"Although this transmitter is not being used for CC service right now it is of great note that I have had it for 30 years - and this is the first time I have really had it on the air!"
Actually, there is a little of both taking place. The RF field is emitting off the loose coupled wire, and at the same time it is sending it through the electrical wiring within the house. You could probably go three doors down and ask the neighbor if they pick it up on their small table radio using the AC outlet for power. This is only probable due to two factors:
1. High power AM station on the channel.
2. Not direct CC coupling onto the AC lines/neutral.
To get a better direct CC coupling effect, just wrap that free end of the wire that remains after the coil around the dummy load, to a yard extension cord.
This approach is obviously not as good as using a coupler unit but is a very basic method no different from coupler units. Just like the coupler units that provide the isolation and transfer mechanism, the method I described above does those two things as well. To improve the coupling efficiency of your basic CC setup, add more winding length around the yard extension cord, even more winding layers at shorter coil lengths, slide coil along length of extension cord to improve coupling effect.
RFB
Thank you Carl and RFB.
RFB, I am going to have many more
questions for your soon - well,
as soon as I can. I just took a
leave of absence from job number 2
because of back problems. It's
no biggie.
Carl, I know you will be reading this.
We talked about that E-mail I was sending you.
As you know, it was accidentally deleted.
I will try to reconstruct it and send it to
you as soon as I can.
Talk to you soon!
Bruce, DRS2
"To improve the coupling efficiency of your basic CC setup, add more winding length around the yard extension cord, even more winding layers at shorter coil lengths, slide coil along length of extension cord to improve coupling effect."
Why would that not have such an effect on frequency that it would be very difficult to get centered?
Moving the coil across the length of the extension cord will allow for increased coupling or decreased coupling, like a variable attenuator. And depending on what frequency your operating at, the "variable attenuator" will have different results along the length of the extension cord because of wavelength.
There is no difficulty with obtaining a maximum coupling point, it merely allows for adjustment just like an actual coupler unit.
RFB
I can only stay on here briefly,
because I have to get rid of this
back problem, so I can go back
to both jobs. I guess all of my
messages will be short for a while.
Now I got that out of the way.
The coverage area of this improvised
CC set-up is interesting. I get a
strong signal all through my back yard,
back about 100 feet. The RF field is
coupling to my 100 foot long wire. After
I leave that area, the signal drops off
rapidly.
The signal does get across the street, very
very weakly. I tried walking down the
street, and it doesn't seem to be audible
under the power lines. So the RF field
is following wiring around my house, mainly,
I think.
I'll have to experiment more when I feel better.
Best Wishes,
Bruce, DRS2
I have discovered a nifty 10 dB attenuator
on the net. This thing takes a 5 watt Rf
signal and reduces it down to - you guessed
it -- 500 milliwatts. It is very clever. It is a
PI net circuit. Each part of the circuit is a
different resistance, of course. But the author
of the circuit uses just 8 100 ohm 1 watt
resistors in total. Different combinations of
these resistors are used to achieve the desired
values for each part of the attenuator.
(Actually, the circuit is really a 9.6 dB attenuator,
when everything is said and done.)
I will have to make some changes to get this to
work with the 6 watt signal from my LPB RC-6A
CC transmitter, which is fine. It's a good starting
point.
Assuming the above is done, the next thing to do
is to feed the 6 watt RF signal from the transmitter
into the attenuator. About 90 percent of the transmit
power will be used up in the attenuator. This will
accomplish 2 things. It will isolate the transmitter
from the load, and it will provide a SAFE 600 milliwatt
signal to feed into the coupler. (At least that is what
I THINK!)
The CC coupler will be something that I used from early
experiments years ago. I have an AM BC band receiving
loop. It will be used as a parallel LC and will be tuned to
max. A length of AC line cord feeding the transmitter
will be wrapped around the LC. How much I don't
know. I guess that will be part of the experiment.
As RFB mentioned, this will have to be shielded. There are
ways to do that. At first, for experiment's sake, it will not
be shielded, though.
Hopefully, this will get some real RF into the AC line without
causing significant problems to the transmitter or the house
wiring.
We talked about this before, but it is getting closer to reality.
RFB, if you are out there, can you think of any other flaws
or problems with this approach?
It still do not have a crystal for the channel I want. But these
experiments will be very brief, so no problems will come
from them interference wise.
It still have to build the attenuator. Hope to have that done
soon.
Bruce, DRS2
The trans-basement roller-rack parade was finally able to roll from the east wall of the sub-ment, or basement, or sub-basement, or sub-floor, over to the west wall, for it's new home right next to the panel.
Yesterday a ground rod was found out in the ivy where the panel upgrade of 2007 took place.
All parts and pieces are here, the grid is running, part15.us is turned on, we are THAT close (hold fore-finger right near thumb).
CC testing could even start tonight!
After not much happening for a long time, today has been highly fruitful as we have gotten 100% wired-into-place and totally verified by a safety expert.
So as to pace it out just another mile, it's time for dinner!
We will be back later with a CC report directly from the scene!
Cancel your evening plans and stay close to your computer.
Waiting to see what happens. Will you do a drive test?
Did not get to the drive test, but it will be very interesting. I'll tell you the best and work backwards.
The carrier at 670kHz is full-scale on every radio anywhere in the entire yard, no hum problem, running 2-Watts.
Once the SWR was tuned with no audio, I put a 440Hz tone on the air, and with just a nudge at the bottom of VU is is very loud on the air.
Now the downside. The best SWR (Standing Wave Ratio) I can get is 3:1.
The top of the GREEN area on the meter is at 2:1.
I think I remember those numbers correctly, but I'm on the wrong floor now and not going back down tonight.
Let it run for 2-hours and all was stable.
Tommorrow... DRIVE TEST!
So that means there is some
reactance somewhere.
It's too bad you can't tune it out.
However, I am very glad to hear
about your modulation and range
test. That is very encouraging!
Best Wishes
Bruce, DOGGRADIO STUDIO 2
It's probably that one woman down the block. She's always reacting to me. And it's never good. I think she has it in for radio.
"So that means there is some
reactance somewhere. It's too bad you can't tune it out."
Yep. However it does not necessarily mean the reactance can't be tuned out.
By adding additional capacitors on the output terminals between line and neutral, that might help bring the couplers on board capacitor bank into range and tune the reactance out.
At this point things are better than they were with the first attempt. A 3:1 ratio is not good, but not all that bad either at the power level range Carl intends to operate at. The coupler will always keep the transmitter seeing a proper load and that 3:1 vswr will not affect the transmitter or what the transmitter sees on the input side of the coupler.
Progress in the right direction! And remember, CC is a flux science and every setup will have it's own unique issues to work out.
The adventure has just begun!
RFB
This morning 10 AM CDT set out east with tone on 670kHz CC.
Three blocks later the signal was gone, not quite as good as 1680 AM with the AMT5000. But of course in the case of CARRIER CURRENT we are measuring carriage along the power line, a different technology.
It would appear that our power transformer is not bypassed in the way that would allow the signal to travel farther. It doesn't appear to be bypassed, but we gave it the chance to prove us right or wrong.
All this with 2-Watts.
SWR (Standing Wave Ratio) was worse this morning: 4:1. Last night it was 3:1. The top of the GREEN SCALE says 2:1.
Next stop.. Neutral Injection. Seat belts suggested.
Not bad for being on the hots. Usually the blocker (utility transformer on the pole for those not following along) puts a stop long before a 3 block run. There obviously is far more than just a few houses tied in on that transformer, and probably will explain why the inductance is so high and
difficult to tune out the excess reactance.
As I pointed out way early in this venture..neutral loading will be the way to go.
On to the next mission.
RFB