Rik Strobbe schrieb:
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.
I have not found time to try such a loop, but this is interesting and pleasing
me. I have just tried an LF broadacast ferrite rod aerial and found it not
sufficiently sensitive.
But with this ferrite rod I discovered that in my home brew equipment voltage
stabilizers such as 78LXX produce a noise at the input side if this is not
blocked by a good 6,8 MFD or more. This noise may be radiated from the supply
cable leading to another power supply and increase indoor noise.
But when studying the QSL card of HB9DCE, he is mentioning a vertical loop
antenna with three turns and a circumference of 50 meters! So You still have to
do a lot to catch up with him.
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.
ZL2CA also has emphasized:
Note that I run all of my shack via a 5 kVA isolation
transformer, including a multisection low pass filter on the mains side,
in an attempt to keep mains noise out of my VLF/LF receiving gear.
73 Ha-Jo, DJ1ZB
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