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Re: [RFI] Compass Vectors

To: dave@nk7z.net
Subject: Re: [RFI] Compass Vectors
From: Michael Clarson <wv2zow@gmail.com>
Date: Tue, 1 Dec 2015 11:44:25 -0500
List-post: <rfi@contesting.com">mailto:rfi@contesting.com>
David: Yes, I was a bit redundant, but I wanted to emphasize that there can
be substantial and very localized variations in the declination that differ
from the predictions. 73, Mike, WV2ZOW

On Tue, Dec 1, 2015 at 10:47 AM, David Cole <dave@nk7z.net> wrote:

> I thought I said that...
> --
> Thanks and 73's,
> For equipment, and software setups and reviews see:
> www.nk7z.net
>
> For MixW support see;
> http://groups.yahoo.com/neo/groups/mixw/info
> For Dopplergram information see:
> http://groups.yahoo.com/neo/groups/dopplergram/info
> For MM-SSTV see:
> http://groups.yahoo.com/neo/groups/MM-SSTV/info
>
>
> On Tue, 2015-12-01 at 10:32 -0500, Michael Clarson wrote:
> > Another caution: Magnetic "North" can vary substantially from the
> > predicted declination. I always calibrate my compass by sighting a
> > physical object and comparing the bearing to a map. I learned this
> > while trying to aim a microwave antenna on top of a ridge between
> > Bethlehem and Harrisburg PA. Mountain loaded with iron ore. My compass
> > was about 30 degrees off! This mountain is one of the few places on
> > Earth where one's compass can be off that much due to local
> > conditions. --Mike, WV2ZOW
> >
> > On Tue, Dec 1, 2015 at 9:01 AM, David Cole <dave@nk7z.net> wrote:
> >         If you are doing this by hand, as I do, then remember, to keep
> >         the map
> >         and your bearings, in either True, or Magnetic North, I always
> >         keep my
> >         maps in True North, and adjust my compass readings to True
> >         North, prior
> >         to plotting them.
> >
> >         If you take a Google map, it will be True North, while your
> >         uncompensated compass, will be in Magnetic North.  I use
> >         Google Earth
> >         images to draw my plots on.
> >
> >         You need to convert both your map, and your readings to the
> >         same units,
> >         either True or Magnetic North, before you draw a bearing line
> >         on your
> >         True North oriented Google map.  Here is how I get them to
> >         match the the
> >         easy no math way.
> >
> >         I go here: http://www.acscdg.com/ and get a map of a long,
> >         straight,
> >         road that runs dead N, S, E, or W in my area, the actual
> >         bearing does
> >         not matter, it only matters that you know the bearing of the
> >         road
> >         exactly, and can read your compass to that same accuracy,
> >         hence why I
> >         use N, S, E, or W, they are easy to find on a compass, and
> >         almost every
> >         city has N/S/E/W roads.
> >
> >         I pick a road that is long, and has a sidewalk, that way I can
> >         stand on
> >         the sidewalk, and sight down the sidewalk, not looking off to
> >         the side
> >         and sighting down the road from the sidewalk, thus introducing
> >         parallax
> >         issues.  I then take my compass to that road, and sight down
> >         the
> >         sidewalk.
> >
> >         I purchased an adjustable compass so I just adjust the compass
> >         to read
> >         the heading of the road, and my compass is now calibrated to
> >         True
> >         North.
> >
> >         See: http://www.ngdc.noaa.gov/geomag/declination.shtml for why
> >         you need
> >         to do this...
> >
> >         I then go home and take a bearing on something far away, from
> >         a known
> >         spot on my property, and write that bearing down.  Then the
> >         next time I
> >         go out and start looking for RFI, I just sight on the object
> >         again, from
> >         the same spot, and adjust the compass if it has moved...  I'm
> >         now all
> >         set to do True North bearing drawings...
> >
> >
> >         --
> >         Thanks and 73's,
> >         For equipment, and software setups and reviews see:
> >         www.nk7z.net
> >
> >         For MixW support see;
> >         http://groups.yahoo.com/neo/groups/mixw/info
> >         For Dopplergram information see:
> >         http://groups.yahoo.com/neo/groups/dopplergram/info
> >         For MM-SSTV see:
> >         http://groups.yahoo.com/neo/groups/MM-SSTV/info
> >
> >
> >         On Tue, 2015-12-01 at 02:18 -0500, Roger (K8RI) wrote:
> >         > Select your area with as much resolution as possible.
> >         > Drive to a location, take a bearing.  using the Google
> >         distance ruler,
> >         > draw a line through your point.  Drive to another point and
> >         repeat.  Two
> >         > bearings are often sufficient, but three leave a small
> >         diamond for the
> >         > region of error.  Much easier to do than explain, although
> >         there is a
> >         > learning curve.
> >         >
> >         > It gets messy with RFI hunting when there are multiple
> >         sources, with
> >         > overlapping and similar patterns as in multiple networks or
> >         an area
> >         > where there are a mix og cable and outside antenna and the
> >         users just
> >         > wired the preamps and cable together.  This sometimes can
> >         lead to a much
> >         > larger region of error.
> >         >
> >         > 73 es good luck
> >         >
> >         > Roger  (K8RI)
> >         >
> >         >
> >         > On 11/30/2015 8:16 PM, Karin Johnson wrote:
> >         > > I'm planning on doing some RFI hunting and wanted to know
> >         if anyone
> >         > > knows how to plot compass vectors on Google Maps?
> >         > > I need to plot intersecting vectors from a direction
> >         finding loop to
> >         > > find the source of an RFI generator.
> >         > >
> >         > > Karin   K3UU
> >         > > Palm Harbor, FL
> >         > >
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> >         >
> >         >
> >         > ---
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