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
|
