Joe,
I'd like to add a low frequ effect to Inge's. Coax cable may be susceptible to the microphonic effect. Mechanical vibrations of the
cable sheath generate low frequency electrical noise. Low microphonic noise cable is equipped with PTFE (Polytetrafluorethylen,
Teflon) insulation.
Tom
-----Ursprüngliche Nachricht-----
Von: Hfjord [mailto:[log in to unmask]]
Gesendet: Dienstag, 27. November 2007 23:22
Betreff: SV: [TN] Low Noise Coaxial Cable Question
It's easy. If you are in room with lots of people, and suppose you are
discussing important things with your boss, e.g. your salary, and he opens
his mouth to tell you, but a guy near you shouts 'one more beer', you will
be very disturbed, especially if your boss says 'listen, I tell yo diss
onnly once'. Likewise, in a signal transmission cable with a wide bandwidth,
electromagnetic waves from transformers, neon lights, relays and a lot of
other sources, can leak through the shield of your cable and distort the
wanted signal performance. In LNAs the background noise from bursts of
electrons can cause 'noise'. In old electron tube amplifiers, the variations
of electron emitting caused noise. Same in masers. There are many ways to
reduce noise, e.g. cool down the source to minus 196 Centigrades, or use
digital instead of analogs, use narrower bandwidth and so on. So, a low
noise coaxial cable is a cable that does not permit electromagnetic waves to
leak through the shield (semirigid copper cables or double shield). Also,
such a cable has low losses and no discontinuities, which both can generate
internal noise. Good matching and no reflexions are also important, though
not belonging strictly to noise. Leakage of signals through the cable
dielectric when transmitting extremely low level signals at high impedance
can also be avoided by a good dielectric. With other words, the signal level
compared to the unwanted noise, should be as high as possible.
My two S/N
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Joe Russeau
Skickat: den 27 november 2007 16:02
Till: [log in to unmask]
Ämne: [TN] Low Noise Coaxial Cable Question
Good Morning All,
Can someone point me in a direction to obtain information that explains what
defines low noise coaxial cable? Thank you.
Best Regards,
Joe Russeau
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