Vaino has many years of experience in that field and I thought
subscribers to the reflector might be interested in his
observations. So I asked Vaino permission to distribute our
communications via the reflector and he kindly agreed.
73, Dick, PA0SE
E-mail: d.w.rollema@gironet.nl
Our attempts to calculate ERP even for e.g. nearby
Decca station (d=12 km) have not been succesful
(after more than 10 yrs of continuous measurements).
ERP's have been checked by overflight measurements,
we use a Piper Arrow for such flight measurements
and specially tailored sofware for calculations.
Allright Dick, surely would appreciate your
comments
about our experiences on the field of measuring
LF/MF
field strengths over various distances.
Please let me know if you wish me to resend attachments.
I have been using Win98 since February, Win95
before that.
Before I retired I was a member of CCIR Study
Group 6
(Ionospheric Propagation) but supposedly have
been spending
more time on monitoring and measuring VLF/LF/MF
stations.
CCIR Ground propagation curves are the best available
and
they give good idea how the different soils can
behave.
Main problem is that they don't work in everyday
practice
while one tries to calculate EMRP from point
measurements.
DGPS advisor has been prof David Last (G3???)
at the
University of Wales. They have their own ground
conductivity
data bank for the whole world. We proved with
our measurements
that their data bank values are not directly
applicable for
our conditions. The situation elsewhere is not,
of course the
same but we were first to start using DGPS on
our car ferries.
I understand the soil in England is much more
homogeneous, not
to talk about the Netherlands. We have our archipelagos
etc.
The seasonal GW variation was already documented
in 1940's
but some people on DGPS business have no knowledge
of it.
The variation on high seas is much less than
on ground paths.
I have about 500 flight hours on that specially
equipped
Piper Arrow. In 1974-75 we produced a ground
conductivity map
of Finland by measuring available and some temporary
stations.
It has been a series of calculations, measurements,
comparisons.
First LF/MF campaign for EBU started in 1948
at Hki/Laajasalo
with RCA 308 and other rather difficult to use
Fs equipment.
Latest assignment was to measure all Finnish
and Swedish
DGPS beacons and to produce reports for Maritime
Authorities.
So we still have 30 LF/MF/HF frequencies being
measured 24h
a day with R&S ESH3 and active CCIR type
1 m monopole.
I surely wish to contribute for this 135 kHz
business before
these ESH3 measurements will be stopped at the
end of 1999.
1989-1998 measurement data have been saved to
a CD Rom
and I have been hoping that some young student
will help me.
Contrary to most DGPS people we have no commercial
interest.
We took it as another interesting and rewarding
hobby. Hi
Glad to hear you are getting along with Win98.
Windows in general can be called a two-edged
sword.
My Windows generally collapses at least once
every day.
Also glad about your efforts to explain people
how to
construct a simple but useful instrument to measure
Fs.
I know we have had a luxury of using calibrated
Fs
equipment ever since 1948, first RCA then R&S
HFH/ESH.
I have been producing most graphics with Lotus
Freelance
and the present version is Freelance 97 edition.
For some special formats the earlier version
is better.
Windows beats DOS in some graphics work, but
DOS is fb.
Freelance automatically produces different colors
for
every day of a month and legend shows the color
vs day.
In general this kind of picture shows a general
daily
variation of hourly Fs during a calendar month.
Of course, the fine structure, eg 'morning effect'
don't clearly show like they are seen in a pen
recorder.
It has been an EBU practice to use dB(uV) for
eg input
voltage and dB(uV/m) for Fs, since the 1950's.
I zipped the available 1998 graphs for 138.83
& 77.50.
Some big Fs excursions must be due to change
in radiated
radiated power. In 1998 the noise threshold level
for
138.83 with 200 Hz Bandwidth is 5 dB(uV/m)->
(-7 dB(uV).
There are some qrt periods on 138.83 but never
with 77.50.
Geri,
Further to my e-mail attached you will find
some explanatory pictures about the meas system.
73 de Vaino, OH2LX
V.K.Lehtoranta, OH2LX,
E-mail: vaiski@dlc.fi - alias: oh2lx@dlc.fi & oh2lx@sral.fi
August 1998
September 1998
October 1998
November 1998
December 1998
January 1999
February 1999
March 1999
April 1999
May 1999
June 1999
July 1999
August 1999