LNBF on the new dish.

 

[magnigyro]

My guess is that you are looking at a spot beam transponder frequency and that you are not covered by a spot using that frequency but, are between spots. You will get that kind of signal strength swing because you are really getting some signal from two different spots and they are interfering with each other. Sometimes, the signal from one spot beam is enough for the strength to be 55% and at other times the strengths interfere with each other so much that you get 10%.

If you are not having any problem with channel reception, then I wouldn't worry.

Yes, I had some interferences with other birds, always happen when I do blind scan to G26@93W, got a bunch of blank channels ( think thats came from the circular bird next to G26). Always I need to delete 30 or more, I must watch scan, if passes from 12200 then cancel scan.

I don´t understand how circular freq can go into linear lnb.

Thanks for your help.

 

[magnigyro]

Can you move the dish to change location in the beam, and if so, how far would you have to move it? This may seem to be a dumb question, but I changed dishes on G25, moving about 50 feet and went from 20 to 60. I credited the dish, but could it have been the location? AMC4 comes in fine at the orignial location, but have not been able to get it as the second LNBF on the new dish.

I´ll do it, and moreover, I´ll change 33" dish for a 36" to look if can catch tip Tv & Patience in AMC3@87W. (that chanels show such behaviour, but I can not see them).

Thanks...

 

[CommCtr]

Can you move the dish to change location in the beam, and if so, how far would you have to move it? This may seem to be a dumb question, but I changed dishes on G25, moving about 50 feet and went from 20 to 60. I credited the dish, but could it have been the location? AMC4 comes in fine at the orignial location, but have not been able to get it as the second LNBF on the new dish.

But, your question above mentioned AMC4 and G25 which are CONUS satellites so, your dish move probably had more to do with your mount alignment.

Just moving 50 feet wouldn't do anything with regard to spot beam satellite signal strength. If your pointing was not peek that may be a cause for the 20 to 60 mentioned in the first posting. You need to move more like 50 miles to make a difference in the spot beam signal strengths and this assuming you were at edge of coverage for a beam.

Oscillating signal from the original question is something I have notice regarding spot beam transponders. Remember, they are reusing the same frequency in different beams. The customers in the spot beam get good (even better) signal strength. Someone just checking signal strength that lives between spot beams would see the strength oscillate because the receiver is dealing with two transponders that are using the same frequency that cover two different areas and carry two different signals and they are interfering with each other.

A simple analog example: Have you ever heard two radio stations that are on the same frequency or seen two analog (over the air TV) stations on the same channel? For radio you temporarily might hear two different stations at the same time and for TV you might see two images.

In digital signals like sat-tv, the receiver has to decode the digital video and interfering signals mean that sometimes, the receiver can lock on the signal and other times there are too many errors. The transmitted digital video has error coding which helps make up for lost bits from signal strength or interference but signal strength and interference will show as oscillating signal strength.

 

[CommCtr]

Yes, I had some interferences with other birds, always happen when I do blind scan to G26@93W, got a bunch of blank channels ( think thats came from the circular bird next to G26). Always I need to delete 30 or more, I must watch scan, if passes from 12200 then cancel scan.

I don´t understand how circular freq can go into linear lnb.

Thanks for your help.

The only linear Ku near 93W is 91W and that is in a different band.
93W is G26 and is linear polarized C/Ku (FSS band).
91W is G11 and is linear polarized C/Ku (FSS band).

Also at 91W and 500MHz higher in frequency is the direct broadcast (DBS) band also known as Broadcasting Satellite Service (BSS) and has two satelites for service to Canada.

 

[magnigyro]

...
Also at 91W and 500MHz higher in frequency is the direct broadcast (DBS) band also known as Broadcasting Satellite Service (BSS) and has two satelites for service to Canada.

Yeah! that bird is meddling to my G26 channels...