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
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2012.0.2197 / Virus Database: 2437/5220 - Release Date: 08/23/12
--
73, Ric, VK7RO
|
