Lowering the noise figure in a rf preamp

[tucker@conninc.com]

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.

 

[Dave (from the UK)]

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.

Reduce temperature is the obvious one. Liquid nitrogen (or better).

--
Dave K MCSE.

MCSE = Minefield Consultant and Solitaire Expert.

Please note my email address changes periodically to avoid spam.
It is always of the form: month-year@domain. Hitting reply will work
for a couple of months only. Later set it manually.

 

[John_H]

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.

Select a different uhf preamp.

 

[Didi]

Reduce temperature is the obvious one. Liquid nitrogen (or better).

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...

Dimiter

 

[Rene Tschaggelar]

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]

A FET is a completely different

story. There the conduction is done by a field
sensitive channel. FETs can work down to LHE.

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.

Dimiter

 

[Rich Grise]

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...

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

 

[Don Lancaster]

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.

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.


--
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

 

[Don Lancaster]

Reduce temperature is the obvious one. Liquid nitrogen (or better).

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