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two beer cans spaced abt 1.5m ..... more
intermodulation
Q was that prediction made when
the cans where full ..or slightly afterwards
?
G..
Sent: Thursday, February 23, 2012 2:40 PM
Subject: Re: LF: DK7FC in North Italy
Hi Alberto,
Interesting. Keep us informed about your
results with the short active dipole. I've never tried such an antenna so far.
But maybe it could be an idea, if the ground is QRM-contaminated...
73,
Stefan/DK7FC
Am 23.02.2012 15:10, schrieb Alberto di Bene:
On 2/23/2012 2:30
PM, Stefan Schäfer wrote:
Hi Alberto,
That looks fine. I'm glad to get a report from you, thank you.
How long was that wire and was it in the house or outside? :-)
Hi Stefan,
oh, that wire was just a dipole for
the 40m band, directly connected to the receiver, without any form of tuning
for the 137kHz band.
Signals are low, but so also is the noise...
:-)
Often is advantageous to have a not so high gain antenna...
the S/N ratio can improve... not always, but sometimes yes.
That dipole
is low in height. Actually it is an inverted V, with the apex at 10m from the
ground.
For the LF band I have also a mini whip, temporarily out of
service, as I used the coax feeding it for some tests of a differential active
antenna,
with two beer cans spaced abt 1.5m connected to the differential
inputs of a high impedance amplifier. It works quite well, as it
does
not need to be referred to a ground potential, but maybe I have to
change the schematic of that transimpedance amplifier, as it
exhibits more
intermodulation that I thought it should have....
73
Alberto I2PHD
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