by RADIO-TIMETRAVELLER © 2014 http://radio-timetraveller.blogspot.com
Note: These pattern maps are the work of Bill, WE7W and his Radio-Timetraveller site. They are not by me. Please visit Bill's site for more great information on broadcast and shortwave listening.
US Mediumwave Pattern References are produced by the Radio Data MW program.
Included is a complete set (daytime and nighttime) of GoogleMap-based, HTML-driven maps which show the most current pattern plots of all licensed US and Canadian mediumwave broadcast stations from 530 - 1700 KHz. The set includes all frequencies for the indicated services: Unlimited, Daytime, Nighttime, and Critical Hours. Individual maps are grouped by channel frequency: 540, 550, 560 KHz, etc. Data for the plots in this offering is based on the current FCC and Industry Canada databases available at the time of its creation (January 22, 2015).
The daytime map series shows expected groundwave coverage patterns for Unlimited, Daytime, and Critical Hours operations. Daytime signal patterns represent groundwave coverage out to the 0.15 millivolts per meter contour (43.5 dBuV/m, a.k.a. dBu). Note that daytime reception of signals out beyond the depicted pattern is very possible, and in fact likely for the DXer. The contour line represents a signal strength at the station's fringe distance, a level usually received on a sensitive portable radio with a low ambient local-noise level. I have chosen this signal level to give a good representation of what should be fairly easily received by most DXers during sunlight hours. Also included in the daytime map series is a web-based HTML table listing all daytime stations in the US and Canada. It has clickable links which will take you directly to the FCC pages for that station (US stations only).
The nighttime map series shows expected skywave coverage patterns for Unlimited and Nighttime operations. Nighttime signal patterns represent the standard SS+6 (sunset plus 6 hours, or approximately midnight), 50% signal probability at 0.25 millivolts per meter (48 dBu). Note also that nighttime reception of signals out beyond the depicted pattern is very possible, and in fact likely for the DXer. The maps represent a signal strength between distant and fringe, a level generally easily received at night on most portable radios. I have chosen this signal level to give a good representation of what should be fairly easily received by most DXers on an average evening. The nighttime signal probability of 50% means that the signal will be received at this level approximately 50% of the time at that location for the sunset+6 hour time. Also included in the nighttime map series is a web-based HTML table listing all nighttime stations in the US and Canada. It has clickable links which will take you directly to the FCC pages for that station (US stations only).
Unfortunately, no Mexican patterns are available due to lack of official Mexican engineering information.
HOW THEY ARE PRODUCED
Using the actual FCC database files Radio Data MW will auto-generate an interactive HTML pattern map, showing the pattern plots for all stations included at the discretion of the user. A complete set of mediumwave pattern maps can be generated within minutes. Radio Data MW generates a real pattern plot based on ground conductivity, ground dielectric constant, and can display actual (but approximate of course) signal level boundaries for Local, Distant, Fringe, Extreme mV/m levels, or any custom mV/m level chosen by the user.
The online Google Maps API is used to generate and plot each station on a map of the US. An accurate flag pin is placed at each transmitter location, and in satellite view may be zoomed in to see the actual transmitter site. Map flags are color-coded to indicate Unlimited (light red), Daytime (yellow), Nighttime (black), and Critical Hours (grey) services. Each flag has a tooltip-type note, and when hovered over with the mouse will display a note on the station.
A pattern plot for each station is generated and displayed. Each pattern is calculated using standard formulas used by the FCC to compute the base values at one kilometer, and field strength formulas at distance based on the works of many people over the years. See Field Strength Calculations: A History and Field Strength Calculator One, previously posted on RADIO-TIMETRAVELLER.
Finally, an accurate ray path can be drawn from all transmitters to a user-specified receiving location by inputting latitude-longitude coordinates on the heading bar at the top of the map. Super-imposed on the pattern plots, the ray paths show the listener where he or she falls on each station's pattern, a handy guide to knowing where you stand.
USING THE MAPS
Note again that these maps are web-based. As stated, they use Google Maps and thus require access to Google. In order to view them you need a connection to the internet. They have been tested in the Internet Explorer, Firefox, Chrome, Opera, and Safari desktop browsers. If using Internet Explorer, best results are had with the latest version, IE 10 or greater.
You will also find that the maps will generally work on most tablet or phone browsers, but no guarantee is given. Android and IOS browsers are in a constant flux of change, and in testing the most recent varieties I have had good success. The Google Chrome browser will work the best. Note also that the maps, being script-driven and with many lines of code are very CPU-intensive, and may cause many tablets or phones to choke.
These are the latest US pattern references available, and coverage is based on actual ground conductivities.
The flag pin for each station is accurate, geographically. Zoom in at maximum level in satellite view and you should see the station's transmitter site. If you are lucky enough that Google has taken a street view photo, you can also see that too.