This section is from the book "The Boy Mechanic Vol. 2 1000 Things for Boys to Do", by Popular Mechanics Co.. Also available from Amazon: The Boy Mechanic, Vol2: 1000 Things for Boys to Do.
The amateur wireless telegrapher may be troubled more or less regarding distances from other stations. The difficulty can be overcome by following a plan similar to that of a parcelpost map. A map should be selected covering the desired territory. With the home station as center, circles should be drawn to diameters corresponding in length to the scale used on the map. By measuring the distance other stations may be from any of these circles, their cross-country distance from the home station can be determined at a glance. - Contributed by E. L. Hartlett, Wausau, Wis.
Ill: Circles on a Map the Same as for Parcel Post to Designate Wireless Distances