Re(2): [Antennas] Wideband Receive preamp for Screwdriver.

Fri Jun 30 18:21:21 EDT 2006

w4tg at bellsouth.net writes:
>In general, preamps do not prove useful (on any antenna) for use in the 
>HF part of the spectrum. There is a good reason for this: In the UHF and 
>VHF spectrum the noise level, which determines the signal-to-noise 
>ratio, comes from within the receiver, so amplifying the input signal 
>improves the signal-to-noise ratio. Whereas in the HF spectrum the the 
>noise floor, which determins the S/N ratio comes in with the signal as 
>picked up by the antenna. Any pre-amp used, therefore amplifies the 
>noise along with the signal. (Does not improve S/N ratio.) You can 
>easily prove this to yourself: disconnect the antenna from a working HF 
>receiver and note that the noise, as well as the signal, disappears. 
>Whereas, removing the antenna from a working VHF or UHF receiver and 
>only the signal is gone, the noise is still there!
>I hope this helps.
>73,
>Harvey/w4tg

Good insight! 
So, it must follow that any receive help about has to be in noise
cancellation somewhere in the receive system of: geographic location, rec.
antenna, rec. feedline, and actual receiver... is that all true?
David B.
W7DBH
Mobile-Only ...in NW Oregon