Hi Dimitris,
Am 15.03.2013 02:20, schrieb Dimitrios Tsifakis:
Hi Stefan,
Opperman is great, they will sell to VK and I can pay via Paypal.
Thanks for making me aware of this shop and the filter.
Nice to hear and know :-)
So, are you using this filter in a DC receiver front end?
Yes i do. My MF grabber
(http://www.iup.uni-heidelberg.de/schaefer_vlf/DK7FC_MF_Grabber.html)
uses a DC RX with that filter. The input- and output impedances are
critical. You have to align the component values to the individual
filter values.
I'm using this circuit:
https://dl.dropbox.com/u/19882028/MF/MF%20Filter%20schematic.png
Looks like that in a prototype:
https://dl.dropbox.com/u/19882028/MF/Mechanical_filter_with_source-followers.JPG
Later i changed the input to the yellow wire and replaced the 18k
resistor on the input by a 500R resistor. This up-transformation gives
you roughly 6 dB more output signal level. The input Z is very high and
the output Z is measured to be close to 50 Ohm. So this may be even
useful as an active antenna (630m band only) frontend in combination
with a longer 50 Ohm coax cable and a usual RX.
My RX is using an SBL-3 as the mixer, also with a 50 Ohm input. This all
fits well together :-)
I also use that filter in my MF TX converter!
I want to
make a simple DC receiver because I want to set up a RX station at the
top of the heavy ion accelerator building, at work. That will put the
RX antenna at the top of a 50 metre tower, which may produce
interesting results. I can also use a simple low power DC receiver at
my block. It's amazing how low the QRM is over there, but of course, I
don't have mains power.
Calls for solar modules! I'm amazed how cheap they are these days.
73, Stefan/DK7FC
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