Ipstar Disc Obstruction

[dive_mistress]

Hi. The landlord planted a palm tree about a meter away from my disk. it is not directly in front of it but is in range of the disc. Then about five meters away there is some new shrubery. My ES number went from about 10+ to 8.5.

Or is it just CSLOXINFO/IPSTAR? the clouds are gone now but still low signal strength.

Am so thankful to all the helpful people in this forum. My questions are always answered!!!

[digitele]

Hi. The landlord planted a palm tree about a meter away from my disk. it is not directly in front of it but is in range of the disc. Then about five meters away there is some new shrubery. My ES number went from about 10+ to 8.5.

Or is it just CSLOXINFO/IPSTAR? the clouds are gone now but still low signal strength.

Am so thankful to all the helpful people in this forum. My questions are always answered!!!

If it isn't directly in the line of sight, no problem. Heavy rain at the IpStar ground station in BKK

has caused some issues in the past few days.

Question-What was your signal reading at it's best? And what is it now?

If it was 100 before and now 97 it isn't an obstruction - i.e. the tree....

[Rimmer]

My ES number is pretty constant at 12.5 unless we get heavy cloud cover then it can drop down to around 7 then the system goes to sleep. That does not happen often.

[mouse]

take a look at the bottom of this image for the ipstar signal does not travel in a straight line but rather expands and then contracts. Get rid of the tree, for it will only grow and get into the way. Surely you have enough land to move the tree.

[astral]

take a look at the bottom of this image for the ipstar signal does not travel in a straight line but rather expands and then contracts.

Get rid of the tree, for it will only grow and get into the way. Surely you have enough land to move the tree.

This is a very valid point.

Not only for IPSTAR, but satellite TV viewers as well.

[digitele]

take a look at the bottom of this image for the ipstar signal does not travel in a straight line but rather expands and then contracts.

Get rid of the tree, for it will only grow and get into the way. Surely you have enough land to move the tree.

This is a very valid point.

Not only for IPSTAR, but satellite TV viewers as well.

You and Mouse are joking right? RF travels in straight lines........ same as light!

[monty]

Digitele, radio waves do travel in straight lines, but on microwave links (which the satellites use) there is another factor to consider called the fresnel zone.

Basically it means the a microwave beam between two directional antennae expands in the middle...

Check out following link:

http://www.airaya.com/support/ai108_path.asp

Theoretically only the path between the outher edges of both antennae should be clear, but practically, in the middle between both antennae a much wider clearance is needed to ensure good transmissions!

However, at the antenna itself, as long as there is no obstruction right in front of the dish, reception should be clear!

Another thing to consider is that both iPSTAR and UBC use off center parabolic dishes. You can see this as the LNB (the receiver head) is not positioned in the optical center of the dish.

This results in the dish actually looking almost straight up (where the Thaicom Satellite is), and not 60 degrees above the horizon as the positioning of the dish would indicate!!!

So it might look like the banana tree is obstructing the beam, while in fact it isn't.

The moveable dishes used for television reception (the black mesh 10ft monsters) have the LNB positioned in the center, and when you aim them at Thaicom, you'll see it's almost looking straight up in the sky...

[Prasert]

take a look at the bottom of this image for the ipstar signal does not travel in a straight line but rather expands and then contracts.

Get rid of the tree, for it will only grow and get into the way. Surely you have enough land to move the tree.

This is a very valid point.

Not only for IPSTAR, but satellite TV viewers as well.

You and Mouse are joking right? RF travels in straight lines........ same as light!

No they're not joking!

Google on Fresnell Ellips

[digitele]

take a look at the bottom of this image for the ipstar signal does not travel in a straight line but rather expands and then contracts.

Get rid of the tree, for it will only grow and get into the way. Surely you have enough land to move the tree.

This is a very valid point.

Not only for IPSTAR, but satellite TV viewers as well.

You and Mouse are joking right? RF travels in straight lines........ same as light!

No they're not joking!

Google on Fresnell Ellips

Nice picture, "Fresnell Ellips" too bad the subject is really parabolic antenna theory - Not Elliptical. Although fresnal zones and side lobes are inheirant in all RF transmissin calculations.

The original post was about IF the tree is directly in the Line Of Sight.

All radios waves EXPAND the further the distance from the Transmit antenna to the Receive antenna, like a "flashlight" the further away you aim it - the wider the beam. Expanding and Contracting?

Also, I agree. They aren't joking. They are wrong! ha ha Instead of a your diagram - try some reading.

In signal receiving, the satellite antenna works as a device to marshal and concentrate the Hertzian wave energy permeated in the air through its paraboloid reflector. In signal transmitting, is works in an opposite way of receiving to project the Hertzian wave beam onto the satellite that it is communicating with. There is a device called feed positioned at the focus point of the paraboloid to collect in or transmit out the signal.

Because the wavelength in microwave band is very small, such as for the satellite communications, in C-band, 4–6 GHz, it is less than 50mm and in Ku-band, 12–14 GHz, it is only about 20mm,

Don't take it too seriously. Many think they know something of which they know "enough to be dangerous" Regards

[monty]

Digitele,

It's a simple fact that if you obstruct the fresnel zone between a microwave link, reception will be seriously degraded...

You can have perfect line of sight between two points, but absolutely zilch connectivity (unless of course you have plenty of r/f power to spare...

Both Prasert and I have long distance microwave links up and running (2.4Ghz, 128mm wave length) and I can assure you I have broken my head why at first my link wouldn't want to work eventhough I had perfectly clear line of sight (between two parabolic antennae). I guess Mr. Prasert will have had his shares of misterious problems

Research indicated that the reason was simply the bottom half of the fresnel zone was obstructed. Watching through the telescope when checking line of sight, there was indeed a condo just under this line of sight... Raising both antennae by 60 ft (by using a mast) made the connection possible...

Nowhere in my post I said that radiowaves contract!!! I only said they expand, indeed like a flashlight. The better your antenna, wether a parabolic dish, a flat panel antenna or whatever, the more directed the beam will be (less expanding).

The detailed explanation is that some waves from the expanding beam might hit something, and then get deflected and reach the receiving antenna out of phase (it traveled a longer distance then the direct radio waves) and thus cancelling out some of the direct waves resulting in signal loss, and reduced snr...

This is especially important for iPSTAR users, since their dish actually transmits radio waves toward the satelite (the uplink). For example trying to aim the dish just beside a condo building might create enough out of phase reflections to make the signal barely receivable by the satelite...

Another link explaining the Fresnel effect:

http://www.zytrax.com/tech/wireless/fresnel.htm

[digitele]

Digitele,

MONTY

It's a simple fact that if you obstruct the fresnel zone between a microwave link, reception will be seriously degraded...

TRUE, BECAUSE YOUR PATH ISN'T SET UP RIGHT.

You can have perfect line of sight between two points, but absolutely zilch connectivity (unless of course you have plenty of r/f power to spare...

IN COMMERICIAL "REAL" MICROWAVE LINKS- YOU DESIGN THE PATH TO HAVE AT LEAST A 20 dB FADE MARGIN- of course you have plenty of r/f power to spare...THATS HOW YOU SET UP RELIABLE

WORKING LINKS

Both Prasert and I have long distance microwave links up and running (2.4Ghz, 128mm wave length) and I can assure you I have broken my head why at first my link wouldn't want to work eventhough I had perfectly clear line of sight (between two parabolic antennae). I guess Mr. Prasert will have had his shares of misterious problems

DOING PATH ALIGNMENTS IS FOR THE SKILLED AND EXPERIENCED. WITHOUT GIVING A COMPLETE TUTORIAL, AS LIKE TRYING TO TEACH TO SWIM ON DRY LAND...QUESTION:

Where is Dive Mistress's tree? One meter where? without a picture it could be behind the reflector

for all we know and that's the point of oringinal post, correct?

Research indicated that the reason was simply the bottom half of the fresnel zone was obstructed. Watching through the telescope when checking line of sight, there was indeed a condo just under this line of sight... Raising both antennae by 60 ft (by using a mast) made the connection possible...

(short version) PATH NOW SET UP CORRECTLY

Nowhere in my post I said that radiowaves contract!!! I only said they expand, indeed like a flashlight. The better your antenna, wether a parabolic dish, a flat panel antenna or whatever, the more directed the beam will be (less expanding).

TRUE, the point is to have the core of the beam in perfect LOS without obstructions or reflected side lobs.

The detailed explanation is that some waves from the expanding beam might hit something, and then get deflected and reach the receiving antenna out of phase (it traveled a longer distance then the direct radio waves) and thus cancelling out some of the direct waves resulting in signal loss, and reduced snr...

TRUE

This is especially important for iPSTAR users, since their dish actually transmits radio waves toward the satelite (the uplink). For example trying to aim the dish just beside a condo building might create enough out of phase reflections to make the signal barely receivable by the satelite...

TRUE, BECAUSE THE TRANSMIT SIGNAL IS REFLECTING BACK TOWARD THE RECEIVE AT A MUCH HIGHER POWER THAN THE CALCULATED RSL - AGC TO SOME AND THE RECEIVE IS INDEED RECEIVING "MULTI-PATH" SIGNALS -OUT OF PHASE. A KILLER FOR DIGITAL LINKS (IPSTAR). THATS WHY TO THIS DAY ANALOG MICROWAVE RADIOS WORK BETTER OVER LONG WATER HOPS. EVEN THEN YOU NEED MORE ELEVATION DUE TO THERMAL INVERSION IN MORNING AND EVENING WHEN THINGS RAPIDLY HEAT OR COOL OFF.

Another link explaining the Fresnel effect:

http://www.zytrax.com/tech/wireless/fresnel.htm

BOTTOM LINE? MOVE OR CUT THE TREE. CAN WE AT LEAST SEE A PICTURE OF HER SITUATION?

AFTER THE TREE IS CUT AND THE LINK STILL HAS A LOW RECEIVE LEVEL THEN WHAT?

IT WILL BE A-Z CHECK (LIKE RE-INSTALL) TO FIND SOMETHING WAS BORDERLINE FROM THE BEGINNING (IPSTAR INSTALLATION) THEN PERHAPS YOU AND PRASERT CAN GO RE-ALIGN AND CHECK ALL THE CONNECTORS ETC

BEST REGARDS

[English Noodles]

At least it won't stop you doing your podcasts Kat.

http://www.expatgirl.com/expatgirl_1.mp3