Saturday, January 15, 2011

LNB internals

In the shack, siting for more than 5 years lays an ATV transmitter. It's assembled in form of a pre-mounted kit and should work, but I never tested. It's companion is an old video camera and a satellite receiver for transmission test. Honestly I bought that just for having ATV capability but no real need. Now I decide to slowly getting ready for ATV. The analog satellite receiver for transmission monitoring comes with it's own LNB and I decided to have a look to try to learn a little more on this small length wavelengths.
On to the dis assembly:


A closer look:

The fist thing noted was the big screw on such a small package (low right side), before removing it I thought it sould be some mechanical protection for a dissipator or EMC protection but even so it was to big for the purpose...
let's open a little more:


WTF? A piece of ceramic, this is new for me...

Now after some searching on the internet and some obvious conclusions (the antenna is quit obvious) here's what I found about this circuit:

1 - Horizontal antenna
2 - Vertical antenna
3 - Fet amp (I was hopping for a MAR something...)
4 - Fet amp
5 - LM324 : Still didn't found yet the porpouse
6 - Filter
7 - Fet Amp
8 - LM555: Maybe for negative voltage to the Fet amps
9 - Filter, looks like a bandpass
10 - LM7806: Voltage regulator
11 - Mixer and amp togheter? it's a metalic case in the unserside.
12 - DRO (Dielectric Resonator Oscillator): It's the oscilator and the screw should be for fine tuning at the factory

There's a lot more on LNB uses and info you can read here: (especially the excellent first link pdf)

http://www.earf.co.uk/sat.pdf
http://www.g4hjw.metahusky.net/3cm_conv.html
http://vitsch.net/ham/homebrew/upconverter/
http://www.microwaves101.com/encyclopedia/lownoiseblock.cfm
http://www.webalice.it/hotwater/3cmXverter.htm#mix

On other subjects:
Still didn't received any UHF signal om the UHF-VHF converter (a previous post)...well.. neither the TH-F7 used for monitoring the bands, looks like that UHF it's sparse around here. But I did received some WFM transmissions.... 40 + 88-108 = 128-148... bloody broadcasters...

4 comments:

pedro said...

http://www.py2bbs.qsl.br/gasfet.php

Ricardo - CT2GQV said...

Thank you Pedro for the link.

There's plenty of info there to. I have to open more LNB's to get a MAR device.

Abraço,

Ricardo

Keelytm said...

I recently purchased a new Japan radio LNB for my dad. I'm not really into the radio stuff, but I know he is. I am wondering if you guys could give me tips on what else I should give him in addition to the LNB. I feel like it's not enough by itself.

Ricardo - CT2GQV said...

Keelytm:
What about a dish?