'So you think that you have a RFI problem ?'
Today it can be a challenge to
obtain clear reception of HF signals.
This plagues Ham radio operators as well as shortwave
At my old apartment the RFI levels were extreme to say
No internal antenna could pick up anything but noise and
even simple outdoor wire antennas were equally poor
Things seemed pretty bleak until I started experimenting
with small loop antennas.
The loop antenna in this demonstration video was
approximately 5 meters (1/10 Wavelength) in
The main loop was actually part of the aluminum window
To connect to the main loop a much smaller pickup loop ,
called a ''Faraday loop'', was made from coaxial cable.
It was 1/5 of a diameter of the main loop and was
similar to this design.
The pickup loop was placed near to the window frame
Typically with small loops like this (aka magnetic loop)
you would use a variable capacitor to resonate the main
As my main loop was the window frame adding a capacitor
was not possible , nevertheless it was still found to be
acceptable for receiving purposes in the upper SW HF
bands , but as expected it did suffer below 5MHz.
To improve performance lower in the frequency range the
main loop would have to have been bigger in size.
When completed this antenna provided a vastly superior
signal to random wire antennas , even though it was much
smaller in size.
This is because loop antennas like this are not
sensitive to near field signals.
As much of the noise that we hear is generated close by
to our listening location most types of antennas that
are close to it will pick it up strongly , drowning out
the comparatively weak radio signals.
As loop antennas are essentially deaf to near RF sources
the signals from further out are now heard.
In the example video below it shows me switching from
frame loop antenna to the random wire antenna
of about 10 meters in length which goes outside up into
The loop is connected to the Lo-Z coaxial connection and
the random wire is connected to the Hi-Z spring
A slide switch on the rear of the radio selects between
Click the image
below to see the short video.
can see , the difference between the two antennas is
like night and day.
RFI problems don't need to end radio listening
pleasure , but sometimes you have to work outside the
box to achieve worthwhile results.