[SEDXC] 3B7C

[James Streible]

The following is from the 3B7C web page.

 


      Propagation Commentary. 13-Sep-07

I received this detailed propagation commentary yesterday evening from 
Eric, K3NA. I have decided to publish it in full to give you all some 
idea of the way that the team is attempting to maximise QSOs in all 
parts of the world at what is absolutely the bottom of the solar cycle. 
The commentary refers to propagation as experienced by the team, up to 
and including 13-Sept-07.

*GENERAL STRATEGY *

Operations begin as follows: 40m: 1100z; 80m CW: 1230 to 1300z; 160m CW: 
1300z. The 80m SSB radio is on 15m during this interval; we move it to 
80m SSB at 1400z but will try starting 80m SSB at the same time as 80m 
CW in the next few days as an experiment.

We are aware of the differences in west coast propagation between 
southern California and the Pacific northwest. We have made some 
adjustments in the last few days as experience with long path openings 
has increased. Openings vary dramatically from one day to the next.

20m is an example: During our afternoon, North America long path 
propagation overlaps with the main European opening. The NA LP opening 
can begin as early as 1215z, or as late as 1430z. It seems to last until 
about 1630z. This opening is very difficult to work as it requires an 
opposite beam heading from Europe. 20m closes sometime between 
1730-1830z. It remains closed for 1-2 hours. But one day, it didn't 
close at all.

After this closing period, the band re-opens short path to North America 
(with almost no European signals). This opening can start as early as 
1845z or as late as 2015z. It can close as early as 2130z or as late as 
0000z. 20m doesn't reopen until local sunrise (0200z) or a bit later. 
Some mornings it does not open until almost 0400z. This is our primary 
LP opening to western North America.

Today (Sep 13) I operated 20 CW position (9M6DXX was on 20m SSB). 
Signals had medium auroral flutter and huge differences in signal 
strengths. The opening expanded all the way to the east coast before 
ending at 034z. This opening ends at 0330-0345z (about the only certain 
thing on the band). After that we can run weak Europeans and Asians 
until late morning. The band may close for 1-2 hours at 08-10z (solar 
absorption), but today (Sep 13) it didn't close at all. Thereafter we 
begin the primary European run of the day.

*LF BANDS COMMENTARY *

*160m*: We are looking for zone 3 beginning 1300z when band noise begins 
to increase as darkness approaches the island. Usually a few VKs and 
KH6s are worked and we can check out some fishing buoy signals. We are 
calling CQ NA continuously on 1821.27 kHz, listening +6 with an operator 
on duty from 1300z (or slightly later). At 1430z we will start listening 
down 7, and some sleepy JAs will start to call us. On Sep 12-13 GMT 80m 
and 160m conditions were very poor from 1300z on.

*80m*: Similar pattern to 40m, with a later start in the afternoon 
(1530z is typical, and CW is more effective than SSB on LP to NA). The 
band closes in the morning about 0230z.

*40m*: Afternoon begins with LP NA (see start times above). This opening 
is substantially over by 14z, with a few NA stragglers in the following 
hour. Then it's time for Asia, and eventually Europe. Short path NA 
begins as early as 20z for un and continues until sunrise (02z). After 
sunrise, the path to NA shifts to a skew path (SW, rather than NW) over 
South America and up into the lower southwest USA (occasionally further 
north and east). The skew path ends at 04z when solar absorption shuts 
down the band.

***30m*: Not as complicated as 20m, but still complicated. We look for 
NA LP when the band opens (varies from 1130-1300z, depending on the 
day). But NA LP ends by 1430z, and we spend the next hours with Asia and 
then Europe. The primary NA opening starts between 2000-2100z and runs 
until the band dies in the evening (between 2300-0000z). The band 
re-opens at sunrise with NA LP until 0330 or a few minutes later. After 
that we can squeak in a few Asians before solar absorption shuts down 
the band at 05z.

***HF BANDS COMMENTARY *

These bands are a bit more straightforward:

*17m*: Has opened as early as 01z, but typically won't open until 
between 0230-0300z. We begin with Asia... and then switch to Europe when 
Asia signals fade (varies by day). North American has been worked as 
early as 1215z. NA signals are typically very weak on this band. 
Operators have been developing the habit of asking every 10 minutes for 
the EU pileup to QRX while we work the few audible NA signals. 
Eventually NA gets strong enough to run continuously, but this might not 
occur until as late as 15z or later. It is then a race between jamming 
NA QSOs into the log and the band shut down. Band closing can be as 
early as 14z and as late as 1730z (on Sep 11).

*15m*: Has opened as early as 03z... but typically opens a bit later 
between 03-04z. Can close as early as 13z (ouch!) but typically runs to 
15z or a bit later. We have worked a handful of NA stations 13-15z if 
the band holds up.

*12m*: Very spotty and irregular. Has opened as early as 0430z, but 
early openings like this are often followed by a closing of an hour or 
so. Usually open by 05z to Asia for a few hours but Asia peters out by 
08z. We can run Europe until band closing (as early as 12z but typically 
15z or a bit later). So far no NA worked on this band.

*10m*: Like 12m but shorter. Opens between 0530-0600z with Asia our 
focus. Asia disappears between 08-09z. Band closes as early as 10z (ow!) 
but can last past 15z (with the last hour rather spotty).

When the high bands are open to Asia we experience some cross-station 
interference. Occasionally we have to sacrifice a band in order to allow 
the others to run effectively. This is due to the relatively orientation 
and location of the antennas for this band. To compensate, we've added a 
second 15m and 10m aerial on Sep 12. so we may have two signals on these 
bands during the remainder of the DXpedition.

One whole wall of our dining area has been plastered with histograms of 
band activity by day, and the operators have been studying the charts 
for openings, trends and annotations made by others before going on 
shift. Operators also are looking at the number of CW and SSB contacts 
made with each geographic area likely to be worked during their next 
shift, and choosing modes on bands with one transmitter accordingly; 
e.g., if we have more CW than SSB contacts with Asia on the band, the 
operator will probably run more SSB on his next shift.

*FOOTNOTE*

In addition to the team's own analysis, I am, on a daily basis, sending 
them significant propagation reports that you folks send to me. These 
reports are very useful, especially those that refer to specific queries 
that the team has made. I publish these requests from time to time in 
the Latest News column.

 

Jim   K4DLI