Tuesday, April 2, 2013

Spring 2013 DX Notes, Noise, And Mobile DXing

Just finished a 3600 mile cross country trek from Arizona to Rochester, NY by way the southern route - through New Mexico, Texas and on to New Orleans via I-10, then north along the Mississippi River to Ohio and home. With so many days on the road, there's always a lot of time to think.

One night I caught a thread in the Yahoo ABDX group that had turned to a discussion of the general noise problem on the AM band. The total lack of noise and interference I experienced out in the wild open spaces of the west is certainly a contrast to what we face at home. I was reminded of the relatively noise-free radio days at home when I was a kid, back in the 1950s and early 1960s.

It is disappointing to this old guy to remember those days and know they aren't coming back, ever.

Fast forward 50+ years. I drive a lot so am in my truck a lot (and lately have been making this cross country trip twice a year) so I like to DX while on the road. I attempt this in two ways.

One, try to DX from my motel room at night using a portable. Fail! Worse than a house, that's usually impossible due to all the RFI from many digital TVs, computers, lighting, bad wiring, aging pole transformers, and every other electronic device imaginable. On a 14 day trip across the country, I found only 3 motels where the noise level was low enough in the room to do any productive DXing at all. You either have to give up or go for a walk outside. That's not very convenient or even fun when you are up north and the temperature is below 40.

Two, the solution. DX from the actual ROAD, i.e., the car or in my case my truck radio. Vehicle radios are fairly sensitive to start with, some better than others. To improve the sensitivity a little more, I went to a hobby store a few years ago and bought a 36-inch piece of spring steel music wire and secured it to the top of the truck's whip antenna. I had to cut the little ball off the top of the whip to get the wire to align parallel correctly, but no matter in the interest of DX. The addition is just long enough (about 60 inches total) to boost the reception sensitivity a noticable amount, but not too long to overload the radio under normal conditions. The music wire is thin and flexible enough to not hurt anything 8 feet off the ground, like the overhead lighting or other ceiling fixtures inside of a low clearance parking garage.

2006 Ford Ranger truck radio

You might be surprised at the DX you can pull in on a car/truck radio with this setup. If you have a quiet electrical system in the vehicle you generally have no RFI noise to deal with except the passing 18-wheeler's noisy computer-controlled ignition. The only thing lacking is a nulling ability like a loopstick, though if you have developed DXer's ears and good concentration your brain can filter out almost anything.

You all probably know by now that I am a nut for daytime AM DX. Anyone can pull in a station at 500 or more miles distant after dark, but can you do it at noon? It is possible under the right conditions. Something about daytime DXing brings me back to those exciting 2 and 6-meter DXing days as a VHF nut on the Ham bands back in the 1960s and 70s. Ground wave again.

In the current cross country trip, the following extreme daytime DX has been heard.

On March 6 at 1430L in the afternoon, I was in Douglas, Arizona which is southeast of Tucson and right on the Mexican border. I heard with positive ID and fair signal KALL-700 N. Salt Lake City, Utah (50KW), some 670 miles distant! Remember, this is daytime, high sun reception, not nighttime DX. And in a quiet, noise-free environment.

The next afternoon at 1400L, KOA-850, Denver, Colorado (50KW) peaked up out of the noise and was ID'ed well into Texas on I-10 near Ft. Stockton using the same setup, right close to 600 miles distant. KKOB-770, Albuquerque, NM (50KW) at 345 miles was also received with even better signal.

At the same point, I did a quick look for KALL-700 again, but only heard evidence of a carrier and unintelligible audio at the time, right at the noise level. Could it have been KALL at a distance of 830 miles? Probably not, but who knows? West Texas is probably a little too far off the side of KALL's generally southern-facing pattern. Two other US stations are within distance range: KHSE-700 in Wylie, TX (15KW) at 426 miles (a possible), and KSEV-700 in Tomball, TX (1.5KW) at 453 miles (not probable). Mexico has several stations licensed to broadcast on 700 KHz, though all are at extreme distances except for one: XEGD in Hidalgo del Parral, Chihuahua (but only 5KW) at 305 miles. That would be the other possibility. Now I wish I had taken the time to wait for the signal to peak, as daytime fades are long and slow, sometimes taking as much as a half an hour or so between fade ups.

While in Galveston, TX on March 10, I took advantage of an hour sitting right at the beach in the truck to see what I could hear. I was hoping to realize some cross-Gulf DX from either Alabama or Florida due to the high conductivity of the open salt water path, but none appeared on this low-overcast, stormy day. I know this happens here, as the distance to the west coast of southern Florida is within range on a good day, at 700+ miles. The panhandle is even closer, at about 460 miles. What makes this possible is the 5000 mS/m conductivity of the salt water path. WWL-870 (50KW) over in New Orleans comes in like a local in Galveston at a distance of 282 miles, an all water path.

So there are ways around noise if being outside or DXing from a vehicle appeals to you. I actually don't DX much at all from home anymore, preferring to DX while mobile or outside. I will jump into the truck and drive to a quiet place to have a listen to what's on, or especially in the summer, grab the portable and go outside. I like the quiet conditions away from home. Part of the battle when in Rochester proper are two 5KW stations within 1.6 miles of me, and a 50KW station at 8 miles. The closest 5KW station is at 1.2 miles, bathing me in nearly 300 mV/m of signal, causing extreme receiver desense for +/- 50 KHz.

My route back home took me through Cincinatti, Ohio and the home of WLW-700. I've got some good pictures of its famous Blaw-Knox tower coming up soon in another post.

KALL-700 daytime pattern at extreme distance (0.05 mV/m)

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