Am 09.06.2018 16:11, schrieb TG9AJR Juan Munoz:
My station is an Elecraft K3 and also a FlexRadio 6600 which whom I am
doing this receptions, antenna just my 40m dipole to begin with maybe
later I can read and learn more about an receiving antenna for LF/MF
but for now is a good start for me.
A dipole can be a fine antenna but it depends on the way you couple it
to the RX input. If you use certain types of baluns it can act as a
shortcut on that frequency. But if your dipole is just two wires
connected to coax or ladder line then it may work. Anyway, most likely
you will need a preamp. But, if you don't have a preamp and/or don't
know how to build, there is still some way for improvements: Use your
ferrite rod or core and build a selective matching. A primary turn of
some ten turns (maybe up 100) connected to a separate clean ground/earth
(a rod in the garden, not the earth from the shack!). The other end is
connected to the dipole including its feeder line (coax). So it will be
a T antenna. Use a small variable C in parallel to tune for resonance at
475 kHz. Then add a secondary winding to feed the RX. Here, you may just
need 10 turns or so. You will need some testing... And you should see a
higher noise level when tuning to resonance.
In any way you should see the QRN bursts in your spectrogram. At night
it will be heavy. If not, then your antenna signal is to weak. WA4SZE
may be a good test signal...
73, GL, Stefan
PS: Or try a tuned loop instead. This works also very well, even better
i would say.