Thursday, April 2, 2015

Auroral Effects-BCB Possiblities

Many DX-ers might look at aurora as a problem.  The band is dead, higher frequencies are filled with flutter, the usual suspects are gone.  But the recent activity has opened another door.

Recent high level auroras due to solar storm activity and mass ejections have affected prop on Earth. The first effect was noted while making my morning BCB band scan on the way to work.  I usually leave home about an hour before sunrise in winter and spring.  Day to day, I notice some differences in prop, but the pattern is usually similar.  The usual " friends" show up.  Sometimes the lower frequencies are not so good and the Chicago stations on 670, 720 and sometimes 780 are weaker, with 890 being stronger.  Comparisons of them is my usual "barometer" for what is happening. If 670 and 720 are weak,  I run more through the higher frequencies and they usually are OK.

In those cases 830 from Minneapolis will be weak, but 1500 from St Paul ( just  "next door") will be strong, as will be 1530 from Cincinnati.  Closer to sunrise,  840 from Louisville will be weaker as will 750 from Atlanta and 870 from New Orleans. That will leave Mexican stations audible.  If Atlanta is already gone, there is little chance of hearing Cubans because the sun is already up there.
If the closer stations are strong,  the Cubans or South Americans will not be audible.

At the same time, 850 from Denver and 1160 from Salt Lake City will be in as the Eastern stations disappear as the sun is rising in those areas. The Eastern Time Zone Mexican stations disappear and the Western more stations start appearing.  Its a matter of letting the sun become a  "barrier" to let different stations be heard.

Some mornings the skip is still uniform,  just shorter.  On those mornings I will note that Kansas City on 710 will cover Amarillo, with 810 and 980 from Kansas City also rolling in.  On those mornings, 880 from Lexington, Nebraska will be in strong as will 580 from Topeka, Kansas.  Shreveport on 1130, Tulsa on 1170 and St Louis on 1120 will be particularly dominant on their channels. Other mornings Mexican stations might appear either behind them, or sometimes even above them.

But on a strong auroral morning, things are very different.  The northern stations are gone. There are no Chicagos, no Minneapolis,  no Louisville, no Salt Lake, maybe even no St Louis.  Even in the earlier hours well before sunset, these "regulars" will be totally gone here in Central Texas.

Is the band dead?  Absolutely not!  At his latitude, the auroral effect is only on those stations in or not too far south of the zone. What happens is that weaker or more distant stations to the south or on my own latitude that are normally masked are suddenly available.  Cuban channels normally blocked by strong US stations are suddenly in the clear.  many might be lower powered stations. Normally unheard  Mexican stations or even Central or South American stations appear.  Stations from the Southwestern US are in,  not stronger, just no longer covered.

An enterprising DX-er in moderate latitudes would do well to keep an eye on Space Weather dot com or other sites that post warnings of solar activity.  Just as VHF amateur or TV and FM DX-ers watch weather maps for approaching cold fronts,  BCB DX-ers should watch solar weather for opportunities or times to particularly try to be tuning in.  You can take advantage of an auroral "curtain" to log some new ones,  just as we daily use the sunrise or sunset lines as curtains to block strong signals to allow weaker ones in.  The main difference is the sunset/sunrise lines are generally for East/West advantages, but the auroral curtain will be for North/South advantages.

Aurora also provides some rather unique opportunities for VHF DX-ers,  but that's a story for another day!

( Listening here is done in Central Texas with home receivers now being an ICOM R-75, Hallicrafters SX-96, Yaesu FT-757-GX, Drake 2B, Hallicrafters SX-111, Hammurland HQ-170,
Mackay LF maritime receiver and BC-342. Antennas are a 95 foot top fed sloper up 45 feet, a 130 foot Inverted L with 40 foot vertical section, various short verticals and a 3 foot home made box loop. Mobile listening is done with the standard receiver in a 1999 Ford Ranger pickup)

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