There are profound differences in the glactic noise
floor/level vs the metro areas. RF wise, we (the
people) tend to polute the noise floor pretty bad.
cheers,
skipp
> "Jeff DePolo" <[EMAIL PROTECTED]> wrote:
> > 2 meters is a little different since most
> > G.E./Motorola radios have a
> > little better sensitivity, & the noise floor of 2 meters is
> > much higher. I
> > once measured the 2 meter noise floor here to be ~3000 K, or
> > -122 dBm in a
> > 16 kHz bandwidth. That's wny I almost never recommend a
> > preamp ahead of a
> > G.E. VHF receiver, but always for a UHF.
> >
> > Bob NO6B
>
> I agree, and to compound the problem, it's difficult to get enough
T/R
> isolation in most 600 kHz duplexed situations to see any increase in
> usable sensitivity even at a quiet site.
>
> A few years back I got called to look at a 2m repeater with a "deaf"
> receiver that had just been relocated to a new site. As it turned
out,
> the new site was beneath a high-voltage power line. Using the
spectrum
> analyzer you could "see" the notch response of the duplexer without
> using a tracking generator - the noise level was *that* high.
Effective
> sensitivity for 12 dB SINAD was measured/calculated using a lossy
tee at
> a little over 5 uV, even though the Micor Rx was working just fine
at
> 0.3 uV by itself when connected directly to the service monitor.
>
> They moved to another site a few months later...
>
> At high-rise sites in downtown Philly I've mesured effective
sensitivity
> of 2 uV on 2m and 5 uV on 6m. In contrast, I have quiet 440 sites
that
> will break squelch and decode PL at 0.03 uV (Angle Linear PHEMT's
doing
> the job).
>
> --- Jeff
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