Graphical analysis of the 40m path from ZL2TLD to F6IRF

The attached graph shows the graphical 40m path analysis for the stations ZL2TLD (RE79tb) and F6IRF (JN35au) for the period Sept28 to Oct09 2008. The path is roughly 19000 kms for the short path and 21000 kms for the long path. (.../...)

The stations
- ZL2TLD is using a windom antenna, located only 4.5m (15 feet) above ground. No more details available today (antenna orientation / soil quality / obstructions /
man made noise).
- I am using a ground-mounted 18m (60 feet) monopole currently matched with an
Icom AT130 ATU. The soil quality varies fm average (dry condx) to rich (wet
condx). There are about 30x 20m burried radials (unequally spaced due to terrain
limitations). My take off to short path is good with sloping terrain (abt 2
degrees obstruction) and poor to the long path (abt 8 degrees obstruction). As
already mentionned, the man-made noise is high, due to a 380kV power line passing 250m away from the vertical (noise increases with rain, snow or fog causing up to 16dB degradation on 40m compared to quiet days).
In very short, 2 modests domestic stations...

The conditions
- On 3 October, middle of the considered period, the ZL2TLD sunrise occured at
1748Z and the sunset at 0625z. At my QTH, for the same date, the sunrise occured at 0537z and the sunset at 1711z.
- 90 days SFI was 67 and The SSN remained 0 for the complete period.

The plot
- the dark blue dots are the levels reported by ZL2TLD on my transmissions. The
pink dots are the levels I reported for ZL2TLD transmissions. Power used ranged
from 0.5 to 20W (at band closure). Most of the spots were collected using 5W both sides. All levels have been corrected to show the equivalent "1W-level", which explains why a few spots are around -35dB, below the WSPR decoding capability.
- the dark blue thin curve is the order 4 polynomial function (excel) for the blue spots and the thin pink one is obviously for the pink spots. The solid blue curve
is the same for all spots.
- the thin lines are the linear functions for the 2 series of data.

Interpretation
- The first maximum occurs near my sunrise (thus near ZL2TLD sunset) and Long path is assumed (based on VOACAP simulations). The second max occurs near my sunset and short-path is assumed. BTW, along the year, our 2 locations not being exactly "antipodal" the grey line conditions never occur.
- The difference between ZL2TLD received levels and my received levels, ranges
from approx 4dB on the long path to a dozen of dB's on the short path. I think
that the main reason for the offset is the higher man-made noise level at my QTH.

In general, here I can note that the lowest noise level is reached just after
sunrise, while it is significantly higher in the evening (on top of the power line
electrical noise, I have also continuous carriers, possibly generated by TV-sets,
computers and other domestic appliances and more interference from other band
users, the band being still open at short distance). Of course there are other
potential sources of incertitude, such as antenna efficiency (and sensibility to Man-made nose*), receiver and sound card performance etc, etc... (as pointed out earlier, feeding the same RX audio to 2 sound cards I could notice important differences in the reported levels).

That's all for now, but the next step is to compair this data, with VOAPROP
simulations... so "stay tuned", more will follow...
Of course comments are welcome !

73's Pat

PS: A full article, including a few sound files, will be published soon on my
personnal blog.

(*) It is commonly admitted that verticaly polarized antennas are more sensible to man-made noise and atmospheric noise than horizontaly polarized antennas.

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