[South Florida DX Association] ARLP034 Propagation de K7RA

[Bill Marx]

 SB PROP ARL ARLP034
> ARLP034 Propagation de K7RA
> 
> Solar flux and sunspot numbers were up a bit this week, with the
> average daily sunspot number rising 25 points to 33.6.  Friday,
> August 11 had a daily sunspot number of 39.  With more sunspots, the
> higher HF bands have better propagation than they did nearly two
> weeks ago when the sunspot number was zero on four days in a row.
> 
> A coronal mass ejection from the sun was pushed out on August 16.
> The result could be geomagnetic disturbances this weekend.  The
> predicted planetary A index for August 18-21 is 10, 25, 15 and 8.
> 
> We are still anticipating the upcoming solar minimum, but a large
> amount of email arrived this week with the news of the first spot of
> cycle 24.  It only appeared briefly, then disappeared.  The clue was
> the magnetic polarity of the spot, opposite of sunspots from the
> current cycle 23.  As time goes on, there will be more cycle 24
> spots, and eventually fewer cycle 23 spots.  See the announcement at
> http://science.nasa.gov/headlines/y2006/15aug_backwards.htm.  A
> thanks for the heads-up goes to KO4WX, WD4DUG, WG4R, VK4AAR, K8MP,
> N4JA, N2JTX, CT1BOH, and others.
> 
> The extra propagation bulletin earlier this week (see
> http://www.arrl.org/w1aw/prop/2006-arlp033.html if you missed it)
> concerning a proposed DARPA project which could disrupt HF radio
> communications generated a huge boatload of e-mail.  After sifting
> through it all, some of it from retired military or defense
> engineers familiar with the VLF transmitters mentioned by Dr.
> Rodger, it may be that Ward Silver, N0AX had the right idea when he
> wondered how it could be done, when ''the sheer energy required from
> the start would tend to rule it out''.
> 
> When Dr. Rodger said that ''two of the US Navy transmitters radiate
> 1 megawatt'', he probably didn't realize that this is the input
> power (before inefficiencies are factored in) to the transmitter,
> and doesn't reflect the efficiency of the antenna.
> 
> David Olsen, W6PSS pointed out that a 2-megawatt Navy VLF
> transmitter in Michigan only radiates 1 watt, and the efficiency is
> around .00005%.  He wrote, ''As I understand it, the limitation in
> achieving efficiency is the coupling factor.  As the operating
> frequency is lowered, there's an exponential increase in reactances
> such that it becomes nearly impossible to couple energy to an
> antenna.''
> 
> Ed Bruette, N7NVP mentioned an article about a more efficient VLF
> antenna at http://coldwar-c4i.net/VLF/design.html, but Ed is also
> skeptical of the article about Dr. Rodger.
> 
> Don Rice, AC7ZB wrote, ''. . . the radiation belts have to be
> heavily loaded due to an extremely large solar storm or a nuclear
> detonation.  In either case, communications are going to be
> disrupted whether or not somebody tries to 'remediate' the radiation
> belts.  So the question is whether fooling with the radiation belts
> will make a bad situation worse, not whether Dr. Strangelove is
> going to push a button and turn off the ionosphere on a whim''.
> 
> ''Scientists have been poking the ionosphere for many decades trying
> to get it to do something, and short of setting off an ionospheric
> nuclear explosion forty some years ago they haven't had much
> success''.
> 
> ''From the amateur radio standpoint, I think the greatest threat is
> that hams will get cranked up and make statements that will get us
> branded as a bunch of alarmist loonies.  That could be very damaging
> to our efforts to curb BPL and other spectrum pollution''.
> 
> John Kelley, K4WY wrote (from his wireless pager), ''. . . space is
> a big place, to shield the LEO birds with this technique would
> require incredible energy levels over a global spectra of satellites
> at varying orbits and ephemeris.  I think of the Northern lights as
> an example of energy and ionized particles that at its peak can only
> cover upper/mid latitudes.  Our current and near term future
> technologies are still wrestling with IP in space environments,
> autonomous control, investigating things like how to maintain a
> human presence on the moon, so when taken in that perspective I
> think we need a  reality check.  That said, every so often somebody
> comes up with the ideas like beaming nuclear power back to earth and
> other sci-fi ideas''.
> 
> If you would like to make a comment or have a tip for our readers,
> email the author at, k7ra at arrl.net.
> 
> For more information concerning radio propagation, see the ARRL
> Technical Information Service at
> http://www.arrl.org/tis/info/propagation.html.  For a detailed
> explanation of the numbers used in this bulletin, see
> http://www.arrl.org/tis/info/k9la-prop.html.  An archive of past
> propagation bulletins is at http://www.arrl.org/w1aw/prop/ .
> 
> Sunspot numbers for August 10 through 16 were 37, 39, 27, 26, 45, 32
> and 29 with a mean of 33.6. 10.7 cm flux was 80.3, 83.9, 84.7, 85.9,
> 86.4, 85.6, and 86, with a mean of 84.7. Estimated planetary A
> indices were 5, 6, 8, 2, 4, 3 and 3 with a mean of 4.4. Estimated
> mid-latitude A indices were 4, 3, 4, 2, 2, 2 and 2, with a mean of
> 2.7.
> NNNN
> /EX
>