Hi Roger,
Any 160 meter receiving antenna laying on conductive soil will have
extremely low RF output and you'll need at least 40 dB of preamp gain
with very low noise figure and you must take extreme measures to control
common mode currents. Antennas NEAR the ground perform dramatically
better than antennas ON the ground.
Vertically polarized small loops like your 6 foot loop must be installed
within about 7 feet of the ground, otherwise the two vertically polarized
deep nulls get washed out by horizontally polarized signals that are no
longer suppressed by ground proximity.
I hope you don't have a lot of wiring and other metallic structures in
or near your loft, otherwise your small loop doesn't have a prayer of
working at all. You also must take extreme measures to suppress
common mode currents when using a small loop.
What constraints must you take into consideration when selecting
the location for your receiving antennas?
73
Frank
W3LPL
----- Original Message -----
From: "Roger Kennedy" <roger@wessexproductions.co.uk>
To: "topband" <topband@contesting.com>
Sent: Tuesday, May 23, 2023 3:05:13 PM
Subject: Topband: Loop on Ground receiving antenna.
I just tried making a Loop on the Ground to see if it would be any lower
noise than my 6ft 160m Loop up in the loft.
I followed several people's suggested dimensions . . . so 15 feet each side,
feeding it in the middle of the side pointing West with a 450:50 ohm
transformer . . . And it's rubbish!
A local station (in the right direction) on my 6ft vertical loop in the loft
needs a 20dB preamp to bring him to the same level as on my Dipole (and the
noise is 6 to 10dB lower).
But on the LOG he was 30dB weaker, that's WITH the 20dB preamp! So the S/N
would be rubbish. Anyone else tried something similar on 160m?
Roger G3YRO
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