Subject: Fwd: Re: LF: DK7FC now on 137.715 in DFCW4 with his
600m earth antenna
Hello Roger,
Below you find
my eport on the todays LF earth antennas test. Currently it seems not
possible for me to send to the reflector. I even do not get mails from
there... (?)
Markus/DF6NM has forwarded the mail to the reflector
but it wasn't reflected. Maybe, you can try to forward it? Can you tell me
if it was reflected?
The mail contains some infos about my todays
activity on VLF/LF! So could be interesting to some RX stations
:-)
Best 73, Stefan/DK7FC
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Hello
Marco, Michel, John, LF,
This is a great day for the optimists,
regarding
EARTH ANTENNAs as a TX antenna! :-)
Until today i
have not spend too much attention to my earth antenna as a TX antenna on
LF. But knowing that my small PA for VLF (12V/300W class D) can also
transmit on 137 kHz i gave it a first try today. I was almost sure that my
signal will be visible on my grabber in 5 km distance but wasn't sure how
the efficiency really is...
We know that the effective area of the
formed loop must be smaller than on VLF but the big advantage seems to be
that the antenna is even longer than lambda/4 for 2200m! Thus, to my
surprise, and probably to the surprise of the most of you, the antenna
seems to be very suitable as a TX antenna although the average height of
the wire above ground is just about 4m!! The ground resistance is about
600 Ohm, currently.
I am VERY happy now to have a fixed antenna in a
quiet location that does not matter of rain and wind or so and can be used
from DC to HF :-)
A first transmission at
25 W was immediately
visible on the DD7PC grabber, about
20 dB above noise in DFCW-3,
distance is 77 km. So, it must have been audible!
A later
transmission at 100 W is visible in France, with a good S/N. Many TNX to
Michel and John! If the signal was 20 dB above noise in DFCW-3 at John's
QTH in
JN17VG (436 km), it must have been audible as well!
:-)
Indeed, i have also never expected this efficiency from an
earth antenna. It is months ago that i tried to convince some people here
to try such an antenna. Maybe this day can help to convince practical
oriented people that it is worth trying things that seems to be "wasted
time" and/or "impossible" :-)))
I also hope that an earth antenna
will be seen as an alternative to a normal closed loop or a vertical,
especially in a woody region.
Attached you find a screenshot of my
grabber and my signal in 5 km distance. Maybe it was 100 dB above noise?
;-)))
I still have no RX that can handle this big input signal. My
706 is not the best idea and i have most of my LF equipment on the parents
QTH but i will try to receive tomorrow with the 706 and my PC on the earth
antenna, using some attenuators and/or transformers. I will build a
suitable RX for this antenna soon. But the QTH is EXCELLENT as you can
image :-)
So, there was a discussion about the radiation pattern of
an earth antenna, if it acts as a loop or not. Since the antenna length is
in the region a lambda, it surely will not be a pure loop and will maybe
have a preferred direction. YOU all can help to find out this radiation
pattern by listening to my transmissions that will be done in the next
days.
Tomorrow, arround 8 UTC i will do a VLF test and later a LF test
on the earth antenna. The VLF test is to reach Michael Oexner again
and later on LF i would appreciate any rprts. But still not sure if i can
come to QSO mode, due to the RX.
Now i know that this antenna is
very worth to keep and improve. This will be done in the next weeks!
:-)
BTW: I cannot transmit on sunday with the kite antenna, due
to the WX, sri...If some people want to try an earth antenna
as a TX antenna, you can ask me any questions!
Sorry, i am a
little euphoric now. The best sign if this happens during a project. Can
it be wasted time then?
Best 73 and hope cuagn on LF this
period!
Stefan/DK7FC
Am 24.09.2010 17:27,
schrieb Michel Brunel:
Hello Marco, LF,
Excellent copy here in JN18HP, hope the capture find its way through the
reflector.
I was definitely not expecting such a signal with an earth electrode !
73
Michel - F5WK
Hello LF,
Stefan, DK7FC is transmitting with his 600m earth antenna on +/- 137.715KHz in DFCW4.
I could see him on my Grabber (see attachment)
http://www.qsl.net/dd7pc/lfgrabber_dd7pc.html and on the grabber from
Markus, DF6NM with a very good signal.
He was transmitting just with 25W and will increase now to 100W.
Any reports of his transmission are very welcome.
Vy73
Marco
DD7PC
