New Japan Radio Co. Ku lnb

[TvMind]

Well I had to replace my shorted out Norsat Ku lnb due to a damaged , by a gardener, dbc ribbon cable ..ouch ! Fortunately the receiver had short circuit protection.
I replaced it with a better specification NJRC 2744HH, but have a very poor (low) signal , especially those erratic RTV DVB-S2 signals on 87 W Lat. The main concern I have is that the new lnb has it's antenna probe offset from the center where I expected it to be. It's in the upper left quadrant. I mounted in several orientations with no difference. The only other changes were replacing an aging and broken servo motor on my Chapparal with an international model. Yes I know about the dieltric losses on C-band, but I was re-assured by Duke Fishman at Chaparral that the dielectric does not affect Ku signals at all - C-band loss is only 1 db they claim, but many argue that it's closer to 3 db or more. The sytem was peaked over a 2 1/2 month period to track from Pas9 (58') actually 55.5 W, and 137 W or AMC-7 with 24' Von Weise.

My dish is a SAMI 10 ft mesh in pretty good shape. For example at 83 W , AMC-9, Luken channels are very weak, but the AMC9 network feed has a strong signal at 70 on my microHD Pro, and only 20-35 on the RTV feeds - yes I know about the poor reception of those signals - btw try 137 for the west RTV feeds, they are much more stable and strong at least at my location despite the low elevation and terrestrial noise.

I like having the Ku as well to peak my dish with, fine tune my C-band alignment. One other concern I have is the servo motor (new). I can't get it to be perfectly vertical or horizontal but it's off by some 30 degrees or so, which I compensate in the skew settings in my Startrak 400 (H=030, V=120, instead of the h=000,v=090).
I took it off and looked at the probe so I can visually confirm this. How can I get it back to straight up and down and across ? Have the gears gone out of alignment inside ? I tried gently to 'help' it by turning the black disk but that didn't do anything.

Sorry about all the questions but I'm anxious to get everything working satifactory before the harsh winter hits - in two weeks !

TvMind

 

[FaT Air]

>> How can I get it back to straight up and down and across ? << Sounds like the only thing that needs to be done is rotate the feed in the scalar 30°.
As far as the LNB?? Try another?? Don't know why the probe would be offset. But another, same model, will(Just looked at a spec sheet) be placed the same, just operate better.

 

[Cham]

Same as Fat Air says, adjust your skew to zero and peak on a transponder by turning the whole feedhorn in the scaler ring. Does the Ku and C-band skew match or are they quite a bit different? I have a Norsat .8 NF LNB on my corotor II, most of the time the Ku is off from the C-band by about 10 degrees for some reason. I just set the LNBF to split the difference. The only sat that really requires changing the skew any major amount is AMC1 at 103W, the Ku and C-band polarity are about 20 deg different on that satellite, something to do with the way the Ku antenna deployed.

 

[TvMind]

I don't have another lnb to try and besides that wasn't what my question was about.
I am wondering , maybe asking, why the motor doesn't go vertical (horizontal polarization) and horizontal (vertical) when the receiver skew is set at H=000, V=090 (as it used to).
At first I thought it was my receiver, but I suspect the servo motor has lost 'alignment somehow (forced ) .
The feedhorn is perfectly aligned with my zenith satellite as per Chapparal's instructions -yes the easy answer is to turn it as you say. But I'd rather compensate in the skew of the receiver than go out again and knock out my 'perfect' alignment I painstakingly worked on over a 3 month period - and the tweaking never stops !

TvMind

 

[FaT Air]

One other concern I have is the servo motor

Because if you replaced the servo, The new servo's "0" calibration is not in the same position. You could, if you want to, is open up the servo and trim the resistors on each side of the feedback pot to match the calibration of the original servo**. Or realign the probe with a positional change of the gear train in the servo. Or, the simplest solution, is to just twist the feed in the scalar, unless it's a non adjustable feed/scalar.
OR is the skew "0' for C band different than Ku? (AMC 1 ignored as that IS different)??
**Some servo mfg used 1ms as "0", others used anything from .75ms to 1.25ms. (plus the allowed 10% error) Had the same problem with swapping servos in my R/C airplanes.

feedhorn is perfectly aligned with my zenith satellite

feedhorns are not aligned with your Zenith satellite. The dish is aligned to the arc and the feed horn is aligned to the dish.

than go out again and knock out my 'perfect' alignment

Twisting the feed horn will not "knock out' your 'perfect' alignment. See previous