Topband: Long Path Direction!]
CHARLES HUTTON
charlesh3 at msn.com
Wed Mar 31 19:56:57 EST 2004
Tom:
A season long study of direction finding on Boston reception of MW stations
from Europe, Asia and Africa was once done by an ex-MIT'er using 4' air core
loops.
The results of those hundreds and hundreds of DF's were compared against the
known locations of the transmitters. I can not recall whether outliers
(skewed path signals generally resulting from proximity to the auroral zone)
were discarded. The result was that the DF angle had an angle error of less
than ten degrees. The MW stations ranged from 529 - 1602 kHz, so at 160 YMMV
somewhat.
Evidence that is more anecdotal: most MW DX'ers use loop antennas (carefully
balanced large air core and also ferrite) of some sort for domestic
reception. While I know of no formal data analysis, I'd say the expectation
is almost always that DF'ing is at least good enough to get you within 30
degrees. I suspect the real limit is that few loops have the physical method
to give a readout of angles; most people just turn the loop and guess as
they don't care what the exactreal angle is.
Chuck
>From: "Tom Rauch" <w8ji at contesting.com>
>Reply-To: Tom Rauch <w8ji at contesting.com>
>To: "topband" <topband at contesting.com>,"Ken Brown"
><ken.d.brown at verizon.net>
>Subject: Re: Re: Topband: Long Path Direction!]
>Date: Wed, 31 Mar 2004 10:03:23 -0500
>
>Single loops won't work well at all for skywave DFing not for the reasons
>you mentioned, but also because there is too much multipath and scattering.
>The null is too sharp, and the response too broad. They are also very
>difficult to decouple from feedlines and are heavily influenced by
>surroundings. Single loops are almost useless for skywave DFing.
>
>The only reliable way to resolve directions of weak skywave signals is with
>large arrays having a narrow clean response, or by measuring phase
>differences in multiple small arrays with wide spacing.
>
>73 Tom
>
>
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