Does anyone have any ideas on how to lower the NF in a uhf preamp? I have two types one had seperate comopnents and the other is a self contained chip.
- posted
18 years ago
Lowering the noise figure in a rf preamp
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- posted
18 years ago
Reduce temperature is the obvious one. Liquid nitrogen (or better).
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- posted
18 years ago
Select a different uhf preamp.
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- posted
18 years ago
Actually LN2 is a bit too cool (though I think I get your point) :-). In gamma particle detectors - made of a large Ge crystal cooled down to liqud nitrogen - the preamp FET is cooled to something higher, about -90 C (rather than the whole -190 C), they seem to work best there...
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Dave (from the UK) wrote:
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- posted
18 years ago
Reducing the temperature depends on the type of semiconductor. A doped silicon one, aka bipolar may stop working when the usually thermally excited conduction electrons do not populate the fermi surfaces anymore. A FET is a completely different story. There the conduction is done by a field sensitive channel. FETs can work down to LHE.
Rene
Didi wrote:
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- posted
18 years ago
Fets are different from bipoar indeed. Perhaps they can work down to LHe. For some reason, though, the detector manufacturers opt for about -90 C - all I know is this is common practice based on extensive experimentation over the last few decades. Invent a major noise reduction technique in this field based on your knowledge and get it sold, I may be among those interested.
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Rene Tschaggelar wrote:
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- posted
18 years ago
On Wed, 12 Apr 2006 08:55:18 -0700, Didi top-posted:
It appears that dry ice (frozen CO2) sublimates at -109.3°F or -78.5°C; I've seen it used in an acetone bath to get not quite as cold as LN2. Then again, depending on your mounting arrangement, you might not need any liquid at all - just drop some chunks into a copper chamber...
Cheers! Rich
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- posted
18 years ago
Raise the antenna gain. And its height.
Shorten the cable between antenna and amplifier.
Improving the noise figure of a UHF preamp will do little or no good if the signal is not there in the first place.
Measure your input S/N on a VFR or something similar.
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- posted
18 years ago
Doesn't seem to work much with tv satellite receivers. Lowering the temperature apparently trashes the gain for no net benefit.
-- Many thanks, Don Lancaster voice phone: (928)428-4073 Synergetics 3860 West First Street Box 809 Thatcher, AZ 85552 rss: http://www.tinaja.com/whtnu.xml email: don@tinaja.com Please visit my GURU\'s LAIR web site at http://www.tinaja.com