[ARDF] maps

[Jay Hennigan]

pete sias wrote:

> Can someone point me to a source that will allow me to
> pick the area and print out maps to use?

As others have commented, orienteering maps are the gold standard but 
rarely free and unlikely to be available for any particular location 
unless it is an active orienteering venue.  Because they show local 
terrain and vegetation, the maps need to be updated by field checking 
frequently or they will become out-of-date and not accurately reflect 
the course.  Topo maps can be downloaded from topozone.com but are less 
than ideal, not enough detail and often rather old.  Google Earth may be 
of some use to fine-tune topo maps but field checking is really the only 
way to get a decent map.  Note that the map should be aligned to 
magnetic rather than true north, or at least draw magnetic north lines 
on the map.

> Second, I notice the rules  state the use of
> horizontal omni directional antennas on 2 meters. For
> ease of setting this course up for the first time I am
> using 1/4 wave vertical antennas. Is there a down side
> to this? Attenuation is more with vertical in foliage?

Tighter receiver beam patterns is the primary reason.  I have made 
turnstile antennas for ARDF use, plans here:

http://www.west.net/~jay/turnstile.html

Marvin expressed an interest in kitting these up for sale, I don't know 
if he has done so.

Alternatives for the elements to the brass rod are aluminum arrow 
shafts, they're threaded 8-32 and work fine, lighter to carry and 
slightly more broadband.

Also, try to rig things so that the antenna is 2 to 3 meters above the 
ground, not just sitting on the ammo can.  This helps to normalize field 
strength among the various foxes.  Otherwise terrain very local to the 
transmitter may block the signal and make it appear much farther than it 
is.

--
Jay Hennigan - CCIE #7880 - Network Engineering - jay at impulse.net
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