Topband: Long Path Direction!]

[CHARLES HUTTON]

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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