I have spent a few days experimenting with a mini whip active
receiving antenna. As advised I decoupled the feeder by winding it
around a ferrite core, and ensured the antenna was earthed to a stake
at the foot of the (20ft) mast. It produced very good results on the
136kHz band - about the same as my much larger and higher
transmitting antenna, which is currently on the ground.
However, the performance on 472kHz seemed poor. I was giving WSPR
reports about 3-5dB below other stations. Eventually I found that the
12v PSU (Watson Power-Mite) I used to power the whip had a lot of MF
noise, and filtering the output failed to completely eliminate it. I
replaced the PSU with another - also switch mode - and that did the
trick. I am now giving reports as good as the best stations.
This is a very effective, yet ridiculously tiny, antenna which anyone
can use to achieve good results on receive, no matter how small their
garden is. But beware of PSU noise sabotaging it.
Not for the first time, I have found Opera and WSPR to be very useful
tools in determining how well my station is working by being able to
directly compare transmit and receive performance of other stations.
Without this facility I might have just accepted the level of
perfomance I was getting.
Mike, G3XDV
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