Hi Markus and Jose, I have just been looking at the ground wave level at
Brian's CT1DRP a little further down the coast. My estimate is based on some
concellation fades that occured on Brian's plot on the last couple of days
during the evening dip. Deep cancelation means that the ground wave and
skywave are almost the same strength. This gives a estimated ground-wave
field strength of around 0dBuV/m. there is no doubt that the majority of the
signals at that range,1960km, is daytime skywave. I think it is probably 2
hop from an altitude of about 50km (which gives 1000km per hop, by simple
geometry.....its not that simple of course!).
These cancellations are only seen in day-time in quiet conditions. Brian's
day-time levels at more active times of when the X-ray flux is higher are
some 10dB
higher than at present.
The above estimate stacks reasonably well with Reg Edwards G4FGQ's
GROUNDWAVE4 program (I think it is actually GRNDWAV4) using a poor ground
option.(10)
I would think Jose's received field strength should be similar to Brian's.
He has a water path across Biscay but I have a feeling this may not matter
too much. He is not placed to get the benefit of incomming "focussing."
At night the signal could be single hop or even enhancement due to additive
effects between in-phase modes or paths. I have seen 6dBs often and an
occasional 10dB over the Atlantic at a favourable time. There is some
controversy about how propagation at 136 should be modelled but I find a
simple explanation can be derived from a "hop" model. I think from memory
Brian's path suggests that there is on average a excess 12dB attenuation
over the equivalent free-space loss
Alan G3NYK
----- Original Message -----
From: <[email protected]>
To: <[email protected]>
Sent: 14 May 2006 21:38
Subject: Re: LF: DCF39 ERP and field strength
Hi Jos�,
though it is not explicitely mentioned in the caption beneath Geri's and
Gamal's curve, I think their data actually mean a power of 40 kW EMRP (i.e.
125.6
dB�V/m at 1 km). Here at 310 km, I see 70 dB�V/m with about 6 dB groundwave
absorption.
Despite this slightly higher EMRP, your measurement would still imply
basically lossless low-angle skywave propagation.
73 de Markus, DF6NM
In einer eMail vom 14.05.2006 13:00:23 Westeurop�ische Sommerzeit schreibt
[email protected]:
> Hello all
>
> In the web of Geri, DK8KW, can be seen that DCF39 ERP is 40KW (22KW EMRP),
> based on measurements made by Geri some years ago. For this radiater power
> corresponds, at 1800 Km, in function of inverse of distance, 58 dB(uV/m);
last
> nigth I made measurement of 60 dB(uV/m), so I wonder if still DCF39�s
power is
> the same as before, and if the previous theorical field strength, with no
> reflection loss, can be exceeded some times due to the several propagation
> factors involved.
>
> 73 de Jos�, EA1PX
>
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