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
-------- Original-Nachricht --------
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
