Rik, Minto, LF,
My old LF TX antenna at the parents QTH in 2003 was about the same, even
a bit shorter. I had 25m wire just about 8m up, surrounded by many trees
and buildings, causing high losses. I just got 2.2 A at 1 kW and about
10 kV. Since the coil was inside the house i had to bring the HV through
the window and used the inner part of a RG213 cable which survived about
2 TX hours per piece ;-)
Anyway i worked OH1TN and OH5UFO as my best DX. Stations like DL4YHF,
DL3FDO or DK7SU were 589 and me too...
That must have been other times. QRM seems to be higher nowadays. Or
not? That's the question!
But QRM can be compensated by QRO! ;-)
RX systems can be placed in a remote location, maybe using a FM link
powered by solar energy. There are always interesting projects and
challenges :-)
Look at the OK2BVG VLF grabber that is in a remote location
http://www.ok2bvg.cz/vlfgrabber/ QRM???
73, Stefan/DK7FC
Am 25.07.2011 22:40, schrieb Rik Strobbe:
Hello Minto,
my old 136kHz antenna seems pretty similar to yours. If I remind well the
antenna capacitance was slightly more (420pF) and the loss a bit less in winter
(130 Ohm) but higher in summer (up to 170 Ohm).
The maximum output power was 450W, good for 1.85 A antenna current and just
over 5kV antenna voltage.
As long as the antenna was dry I never had any problems with the antenna voltage. I had
about 50% of the loading coil at the top of the vertical section, so the vertical section
had "only" 2.5kV.
It seems a good idea to keep the hight voltage outdoor. Maybe you can put a
large fixed coil outside and just have a small variometer for daily tuning
inside. This will also reduce the losses.
73, Rik ON7YD - OR7T
________________________________________
Van: [email protected] [[email protected]]
namens Minto Witteveen [[email protected]]
Verzonden: maandag 25 juli 2011 21:34
Aan: [email protected]
Onderwerp: LF: Re: DL6NN on 137
Hi Rik,
Thanks for the heads-up.
I think your antenna is better than mine, but possibly not by much. I do
have another concern however, and that is the high voltage at the antenna.
The capacitance at 136 kHz is (measured) 390 pF. With a total system
impedance of 150 Ohm and 1 kW this translates to 7.7 kV!!
On 500 I already had some "interesting" phenomena with 5 kV. The antenna is
end-fed here in the shack in the attic.
So I will have a fire extinguisher at hand when tx-ing on 136..
Regards,
Minto pa3bca.
--------------------------------------------------------------------------
Ceterum censeo Carthaginem delendam esse
-----Original Message-----
From: Rik Strobbe
Sent: Sunday, July 24, 2011 20:51
To: [email protected]
Subject: RE: LF: DL6NN on 137
Minto,
I was active on 136kHz with a similar antenna (15m high, 25m long "lazy-L"
antenna) and in addition the losses were very high (abt. 130-160 Ohm).
Despite that I managed to work distances up to 1600km in regular CW (best DX
= OH1TN).
So don't dispair.
73, Rik ON7YD - OR7T
|
