SB PROP @ ARL $ARLP034
ARLP034 Propagation de K7RA
ZCZC AP34
QST de W1AW
Propagation Forecast Bulletin 34 ARLP034
From Tad Cook, K7RA
Seattle, WA August 21, 2009
To all radio amateurs
SB PROP ARL ARLP034
ARLP034 Propagation de K7RA
The quiet sun continues to baffle us. If there are no sunspots
today, and I don't expect any to emerge, this will be the
forty-second day in a row with no sunspots. July 10 was the last
day we saw any spots. There is really no way to predict when the
next sunspot will appear. If we see no sunspots through the end of
the month, then nearly 80 percent of 2009 so far will have been
spotless.
Unsettled to active geomagnetic conditions were predicted for August
19, with a planetary A index of 20, lowered to 15 by August 17. As
seen at http://www.swpc.noaa.gov/ftpdir/indices/DGD.txt, the
planetary A index rose to only 10 on August 19 and 11 on August 20.
The current prediction from the NOAA Space Weather Prediction Center
shows a predicted planetary A index of 5 for every day through the
end of August. Geophysical Institute Prague also predicts quiet and
stable geomagnetic conditions through the rest of the month.
The summer sporadic-e season appears over, or at least there were no
reports this week. There is a shorter, less intense winter
sporadic-e season, and December's ARRL 10 Meter Contest often
benefits from that mode.
George Munsch, W5VPQ, who lives in Medina County just west of San
Antonio, Texas (EL09ok) sent comments responding to Pat Dyer's
(WA5IYX, who is about a dozen miles east of W5VPQ, in EL09ql)
remarks about digital vs. analog television as VHF propagation
indicators.
George wrote, ''I have not had the pleasure of meeting Pat Dyer, but
have followed his exploits on monitoring commercial signals for many
years. Some early background on TV allocations may give some
perspective.
Back after WW2, Ken Bullington's 1947 smooth earth models were just
about all the FCC and anyone else had to use for VHF propagation
predictions. Ham reports of extended propagation were dismissed, or
downplayed as rare. So the initial table of VHF-TV allocations was
developed. After a few stations were finally constructed along the
Gulf coast, the extent of commonplace temperature inversions and
thus extended VHF propagation became horribly evident. Florida
stations were often stronger than ''local'' Texas stations. So, the
''Freeze'' happened. No new VHF TV licenses were issued for several
years in the 1950s until a new allocations table could be worked
out. Even so, interference problems continued to July 2009. I
would occasionally catch UHF openings where EVERY UHF channel
(except 39) displayed a signal of some kind, and VHF interference
could make the low channels unusable. In the early days of (ham)
VHF-FM, one Saturday I listened to a new repeater being set up, and
mobiles going out to range check. I called in from my mobile and
told them they were full quieting in San Antonio. This kind of
broke up their party, as they were in Ft. Walton Beach, FL.
Fast forward to DTV. I have a converter which scans the spectrum
and records station information whenever it is ''off''. (Hisense
DB-2010) So far, several New Orleans stations have appeared on the
list. I haven't tallied the list lately, but many of the VHF and
most of the UHF channels are now represented. Houston stations are
regularly seen, and often in the mornings, local stations do not
manage the 15 dB margin over the distant signals, and are
unavailable. I thought that the locals were having transmitter
problems until I fired up the spectrum analyzer. Big noise there,
but the TV refuses to present a picture. Again, the FCC ignored the
real world in developing the allocations table, putting too many
co-channel stations in ducting range of each other. Since I have an
unamplified 10 way distribution system off my antenna, I don't have
quite the sensitivity that Pat does, but I still see a lot of out of
area digital stations''.
Thanks, George for the fascinating comments. I tried responding to
George, but unfortunately the address that his arrl.net email
address forwards to is rejecting incoming email.
George refers to ''Ken Bullington's 1947 smooth earth models'', and
this was an early model describing a simplified method for
calculating propagation over a theoretical smooth spherical earth on
frequencies above 30 MHz.
Carl Luetzelschwab, K9LA has a new propagation column in the
September issue of World Radio Online. This month's column concerns
making propagation predictions for the public, and whether to assume
small station or big station capabilities when making the
calculations. You can download it for free at
http://www.worldradiomagazine.com/wro_issues/2009/0909_toc.html
which shows the table of contents. Just right-click on the four
sections numbered at the left to download.
In response to the mention in last week's bulletin of the K7JA and
K6CTW televised victory with Morse code over text messaging, Tom
Segalstad, LA4LN mentioned a similar demo that he and LA8AJA did for
Norwegian television. You can watch the ''Eksperimentet'' at
http://www1.nrk.no/nett-tv/klipp/222270, which is a children's
science program called ''Newton''.
Tom wrote, ''We asked if the Morse receiver could copy the message by
ear and reproduce it from memory, but that was not accepted. In
that case we could have exchanged the Morse message much faster.
Next we asked if the receiving ham could type the received message
into a computer, because that would also permit a faster exchange.
But that was not accepted either. The message would have to be
recorded by handwriting. Then we would be limited to the speed of
the receiver's handwriting, which is 30 words per minute. We
objected that this was not reasonable, because the receiving SMSer
would not have to write down the message, but our objection was
overruled.''
''The Morse code message was transmitted at a speed of 150 characters
per minute, and was completed in 45.5 seconds. The SMS message was
completed in 2 minutes. The conclusion was that the Morse code
exchange won with a wide margin''.
''The received message was controlled vs. the original, and was found
to be identical. 'But even though the Morse code is faster, the cell
phone is much smaller than the radio', says the anchor. But LA4LN
replies that your use of cell phone is restricted to where you have
coverage by an operator company, while amateur radio telegraphy has
no limits -- even from a desolated island in the Pacific Ocean''.
''Can you flirt on Morse code?'', the female SMSer asks. 'Sure', LA4LN
answers, ''On Morse code we can transmit the code 88, which means
love and kisses. 88 was chosen because it pictures the cross
section of kissing lips''.
I didn't know this about 88 having a graphic reference, but you can
watch LA4LN explaining it with the aid of his hands, while saying
something in Norwegian which sounds to me like ''octo octo''.
If you would like to make a comment or have a tip for our readers,
email the author at, k7ra@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/.
Monthly propagation charts between four USA regions and twelve
overseas locations are at http://www.arrl.org/qst/propcharts/.
Instructions for starting or ending email distribution of this
bulletin are at http://www.arrl.org/w1aw.html#email.
Sunspot numbers for August 13 through 19 were 0, 0, 0, 0, 0, 0, and
0 with a mean of 0. 10.7 cm flux was 67.2, 67.6, 68.1, 68.8, 68.1,
67.4, and 67.1 with a mean of 67.8. Estimated planetary A indices
were 5, 4, 3, 3, 3, 4 and 10 with a mean of 4.6. Estimated
mid-latitude A indices were 3, 2, 1, 0, 2, 2 and 8 with a mean of
2.6.
NNNN
/EX
