From PA0SE
Rik, ON7YD wrote
At my QTH noise is rather low, with the 'big' TX-antenna that is located
about 30m from the house. Few weeks ago I tested a small loopantenna indoor
and noise was awfull. The 1 meter loop produced about 6dB more noise level
than the big outdoor vertical and signals were about 20dB down on the
indoor loop.
So the overall S/N ratio was at about 26dB worse.
Placing the loop in the back yard at about 25m from the house resulted in
the same S/N on loop and vertical.
My tip : try to place your RX-antenna as far away as possible from
'civilisation' and use good coax between antenna and RX. I have bad
experience with the shielding of cheap RG58.
That confirms my experience with "magnetic" antennas. I have used both a
frame-type antenna and an active ferrite loopstick antenna in the shack and
at the back of he garden. That is no more than 10 m from the house. The S/N
ratio in both cases was worse than with the transmitting antenna for
reception.
I also tried a small active electric antenna at the back of the garden. No
good either.
The only thing left I could try is a noise cancelling system with a second
antenna that picks up mainly noise which is then balanced against the noise
from the main antenna. It is reported to work fine in case of a single
interfering signal. But I'm rather pessimistic about the result in case of
noise coming from many different sources.
Anyone having experience with noise cancelling systems in this respect?
73, Dick, PA0SE
| 