Dish Peaking

[chadg2]

Anyone repeak their dish for the strongest possible signal and get faster speeds up or down? Just wondering cuz my installer didin't take long to peak the dish but maybe he's done so many that it's second nature. I have a dish peak meter and have done other dish installing in the past so I know how important a perfectly peaked up dish can be.

[joel]

I don't think peaking will do much for speed. as it's digital, It will however help a LOT if the weather is marginal.

Joel

[N4ST]

Originally Posted by chadg2

I have a dish peak meter and have done other dish installing in the past so I know how important a perfectly peaked up dish can be.

But do you have WildBlue's Antenna Pointing Aid (APA) that goes in front of the signal strength meter? I don't really know how important it is to peak on the correct channel as opposed to peaking on the composite of all of the channels. But the installer's manual shows the use of the APA and my installer used it in aligning my dish.

I suspect that the main advantage of fine alignment is more tolerance for rain fade. I guess a marginally pointed dish might keep your TRIA ramped up to maximum transmit power more than necessary.

[News]

Originally Posted by N4ST

But do you have WildBlue's Antenna Pointing Aid (APA) that goes in front of the signal strength meter?

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Your question answered here:
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[News]

Originally Posted by N4ST

I suspect that the main advantage of fine alignment is more tolerance for rain fade. I guess a marginally pointed dish might keep your TRIA ramped up to maximum transmit power more than necessary.

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I don't think there is a lot of "slop" alignment possible in Ka band.
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Longer cable runs ramps up the TRIA power [lower value means higher output].
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I called support and asked about SVT screen; they gave me the numbers requested. I did it on a cool/clear day...some -27 or so.
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Installers now can get these graphs, if they have the login password or codes [whatever]...and my installer checks everyone via office clerk.
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[grohgreg]

Originally Posted by chadg2

Anyone repeak their dish for the strongest possible signal and get faster speeds up or down?

There is no correlation between signal strength and throughput. And it's my guess that your previous experience is with satellite TV dishes and received signal meters. With two way satellite internet hardware, you've also got a transmitter to consider. Peaking a two way antenna based upon received signal only, opens you up to the probability of screwing up transmitter isolation in the process.

//greg//

[N4ST]

Originally Posted by grohgreg

... Peaking a two way antenna based upon received signal only, opens you up to the probability of screwing up transmitter isolation in the process.

//greg//

So how does the WB installer take this into consideration? I've watched a provisioning and a re-alignment and all I ever saw the installer do was put the APA and signal strength meter on the receive lines. I guess he did use attenuators during the provisioning process...

[grohgreg]

Originally Posted by N4ST

So how does the WB installer take this into consideration? I've watched a provisioning and a re-alignment and all I ever saw the installer do was put the APA and signal strength meter on the receive lines. I guess he did use attenuators during the provisioning process...

Installation manual pg13 (PDF pg18):
"Circular Polarized Antenna Skew:
Because the broadband satellite ODU dish is elliptical, the skew is used to align the antenna
horizontally with the GEO Arch. Broadband satellite Circular Polarized antennas are directional.
This is necessary for the antenna to exclude transmission or reception from unnecessary
directions (away from earth). Circular Polarization combined with an elliptical ODU dish allows
a precisely positioned antenna to receive the greatest antenna gain and ignore competing signals,
therefore reducing the Carrier-to-Interference Ratio (CIR) and the Carrier-to-Noise Ratio
(CNR)."

Skew (rotation on the horizontal plane) is independently set by virtue of it's own axis and fastening devices. But if AZ/EL are changed after SKEW is set, the geometry of the skew angle can be affected - which in turn can degrade transmitter isolation.

Not sure, but the APA beam filter select may have a bearing as well.

//greg//

[mistergadget]

Originally Posted by grohgreg

Installation manual pg13 (PDF pg18):
"Circular Polarized Antenna Skew:
Because the broadband satellite ODU dish is elliptical, the skew is used to align the antenna
horizontally with the GEO Arch. Broadband satellite Circular Polarized antennas are directional.
This is necessary for the antenna to exclude transmission or reception from unnecessary
directions (away from earth). Circular Polarization combined with an elliptical ODU dish allows
a precisely positioned antenna to receive the greatest antenna gain and ignore competing signals,
therefore reducing the Carrier-to-Interference Ratio (CIR) and the Carrier-to-Noise Ratio
(CNR)."

Skew (rotation on the horizontal plane) is independently set by virtue of it's own axis and fastening devices. But if AZ/EL are changed after SKEW is set, the geometry of the skew angle can be affected - which in turn can degrade transmitter isolation.

Not sure, but the APA beam filter select may have a bearing as well.

//greg//

Stop and think about what you are saying . . . like saying that if you hold your rifle offset to the horizontal plane that you will hit the target better ? ? ? Sorry, but it just doesn't compute with me.

In circular polarity, skew adjustment is not necessary nor does it make any difference to the signal. And from my WB Installation training notes:

SKEW ADJUSTMENT
• The following information reviews the steps to set the antenna Skew.
Step By Steps
NOTICE: The Skew adjustment is set to 90 degrees during the Base Assembly process. Only set the Skew of the antenna if the DBS Upgrade Kit (DUK*) is a part of the installation. Otherwise, leave the Skew set to 90 degrees.
*NOTE: The DUK is unavailable at this time.

Another issue along the same lines:

Originally Posted by grohgreg

Peaking a two way antenna based upon received signal only, opens you up to the probability of screwing up transmitter isolation in the process.

Peaking the WB dish is achieved only with the receive signal . . . the meter is in line with the receive signal, not the transmit signal. We do not have isolation issues with the circular polarity signal like we do with the linear polarity systems that Direcway and Starband use. The transmit signal will follow the same path/pattern (just reversed) that the receive signal does. When you peak the receive signal for maximum signal, you are done . . . no isolation or cross-polarization issues to check or adjust for.

That is what makes this dish easier and quicker to install and align.

[grohgreg]

Originally Posted by mistergadget

...like saying that if you hold your rifle offset to the horizontal plane that you will hit the target better ? ? ?

No, it's not David, the satellite locations scribe an arc - you're comparing it to a plane. By transmitter isolation in this case, I'm referring to the act of suppressing transmit sidelobes. Military/commercial terminals use hardware filtering (bandpass) to accomplish this. Consumer grade equipment has to rely on skew to "focus" the dish to it's aiming point on the orbital arc. Think MagLight.

Perhaps WB isn't concerned with sidelobes. But if you're satisfied to let the home user go out and play with the antenna.......

//greg//

[mistergadget]

Originally Posted by grohgreg

No, it's not David, the satellite locations scribe an arc - you're comparing it to a plane. By transmitter isolation in this case, I'm referring to the act of suppressing transmit sidelobes. Military/commercial terminals use hardware filtering (bandpass) to accomplish this. Consumer grade equipment has to rely on skew to "focus" the dish to it's aiming point on the orbital arc. Think MagLight.

Perhaps WB isn't concerned with sidelobes. But if you're satisfied to let the home user go out and play with the antenna.......

//greg//

How do you get a plane from a rifle ? ? ?

This is where we don't see eye to eye because if your claim that Consumer grade equipment has to rely on skew to focus the dish, then we would be required to skew the dish and run some type of isolation test . . . but that is not the case.

And your MagLight statement is just as skewed! In that scenario the focal point is being adjusted . . . not the skew.

The transmitter isolation you are referring to is not affected by skew in CIRCULAR polarity.

Try to follow me on this . . . draw a line like the arc, then lay a quarter on it and move it until you cover as much of the line as possible. While keeping it centered at this spot, now twist the quarter left or right and keep it covering the same amount of line . . . you should notice that by twisting the quarter you cannot cover any more of the arc. This is exactly how circular polarity relates to the arc.

Linear polarity on the other hand will require us to skew the dish . . . like having to lay an envelope flat to fit it in the mail slot.

I did not make any statements regarding a home user playing with his dish . . . so please don't try to put words in my mouth.

My previous post was only to set straight some "skewed" information ! ! !

[grohgreg]

Originally Posted by mistergadget

How do you get a plane from a rifle

Because the rifle and the target are on the same dimensional plane.

But to grasp what I'm attempting to describe will require that you forget polarization for a moment. To use your own example, place the rifle and a fixed target on the perpendicular. Move the rifle uphill or down, and you have to change it's elevation angle to hit the target. Relocate the rifle to the right or left, and you have to change azimuth angle (relative to perpendicular) to hit the target. Two dimensions. Pointing a transmitter at a GEO satellite involves a third dimension. Assuming unfiltered transmissions, the reflector is rotated on it's horizontal axis relative to the satellite's observed position in the orbital arc; skew (or tilt) angle.

You're still trying to equate SKEW/TILT exclusively with polarization. So please consider that I also identified transmitter isolation relative to unwanted sidelobes (RF harmonics). Fact; the satellite is orbiting at a fixed longitude. Fact: it's antennas are fixed on specific latitudes/longitudes on earth. Fact; viewing the satellite through a strong enough telescope will give an impression that the satellite isn't completely upright. It's "skewed" to one side or the other, depending upon the location of the viewer. Now imagine that there's a big X painted on the orbiting antenna, and another on your WildBlue antenna. If you're east of the satellite, the "X" will appear tilted to one side. You rotate your own antenna to align the two imaginary Xs. If you're west of the satellite, it's "X" will appear tilted to the other side. You rotate your antenna accordingly. In the absence of mechanical filters, this is the usual method to minimize RF sidelobes. Three facts, three dimensions, three angles.

So yes - in linear polarization, skew (or tilt) helps achieve a usable H/V balance. But regardless of polarization, skew/tilt also serves to minimize unwanted sidelobes by aligning the earth bound parabola on the orbiting parabola (or parabolic array). Focusing for lack of a better term, thus the apparently less than effective MagLight comparison. Depending upon how far east or west (and to some degree north and south), dictates the angle of rotation on the horizontal plane - or skew/tilt angle.

Again I'll say, WB may not concern themselves with sidelobes. And again I'll say I don't know what the beam filter select does. Maybe they're related.

//greg//

[mistergadget]

Cant FORGET polarization . . . it is what makes the skew a NON-ISSUE. The signal doesn't change nor does it eliminate any side-lobes by adjusting the skew on a WB Dish. Did we ever have to set the skew on a dbs dish prior to the multi-sat dish ? ? ? NO ! ! ! Why ? Because it was and still is "Circular Polarity" So why would receive signal be any different here than the transmit ? ? ? Other than in this case the frequency is higher.

And you are trying to use the X factor when it does't apply . . . the 'X' would represent vertical and horizontal polarity, i.e. linear. Still not following that path with you. Adjusting skew won't compensate for the tilt caused by being east or west of the bird. But a circular polarized signal will.

Have you even seen a WB Dish ? ? ? Other than in the manuals ? ? ? I can put my meter on my WB dish and move the skew anywhere I want and it does not change my receive or transmit levels. Sure, there will be marginal movement on my meter because of the design of the dish and how loose you have to make it just to adjust the skew. But the signal levels will not signifigantly change.

So I just completed the test . . . download before moving the skew (set @90 since install) and then after moving it to 60 . . . and the results are in and guess what, the speeds are comparable but actually a bit lower than before. Could also have something to do with the time of day as we are fast approaching peak hours.

==========================================
Skew at 90

:::.. Download Stats ..:::
Connection is:: 1559 Kbps about 1.6 Mbps (tested with 2992 kB)
Download Speed is:: 190 kB/s
Tested From:: http://testmy.net/ (server2)
Test Time:: Fri Dec 09 2005 16:24:07 GMT-0600 (Central Standard Time)
Bottom Line:: 28X faster than 56K 1MB download in 5.39 sec
Diagnosis: Awesome! 20% + : 61.72 % faster than the average for host (80.39)
Validation Link:: http://testmy.net/stats/id-JIRMSBG2Z


:::.. Upload Stats ..:::
Connection is:: 236 Kbps about 0.2 Mbps (tested with 2992 kB)
Upload Speed is:: 29 kB/s
Tested From:: http://testmy.net/ (server1)
Test Time:: Fri Dec 09 2005 16:27:29 GMT-0600 (Central Standard Time)
Bottom Line:: 4X faster than 56K 1MB upload in 35.31 sec
Diagnosis: Awesome! 20% + : 124.76 % faster than the average for host (80.36)
Validation Link:: http://testmy.net/stats/id-3NFV0J2X7

================================================== ====
Skew at 60

:::.. Download Stats ..:::
Connection is:: 1544 Kbps about 1.5 Mbps (tested with 2992 kB)
Download Speed is:: 188 kB/s
Tested From:: http://testmy.net/ (server2)
Test Time:: Fri Dec 09 2005 16:31:01 GMT-0600 (Central Standard Time)
Bottom Line:: 28X faster than 56K 1MB download in 5.45 sec
Diagnosis: Awesome! 20% + : 42.7 % faster than the average for host (80.38)
Validation Link:: http://testmy.net/stats/id-U2NZST5EI


:::.. Upload Stats ..:::
Connection is:: 219 Kbps about 0.2 Mbps (tested with 2992 kB)
Upload Speed is:: 27 kB/s
Tested From:: http://testmy.net/ (server1)
Test Time:: Fri Dec 09 2005 16:34:26 GMT-0600 (Central Standard Time)
Bottom Line:: 4X faster than 56K 1MB upload in 37.93 sec
Diagnosis: Awesome! 20% + : 106.6 % faster than the average for host (80.38)
Validation Link:: http://testmy.net/stats/id-2IG9Y5KH1

And the numbers in SVT show no variance either:

Upstream Transmit power: -25.3 dBm Before -25.3 dBm After
Downstream S/N: 14.6 dB Before 14.7 db After

Did you ever stop to think that maybe there isn't a side-lobe issue with circular polarity? So let's not try to make it one ! ! ! It is much easier to eat soup with a spoon than a fork.

And as far as the APA and beam filter goes, I installed my unit without using the APA nor the Attenuators and provisioning sailed right through without a hiccup. Disclaimer: I am near the center of my beam and should not have to worry about any overlapping signals . . . but I intentionally did it to test things out.

[Lost in Space]

When my installer showed up the first day he didn't have the WB APA and just used his sat meter to aim and peak the signal. The result the SM wouldn't lock on to complete the provisioning process. He came back the next day with the APA and I was up & running in 30 minutes after he did it like the WB book stated.

[grohgreg]

Originally Posted by mistergadget

Did you ever stop to think that maybe there isn't a side-lobe issue with circular polarity?

I have absolutely nothing to gain by making this up David. There's no "X-factor" involved here, it's a simple application of basic antenna theory. But you really have to get beyond this death grip you have on polarization. It's but one consideration involved in achieving overall transmitter isolation. Besides copol/crosspol isolation, others include TX/RX isolation, antenna isolation, harmonic sidelobe isolation....

Antenna radiation patterns include sidelobes, and exist in every single antenna known to man; transmit AND receive, regardless of polarization. They're of major concern with parabolic satellite reflectors because (1) they're highly directionalized, (2) they're usually high gain, and (3) the "targets" are sometimes separated by less than two degrees of longitude. Suppressing/minimizing harmonic sidelobes prevents " collateral damage " to adjacent receivers (satellites), by attempting to keep harmonic sidelobes at least 30dB down from the main lobe. Suppressing harmonics also minimizes intermodulation distortion (frequency mixing) and mutual interference (the originating signal and a sidelobe arriving out of phase at the receiver).

Receive antenna radiation patterns are of no concern here, but transmit sidelobes must be minimized - if not suppressed - as no to create a potential for interference to adjacent satellites. As I stated before, commercial and military terminals use mechanical suppression (SENU filters or equivalent). Most consumer grade stuff simply relies on precise antenna pointing (tilt/skew) to minimize sidelobes.

The blue graphic is what sidelobes look like on a spectrum analyzer cut to the center frequency. Mechanical (bandpass) filters slice all those harmonics off at the edge of the main lobe. If that's not accomplished, the sidelobes as represented in the other graphic could actually reach another satellite. When mechanical filtering is not employed, the last line of defense is accurate tilt/skew of the reflector.

I'd love to learn whether or not the APA beam filter options have anything to do with minimizing sidelobe harmonics. If so, it might justify WB installers defaulting to a universal SKEW angle of zero. It would also have made this whole argument unnecessary.

//greg//