S band digital HD LNBF

Discussions about low-noise blocks, waveguides, horns and other components used at the prime focus of your reflector dish.
elko
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Re: S band digital HD LNBF

Post by elko » Thu Aug 11, 2016 8:59 pm

I think the idea is that because at longer wavelengths, the convergence 'point' is more like an RF cloud of energy several wavelengths in diameter, therefore, he has immersed a couple of directors into that cloud so they can radiate to the active element. If 2 or 3 of those directors can radiate efficiently towards the active element, then he will get a bit of extra gain. If he put the active element at the focus, I think the reflector (of the yagi) would get in the way.

Either this explanation is correct, or foxcreek was a bit drunk :beermug: when he decided to combine a terrestrial yagi with a satellite dish reflector.

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Re: S band digital HD LNBF

Post by Titanium » Fri Aug 12, 2016 6:46 pm

LOL... some of the best science has been influenced by the spirits!

I don't understand how the directors would increase gain from a convergence point "cloud", but I have never dabbled with pointing a yagi into a reflector. The Reflector would be below the LOS, so in theory, it should not present a shadow, but the return phasing of the dispersing signal past the convergence point would be of interest. Be interesting to find out the real-life performance of this set-up. Proof is in the performance! :grin:

I have constructed WiFi cantannas and mounted them in the sweet spot with excellent gain and performance. :bigsmile
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Re: S band digital HD LNBF

Post by Foxcreek » Sun Aug 14, 2016 11:51 pm

Brian,

All feed antennas have gain. Even a Dipole.
The referrence source antenna is Omni directional
it's reffered to as an isotropic radiator which radiates
equally in all directions. Any time you increase gain
your directing RF energy in a particular
direction. This of course is what a Yagi does with
elements called Directors and Reflectors.

I'll admit that a yagi doesn't make the optimum dish
feed but there are many dishes that use them. The
combination of the high gain Yagi and the dish at 2.5
to 2.7 GHz. works fantastically !
foxcreek :cool2

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Re: S band digital HD LNBF

Post by elko » Mon Aug 15, 2016 5:49 pm

Hey Foxcreek, have you tried sticking that yagi into your prime-focus c band dish yet? :biggrin

At longer wavelengths (i.e. s-band), bow-tie primary feeds are known to work well. You should be able to receive UHF TV fringe terrestrial signals, in addition to Wi-Fi.

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Re: S band digital HD LNBF

Post by Foxcreek » Mon Aug 15, 2016 7:04 pm

elko.

No I haven't feed the C band dish with the Yagi but I have had
all sorts of feed types and frequencies on the C band dish previously.

If you google coffee can feeds you'll find the basic can sizes and
dimensions for a wide range of spectrum. I've built several .
You'd be surprised how well coffee can / soup can feeds work !
Obviously their not optimum but they do work and their cheep.
Here's a picture of an S band coffee can feed I built a while back.

foxcreek :cool2
Attachments
IMG_0276.JPG
IMG_0277.JPG

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Re: S band digital HD LNBF

Post by Titanium » Wed Aug 17, 2016 2:28 pm

Thanks for the explanation Foxcreek. I would be interested in any future S-band comparison testing that you might do with the yagi vs the cantenna.
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Re: S band digital HD LNBF

Post by Foxcreek » Wed Aug 17, 2016 6:09 pm

Titanium,

Your welcome....... did that list of S band sat's stir your interest ?

I was a bit hesitant to post that because a lot of those birds are

classified ! ( at least the frequencies ).

There's a whole world of Electromagnetic spectrum out there.......

It's actually a natural resource and therefore belongs to everybody !

Go and explore !


foxcreek :cool2

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Re: S band digital HD LNBF

Post by Foxcreek » Fri Aug 19, 2016 1:27 pm

All,

Speaking of S band .......... Are you guys aware that D/N has 2 S band
sat's currently on orbit. I don't recall their orbital locations but you can find
them at satbeams.com. These birds are intended for D/N's interest in competing
in the cellphone market. Point a dish at these sat's you may find something
interesting going on !

Foxcreek :cool2

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Re: S band digital HD LNBF

Post by Titanium » Mon Sep 19, 2016 3:26 pm

Definitely interested in the content on S, KA and L bands, but never seem to have enough hours in the day to play!

I've have placed the SDR at the dish and directly connected to varying length probes in the convergence point and played around with LNB multipliers and harmonics in the Clarke Belt. Often have found signals, but usually have no idea what they are or have the capability to demod let alone extract anything.

Used to be much easier when sampling the 70MHz AM/FM/SSB with wide/narrow filtering! :grin:
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