Satellite LNB as an Amplifier

[scuba840]

Has anybody ever tried/thought to use a satellite LNB to amplify the signal in a detector? After all it is a low noise amplifier. Any thoughts?

[mikebg]

Has anybody ever tried/thought to use a satellite LNB to amplify the signal in a detector? After all it is a low noise amplifier. Any thoughts?

Scuba, do you know at what frequencies operate satelites and what frequencies are suitable for metal detectors?

[scuba840]

Satellite LNB as an Amplifier

Scuba, do you know at what frequencies operate satellites and what frequencies are suitable for metal detectors?

Yeah, GHz vs kHz. With the abundance of cheap surplus LNB's out there, I was wondering if removing/changing the filtering could lead to a source of cheap, low noise preamplifiers. Just looking to stimulate a discussion.

[Carl-NC]

LNAs & LNBs are typically bandpass amps, where the bandpass region is in the GHz range. They have a low noise figure specifically because they are bandpass. Make them low-pass, and they will be average. Better to use a good low noise opamp. You could do a little better with a discrete front end but usually not worth the trouble.

- Carl

[Fred]

To be exact the 10ghz (for ku band) is bandpass filtered, but i don´t think there is much filtering in the IF (1.5...2ghz) amplifier.But NF of those are not so special.
They are sometimes in separate boards and easy to use for other applications.

[Funfinder]

I modded already 2 LNBs into UHF amplifiers.

The gain is around 20 dB and the frequ.-range ca. 900 MHz - 2.2 GHz.

The original usual consumers Sat signal is from 11.5 GHz - 13 GHz
but fot better coax-cable transmission it gets downconverted into the LNB to ca. 1.5 GHz.

As long as micro-waves can't penetrate the ground very well such
amps are almost usesless for metal-detection, but you can use it for amateur-radio stuff or better WiFi-reception.

[Fred]

I modded already 2 LNBs into UHF amplifiers.

The gain is around 20 dB and the frequ.-range ca. 900 MHz - 2.2 GHz.

The original usual consumers Sat signal is from 11.5 GHz - 13 GHz
but fot better coax-cable transmission it gets downconverted into the LNB to ca. 1.5 GHz.

As long as micro-waves can't penetrate the ground very well such
amps are almost usesless for metal-detection, but you can use it for amateur-radio stuff or better WiFi-reception.

I did it too for meteosat and inmarsat reception, (using an attenuator), but i have no idea of the noise figure of this (IF) amplification chain.Works great.

[mikebg]

The main problem of metal detectors is that sensitivity is not limited by thermal noise but by three much larger signals:
GND (ground),
AIR (induction disbalance) and
INT (interference).
They so limit usable gain (radio frequency amplification), that depth of detecting can not be improved by low noise amplification (LNA). Only automatic suppressing of mentioned three signals can improve sensitivity and then using LNA makes sense. See this thread:
http://www.geotech1.com/forums/showt...eferrerid=2910