LNB fine tuning with meter

[tvrohunter]

Hello Experts,

I have a question regarding fine tuning an LNB. I am trying to fine tune the LNB for C/KU band reception on a 10 foot unimesh dish. The dish tracks tracks the arc nicely from 83W - 135W. I have had the setup on C-band working okay for the past several years with a few different FTA receivers. Recently I purchased a new STB that is DVB-S2.

I wanted to tune up the KU side of the dish as it never has really worked all that well. Currently on SES2 for example I get 90% signal and about 78-85% on average for quality. I get consistent results on other satellites also. (Using the signal / quality on the STB) I am using this bird as it's easy to work on the dish. It's on a side of a hill and the LNB is harder to reach on the western arc.

I recently obtained a Birddog Usb Plus meter. I have been trying to improve the KU side. On SES2 I fine tuned the KU from 8% to 43% quality on the meter. (Best I could fine tune it). Now on the C-band side things seem to have gotten worse. On SES2 I get 0-1% quality lock almost nothing. (On the meter) On my FTA receiver the C-band signal is pretty much gone.

According to the C-band setup guides I have read the C-Band should work in nicely after the KU has been fine tuned.

I haven't had a chance to try and peak the C-band signal again with the meter. The LNB is one of those DBS 621 dual C/Ku Band LNBF. When I started tweaking the LNB was out past the scaler ring about 2-3 inches. With the KU peaked It's back about 2-3 inches inside the scaler ring. The measured the focal point and it is 48" as per the manual specifications.

I am located in the North West. I was thinking of peaking it back on C-Band and leaving it. I am okay with just C-band. Any suggestions?

 

[Hockeynut]

A finely tuned Unimesh will work no better for Ku than a 1.2m.....Not much margin for error so a 1m would be more comparable...Best advice I have is never mess with a mesh for Ku!..Much much better off using a ortho feed on the Unimesh for Cband and finding a nice solid 1.2 or 1.8 Ch Master,Prodelin etc and setting it up with a Polar mount.

 

[FTA4PA]

Welcome to Satellite Guys tvrohunter! I have tried C and KU on a single dish and always found that when one was tuned nicely the other was off. I finally decided it was more trouble than it was worth and went with separate dishes. In our living room we have C band from 55.5W to 125W using Diseqc and KU from 30W to 125W using USALS. Also have a few stationary dishes feeding our bedroom. Just my two cents!

 

[tvrohunter]

Thanks that's what I was suspecting. Next chance I get I think I'll use the meter to peak it back on C-band is that's where I plan to use it.

After reading some more I did notice the focal point differences between C-band and KU LNBF's.

 

[wvman]

Many C/Ku feeds are off center slightly on the Ku side. Also the size of the holes in the mesh are not always up to spec either. When I was installing dishes, I found several mesh dishes that said Ku compatible, but the holes in the screen were way to big, allowing the Ku signal to pass right through. The higher the frequency, the more critical these things are. Hockeynut is correct. Solid dishes work much better on Ku, and you want to make sure they aren't egg shaped of badly dimpled if they are spun aluminum. The surface is very critical.

 

[tvrohunter]

Update - After tinkering with the BSC 621 I am pretty sure its toast. Using the meter I am only now getting a 8-12% quality lock on 83W which was coming in about 78% before on C-Band. I have spent quite a bit of time trying to adjust the skew and focal point without success. After reading up on this I suspect the LNB is drifting. It's about 5-6 years old.

I ordered a new Titanium C-Band PLL LNB and mounted it last night and boom I am back getting about 78-82% on most birds on C-Band. Thanks Brian. Shipping was super fast 5 days.