LNBs in the raw

pedro2000uk

This thread was started to show LNBs internals - If you have a dud etc.. why not pop it open and photo it's workings... !

If you do open a working one (not a really good one though....), it's up to you, it should go back OK (hmm), especially if it's an all screw type - reseal it with acrylic mastic (not water based) and do it in as warm/ dry an atmosphere as possible. The LOs might need tweaking though.

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This first one is the older big case Grundig Sky LNB .7db ..


PIC 1# = the two LOs on the right are fine adjusted with the two screws on the left in the lid.. to the left is the lid with heavy shielding compartments when in place.

PIC 2#= the two LOs - obvious which is which (smaller 10600/ larger 9750).

PIC 3# = the pcb....... anyone want to break it down...

top left hole is where VERTICAL comes into a chamber (formed in the lid) and looks like it’s picked up by the antenna on the board

HORIZONTAL comes in, in the bottom left corner (solder blob)... both look like they greet switches (13v/18v?) and then combine their route...

Roughly… filters next… then the 22kHz switch to the LO HIGH or LOW band drop to the IF more filters… amp…... more filters ……….and out … ( something like that …anyone…?)


The pcb looks as though it uses board strips to form part of the filters/mixer system.... anyone?



ed--- just noticed the rather brutal way it had to be opened - hacksaw/ chisel /screwdriver (bottom right PIC 1#)... not easy that one as it's glued in place with mastic ... most are screwed...


Grundigs are very good build quality compared to most today apart from perhaps Invacoms... and do very well still regradless of the 0.7db figure.

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satelliteman

Good pictures

satelliteman . ..... A Detailed DiSEqC Motor Installation Set Up Guide > HERE Quick Reference Guide also > HERE Satellites UK site Advertisers . An Installers Choice ...... Follow us on .

Robbo

Bottom right is an interdigital filter, bandpass I think.

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Robbo

Slightly different PCB layout on this one by the looks of it, found it in the bottom of my toolbox.

And yes, there was a dead spider and a some fluffy wool stuff in the plastic case.


I carefully jimmied off the metal lid as you can see.

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satelliteman

yes, can see the crowbar marks

satelliteman . ..... A Detailed DiSEqC Motor Installation Set Up Guide > HERE Quick Reference Guide also > HERE Satellites UK site Advertisers . An Installers Choice ...... Follow us on .

rolfw

LOL, that reminds me of a mate of mine, a youngster brought playstation into his shop for repair, he'd obviously taken a look in side to see what was wrong.

My friend enquired, "What did you take the top of with? A ******* Kango?

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Robbo

Didn't have to crowbar the plastic off, it fell apart when I took it off the dish.

pedro2000uk

The Cambrdge Sky FROG LNBf ....

no hacksaw/ chisel needed on this one ... all screws..


There is an inner cap over the entrance to the waveguide (removed )..


edit.. for mapping the pcb .... VERTICAL comes in middle right (larger solder blob just on screen) not 100% sure about Horizontal... I think it must be the other side of the largest area of conducter 15mm to left (real size).

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Robbo

Interesting, similar discreet components, but the filter is a coupled-line.

Designed one of those once, but it didn't work very well, etched it myself.


Explanation how to design these components in this book

"Microwave Filters, Impendence-matching Networks and Coupling Structures"

written by Written by George L. Matthaei, L. Young and E.M.T. Jones.
Published 01 January 1980.

Not your bedtime reading that's for sure.

BombedOne

I've dismantled a lot of LNBs, and checked their transistor parameters. IN ALL CASES (12 types of LNB), used transistor had minimum S/N 0.5DB, TYPICAL - 0.7DB. All this applies to modern, manufactured since 2007 lnb's.

pedro2000uk

SLX LNBf .3db

A new one this, tiny pcb ... a 1/4 the size compared to the above Sky LNBfs similar to a Smart Titanium (size wise only) ... you can see all the same basics and far less shielding in the lid. The LOs are about the same size so they offer a way to compare sizes without including a 20p or something.

Performance= OK but no winner.

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pedro2000uk

C Band Pauxis 17k LNBf

An example of a C Band LNBf voltage switched H/V with the dielectric plate guides for circular conversion and f/d ratio markings for the scala / feed support plate.

Used on an offset dish the scala plate/ring thing is, I think, pretty useless and best left off or fabricate a feed horn of sorts for the .6 f/d ratio usually found on offset dishes to get better performance out of an offset dish. Works without though.

The feed cover has holes in it to allow water to drain on a prime focus as it points down on prime focus dishes, so it needs sealing or replacing for an offset to prevent water getting in.

This shows the difference in sizes of the KU band LOs & the C band LO and the size difference of the waveguides for C & KU.. and antenna sizes.
Otherwise the pcbs are very similar ... the IF is quoted as 950-1750MHz...

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pedro2000uk

Any pictures BombedOne..

rolfw

Here's the inside view of a California Amplifier 0.5db LNB.

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BombedOne

Unfortunately, no photos at hand now (have somewhere), but you can check this:

_ttp://www.juras-projects.org/eng/hardware.php#lnb

here you can find a generic cheap lnd insidings and also schematics.

pedro2000uk

Thanks BombedOne..

nice to see a CalAmp...





Found this for anyone interested in LNB internals ... (not everyones' cup of tea) but flip though it and there is some very clear basic stuff and goes quite detailed too.

_http://www.uni-duisburg.de/FB9/HFT/lehre/hft_skript_v6.pdf


and this

_http://www.microwaves101.com/ ... waveguides etc..

pedro2000uk

A different KU Band LNB, this one's a short, single band LNB at the top of broadcast to home KU band about 12200 to 12700

It is a single pole (H or V only) and uses +15v to +24v (single) supply voltage. It has an oblong waveguide (c. 75 I think) with an adapter plate to C120, originally installed with a Channel Master c120 KU offset feedhorn on a CM dish.

Note the actual antenna is smaller than KU universals as it only is intended to operate at the higher end compared to the longer standard KU universal LNB's antennas that have to operate down to 10700MHz to 12700MHz.

It's only 1.0db but should perform better in it's frequency range than a universal LNB.

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BombedOne

If you going to handle delivery fees, my friend has 30+ LNB's of various type, some working partially, some not working at all so he can send them all to you...

pedro2000uk

Just off out now on a job.... sounds interesting BombedOne..

I'm doing a breakdown of the circuit boards and components.
I would like to see someone do one on a dead Quad & Quattro or any unusual lnbs.

cheers..

BombedOne

As far as I remember, he even has dead octo lnb somewhere...
From my side, I'll also contribute several working and dead LNBs

BombedOne

also, check this and next pages:

_ttp://forum.sat-expert.com/sdelai-sam/13343-obzor-konverterov-3.html

a lot of disassembled LNBs and their internals, including quad ones

pedro2000uk

Had to include the CM feedhorn.... opened up that is ... so er' it be...




btw.. the angle of the cone / scala rings is c. 45 degrees ... compare that to 60 degrees for the SLX...

that over simple 45 degrees makes you think when the lnb/ feed horn / dish relationship was originally conceived they just said ..... right.... what angle should we make the feed horn / scala rings then?...

......er..... hmmm... 45 degrees?…...

.....er.. yeah.... that'll do... mate……

….. then we'll match the focal length / parabola to it ....

....job done!

… get the kettle on then.. !

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pedro2000uk

I forgot this and the EDIT window ran out if any Mod wants to merge it..

These pictures show the KU Band circular dielectric plate guides in the Channel Master feedhorn for the US market etc.....

Wonder what those deep slots in the waveguide do to the signal when used for linear..


the blue shows just how crude the cast finish is on the scala ring edges..

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pedro2000uk

Philips single band 9.75GHz LO (very old)... found this lurking in a box after a clear out.

What's interesting is how design has progressed over the years and the fact that it's a single band lnbf so any excess circuit for the 2nd LO is not present.

Significant also is the fact the integral feed horn has no scala rings and functions more like a crude horn antenna in front of the dish with no real cone relationship to the parabola's focused beam. In practice though, the outer rim of the feed horn might act as one scala ring and the focus of the beam might be at the entrance to the waveguide although it looks too steep- the horn would shield noise too.

The final feed horn to waveguide stage is a bit of an abrupt step going from a short 29mm tube (formed where the 40mm feed clamp sits on the outside) to the short 18mm waveguide.

The antennae at the end of the waveguide are both just circuit board strips.

Most of the pcb looks not unlike newer ones with the same on board band pass, low & high pass filters .. main controller chip (ex 22khz/ hi LO etc..) .. and apart from the missing 2nd LO, only the feed horn shows a significant change in design to modern ones in lnbfs with scala rings, a more gradual cone down to the waveguide and some metal antenna with optional reflector. and the case is thick, heavy alloy, unlike the thin aluminium ones.

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