Purpose of Feedhorn

[The Rascals]

Good Evening to Everbody.

The plan is to purchase a Laminas Dish 1.2M or 1.5M later in the 3rd quarter of the year, should I buy a feedhorn for it, and if so what improvement (if any) this would give me.
I am sticking with Ku Band but will venture into the Ka and C Bands later.

Regards

The Rascals

 

[archive10]

The plan is to purchase a Laminas Dish 1.2M or 1.5M later in the 3rd quarter of the year, should I buy a feedhorn for it, and if so what improvement (if any) this would give me.
I am sticking with Ku Band but will venture into the Ka and C Bands later.

You will need a feedhorn regardless.
However, the so-called Universal LNBs (really LNBFs) comes with one built-in.
For example, the Inverto Black Ultra comes with a die-cast metal one inside the plastic outer casing.
Indeed, som of the cheaper LNBFs actually have a feedhorn of metalicised plastic, making them very light (and cheap).

But until the advent of universal LNBs (through big-time sat tv, mostly digital), the LNB was sold separate from the Feedhorn.
You can still buy them separate, the LNBs usually are called "flange-LNBs".
The Flange is the connection between the feedhorn and the LNB.
This is normally C120 for Ku-band, but comes in many sizes and shapes.

For Ku on a Laminas 1200 or 1500, just use a universal LNB with built-in feedhorn for most purposes.
If you really want a feed-horn, any feedhorn designed for a f/D of 0.6 will work.
There's a Gibertini one, plus the Channel Master ones.
Empirical evidence on this very site shows me that most feedhorn/LNB combos are outshined by a few universal LNBFs.

So you should in any case have a good start with one of the top contender Universals (Inverto Black Ultra, Octagon, MTI etc)

 

[The Rascals]

Thanks st1 for your great explanation, and what Universal LNB to use.
Should I get a very narrow LNB (image attached)to allow a future C-Band lnb to be closer to the focal point.
Regards
The Rascals

 

[archive10]

Should I get a very narrow LNB (image attached)to allow a future C-Band lnb to be closer to the focal point.

No, my opinion is: Get the best Ku-band LNB you can find for initial exploration, and enjoy.
The narrow Ku LNBs mostly do not performa as well as the "normal" Ku ones.
They have a special plastic dome instead of a feedhorn; this is nearly as good, but not quite.
If you add C-band later, you should re-evaluate your setup at that point.
The Ku LNBs are really not very expsenive (15-20 GBP or so), so you can swap later if you wish.

 

[Terryl]

The real general purpose of the feed horn is to help shield the receiving antenna(s) of the LNB from stray signals from outside the beam of the directed signals from the dish.
Older "C" band LNB's with single polarity antennas were highly susceptible to outside interference,(others used the the frequency's above and below "C" band frequency's for other purposes) so the antennas were located further down in the throat of the casing thus creating a feed that was shielding the LNB's internal antenna(s).

Some of the bigger professional dishes used wave guides and tunable filters to cut down on interference, but this was not very practical for the consumer dishes as they were very expensive.

Now days on a "C" band LNB the feed horn would just be a tube with the antenna(s) down inside it, some of the older ones used a servo motor to change the antenna polarity, but on a "kU" band LNB it actually looks like a horn, thus the name "Feed Horn" stuck.

 

[The Rascals]

Thanks ST1, Terryl for the info.
Would different LNB's be better at seperating 10E from 9E or is it down to the dish size, ie (bigger the dish narrower the focal point)

regards

The Rascals

 

[moonbase]

Thanks ST1, Terryl for the info.
Would different LNB's be better at seperating 10E from 9E or is it down to the dish size, ie (bigger the dish narrower the focal point)

regards

The Rascals

You can selectively scan 10E and 9E as they each have precise frequency ranges that do not overlap.

If you scan 10E using frequency ranges 10700 to 11700 and 12500 to 12750 you will not pick up any signals from 9E
Reversing the logic, if you scan 9E using frequency range 11700 to 12500 you will not pick up any signals from 10E

It would need a large dish to resolve individual satellites that are only 1.0 degree apart, your planned 1.5m dish purchase would not be large enough to resolve these two satellites individually.


Rgds