[ARDF] Re: Protractors, 80m accuracy

[Charles E. Scharlau]

Matthew Robbins:
I walked at the 80m Park O in Brno, and I know for
certain that 80m gets weird sometimes.  I was surprised.
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I've found that 80m bearings are severely affected by nearby power lines, and other long stretches of overhead wires. Don't trust any bearings you take while standing near wires. I haven't noticed that chainlink fences, or barbed wire fences, have the same effect on 80m bearings, but I can't rule them out as sources of weirdness, so I avoid them too, on both bands. I've wondered if underground conductors (pipes and wires), especially in dry soil conditions where the ground wave can more easily penetrate the surface, can also be problematic on 80m.

If you find that movement actually helps your 80m bearings, I'd suggest taking a careful look inside your receiver. Perhaps you have a loose connection.


Sam Smith wrote:
I just think that taking a vague direction (from your ARDF receiver)
from a vague location (Do you really know where you are?) and plotting
a perfect bearing on the map (How accurate is that map anyway?) is a
waste of time. It's the old significant digit problem. 
===

I think that one's skill level determines which source of error is most significant. For hams coming to this sport, the error in their location is likely to dominate. For orienteers coming to this sport, the uncertainty in bearings is more likely to dominate. For the WC medal winners in this sport, major errors are most likely to be caused by nervous mistakes, equipment malfunctions, and strange RF propagation effects (especially on 2M).

I agree that removing 10 degrees of error from a bearing line when the bearing measurement is only accurate to within +/- 40 degrees isn't going to help much. But when one's skills improve to the level where trusted bearings (those taken under good receiving conditions) are typically within +/- 20 degrees, an additional 10 degrees of error can significantly affect performance, especially for bearings taken far from the transmitter.

For most of Team USA, I think it's the little things we can do to eliminate silly mistakes, and time spent standing still, that will help the most. (Note: the two work against one another.) An azimuth grid can help (a little) with both those things.

73,
Charles
NZ0I