Hello Alan, Markus, Jim, Warren, Hartmut, Ben, Laurence, Clemens,
Roelof, LF!
Perfect. Many thank for the big resonance to my query :-)
The page of F1AFJ and the EZNEC file from Hartmut is very helpful, also
the general explainations and links!
OK, we'll start in this week and will see what comes out. At least the
loop will be installed and a cable to the RX. Then we will build a 1:3
transformer and just test what comes out if a 1k pot is used. I'm
looking forward to the results. Maybe a preamp will be needed but
hopefully we will get first impressions without one...
Loop, cable, xfmr, ground rod, loop orientation, resistor, alignment...
These are the steps for the week...
73 to all,
Stefan/DK7FC
Am 14.05.2012 00:36, schrieb Alan Melia:
Hi Stefam I am not sure about what you are doing so my comments may be way
off target. If the loop is not tunes yes it will be high impedance like a
short wire (much less than 1/4 wave) BUT Finbar did some experiments with
K9AYs for NDB listening. He tuned the loop to resonance at the opposite end
to the resistor, then he matched the feeder by tapping he tuning coil. I
have buried on my machine somewhere Finbar's notes. You will be told "its
not necessary to tune a K9AY but these are people who are looking at notes
or using it on MF/HF where the pick-up is a lot better and the impedance is
lower. For narrow band reception tuning is always an advantage.
As Roelof says Hartmutt used a K9AY, a two turn version, I think
Alan
G3NYK
----- Original Message -----
From: "Stefan Schäfer"<[email protected]>
To:<[email protected]>
Sent: Sunday, May 13, 2012 6:08 PM
Subject: LF: Cardioid RX antenna for LF...
Hello Group,
I've just started to play a bit in EZNEC, trying to simulate a receive
loop antenna for the new YV7MAE grabber.
http://dl.dropbox.com/u/74746618/LF/YV7MAE_LF_Grabber.html ... still
using a wire receive antenna with excellent results but now a
directional antenna is needed.
So i modelled a loop with a possible shape and a ground connection. Then
i added a R on the far end of the source. The results of the elevation
and 3D plot are surprising good. Maybe i have done a mistake in
modelling? Optimal performance was obtained at R = 8 kOhm. This resulted
in the best F/B and beamwidth... Results of ZENEC are here:
http://dl.dropbox.com/u/19882028/LF/Cardioid%20for%20LF.png
Any ideas, experiance or advice?
I guess a preamp is needed when such a antenna is used. The typical 1:9
un-un does not look useful for me...
73, Stefan/DK7FC
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