Have we any Carrier Current gurus in the house that might explain my observations?
I've finally gotten my Radio Systems TR-20 with matching CP-15 coupler going. Transmitter needed work - turned out to be a shorted zener diode on the 12v supply as well as both oscillator IC's (nand gate and flip-flop) bad. Plus an intermittent crystal that, after warm-up, jumped to a higher (and non-standard) frequency. Anyhow, I ordered a few more crystals, and was testing out a couple of them to compare performance.
I tried the lowest (600) and highest (800) frequencies I had crystals for. The result was that at the lower frequency of 600KHz, I had almost double the usable range when compared to 800KHz. OTOH, while 800KHz is almost hum-free, 600KHz is significantly more hummy.
I imagine the lower frequency might couple more efficiently into the power line, and/or do a better job of jumping the transformers, resulting in a bit more range, but what would account for the lower frequency also being more hummy?
I also observed that, into a dummy load, the transmitter was putting out a bit less power on 600 than on 800, though it might be that my power meter (part of a ham antenna tuner) might just not be accurate at that low of a frequency. And it's possibly also a red herring.
I am a carrier-current station but have not had a TR-20.
It is true that every electric panel coupler connection will vary wildly because of a huge number of variables in the electrical systems we feed into.
But your finding of differences into a dummy load is something else.
Luckily there are several members here who have experience with the TR-20, and eventually they will see this thread and provide input.
The hummy aspect is interesting, and I have been amazed that my system in the middle of the AM dial has had no hum problem.
Yup!
No two cases are the same!
I never thought I'd be
sitting here on 1020 kHz,
but so far so good!
I'm not on right now, but not much
hum when I was.
And Thanks for the crystal info on
the other thread, MrNaturalAZ!
Best wishes
Bruce, DOGRADIO
P.S. MrNaturalAZ - both you
and Carl hsve done very well.
I think each installation has characteristics
that are very complex. And as we know -
everything changes all the time - as the
AC line does it's thing. Just thinking about
it makes me not want to think about it.
I spent some time browsing the manual for TR-20, downloaded from Radio System's website, and there's almost nothing much about the transmitter itself as far as setup and adjustments. Everything is mainly focussed on getting the coupler configured.
There must be more technical info somewhere.
Everyone with interest in AM carrier current should have a print of two documents previously available in this website's Library:
LOW POWER RADIO BROADCASTING - JAMES R. CUNNINGHAM
CARRIER CURRENT TECHNIQUES - ERNEST G. WILSON
Perhaps the Admins will know what happened to these documents and can restore them.
They contain valuable Carrier Current information, including...
1.) The History of Carrier Current in the U.S.;
2.) An Example of Designing and Building a Coupler;
3.) A very Novel Approach to Coupling Directly, WITHOUT a Coupler!
4.) Carrier Current Transmitter Schematics.
I saw Carrier Current Techniques
on line way back when. It was
amazing.
I just fired up the LPB RC6-A last
night into a dummy load and watt
meter. 7 watts.
I'm going to try to put some kind of CC
station on here before we move.
The last hurrah for DOGRADIO in this
location.
As you probably remember, I was
building a lot of experimental
couplers. I kept changing components.
There was a 10dB RF pad between
the transmitter and the coupler.
This worked very well. 700 mW
into the AC line still went at least
1000 feet down the street and
stayed in the line.
My problem with running any kind of set-up
here is lack of space. We have stuff out all
over the place - you know - it's all part of
the moving process.
I miss the old DOGRADIO studio.
Bruce, DOGRADIO
Some things pertaining to carrier current are here:
http://www.part15.us/content/pdf-file-reading-room
The article by Wilson (found via web search):
http://home.comcast.net/~filebay1/pdf/cct.pdf
And Cunningham's article (also via web search):
http://home.comcast.net/~filebay1/low_power_radio_broadcasting_me.pdf
Good reading for a cold, dark autumn evening.
Neil
Dear CC People.
GRAB the links made available by Radio8Z.
This material will be an important part of your Carrier Current Library!
Don't regret someday not having gotten it while you can.
Neil, you found the "unfindable."
Or, at least that's what I thought
it was.
You're right - there's a lot of great
reading here.
Thank you!
Bruce, DOGRADIO
Great stuff. I've seen or already have the LPB stuff, but the others I hadn't yet. Thanks, Neil/radio8z!
After being out of commission for a bit due to coupler problems (initial symptom was blown diodes in the SWR meter circuitry - ultimately due to tiny bits of wire strands having fallen into places they shouldn't be) I've made a few more adjustments to my installation:
I'm think I've settled on 750 KHz (perhaps I can call it "Super Seventy-Five") - I'm able to get a good match with the coupler at that frequency and almost no hum.
I've elevated the power cable from my motor home to the power pedestal - not much; just enough to get it up off the ground (about a foot) to avoid capacitive losses before my signal even makes it to the power lines.
With those couple changes, and despite the fact that I am at the end of the line and on my own transformer, I get about a half-mile good quality coverage along the power line, checked with a car radio while driving down the road. Possibly a bit more for a radio actually connected to or very close to the power line (like inside peoples' houses). In the oppsite direction, where there are no power lines (so it is all free-radiation) I get a good signal for almost 1/8 mile, a noisy signal for another 1/8 mile or so, and can at least detect the presence of my signal for almost 1/2 mile away (opposite directions from the power line).
Very pleased you solved the technical breaks in the coupler and got such a good performing CC system on line.
My CC transmitter is over in the corner on the floor waiting for me to troubleshoot it since it stopped doing its thing.
There are so many projects happening here that I can't get to them all for awhile.
Keep the reports coming.
It's funny. I guess all of the Part 15
people started out with transmitting
"though the air." You would put a transmitter
on, go somewhere else, and you would hear
your programming on an AM or FM radio.
It's was a thrill back then and always will be.
Carrier Current is a thrill, too. I remember
going into my friend's house 1000 feet down
the street and getting my CC signal in their
livingroom. It was a strange feeling - because
it became quite apparent that everything was
working as it should have. No signal out on the
street. But in that living room - there it was.
My set-up is simple and runs low power.
My hat sure is off to you guys who really
know how to do it, and can feed a substantial
amount of power into the line and get real range.
Bruce, DOGRADIO