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Saturday, February 1, 2020

2020 US-Canadian Mediumwave Pattern Reference Is Here

The 2020 US-Canadian Mediumwave Pattern Reference for all stations is now available. Find the download link at upper right. Remember, the links change each time a new set is uploaded. Always look to this RADIO-TIMETRAVELLER site for the current link. Download is 52 MB.

DOWNLOAD LINK

Media Fire link here.

When downloading from the Media Fire link, be sure to click the DOWNLOAD button.


The Media Fire site is ad-supported and has several ad links on the page and will also issue an ad pop-under. Just ignore these.

A mirror link for the 2020 files has not been established yet.

INSTALLING

The maps are HTML-based, so no regular install is necessary. Simply unzip the downloaded file and click on the individual map file to run. The map will open up in your web browser. They are self-contained, with image icons embedded right into the code. You must have an internet connection to view the maps.

IMPROVEMENTS FOR 2020

January 21, 2020:

1. Much of the summer and fall of 2019 has been spent bug fixing and tweaking the skywave formulas for accuracy. A slight tweak to the groundwave formula has brought the predicted groundwave strengths more in line with V-Soft (https://www.v-soft.com/on-line-based-software/zipsignal). Skywave values now more reflect actual received signal strengths as measured. Consequently the mV/m threshold was upped this year to 0.1 mV/m (40 dBu). If signal overlap is a problem, simply turn off all plots and select the ones you want.

Additionally, a rather lengthy skywave overhaul now permits skywave calculations for any date and time of the year, accurate to the solar latitude of the chosen location. In order to show a median skywave calculation value, the date of November 5 has been chosen, exactly halfway between the Autumnal equinox of September 21 and the Winter solstice of December 21, the dates of the most extreme deviation from the median.

The nighttime skywave calculation is based on midnight Central Standard Time (SS+6). The daytime groundwave calculation is based on noon Central Standard Time (SR+6).

Los Angeles station KABC-790 was missed in last years maps due to an error in the FCC's database archiving its license to cover. It has been patched in this year, as the FCC has not corrected the problem.

Daytime Franklin, VA station KJZU-1250 is missing this year due to errors in its tower record.

Missing Canadian Nova Scotia and Newfoundland stations have been added. In previous years an error in RDMW's filtering had bypassed them.

Missing Canadian station CHHA-1610 (Toronto) has been added. The Industry Canada database is missing a class identifier for this station, so I have placed it in Class C which I believe to be correct. I have written to IC about this omission, but they have not responded.

New on the maps this year are the Canadian low power stations, which generally run 20-40 watts. Due to the low power, they generally will not generate a skywave pattern, but the daytime pattern should be substituted. They may be receivable at distance, however, don't give up!

Again for 2020, the following parametrics are considered in the skywave calculation:

   * Hourly transitional loss variance from sunset to sunrise.
   * Seasonal gain or loss, January - December.
   * Diurnal enhancement at the sunrise and sunset period.
   * Winter daytime skywave enhancement (only on maps created for times during the day).
   * Daily seasonal nighttime skywave enhancement.
   * Take off angle variances for stations at relatively close distances (experimental).

2. Colored plot (yellow), again, for groundwave 1.0 mV/m level.

3. Small changes made to the map's title bar heading. Signal dBu (dBµV/m) is now displayed instead of millivolts per meter. Also the map's day of year (DOY) and GMT time "z" are displayed.

4. Unlimited, Daytime, and Critical Hours plots are at the 1.0 (60 dBu) and 0.1 mV/m (40 dBu) levels. Skywave is set at the 0.1 mV/m level. Levels have been chosen to minimize pattern overlap yet still attempt to show what you can accurately hear during the day and night.

ABOUT THE MAPS

Included is a complete set 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, .. 1700 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 21, 2020).

The daytime map series, in two parts, shows expected groundwave coverage patterns for Unlimited and Daytime (part 1), and Critical Hours (part 2) operations. Daytime signal patterns represent groundwave coverage at two levels, out to the 1.0 and 0.1 millivolts per meter contours (60 dBu and 40 dBu respectively). The choice of these levels is made in order to more closely match those which might be helpful to the mediumwave DXer. Note that daytime reception of signals out to and beyond the depicted 0.1 mV/m pattern is very possible, and in fact likely for the DXer. The contour line represents a signal strength at the station's extreme 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 can be received by most DXers during sunlight hours.

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 Central Standard Time), 50% signal probability at 0.1 millivolts per meter (40 dBu). Note also that nighttime reception of signals out to and beyond the depicted pattern is very possible, and in fact quite likely for a skywave signal. The maps represent a signal strength at the fringe level. I have chosen this signal level to give a good representation of what is possibly 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 Central Standard Time.

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 in about eight hours of processing time. Processing time had increased by nearly two hours by 2019 due to enhanced skywave calculations and other upgrades.

For daytime signal maps, Radio Data MW generates a real pattern plot based on transmitter power, antenna array efficiency and directivity, ground conductivity and ground dielectric constant of the path to the receiver. Increased conductivity of water paths over the Great Lakes are also accounted for. It displays 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.

For skywave signal maps, predicted signal levels are calculated in accordance with current FCC or ITU methods of recent years (1999 onward). A number of parametrics are now analyzed and accounted for in the calculation, namely diurnal and seasonal changes, and daily sunrise and sunset enhancements to the signal. The process is rather complicated.

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 can be calculated using standard formulas used by the FCC or ITU 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. See the RADIO-TIMETRAVELLER blog at: http://radio-timetraveller.blogspot.com/

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.

Individual station plots can be turned on or off by a checkbox. Click the station flag and you will see the option in a pop-up balloon. Check or uncheck the box, then click the ReDraw button. The entire plot set can also be turned on or off by buttons at the top of the map.

Included in each station's flag tooltip are FCC facility ID, engineering (application) ID, and distance of the station from the home latitude-longitude. Of interest to the DXer, by setting the home location latitude-longitude to your location and redrawing the map, each flag tooltip will have the distance from your location to the station.

ON PATTERN OVERLAP AND PLOT SWITCHING

A varying amount of pattern overlap exists on the maps, some extreme, as it does in real life. For the Daytime and Critical Hours plots, the outer 0.1 mV/m signal level ring represents an extreme groundwave fringe distance where a station can be heard. At that level, there may be some minimal overlap with co-channel stations.

Pattern overlap is of course much more severe for skywave on the nighttime plots. A level of 0.1 mV/m was chosen to represent the fringe distance a station is heard at night about 50% of the time. This may seem low to many, why not increase it to lessen the overlap? Unfortunately, increasing it even to 0.15 mV/m results in no skywave plot at all for many stations under 1500 watts as their skywave signal never reaches the 0.15 mV/m threshold at points around the compass. This is particularly bothersome in the northern latitudes above 40 degrees north where signals are weaker.

The unusual case exists on the graveyard channels (1230, 1240, 1340, 1400, 1450, 1490 KHz). The plots are a massive overlay of signals (as it is in real life!). There is no real good way to display a graveyard channel for station-to-station comparison but to throw them all in there and then allow you to choose which ones to compare. Virtually 99% of all graveyarders run 1 KW power to a single tower. The technical reality is that a one kilowatt station does not produce a skywave signal in any direction above a level of about 3 mV/m. Raising the plot mV/m level to reduce the chaos unfortunately results in no plot at all for most stations.

The solution to the graveyard confusion (all, really) is simple, and one of the enhancements added in 2016. You can turn plots on or off individually, or all at once. Turn all plots off and simply check the plots you wish to see.

SPECIAL NOTE ON SKYWAVE PLOTS

As of 2019, the skywave calculation has been totally overhauled and enhanced to more reflect actual signal expectations across the U.S. at night. The fact of life is that pattern overlay occurs on many frequencies. Simply select the plots you want to analyze. Check the No Plots checkbox then ReDraw to turn off all plots. Click any station flag and check the box to plot that station then ReDraw.

You will occasionally see a skywave plot which looks much smaller than surrounding plots. This is a case where the station's skywave signal did not meet the mV/m threshold (0.1 mV/m). The groundwave plot level is substituted in this case. The station does in fact have a skywave component, however small, it will be measurably less than the 0.1 mV/m level (very weak). It may be receivable!

The darker line defining the outer edge of the skywave plot shows the location of the 0.1 mV/m signal point at all compass points. Be aware that skywave signal strength does not decrease linearly with distance from the station. From the station outward, the signal strength will generally increase to a point usually 200-400 kilometers distant where it will peak, then decrease somewhat linearly from there.

Also note that the atmospheric background noise level on the mediumwave band is generally considered to be approximately 36 dBu (dBu in this case = dBµV/m), equivalent to 0.063 mV/m. Signals below that level will not be heard unless they fade up above the noise. A gain or directional antenna can be used to increase signal strength while limiting or even reducing the overall atmospheric background noise level.

Image below is an example of the 1040 KHz skywave map.

Hope you enjoy.


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