> It is almost certainly NOT based
> on a very directional antennas, in particular inefficient antennas,
> since the more directional the antenna the lower the noise level is.
We assume that atmospheric noise is evenly distributed in the space around
us.
Very directional and efficient antenna will exibit high gain and pickup that
much MORE noise.
Inefficient antenna will get proportionally less noise in the linear
fashion.
There seems to be a confussion between noise and QRM from the unwanted
direction.
Any modern RX has preamp and attenuator. Later should be more often used.
Even for TX clicks :-)
73 de Mario, S56A, N1YU
----- Original Message -----
From: "Tom Rauch" <w8ji@akorn.net>
To: <i4jmy@iol.it>
Cc: <topband@contesting.com>; <cq-contest@contesting.com>
Sent: Tuesday, January 08, 2002 5:48 PM
Subject: Re: Topband: Re: [CQ-Contest] Re: Topband: TOP BAND RECEIVING
ANTENNAS
>
> > gets well alive when connected to the antenna. Playing with N stacked
> > beverages (1 to 2 WL beeing probably best choice) insures a good
> > pattern control and offers an output level that surely meets or exceed
> > PY5EG system needs. I agree that antenna preamplifiers should be
> > avoided when it is possible.
> >
> > 73,
> > Mauri I4JMY
>
> The old argument or idea you never need an amplifier is just as silly
> as saying you always do need an amplifier.
>
> I would guess the "rule" we never need -140dBm sensitivity is
> based on a suburban location, perhaps with a wide filter, or
> perhaps a very efficient antenna. It is almost certainly NOT based
> on a very directional antennas, in particular inefficient antennas,
> since the more directional the antenna the lower the noise level is.
>
> Suggesting people always do NOT need an amplifier or a very
> sensitive receiver because we read it someplace is like telling them
> they always DO need one. Both are very wrong, because the
> circumstances vary greatly!
>
> There is one rule that always works.
>
> Set your gain with use of preamplifiers or attenuators so you can
> just comfortably hear a noise increase when the antenna is
> connected, and a definite decrease with it removed. If your receiver
> can not take you comfortably into the noise without overloading on
> the strongest 160 signals, then you need to buy another receiver or
> have your receiver repaired...or give up working some weak signals.
>
> My web page covers this in detail.
> 73, Tom W8JI
> W8JI@contesting.com
>
>
> --
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