Hi All, as John is back on the other end again, I thought maybe I ought to
post an opinion about the conditions at present.
We had a monumental series of X-ray flares on 24 and 25 of Nov. These
'wiped' the band for quite a while with lots of heavy absorption. (I think I
am beginning to get a handle on these events now) I have also been reading a
lot of references, and I now realise that the band conditions do not follow
in line with the K index as we at first thought. It tends to start that way
with a slight lag of maybe 24hrs, but the injected particles from CMEs or
Coronal Hole events seem to hang around for a lot longer than the K index
shows a disturbed geomagnetic field. (The K index is a magnetometer
measurement of the the geomagnetic field disturbance, whilst the radio
conditions are dependent on the injected particles from the event and their
decay rate) We only started to come out of the absorption mid last week, as
the path went into 'violent-fade routine'. Very deep dips, but on Wed night
the highest peak I have seen in the logging project so far, and probably
lasting for almost an hour. Thursday CFH was off air, and Friday was not
spectacular here, though the plot did reach about 45dBu between 0100z and
0200z. Saturday night produced some sustained high levels, with 40dBu
between 2330 and 0100z. The levels were well above 30dBu for most of the
night, probably averaging 35dBu, with several peaks to 39dBu. This is the
right kind of territory for a successful trip across to John from out
previous experience.
The state of the path will return slowly to 'normal', which is distinguished
by the lack of any deep or 'rapid' (30min cycle) fading, unless we are hit
by any further particle streams. the average level for these stable periods
is 32-34dBu just about possible for a station with a good take-off and the
full 1W ERP.
Just a warning....the fading times shown on my graphs are a function of my
geographical position. They will differ for anyone further away that 25kms
from me. Also the coincidences may not be the same. I may not see a full 6dB
enhancement that you see, and you may not see the same picture as I do. So
it is worth plugging away during these conditions, monitor 137.00 if you can
during your breaks, and note CFH strength. Dont be disheartened if it is
down, it can climb 20dB in a little as 10 minutes under these unstable
conditions.
So far the most favourable conditions have seemed to occur either 24hrs
after a big X-ray flare (just before the accompanying CME shock arrives) or
much later as the after-effects of the disturbance die away 4 to 10 days
after the CME impact. There are so many variables that each event is
different in detail, although I am beginning to see a pattern.
The above is my opinion, and I could just be wrong!
Rik ON7YD is using up his excess holiday entitlement running up to Christmas
so there may be some slight delays in posting the CFH plots on his site. I
can forward a GIF file (about 8 to 10Kbytes) as an attachment to anyone who
wants a to look at them urgently.
CFH has been transmitting just a sub-carrier on the HF sideband (about
137.040) for the last 3 days with no sign of 'data' or modulation. It is
probably going through another experimental phase so may disappear at short
notice (dont rip your RX apart if you dont hear it!!) The advantage is
probably lower levels of sideband noise for John. SXV has moved down to the
bottom 100Hz of the band so you will probably need to negotiate a different
set of frequencies to those used earlier in the season.
Good Luck to you all
Cheers de Alan G3NYK
[email protected]
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