Message-ID: <004401c2c0a2$25622860$9801a8c0@gigacom.com.br>
From: "PY2PLL" <py2pll@py.qsl.br>
To: lowfer@mailman.qth.net,  rsgb_lf_group@blacksheep.org
References: <23.2aadfb3f.2b5c5522@aol.com>
Date: Mon, 20 Jan 2003 13:35:59 -0300
MIME-Version: 1.0
Subject: LF: Loops x Q
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Hi ...

After read an article last year (Wireless World) about loop antennas X DCF39
calibration, I constructed a octogonal RX loop, #16 awg wire, to cover from
400KHz to 1.6MHz.

There´s 9 turns, 5mm spacing, 1.9 meter diameter. About 55 meter of wire.

This is the first version. Later I´ll build another one to 136KHz.

Acording with this article, I should expect a Q=200 ... 220 from such loop.

I considered the NTE618 to tune it and a push-pull pre-amp (J310) with gates
conected to the loop ends. No resistors there. The article consider that for
such loop at this frequency will have something like .20uV of thermal noise.
The resistors will add some extra noise there so I removed them.

But the Q=210 ... and the NTE618 Q is 200.

Is there any gain If I use a dual-gang air variable driven by a step motor +
reduction in place of the NTE618?

P.S.: I put two tables, considering standard loop areas, both for 136 and BC
band at:

http://py.qsl.br/loop136e.gif and
http://py.qsl.br/loop-om-e.gif

73
Marcus
PY3CRX/PY2PLL
http://py.qsl.br
Active from "DC" to Laser ...