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Radio Direction Finding
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PA3BNX:
Hello Every Body,

I did work quite some time on the MyMapping.exe software this week
but I also have a nice antenna hardware hint.

Just clamp 3 a 5 ferrite clamps around the coax and control cables that
go  vertical under from the antenna switcher.

The vertical cables act as field disturbance for the 4x 1/2 wave length dipoles
So make them more or less invisible for the radio field by using clamps so the length in the field
never reaches a 1/4 wave length of the Doppler reading frequency.
Sort of stealth technique.

Of course also use a wooden or PVC tube to hold the 4 antenna's support.
 

Take a look at this link to from DopplerSystems.

http://www.dopsys.com/products/Series%207000/Antennas.html

Have fun.
PA3BNX:
Hello Every Body,

I found some new stuff about getting the most out of the
doppler antenna system.

[url=http://members.chello.nl/~w.hofman/pa8w]http://members.chello.nl/~w.hofman/pa8w] [url]http://members.chello.nl/~w.hofman/pa8w]http://members.chello.nl/~w.hofman/pa8w]http://members.chello.nl/~w.hofman/pa8w] [url]http://members.chello.nl/~w.hofman/pa8w ... Arrays.htm[/url]

http://www.qsl.net/df9ie/

Today I heard even more antenna information.

The 1/2 wave antennas may not be 1/2 wave dipoles with gamma match
because the antenna is resonant and influenced the near field.


So you definitely need to use 1/2 wave open dipoles.

Make sure the antennas are not resonant so use some resistors in series
in the dipole from 10 ohm to 1k ohm from current center to top
to make sure they do not resonate

Take also a look at the nice R&S DDF007 Handheld Portable Direction finders.

http://www2.rohde-schwarz.com/en/products/radiomonitoring/direction_finder/DDF007-%7C-Side_View-%7C-32-%7C-7349.html

Have fun,
PA3BNX:
Hello Every Body,


Some pictures of my Super Simple Sound Doppler
with 1/2 wave dipole antennas.

I did use a extra diode in series of the coax shield at the end of the

open dipoles of about 1 meter length.

And I used some ferrite cores around the control and coax to the switcher unit
and used a PVC pipe

So take a look...
PA3BNX:
Hello Every Body,


Today I saw a other improvement from PA8W
for the dipole 1/2 wave antennas.


Not only add a series diode between the coax shield
but also a 1 m Ohm static discharge resistor across the (PIN)diode.
so the antenna elements never can get static charged.

When the no control voltage there  the antennas can be static charged.

I have an update software version of my SoundDoppler120Gall.zip on the site of PI4WAG
PA3BNX:
Hello everybody,

I did some drawing work on the antenna switcher circuit diagrams
for the Super Simple Sound Doppler.

You can see the circuit if you use 4x 1/2 wave dipoles.

With the diodes and bleeder resistor at the antenna feed points.



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