pre-amp

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  • Question
  • Updated 3 years ago
  • Answered
using software 1.4  and flex 6300  why is there always a noise floor of 3 s units even with no antenna?  I put pre-amp on and the noise drops slightly .
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Cliff

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Posted 3 years ago

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Photo of Tim - W4TME

Tim - W4TME, Customer Experience Manager

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Official Response
Because the radio is not at absolute 0 and inside of a Faraday cage ;-)

Seriously, the S-meter accurately reflects the integrated (sumed) RF power of the individual FFT bins inside of the slice receive filter.  There is always RF power (energy) being digitized by the SCU even with an antenna disconnected.  There is an ambient level of environmental RF noise, cosmic RF noise and other RF signals.  The only way to eliminate these noise sources is to cool the receiving device down to a temperature near absolute 0 and block outside RF energy using a Faraday cage (hence my joke to open this post).

Now on your preamp question, if you are not noise limited at the antenna and you add pre-amplfication, the signal levels will stay the same, but the noise floor will drop which improves the signal to noise ratio,  I recommend reviewing this HelpDesk article on the proper way to use the preamp for a more detailed description of how the preamps work: https://helpdesk.flexradio.com/hc/en-us/articles/204923669-How-to-determine-the-amount-of-RF-Preamp-...