Dumb question here....
You guys are trying to check the output from your transmitter,
right?
Don't you have enough RF in your shack that you could just us the
tinySA antenna
to get enough signal to check it?? It is a form of inductive
coupling, no?
If you are checking a qrp rig, maybe wrap a wire around your dummy
load to get
more coupling.
73,
Gary
WB6OGD
On 1/14/2021 8:36 AM, Miro, N9LR via
groups.io wrote:
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Hi Dennis!
inductive coupler still requires dummy load, and if you have one,
then your resistive attenuator does not need "large power
absorbing resistors".
In another thread in this group someone posted this link to the
excellent article on theory and practice of inductive couplers ()
Article in your comment is quite misleading if not wrong -
inductive coupling is done by means of current transformer. If you
leave secondary side of current transformer "open" (no terminator
with resistor), in theory potential at it's ends will be infinite
value and in practice can reach thousands of volts!
Also, reflected impedance in primary will be quite high and will
cause significant voltage drop and dissipated power in turn.
Simply said, current transformer MUST be terminated on the
secondary side at all times!
The "fix" is surprisingly cheap and simple - just have properly
designed resistor :)
Also, number of turns and selection of toroid material is not a
random effort - just check the link above, and if you desire to
learn even more, check the link in that document that takes you
here?
I still don't know what are comparative advantages/disadvantages
of "resistive vs inductive" high impedance taps. Resistive are
easier to make and have wider bandwidth (when done correctly),
inductive gives you galvanic isolation, but not sure if there is
anything else.