ESX242 C-band LNBF skew on motorized dish: 90 degrees off?

[ChrisW6ATV]

Hi all-

I bought an ESX242 dual-output C-band LNBF, and since my dish (10-foot KTI, I think) is motorized, I set the skew at 0 with the dish pointed at its apex/southernmost satellite (121 in my case). To me, zero meant "straight up" with the dish at the top of the arc.

I connected one output to my 4DTV DSR-922 receiver. Some notes say to set 4DTV receivers to "rotated 90 degrees" when using an LNBF, but I seemed not to have to do that. Next, I connected the other LNBF output to my X2 Premium receiver, and guess what? It is receiving signals (in a blind scan) with reversed polarity. (87 SES 2 3735 is received as "horizontal", for example.) OK, so the fix is simple: Go back and rotate the LNBF 90 degrees, and check the box for "rotated 90" on the DSR-922, and things will be fine on the X2.

My question is: Is all of this normal, and what I thought was "zero" skew is incorrect? (I did see one note that implied to point the 0-degree mark on an LNBF to the "3 o'clock" position on the dish, but it was not entirely clear to me.) Thanks.

[rrob311]

From what I remember the 4dtv is opposite of the x2. I had to tweak my settings that way to get everything to sync properly.

[ChrisW6ATV]

rrob311-

Thank you for the quick reply. I just moved the LNBF 90 degrees, and the "problem" is gone.

[el bandido]

You have discovered a common Manufacturing Defect.

Most of our lnbs are made on cheap assembly lines in China It appears that they stop the line only to change the brand name of the lnb without doing any other changes. I say this because several different brands of c band lnbs have the skew markings wrong, where 0 is really 3 o'clock.
Set the lnb skew to "3 o'clock" and everything should work correctly. Try to remember this if you buy any other c band lnb. Remember, not all of the c band lnbs have this defect but a lot of them do.

On another note, sometimes you can change lnbs and your current channel list in your receiver will become useless because not all lnbs receive the signal the same way. I found this out the hard way by spending about 1 hour trying to figure out why my new lnb would not work. This problem was solved by doing a fresh scan of each satellite. Some lnbs can be changed and the receiver will work without doing a thing, but if you put a new lnb on and get no signal from the satellite, try doing a blindscan before changing anything else! EB

[ChrisW6ATV]

Thanks, el bandido.

[Sublime]

Having 0 degrees at the 3 or 9 O'clock position makes perfect sense to me. When I set up the feedhorn/polarotor on my 10 foot dish years ago, I ended up with horizontal polarity at 0 degrees and vertical polarity at 90 degrees. (Actually, it ended up more like H=16deg, V=74deg, but close enough!) I guess it all depends on which polarity you prefer to call 0 degrees whether or not it makes sense to you or not. I know with a protractor in school, we always laid it flat on the desk with 0 being the horizontal line and 90 at the top.

[cpr43]

I also got one of this and have similar problems. All my previews skew setting where way to off on NSS806 compared t o the old model. So I decided to contact WSI, this is a c/p from their answer:

WSI International explaining the skew angle correction for your reference


Thanks for the email.

Yes, the polarization on this new unit is off by 45°. In addition, please make sure to slide in the dielectric plate perpendicular to the isolation bar.

Thanks,
WS International

[ChrisW6ATV]

Having 0 degrees at the 3 or 9 O'clock position makes perfect sense to me... I know with a protractor in school, we always laid it flat on the desk with 0 being the horizontal line and 90 at the top.
It took me a few minutes to think about this, but now it makes complete sense. My original comment "zero means straight up" was based on maps, with north (0 degrees) being "up", but maps refer to azimuth (horizontal/flat directions). Polarization refers to elevation ("vertical" directions, or lack of the same), and indeed zero degrees is horizontal in that context.

[77ta]

I've owned 2 c-band lnbf's, an esx241 and a ns741. Both sold by WSI and both with 0 skew set at 3 o'clock.

[ftanut]

I have jusr received my ESX242 LNBF and worked with it for about 1/2 hour. I scanned two satellites and the polarity are comming out wrong. The LNBF is connected to a ChannelMaster 4x4 switch, does swapping the coax cables from the LNBF to the 4x4 switch be the same as skewing the LNBF in the scalar ring.

It seems that somehow I have the LNBF skewed wrong.....So, is this LNBF zero have to be pointed to the 3 o'clock position for everything to be allright. Post # 7 of this thread mentioned that the LNBF is off by 45 degrees, if I place the zero at 3 o'clock then the LNBF zero is actually set at a 90 degrees angle.

Any less confusing explanation on the LNBF skew is greatly appreciated.

Thanks.

[el bandido]

To clarify, The lnb is supposed to be skewed at 0 degrees or straight up when the dish is at due South or centered in the arc. You need to move this lnb from 0 or straight up (12 o'clock) to about 3 o'clock in order to get the correct polarity.

[77ta]

On a motorized dish the zero should be at 3 o'clock (straight out to the side) when on your true south satellite. A correctly aligned mount should automatically adjust the skew from there as you change satellites. A stationary dish should be skewed based on the satellites location in relation to your location.

[ftanut]

Ok, Thanks. I have a motorized dish so I will set the zero at the 3 o'clock position when the dish is pointed straight up South or 12 o'clock.

Slightly off topic, is it better to use the ChannelMaster for this setup or will a DiseQc switch (2x1, 4x1) do the same job.

Thanks.

[ftanut]

I have just had a chance to clock/skewed the ESX242 LNBF to the 3 0'clock position per instructions. I am able to scan some of the channels, do I need to insert the dielectric plate in order to receive the channels laveled as DVB-S and DVB-S2, so far those channels are being skipped when TPs are scanned. Most of this FTA hobby is very new to me, so I keep asking questions and hopefully someone will be kind enough to give me the right answer.

Thanks

[Costactc]

Dilectric plate insertion is for circular sats on the Atlantic side. If your scanning in the c band sats on the American side do not insert it as you will loose signal quality. Personally, I have used at least 10 c band lnbf over the years including the esx242- I take my little tv outside and skew until optimal signal quality is attained. I have never paid attention to what is on the lnbf.

[el bandido]

DVB-S2 channels can be hard to get. Can you tell us what size dish you are using and what DVB-S2 channels you are trying to get?

[ftanut]

I have the 6 foot $69.99 dish special. Had to start from scratch because everything was getting all fauled up. Will report tomorrow on the channels that the receiver is not scanning or skipping over, they are not just of the DVB-S2 type. For instance before the ESX242 was intalled I was able to scan 91W Galaxy17, not anymore, and there are quite a few other TPs and satellites channels that are not scanning as before.

The LNBF Zero marking is clocked/skewed at 3 o'clock when the dish is at it's zenith per in structions....The only thing that I am not too sure of, is how deep to locate the LNBF into the scalar ring, I have moved it in and out, with very little changes of Quality signal.

Will try again tomorrow and see if anything changes or improves.

[77ta]

6300

This should give you a good starting point and you can fine tune from there. If you are unsure of the f/D ratio then setting it around 38 to 40 will probably work.

[Costactc]

Most s-2 channels will not scan in due to dish size. Placing an lnbf to a set position and expecting results is like an exercise in futility, you need to go out to the dish and play around with-no one dish nor lnbf are going to give identical results.

[77ta]

Placing an lnbf to a set position and expecting results is like an exercise in futility, you need to go out to the dish and play around with-no one dish nor lnbf are going to give identical results.

I agree. The recommendations given so far are to rough in the lnb to get you in the ballpark. From there you should tweak (not twerk :smiley14:) the lnb to your specific system. A couple of degrees on the skew or a 1/8 of an inch in or out may be the difference in receiving a channel you want or not.