Friday, June 10, 2011

Signal Patterns - 670 KHz - American Southwest

Though I am back in New York for the summer, lets temporarily time travel back to the southwestern United States to January of this year. This article was written then but never posted.

January, 2011. Southwestern Arizona.

The Players:

KIRN-670 Simi Valley, CA 5KW 260.6mi
KMZQ-670 Las Vegas, NV 30KW 197.9mi
KBOI-670 Boise, ID 50KW 683.6mi
KLTT-670 Commerce City, CO 50KW 681.0mi

In the hour just after sunrise this time of year, little KIRN-670, Simi Valley, CA (5KW at 260.6 miles) is sometimes audible here, fading in and out weakly amongst a handful of stations. An ethnic station, KIRN (K-IRAN) plays a wonderful selection of Iranian music. KIRN has three main competitors at this time of day. The strongest and main signal heard during this hour is news-talk KBOI-670, Boise, ID (50KW at 683.6 miles). Weaker, though closer to me is Las Vegas, NV station KMZQ-670 (30KW at 197.9 miles), usually down in the mud for some reason. Last, christian affiliate KLTT-670 in suburban Denver's Commerce City (50KW at 681.0 miles) has already peaked about an hour before and is fading away for good as the sun heads west. Or is it?

KBOI in Boise disappears for good about one hour after sunrise. Then follows KIRN, farther west. As high-daylight emerges, left on frequency seems to be KMZQ in Las Vegas - weak, but audible throughout the day on a sensitive radio like a Sony 2010. KMZQ's pattern is directed mostly northwest (335 degrees), so most of its signal is funneled away from my location approximately four hours south of Las Vegas. It is sometimes weakly audible at certain times of day on the truck radio, a somewhat sensitive beast. Without an assist, most ULRs offer up only noise on this channel during daytime hours.

My loop of choice, a 24-inch passive loop, does wonders during the day. KMZQ-670 becomes clearly audible at medium strength on any radio. Rotate the loop a little to the east, and surprisingly Colorado's KLTT-670 is often present at varying ultra-weak to weak signal strength. KMZQ-670 is always in there, though. KLTT sometimes rises above and is nearly in the clear with proper nulling, particularly late in the morning. KLTT is an excellent DX catch here during daylight hours - at an astounding distance of 681 miles. Helping tremendously is KLTT's signal pattern. I am in the main lobe of its daytime pattern, which points roughly southwest (247 degrees). A resounding 5.0 dB pattern gain results in 161 kilowatts ERP being pumped this way after sunrise, crossing the high continental divide running through the center of Colorado. So far, KLTT-670 is my Arizona fixed location distance record for daytime DX. Two other personal records of longer distance are documented in a previous article.

Returning to 50KW outlet KBOI-670 in Boise, if we can receive 50KW KLTT-670 in Denver at 681 miles during daylight hours, why can't we receive KBOI at 683 miles? So far this station has only been audible during nighttime hours. Part of the problem here is KBOI's pattern. During the daytime, it is an omnidirectional one without gain. Secondly, and unfortunately, Las Vegas's KMZQ is also almost directly in-between KBOI and me. Null KMZQ, and I am nulling KBOI. Daytime reception will probably never happen.

Still I listen for little KIRN-670 over in Simi Valley. I have not caught it during daytime hours yet, but continue to try. The possibility exists that its 5KW signal could one day make the grade over the relatively short distance of only 260 miles. KMZQ in Las Vegas is a major problem, though. Little azimuth exists between these two stations from this location, making it hard to null KMZQ effectively enough to quiet the frequency. It is interesting that KLTT makes the grade all the way from Denver over the 681 mile path at 50KW, but KIRN cannot manage 260 miles with 5KW. Partly, KIRN's pattern is due south, and I am off the side of it. The return pattern loss is a negative 5.5 dB, so only 1384 effective watts are sent this way.

It would be nice to one day hear Chicago's 50KW WSCR-670, at 1530 miles distance from southwestern Arizona. It is on a bearing of 60 degrees, slightly east of Colorado's KLTT at 47 degrees. Looking at a grayline map, it might be possible to snatch WSCR at its local sunrise time, as KLTT is still at low power for the darkness period (at 700 watts), and Las Vegas's KMZQ is still at low power as well (600 watts). Evenings may be possible too. On another channel, WWL-870 in New Orleans is receivable here at 1437 miles many evenings, though it has less competition.

Check out the pattern plot for KMZQ. See how nicely KMZQ avoids KIRN and KLTT, fitting them exactly into the deepest nulls of its pattern. Nice work!


gkinsman said...


I live in Simi Valley, so "little" KIRN 670 is my strongest station, and sometimes a pest; for example, when trying to listen to KTNN 660 (Window Rock, AZ).



Hi Gary,

Ha! Guess little KIRN isn't so little after all!