Hi Mal,
Yes fluorescent lights (old AND new ones) are an annoying source of QRM. But
I don’t think my neighbors would appreciate me getting rid of _their_ lamps
as well.
You are right w.r.t. the cable being (a significant) part of the working of
the Miniwhip antenna. This is unavoidable. Suggestions have been made to
feed the Miniwhip with its own battery, and use fiber to connect to the
shack to avoid the influence of the coax.
One of the problems with the coax is that it picks up QRM in the house (my
coax now runs from the shack in the attic through a large part of the house,
through a window and then to the end of the backyard. The QRM travels on the
outside of the coax TO the miniwhip, where it is picked up (in order to
annoy me I think). Using a common-mode choke as is commonly used with
“normal” antennas is of little use due to the very high impedance of the
E-field probe.
How much of the increased signal is due to added height of the probe and how
much by the coax I don’t know. But in my case the signal strength increased
(as did the band noise, but it looks like not by the same amount) but the
QRM from lamps, smps’s, TV’s etc remained the same, so overall things got
better.
Regards,
Minto pa3bca
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Ceterum censeo Carthaginem delendam esse
-----Original Message-----
From: mal hamilton
Sent: Tuesday, August 09, 2011 21:54
To: [email protected]
Subject: Re: LF: HB9ASB...
Minto
Get rid of fluorescent strip lights from your house, only QRM generators for
radio amateurs.
It seems MINIWHIP antennas work better the higher they are installed above
ground which makes me think that the cable connecting the probe to the RX is
in fact the REAL antenna. !!!!!!!!!!!!!!!
A probe antenna should work equally well at ground level in the clear as in
an elevated position.
G3KEV
----- Original Message -----
From: "Minto Witteveen" <[email protected]>
To: <[email protected]>
Sent: Tuesday, August 09, 2011 8:44 PM
Subject: Re: LF: HB9ASB...
.. And he is even visible on my grabber!
I raised the miniwhip from +4 to +11 meters (large fishing rod in the
backyard).
Signal levels increased by 15 dB. Noise level was raised too, but the QRM
from my fluorescent lights in the house no longer show up. so there must
be
some improvement.
Tomorrow I will again measure de DCF39 to noise ratio.
73's
Minto pa3bca
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