Sparkles

[elgemcdlf]

OK here is the story. Started wit an Eagle C Band lnb. Swapped out for a California Amp and yesterday went with a Norsat 15 degree 65db gain lnb. Still have sparkles in my analog channels. Using the same dish for the dvb MPEG2 receiver and have decent signal and quality readings across the board. I think the lowest quality I have with the 922 is 79. I am sweeping from 133 to about 50 in the east. 8.5' mesh dish.

Still have those pesky sparkles on analog C Band channels. Any ideas?

[rainman]

how long of cable run do you have Steve. I have heard to short of a run on c band analog can cause the sparkles I think a 150 foot run of cable was recommended.thats what I have and don't notice any sparkles.


also you can try adjusting the freq on the analog channels up or down a few Mhz sometimes that helps.

[Larry Acklin]

It's been a year or so since I had the analog side up on C- but I always had white sparkles in the red colors. The amount of sparkles were dependent upon the transponder I was on (same bird). I had black/white sparkles on occasion, but adjusting the skew and tweeking the LO freq would make that go away. Also, the TI (terrestrial interference) filter would help sometimes.

But the biggest help was when I adjusted the feedhorn to the correct F/d setting and distance from the dish. I never got it perfect, but there were times that it was really good.

I seems that the design of the support arms and how they screwed on the rim of the dish was the problem. I'm currently rebuilding the dish, and I thrubolted the brackets to the rim. Before, they were screwed to the outer trim piece, which caused the trim to work away from the structure. #10 stainless screws and nuts have greatly stiffened the bracket mounting, to the point that the scaler ring is quite stiff in the 4 arm support.

I'm going to an orthomode feed for c band, and I cut a portion of the scalar ring to accept a prime focus lnbf for Ku. (that will be after I get C working.)

Tough part is that I have to attach an actuator to a dish and inoperative HH mount. So i'm fabricating a beefy mount for the tail of the actuator.

And the real challenge will be finding the arc again- because I had to completely loosen the settings for latitude angle to get bolts to back out.

I did mark polar north on the pole, so I should be close (enough) to make it a fun exercise in hunting.

Larry

[elgemcdlf]

Adjusting skew and freq have already been gone through. Best I can get is a balance between white and black sparkles so that it looks like they are not there. All it takes is a switch to a digital channel to realize how bad it really is. I will work with FD as I was beginning to suspect something of this nature. This is a corotor II so the biggie is do I set FD using Ku or C? My cable run is probably 85' or so. Can I cheat the FD with something like using the DVB MPEG2 receiver on Ku and adjust for effect?

I think Bill had stated that when C and Ku are not in the same location the FD is off. I know my KU & C sats on the 922 are landing in different locations to get optimum signal. This is the dish that I had a "professional" installer put in. The mount was binding against itself causing bad landing which he claimed was a bad hall effect switch in the actuator. Once I got the thing adjusted decently that problem ceased. Would not surprise me at all to find out the FD was not correct. Hopefully I will get some time this weekend to look into it.

By the way to anyone out there Norsat rules! My PQ is far superior to both the Eagle and California Amp lnb's. Not just a little better we are talking crystal clear on digital channels. I currently have an Eagle lnb on the Ku side of the dish and before long it will be getting replaced as well.

[Larry Acklin]

Bill is referring to the fact that the dish focus is critical at Ku freqs. If you are too close or far from the true focal point, then you have to adjust dish position to get anything- and you are getting a side lobe "reflection?" rather then the main beam, so it would seem that your f/d is the problem.

I'd get good enough with C, switch to Ku on the same bird, and adjust the f/d at the scalar ring/feedhorn location. My Corotor did not have the f/d scale, the newer ones do. So I always have had to tweek and hope for the best. And- it's really critical at Ku freqs. I heard 1/8" wrong looses 50% of power (3 db) at c band- it would be someting like 1/16" at Ku (?!)

It would seem that quality numbers on digital would be easier to use than the signal strength on analog. Remember to take away the ladder when you are comparing.

My current thoughts are to try the old Bullseye feed and see how it works for C. The probe is broken for Ku, so I will have to try the LNBF and see if that works for Ku.

I'm trying this rather than adapt the Corotor with servo. If that fails, I'll put it back on and use the ebay special pansat 2500, which has skew output control, in combination with a Vbox II.

Larry

[1captain]

If you have gone tru you're dish set up an the dish is right on as far as peaking, an focal depth. you're DSR 922 tuner may have shifted frequencey, now if you're getting black sparkels try running the freq higher , or if you have alot of white sparkels then run freq lower. an normaly 1 to 3-mhz you will see a difference. alot of times lnbs will cause this if they drift but you have changed them, an can not see all 3 having the same problem. Good Luck..