RadioBanter - View Single Post

Telamon · December 1st 07, 03:55 AM posted to rec.radio.shortwave

In article
,
wrote:

On Nov 30, 11:22 pm, Alex wrote:
Many thanks for that - I will look at these sources before deciding on a
permanent installation.

Cheers

Alex

Try the simpler antenna in the "Reducing noise" file first.

While the specified FET is clearly the best, if you are lucky enough
to be far enough from local MW stations, a MPF102 or 2N3819 will
work. They are both far from optimal but may be easier to find
locally.

There are objective ways of looking at information to see whether it
makes sense.

There are principles of operation of antennas that can work for or
against common mode noise, which is generally object of a low noise
antenna. As far as far field noise is concerned about the only way to
improve that aspect would be to limit the BW of the antenna. Generally
as a side effect of balanced antennas, or complete antennas, or what is
known as Hertzian antennas are that they are resonant and have by their
nature a narrow BW.

If you add amplification to an antenna design then another dimension is
added to the design. Here generally you would want a high degree of
common mode rejection and of course the amplifier would have to generate
very little noise by itself. Here you might decide to limit the BW of
the amplifier.

--
Telamon
Ventura, California