Single output LNBF has more efficiency that Dual Output?

[Vallenato]

Single output LNBF C band has more efficiency and performance that Dual Output?.. Why?..
I know about the advantages of use dual output to use on different receivers but why some people recommend to use one single output?..

 

[FaT Air]

Single output LNBF C band has more efficiency and performance that Dual Output?.

example?
Was said that the geosatpro dual output C2 outperformed the single output C1. Neither are available today. But that's the reason I went with the C2.

 

[Vallenato]

Example? I am talking about generally brands (including KU and C band LNB’s)..”Technical specifications ” reasons.
or This depends of the efficiency & performance of specific brand ?

I am asking due the tester guy recommendations and not is the first time that I am hearing the same thing. ( I can not remember the other post)
On this thread Post#13 the user recommends: use a single output C-band LNBF.
http://www.satelliteguys.us/xen/threads/12-foot-vs-10-foot-dishes.337665/
Post#13
I have experimented with my 8ft dish and I can report that almost all transponders in North America can be locked, but you have to be spot on with your dish alignment (especially declination adjustment) and use a single output C-Band LNBF with short coax run. If you want to get a bit of extra signal, then go with the 10ft dish, you will be happier during inclement weather when signals can get a bit attenuated.
I am current using geosatpro dual C2 on Ses-6 40.5 W (with dish sadoun 6 ft) and probably I can replace it and put my geosat pro C/ku (single output ) to get little bit more quality on weaker signals on C band

 

[updatelee]

single output's are cheaper then dual outputs. But they limit your future expandability. Thats the only reason to choose a single vs a dual

UDL

 

[Vondertrenk]

It could be a reason, it could be a matter of perception, it could be the time both units were tested. I personally lovedthe dual units and have never seen any difference in gain compared with a single unit.
I personally don't see any technical reason to be better or worse. Hope it helps

 

[FaT Air]

I can replace it and put my geosat pro C/ku (single output ) to get little bit more quality on weaker signals on C band

Now here you'll see a difference. Dual Band LNBF's will have lower performance than a single band LNBF. It's the 'nature of the beast' Some compromises have to be employed to enable reception of both bands.
IMHO: On a 'dual band' LNBF, the feed throat dimensions and scalar are optimized for C band, and there is no effective scalar for Ku. (a Ku scalar would completely cover the C band throat) The C band is blocked slightly by the Ku assembly within the feed throat. The feed throat is not optimum for Ku.
I couldn't find a suggestion to use a single, band or output, lnbf in post #13 in the other thread, but in post #14

A dual C/Ku-band LNB will result in 1 dB of loss over an optimized C-Band LNB.

I personally don't think a dual output, single band, LNBF would have poorer performance than a single output, of the same design. May be if there is a difference in the electrical design. (and there could be some out there that have similar model #'s but different electrical design - Think that was the case of the C1 & C2)

 

[Vallenato]

Ok guys thanks for your answers.. Is Clear to me

 

[beavs2112]

IMHO: On a 'dual band' LNBF, the feed throat dimensions and scalar are optimized for C band, and there is no effective scalar for Ku. (a Ku scalar would completely cover the C band throat) The C band is blocked slightly by the Ku assembly within the feed throat. The feed throat is not optimum for Ku.

Just an FYI my old WSI 741 dual band LNBF has a ku scalar and feedthroat bolted to the back of the c band throat. how effective the ku scalar is .... open to conjecture.

 

[Titanium]

The problem with this C/KU design where the KU LNB is bolted on the back of the C-band cavity is that this space is tuned for C-band frequencies. KU signals enter the cavity and bounce around, often arriving out of phase after passing through the mis-tuned cavity. Some folks have adjusted the KU LNB and optimized the KU reception, but this adjustment is specific for their specific dish type and feedhorn positioning.

As fat Air correctly pointed out, the performance gains of the GEOSATpro C2 over the C1 model was only due to the components that we used in the build. The C1 and C2 could have been similar.

 

[77TA]

I agree that c/ku combo lnbfs are designed for optimal c band reception and ku is not as good as it could be. My 6ft sadoun with NS741 gets only slightly better reception on ku than my geosat pro 90cm offset. I don’t however believe there is ANY reduction in c band reception with a c/ku combo lnbf. I'll put my NS741 up against any c band only lnbf.


Edit: Against any DRO c band only lnbf. Haven't tried a PLL one yet

 

[richyrich]

Dual Band Feed designs; without internal switch characteristics, which are the consideration of insertion losses. My favorite would be when both focal's at the same time strike the probe; like a Chaparral Corotor II+! Here, the designed single focus of both waves go around each other AT THE FOCUS OF EACH and the guides do not shadow each other; whereby the C Band bounces past and around the designed KU waveguided "tubular effect" just in front of the C Band focus and small enough to focus both upon each guiding principle (the probes today are located C Band in the middle and Ku in the very back of the lnbf (in the small waveguide). Here the effect is that nothing stops either wave in shadow; as the only shadow is the first probe which is the C Band antenna. The wire (probe) of the C Band feed design does block a small amount of the "effective air wave pinpoint" the Ku probe is relying on.

If both C and Ku were likened to the Corotor II+; it would be efficient at both!

 

[richyrich]

Dual Band Feed designs; without internal switch characteristics, which are the consideration of insertion losses. My favorite would be when both focal's at the same time strike the probe; like a Chaparral Corotor II+! Here, the designed single focus of both waves go around each other AT THE FOCUS OF EACH and the guides do not shadow each other; whereby the C Band bounces past and around the designed KU waveguided "tubular effect" just in front of the C Band focus and small enough to focus both upon each guiding principle. When you look at the squared wave it plck's before the focused point of C Band; the upside-down house-top or roof; that focuses a linear progression from the circling and feeds it back to the single polarity "probes" at the very point the feed is before the focus of the C Band signal (at the circular waveguide edge) and removes its own shadow instead.

The probes today are located C Band in the middle and Ku in the very back of the lnbf (in the small waveguide). Here the effect is that nothing stops either wave in shadow; as the only shadow is the first probe which is the C Band antenna. The wire (probe) of the C Band feed design does block a small amount of the "effective air wave pinpoint" the Ku probe is relying on. A part of the signal removed from the air wave of Ku linear would be a square standing pointed nest! If the ku waveguide was square instead at size the feed would be larger type to help the linear choose the required frequency and polarity; the feed would then need moving parts (or doubles); as the square standing would need both hor. and vertical selection points and the switch would be for dual polarity LNB style!