Prime focus Ku ONLY LNB

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hotsat9
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Joined: Thu Jan 18, 2018 11:11 pm

Prime focus Ku ONLY LNB

Post 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.

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owhite47
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Re: Prime focus Ku ONLY LNB

Post 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
10.5 cband western arc 75deg to 139deg. 4ft ku with motor, full western arc.

STRETCH
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Re: Prime focus Ku ONLY LNB

Post 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

Cornhusker
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Re: Prime focus Ku ONLY LNB

Post 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.

Cornhusker
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Re: Prime focus Ku ONLY LNB

Post by Cornhusker »

Code: Select all

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

hotsat9
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Re: Prime focus Ku ONLY LNB

Post by hotsat9 »

My prime focus is 71" wide x 24" deep

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

Satman43
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Re: Prime focus Ku ONLY LNB

Post 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

oscar2873
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Re: Prime focus Ku ONLY LNB

Post 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

mos
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Re: Prime focus Ku ONLY LNB

Post by mos »

can you line the back of a big mesh dish with aluminum foil will that help bounce a better ku into lnb?
V8 Golden / V8 Novas / V8X/ GTC / V8 UHD

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iq180
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Re: Prime focus Ku ONLY LNB

Post 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.

mos
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Re: Prime focus Ku ONLY LNB

Post 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.
V8 Golden / V8 Novas / V8X/ GTC / V8 UHD

Wilis13
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Re: Prime focus Ku ONLY LNB

Post 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.

Jim
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Re: Prime focus Ku ONLY LNB

Post 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

Jim
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Re: Prime focus Ku ONLY LNB

Post 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

melvinfta
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Re: Prime focus Ku ONLY LNB

Post by melvinfta »

Please let us know if that worked?

kroll
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Re: Prime focus Ku ONLY LNB

Post 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
10 foot prime focus c band dish w/36 actuator pansat ap-3000 positioner at full arc & freesat V7,V7S2X & sg2100 motor W/ 90cms offset antenna and lnb universal KU 45º at 131º

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Feralkiwi
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Re: Prime focus Ku ONLY LNB

Post 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 8162 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 8162 times
Owen
Dishes; 3x3m, 2.4m and 4.1m, 10+ ku, 2 movers, USARLS. V8 Combo, Pro, V8 Golden, Nova V8Pro2, GTC, Super.V7HDs, Combo and V7s V7Plus Finder, Finder-Meter V8X / UHD V7Pro GT/XCombo. Sats 100.5E to 177W. I'm a Sat hobbyist who helps out.

highswr
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Re: Prime focus Ku ONLY LNB

Post by highswr »

Nice "bird" what transponders does it have? My wild turkeys never get on the dish, thank goodness.

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Marsat
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Re: Prime focus Ku ONLY LNB

Post 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

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Marsat
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Location: Miami

Re: Prime focus Ku ONLY LNB

Post 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

zoricua1981
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Joined: Thu Jan 11, 2018 11:15 pm

Re: Prime focus Ku ONLY LNB

Post 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

Pionex2020
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Re: Prime focus Ku ONLY LNB

Post 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.

sareba
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Joined: Sat Aug 03, 2019 1:23 pm

Re: Prime focus Ku ONLY LNB

Post 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 ....

Vuerite
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Re: Prime focus Ku ONLY LNB

Post 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.

Marantz
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Re: Prime focus Ku ONLY LNB

Post 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

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