I'll be searching... great stuff. Very very informative!
My experiments with CC are on
going and probably always will
be. I keep taking little steps
forward and then realize what
I don't know.
My coupling circuit is not done
by any means. I can tell just
by listening to my signal on
the car radio out in the driveway
that the impedance of the AC line
keeps changing. The car radio is
sort of a good reference. The car
is always parked in the same place,
and is has a very good radio/sound
system for critical listening. Hum
on the signal changes, strength
changes, and the quality of modulation
changes, if the transmitter really
hits a mismatch.
As you probably remember, I am using
a 6 watt LPB transmitter from 1971.
It is a vacuum tube transmitter, and
I spend half of my time just looking
at the glowing tubes.
Anyway, instead of driving the AC line
with the 5 or 6 watts, I am going into
a homemade RF attenuator. So only
500 or 600 mW is actually going into
the AC line. This helps isolate the
transmitter. I did try to go into
the AC line with a full 5 watts, and
all I got was a motorboating signal.
It all sounded wrong - so I went back
to the attenuator. This is followed by
a homemade coil, which is in series
with a cap and a fuse. I have heard
many many different opinions on what
the size of the cap should be, and this
also depends on the operating frequency
of choice. My only choice is 1020 kHz.
I have a good crystal for this channel,
and 1020 is very clear during the day.
Anyway, surprisingly enough, I have had
some success. My signal is definitely
just in the power line. I have received
it in a friend's house about 1000 feet
away. The signal was not that strong,
but that was before I added the coil
that I mentioned above. This coil is
a homemade 10 uH coil - that I used
based on some notes that I had sitting
around. The 10 uH coil seems to help -
tests with my radio next to telephone
poles seem to indicate this. The purpose
of the coil is to load up the AC line a bit.
It is just luck that it is doing some good.
There are many things I want to add to
this developing coupler. I want to add
further attenuation to bring it down
to 50 mW for tests. I want to add taps
to the 10 mH coil. And I have been
trying to make an RF matching transformer
that is tuned by a capacitor. There is
also the matter of measuring the SWR on
the AC line side - and not just the
transmitter side. I have not done the
former yet.
So far the only thing I have gotten from
this matching transformer circuit has been an
RF burn! Yup, it's really true. I didn't
think 500 mW on the AM BCB would do that,
but the primary was peaked with a 365 pF
cap, and I guess that was enough. My
secondary coil, which was part of this
didn't work - in fact, with it in line,
everything got weaker.
I am finding this to be an extremely
enjoyable project. One of the hardest
parts, though, is getting into neighbor's
houses on the street to try to hear my
station. I am fortunate. I have a lot
of nice friends on the street, but I
am treading very lightly, because I don't
want to overstay my welcomes, so to speak.
In your case - I really don't
know what to say about your matching situation.
It is very different from mine, and I am
still just learning here.
Just go slow, be safe, and let us know what
you find.
Best Wishes,
Bruce, W 60 HZ
My carrier current range is
limited by the neighborhood
power grid wiring.
I can track the signal on
telephone poles about 1000
feet east of here and about
1500 feet west. The signal
is confined just to that
section of my street and that's
mainly it. I can hear my signal
on the very first telephone poles
on some side streets, but that's
as far as it goes. And as mentioned
in another thread, I am puzzled that
my signal gets into a house 1000 feet
away, but not into a house in the
same direction on the street - which
is only 700 feet away. The wiring for
some houses must be different.
Still, I am really enjoying this. It
is a great experiment.
Best Wishes,
Bruce, W 60 HZ
I bought a coil because of your post. hopefully it will be the right one. how inspiring. i love this stuff too. thank you so much for sharing your experiences Bruce!
" thank you so much for sharing your experiences Bruce!"
Indeed. It's better to listen to those with experience than those who pretend and attempt fear mongering or discouragement.
RFB