Hi, Don
Well, we can improve on that by using a solar determination of true North.
The way that I do it for my antenna arrays is:
1.0 Use a weather site to determine local sunrise and sunset times for your
location on the day that you are going to make the determination.
2.0 Split the difference to determine the time for your local solar noon.
3.0 At the time of your local solar noon, a vertical shaft (determined by
plumb line or spirit level) will cast a shadow that points to true North.
(Best done on sunny day of course!)
73.
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Don Kirk
Sent: Friday, November 01, 2013 11:31 AM
To: Tom W8JI
Cc: topband
Subject: Re: Topband: Steady Carrier on 80 CW -BTW
OK, while we are on the topic another very big factor to think about is
magnetic north vs. true north (I have tried to not bring this up in the
past). I don't expect any response to this, but this has always been in
the back of my mind and wonder what headings are really being reported
(what is the reference, magnetic north or true north that each station is
using when he reports a heading).
15 to 20 degrees difference for those of you in the New England
states................... Same problem out in the Northwest US, but
opposite polarity 15 to 20 degrees.
Don (wd8dsb)
On Fri, Nov 1, 2013 at 11:08 AM, Tom W8JI <w8ji@w8ji.com> wrote:
My resolution is not as good as some people here, either. But where
there's
a will, there's often a way. :-)
Many of the headings are misleading. Having been through this before
several times, much of the data is always grossly overstated.It is common
to exaggerate ability to determine direction.
It's almost impossible to obtain several degree direction accuracy without
either a rotatable loop with GOOD common mode rejection (some popular loop
antennas can have a ~20 degree or more skew between what are supposed to
be
180 degree apart nulls, because they have poor feed designs) or an
interferometer of normal receiving antennas.
An 8-circle array in a very clear location with proper hardware design and
good element spacing can get within about 20 degrees.
Single long Beverages in an array of 8 antennas maybe within 30-35
degrees.
Broadside Beverages with wide spacing (~5/8th or wider) within about 20
degrees.
A three direction array only within about 60 degrees or so, if in a clear
spot and properly constructed.
An interferometer with a few wavelengths spacing within a few degrees.
A calibrated rotatable small loop without common mode skewing and in the
clear, which is actually a pretty rare case, can be within a few degrees.
My eight direction 350 ft diameter 8 circle, located out in a field 1500
feet or so from any re-radiators, can only resolve within +-22 degrees
with
good reliability. When I use it as part of a calibrated interferometer
against Beverage arrays spaced ~1000 feet away, I can resolve the
directional difference between two signals 50 miles apart in New England.
When you draw the lines, be sure to allow for resolution of the antennas,
and not the absolute numbers.
_________________
Topband Reflector
_________________
Topband Reflector
_________________
Topband Reflector