Friday, January 18, 2019

2019 US-Canadian Mediumwave Pattern Reference Is Here

The 2019 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.

If you download 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.

The other link at the upper right of this page is to Tomas Hood's NW7US site. It is ad-free. Thank you Tomas for mirroring this download. Both downloads are the same.


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.


1. The previous 2016 map version became crippled due to Google's new precondition for all Google Map usage now requiring a user key. I have applied for and received the requested key. It allows a fixed amount of map-usage bandwidth. All maps should now display fully.

Note: Google may throttle map-usage bandwidth based on excessive use. Whether this will happen is unknown at this time.

2. Skywave signal maps have been totally recoded for 2019. Many months of coding and testing were involved. Predicted signal levels are calculated in accordance with current ITU methods of recent years (1999 onward). The following new parametrics are now additionally 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).

3. Colored plot (yellow) introduced for groundwave 0.1 mV/m level.

4. Small changes made to the map's title bar heading.

5. Unlimited, Daytime, and Critical Hours plots are at the 1.0 and 0.1 mV/m levels. Skywave this year is set at the 0.15 mV/m level. In all cases except for the nighttime graveyard stations, levels have been chosen to minimize pattern overlap and to more closely follow those which might be helpful to the mediumwave DXer.


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 16, 2019).

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. 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 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 0.15 millivolts per meter. Note also that nighttime reception of signals out beyond the depicted pattern is very possible, and in fact quite likely for a skywave signal. 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 Central Standard Time.


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 five hours of processing time. Processing time has increased by nearly two hours in 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 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.

For skywave signal maps, predicted signal levels are calculated in accordance with current 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:

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.


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 (0.15 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 0.15 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 0.15 mV/m signal point at all compass points. Note 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 1370 KHz daytime ground contour map.

Hope you enjoy.

Daytime Ground Contour Map 1370 KHz

Friday, January 11, 2019

The KKOB-770 Synchronous Operation In Santa Fe

Returning back to Arizona from Denver after Thanksgiving, I decided to stay in Santa Fe, New Mexico. This was a perfect opportunity to check out the status of the KKOB-770 synchronous transmitter site in Santa Fe.

KKOB-770, as most of you know, is Albuquerque's 50 KW blowtorch outlet, "The Talk Monster". A single tower does duty during the daylight hours. At night, a second tower is switched on, the signal covering most of the western U.S. with a westerly-facing cardioid pattern. The nighttime notch at the base of the cardioid falls over Santa Fe.

KKOB maintains a 230 watt synchronized transmitter just one mile west-northwest of downtown Santa Fe, adjacent to the John Griego Vietnam Veterans Memorial Park. A single tower is visible just a couple of hundred yards or so from the parking lot of the park. The tower is a 231 ft. (70 meter) high affair, with an effective height of 65 electrical degrees.

The purpose of this operation is to fill in KKOB's nighttime pattern in the Santa Fe area. Santa Fe is 56 airline miles from Albuquerque.

Driving past the location at mid-afternoon about 2 PM, it was evident that the tower was transmitting during the daytime hours. Driving along the road past the park's parking lot, and closest to the tower at about 200 yards, I had the car radio tuned to 770 KHz. Weird signal fluttering occured for several hundred yards along the road as the Santa Fe and Albuquerque signals combined. For several seconds, the phasing of the two signals completely nulled, resulting in no signal at all.

It was a strange listening experience, as Albuquerque's KKOB-770, at 50KW, normally puts out a respectable signal to this area in the daytime.

The following synchronous operations are authorized through FCC license in the U.S. The FCC terms them as "Experimental":
Call          Frequency     Power     Location
---------     ---------     -----     -----------------
(D)WI2XAC      740.000       500      Ponce, PR
(N)WI2XAC      740.000       100      Ponce, PR
(U)KKOB        770.000       230      Santa Fe, NM
(D)KM2XVL     1220.000       170      Huntsville, TX
(N)KM2XVL     1220.000        11      Huntsville, TX
(U)WBZT       1230.000       800      Pompano Beach, FL
(U)KCOH       1230.000       410      Houston, TX
(U)KDTD       1340.000       200      Kansas City, KS

I've been wanting to check out this operation for awhile.

Click image for a larger version.

KKOB-770 Santa Fe. 230 watts synchronous operation.

KKOB-770 Santa Fe. 230 watts synchronous operation.

KKOB-770 Albuquerque. 50,000 watts. Single tower daytime, both towers at night.