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Prime focus Ku ONLY LNB

Posted: Sun Jan 28, 2018 7:20 pm
by hotsat9
Can anyone recommend a Ku ONLY LNB for a prime focus dish? I would like to run some Ku tests comparing the signal strength differences of a 6ft mesh prime focus vs a .96m offset Ku dish.

Im curious if some frequencys will do better on one dish or another.

Also curious if one dish will respond better than the other in hot signal areas. Also curious if one dish will respond better than the other in fringe signal areas.

Re: Prime focus Ku ONLY LNB

Posted: Mon Jan 29, 2018 9:23 pm
by owhite47
I would supect that the mesh would degrade you signal so that you wouldn't see any improvement at all........Just a guess

Re: Prime focus Ku ONLY LNB

Posted: Tue Jan 30, 2018 3:44 pm
by STRETCH
You could try a INVERTO ULTRA SINGLE BLACK, the dia. is only 40mm, you may have to mod your dish for this LNB to fit.

DEN

Re: Prime focus Ku ONLY LNB

Posted: Tue Jan 30, 2018 11:05 pm
by Cornhusker
What is the f/d of your prime focus dish? Most offset lnbs are usually made to illuminate an offset with a f/d ratio of .6.

Re: Prime focus Ku ONLY LNB

Posted: Wed Jan 31, 2018 3:42 pm
by Cornhusker

Code: Select all

http://www.linkboxusa.com/pf7900u.htm
Here is a lnf made for a prime focus reflector.

Re: Prime focus Ku ONLY LNB

Posted: Fri Feb 02, 2018 10:50 pm
by hotsat9
My prime focus is 71" wide x 24" deep

Ill see if I can get my hands on a linkbox LNB

Re: Prime focus Ku ONLY LNB

Posted: Sat Feb 24, 2018 6:41 am
by Satman43
hotsat9 wrote:My prime focus is 71" wide x 24" deep

Ill see if I can get my hands on a linkbox LNB
have you come to any conclusions yet?? I have ran similar tests on a c/ku setup on a 10' big dish vs an offset small dish and a prime focus small dish

Re: Prime focus Ku ONLY LNB

Posted: Wed Apr 04, 2018 1:18 am
by oscar2873
If you need a standard ku lnbf for prime focus you can buy the GEOSATpro SL1P SINGLE STANDARD 10750 with 60db gain and 0.6 noise figure, if you need a universal ku lnbf for prime focus recommended the Golden Interstar GI-209P with 60db gain and 0.2 noise figure or the MTI AP8-TFT with conversion gain: 65dB and noise figure: 0.1 , all three you can buy in ebay.

Regards

Re: Prime focus Ku ONLY LNB

Posted: Mon Apr 30, 2018 4:22 am
by mos
can you line the back of a big mesh dish with aluminum foil will that help bounce a better ku into lnb?

Re: Prime focus Ku ONLY LNB

Posted: Mon Apr 30, 2018 1:17 pm
by iq180
mos wrote:can you line the back of a big mesh dish with aluminum foil will that help bounce a better ku into lnb?
You can take out the mesh and replace it with sheet metal, I have done it and it works great, remember to paint it with flat black or flat gray paint before you put your LNB on it, if you don't paint it you will kill your LNB just as soon as the sun hits it.

Re: Prime focus Ku ONLY LNB

Posted: Wed May 02, 2018 5:31 am
by mos
yes thanks i have an idea now i will try it also is there a difference with the focal point distance of ku lnb compared to c lnb? i have 8 feet dish.

Re: Prime focus Ku ONLY LNB

Posted: Tue May 15, 2018 2:02 am
by Wilis13
I have a mesh dish and it works great with both c band and ku. I use the same focal distance. If your dish is well aligned you should be able to scan ku.

Re: Prime focus Ku ONLY LNB

Posted: Tue May 15, 2018 9:44 pm
by Jim
mos wrote:yes thanks i have an idea now i will try it also is there a difference with the focal point distance of ku lnb compared to c lnb? i have 8 feet dish.
The focal point for your particular dish is the focal point no matter if it's C or Ku. I have a 10' Mesh dish that gets excellent C/Ku. The distance is calculated

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http://www.satsig.net/focal-length-parabolic-dish.htm

Re: Prime focus Ku ONLY LNB

Posted: Tue May 15, 2018 9:48 pm
by Jim
Jim wrote:
mos wrote:yes thanks i have an idea now i will try it also is there a difference with the focal point distance of ku lnb compared to c lnb? i have 8 feet dish.
The focal point for your particular dish is the focal point no matter if it's C or Ku. I have a 10' Mesh dish that gets excellent C/Ku. The distance is calculated

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http://www.satsig.net/focal-length-parabolic-dish.htm[
/quote] . If you know th the brand of your dish this chart will help too!

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http://www.bigdish.info/mainten/lfocal.html

Re: Prime focus Ku ONLY LNB

Posted: Wed Jun 06, 2018 12:49 am
by melvinfta
Please let us know if that worked?

Re: Prime focus Ku ONLY LNB

Posted: Wed Jun 06, 2018 4:00 pm
by kroll
owhite47 wrote:I would supect that the mesh would degrade you signal so that you wouldn't see any improvement at all........Just a guess
Completamente de acuerdo contigo,el ancho de banda de la frecuencia en KU requiere que el plato sea de lamina y no de malla para que funcione en esa banda,si es malla pierde ganacia cuanto mayor sea el diametro de las perforaciones de dicha malla,saludos

Re: Prime focus Ku ONLY LNB

Posted: Wed Jun 06, 2018 10:24 pm
by Feralkiwi
Some mesh dishes with flat sheet that is punched with small holes is spec'ed or said to be Ku / c band.
This sheet has a smooth surface.
IMG_6813.JPG
IMG_6813.JPG (112.06 KiB) Viewed 8179 times
As I went to photo my dish I find my turkeys on my highest dish.
One jumped off before I took the pic.
IMG_6812.JPG
IMG_6812.JPG (57.35 KiB) Viewed 8179 times
Owen

Re: Prime focus Ku ONLY LNB

Posted: Sat Jun 16, 2018 9:37 pm
by highswr
Nice "bird" what transponders does it have? My wild turkeys never get on the dish, thank goodness.

Re: Prime focus Ku ONLY LNB

Posted: Tue Jun 19, 2018 7:19 am
by Marsat
Feralkiwi wrote:Some mesh dishes with flat sheet that is punched with small holes is spec'ed or said to be Ku / c band.
This sheet has a smooth surface.
IMG_6813.JPG
As I went to photo my dish I find my turkeys on my highest dish.
One jumped off before I took the pic.
IMG_6812.JPG

Owen
lol

Re: Prime focus Ku ONLY LNB

Posted: Tue Jun 19, 2018 7:24 am
by Marsat
I do have installed a Universal LNB in a 2.4m along with 2 for C band

It does work however I do not see much of signal improvement due the signal here mostly is over 85%. BUt..... I do see the difference when it rains

On 76cm I lost the satellite.
1.2 m almost lost
2,4 some flickering

I havent tried one for Prime Focus, still. I like to hear about those PLL LNB Downconverters though

Re: Prime focus Ku ONLY LNB

Posted: Sun Jul 08, 2018 12:23 am
by zoricua1981
thanks for the info
i bought a c/ku lnb and i was never able to get ku to work properly maybe 2 or 3 channels on 87w but that was about it

Re: Prime focus Ku ONLY LNB

Posted: Tue Apr 30, 2019 2:50 am
by Pionex2020
zoricua1981 wrote:
Sun Jul 08, 2018 12:23 am
thanks for the info
i bought a c/ku lnb and i was never able to get ku to work properly maybe 2 or 3 channels on 87w but that was about it
Ku is not forgiving like c-band, the dish must be almost perfectly focused on the feedhorn.

Re: Prime focus Ku ONLY LNB

Posted: Sun Aug 04, 2019 4:25 pm
by sareba
Pionex2020 wrote:
Tue Apr 30, 2019 2:50 am
zoricua1981 wrote:
Sun Jul 08, 2018 12:23 am
thanks for the info
i bought a c/ku lnb and i was never able to get ku to work properly maybe 2 or 3 channels on 87w but that was about it
Ku is not forgiving like c-band, the dish must be almost perfectly focused on the feedhorn.
Fully 100% agreed. Tracking Ku signal can sometimes caused pain in the ....

Re: Prime focus Ku ONLY LNB

Posted: Tue Aug 27, 2019 4:32 pm
by Vuerite
The mesh dish is done to reduce wind resistance for 6' and up. The frequency wavelength for C-Band and especially Ku sees a mesh dish as a "solid" reflector.

The definition of a parabolic is any line crossing the focal plane to the reflector and back to the focal point will be the same length. The focal point is where the feedhorn resides. All signal energy captured by the dish reflector is sent to the focal point.

To say it doesn't matter what frequency band you're in, it matters the wave length of the antenna in the feedhorn (i.e. if you have a feedhorn that is tuned to capture C-Band and Ka-Band you will receive both.

However for a 6' dish C-band will be harder to get a signal (it depends on the Satellite's footprint), Ka-band works great with a 6' dish.

Re: Prime focus Ku ONLY LNB

Posted: Tue Aug 27, 2019 11:30 pm
by Marantz
if the holes on dish are too big in diameter you could have trouble.
The 4 ghz longer wavelength c band signals will be reflected back to the focal point/ feedhorn but the KU band signals at 12 ghz have a smaller wavelength , if the holes are too big , some of those 12 ghz signals may pass through the holes and all will not be reflected back to the feedhorn , as if there was no dish at all and KU will suffer losses

this was a big problem in the late 80s and early 90s went people started to try and capture ku band signals on their c band designed/optimized dishes ,i seem to remember if a 1/8 drill will pass through the hole , the holes are too big for optimum refection of 12 ghz signals .

you will have to do a little digging around and searching web sites but there is a definite hole size upon which KU band signals will suffer