Hello Richard,
Thank you for the input. It is certainly a circuit/image that will find
its place in my LF folder!
About the broadened noise pulses: Martin's loop has 8m^2 and produces a
bg signal for the RX. So the BW is quite wide, probably > 3 kHz. So i
don't expect this problem here. Her has no possibility to buy all the
parts of the circuit so we will go on with the more easy config.
Thanks and 73!
Stefan/DK7FC
PS: Can you still receive on LF? If so, we could try if you like! VK7ZL
copied traces of my signal in March this year...
Am 24.08.2012 01:04, schrieb Richard Rogers:
G'day,
When I used to listen to the ZLs on 180KHz (15 years ago!), I used an
active vertical and a loop combined in this circuit
https://dl.dropbox.com/u/100084148/Phasing%20antennas.tif
The circuit was published by the late Andrew Corney, ZL2BBJ, in
Break-In in 1996. It certainly allowed me to null out signals, but I
found that it did not help greatly in the reduction of noise as I was
listening mostly just after sunset when the signals and noise were
both coming from the East.
One problem I found when using a tuned loop was that the selectivity
of the loop broadened the noise pulses and stopped the noise blanker
in my TS-920 working well.
On 8/24/2012 7:43 AM, Stefan Schäfer wrote:
LF,
Currently i'm working on a E-H combiner together with Martin/YV7MAE
in Venezuela.
He has a well working E field antenna, about 80m wire, some m up,
resonated with a ferrite rod and a variable transformer and some
output turns on a separate winding and a separate LF earth system.
The bandwidth is wide and the signal levela are high.
He also has a loop which is resonated to 137 khz. He can see and hear
DCF-39 in 8000 km without problems in a 300 Hz CW filter. With this
loop he can receive my DFCW-90, so far the best S/N was 15 dB in 22
mHz. The loop is very directional. Turning the loop by +-15 deg shows
a clear decrease of the DCF S/N.
Now we're planning to combine the two signal sources to obtain a
cardioidal pattern like the K9AY and similar provides (used by W1VD,
F1AFJ and others). The signal levels of both, the E and H antenna are
producing roughly the same signal levels on the RX (difference < 5
dB). This is the circuit that we want to try tonite:
https://dl.dropbox.com/u/19882028/LF/DSC04412.JPG
The H component is fixed and then it is possible to "add" a certain E
level, hopefully resulting in some noise reduction of QRN coming from
the backside (SW). Later, the F/B may be optimised by adding some C
on the loop to change the resonance and so the phase between E and H.
Does someone have additional advice or tried a similar project? Is
there a better way to start?
Note that just one ferrite core is available, i.e. no high end, low
noise op amps and so on.
73, Stefan/DK7FC
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