LNB cover modification

[linuxman]

I was reading in PSB's thread about modifying the lens cover on an LNB to try and coax a little more KU signal out of it.

I was wondering if the same idea would work on a Co-Roter II+? I went to the local lumber yard yesterday and they gave me a piece of clear plexiglass, and I brought it home and made one. (I happened to have a spare cap from an old polarotor here).
See these pics:

My questions are:
Has anyone tried this idea on a Co-rotor II?
Does it give better KU signal on a Co-rotor II?
What are the down sides, if any?

I already get pretty good KU SQ, but as PSB said "every little bit helps".

Thanks, Fred

 

[PSB]

The modification never helped at all with C-band signals!

 

[linuxman]

Hi Pete,

I understand, and I already get super C-band signals.

My question was about helping KU signals.

Will it help with KU signals using a Co-rotor II?

Thanks, Fred

 

[linuxman]

Ok, I put a piece the same size with out the corners being cut off and rounded for 10 seconds. I know that is not a long period of time, but it is enough to take a stick of butter out of the fridge, and start it melting.

The plexiglass stayed the same temperature, so I guess it is transparent enough.

 

[GrumpyGuy]

Sounds like a winner!

Do you still have the cutout from the original cover. It would be interesting to learn how it compares to the plexi.

 

[linuxman]

This is just an experimental cover from an old polorotor I had gotten with the BUD, so I have the original new cover to put back on if this doesn't work.

I just wanted to make sure I wouldn't allow anything to be fried by putting this clear cover on.

The dish is mesh, and is the flat gray primer color that most are painted with.

 

[linuxman]

Well I tried it, but it didn't pan out for me. In fact, it killed all the KU signal on the 3 or 4 sats I tried it on.

I put the original cover back on and all is well.

It must have been the plexiglass I used.

Will look around for a colored or clear plain plastic piece like the other thread suggested.

Maybe try again tomorrow.

Nothing ventured, nothing gained. Just trying to elimate rain fade as much as possible. I get pretty good KU signal like it is, but always looking for something better.

 

[linuxman]

I wanted to report on the findings of my experiment with the LNB cover modification.

I tried two different pieces of plastic today. The first was a piece from a Lincoln Welder hood replacement cover which can be bought at any Home Depot or Lowes. Unfortunately it didn't help improve the signal, but it didn't kill it either. The signal was about the same or just a little lower.

The second piece was a 5" x 7" piece of plastic picture backing I bought at the Hobby Lobby. It did result in a gain in signal although not astronomical. The results for KU only are below:

Before After
White Springs 40 - 45% 45 - 50%
11720 on G10R 73 - 75% no change
GNF Music 70 - 75% 75 - 80%
Trinity Work LC 55 - 60% no change
Montana PBS 30 - 33% 40 - 45%
KU TP on an E SAT 33 - 37 % 40 - 44%

It appears that on the TP's that I already get pretty darn good KU, signal for example SBS 6 ONN is at 99% there seems to be very little to no change, but on the weaker TP's there is a definite increase in signal and stability.

I have put the original cover back on for tonight. I will silicone in this piece of plastic and allow it to set overnight and put it back on for further testing.

I don't know how this piece of plastic will hold up with sun and heat etc. I am also hoping someone will chime in with some information on whether a clear piece will allow damage to the feedhorn.

This experiment is a little different than the one linked to above by PSB in that the signal doesn't go directly into the LNB like his experiment did. The Co-Rotor II is a feed horn that distributes the signal between the two LNB's. I think that helps to explain why the signal increase is not more dramatic.

I hope this helps someone who is trying to coax a little more out of their dish for KU signal. Every little bit helps.

Just remember that any experiment is something you try at your own risk and also probably voiding any warranty on your LNB's and feedhorn.

 

[PSB]

"Every little bit helps"

I LIKE that catch phrase

Glad to hear you got some positive results!

 

[linuxman]

Couldn't have done it without your experiment leading the way.

I can't get over how much information is stored on this site. It is incredible. I just keep browsing through what has already been written, or do as I did this time, a search on plexiglass, and there was your experiment.

So thank you and everyone else who has contributed so much for this site.

 

[linuxman]

I sent the following email to Chaparral's tech support regarding the feedhorn cover modification, and asked these questions, and today received the answers interspersed with my questions:

I bought a new Corotor II plus a couple of months ago and a new
Chaparral 20K C-Band LNB, along with a new Eagle Aspen .6K KU LNB
mounted on the feedhorn. The C-Band signal is outstanding. The KU is
pretty good, but could use some improvement. I am using this on a used
10' Winegard Quadstar mesh dish for both analog and mpeg DVB digital
reception. The analog KU is fine, but the digital KU could stand some
improvement, especially on some of the weaker transponders.

Two things that may help you receive a stronger signal:
Peak the dish using the Ku signal instead of the C-band signal.
Try moving the polarity settings up or down.
The digital receivers usually have a signal strength or quality number that can
be used to observe the best positions for these settings.​

I have been reading on a satellite forum about experimenting with
the feedhorn end cover and different materials that allow better
reception of KU Band digital signals.

Have you guys ever experimented with any other materials other than the
one that currently comes with your feedhorn?

Chaparral has tried many types of materials, and the blue cover which has been used for the last 15 years is best.​

Will a clear plastic lens cover help with KU Band signal reception?

You can try, but I doubt it will improve.​

Will clear plastic as a lens cover allow too much sunlight into the
feedhorn and damage anything?

Sunlight will not damage the parts inside of the feedhorn.​

If you are experimenting with anything new or different, I would love to
participate in your tests.

The most important settings, is to accurately set the focal point correctly.
For the Corotor, the focal point is from the front of the throat and 1/4" inside.
Also make sure the f/d is correct as this setting makes sure the dish is
fully illuminated.​

Most of what he wrote back we have all read here before, but I thought I would share it from the horse's mouth.

 

[jjstaus]

Very interesting, but I wonder what material is used to cover the waveguide on some Ku LNBs. It is a clear thin celophane-looking sheet. could possably be glued onto the feed Horn directly???

 

[linuxman]

I have seen the material you are describing. don't know what it is, but it might be worth a shot.

I ended my experiments trying to get better Ku performance on the BUD Feedhorn, and just installed a motorized dedicated Ku Primestar dish. I get just as good SQ numbers from it as I do with the BUD. High wind (anything over 20mph) was causing most of my Ku problems on the BUD.

Will probably put an Invacom QPH-031 on the Primestar soon, or something similar to get both linear and circular feeds, and even better SQ numbers.