BACK TO THE LC!
BRUCE, DRS2
The problem is the lack of proper TX termination doing the "direct" coupling method while bypassing the matching and attenuator network.
In order to get the proper match with the "direct" coupler method, there has to be a way for the direct coupler to do 4 things, 1-match the TX, 2-Isolate the TX, 3-Tune to the line, 4-tune out excess capacitance in the line.
So far, you have three constructed parts to building a whole.
Keep going! 🙂
RFB
Glad to hear from you. I wondered
where you went. You must have been
busy.
Yup! I'll keep messing with it.
I have to say, it is A LOT of fun,
and I'm learning a lot.
Everything will be fine as long as
the transmitter doesn't blow up
into orbital space, and actually,
I'm not gonna let that happen.
Best Wishes,
Bruce, DRS2
"Glad to hear from you. I wondered where you went. You must have been busy."
Indeed. Going from one tower site to another (post winter season maintenance), especially when the distance between sites is as much as 300 miles, well that does tend to keep one out of reach for a bit! No such thing as freebie wi-fi hotspots out in the middle of nowhere! 😉
Right now I am sitting in a small hotel room using another engineer's laptop to check in.
Yep, this home brew coupler is going along fine. Your learning quite a lot with it and finding out already what works and what won't work. But the neat thing is that you are so close to having a complete coupling system, one that provides both proper TX matching and isolation and also provides a means of variable coupling to the line side. This will be necessary as the line side will change it's inductive loading effects on the coupler output side as loads change throughout the day and night.
What you need in between the LC section and the output is a means to measure VSWR on the line side. A VSWR circuit will go between the coupler output and the capacitor/inductor/fuse set. From there it connects to the line..be it neutral or one of the hots. If you want to couple to both hots, simply build a second capacitor/inductor/fuse set for the other hot line.
I have a complete manual for the TCU-30 coupler, once I get my scanner working I will make a PDF of it and provide that to the Part 15 forum library resources. Once you see the schematic of that commercial coupler, you will be quite surprised at how close your own home made coupler is to one such as a TCU-30.
Again, all that is missing is a means to measure the VSWR on the line side. Through a wafer switch, you could also make that VSWR circuit measure the TX side and make the VSWR circuit a dual function system. It could help you tune to the line side, as well as monitor and ensure the constant 50 ohm load to the transmitter.
Please Please Please be careful with this direct coupling approach, particularly working with the hots, and even with the neutral. Safety first and foremost!!
That advice goes to anyone thinking about working with Carrier Current and the electrical systems. It's so easy to overlook something by mistake. Sometimes the excitement and rush to fire it up can bite you back with one heck of a zap!
RFB
First, I can't thank you enough
for the information.
And I am being very very careful.
There are several more things I
want to try.
After all of this excitement trying to
make this thing operate, something
struck me.
I AM AFRAID this might be a major question
and/or problem. (With no real answer.)
A while back, the power meter on the side of
our house was removed (by the local utility)
and was replaced by another kind of energy
measuring system.
There is now a unit in our basement that measures
our electrical power expenditure over the required
time, and then apparently transmits this data out
of the house by RF.
The story I have on this is, that somebody drives
by in a local utility truck with a compatible
receiver and their device tells them how much
the power bill will be.
So I'm sure you know what I'm thinking.
And there is no real way to know - will the
CC operation interfere with the utility
wireless "power meter?"
I'm almost laughing now. What if I get this
CC thing running and then a month later I
get a power bill for three hundred billion
gozillion dollars? I don't have three
hundred billion gozillion dollars. That
would be a problem.
I'm sure there is really no answer to this
question. Every house would be different.
So, if you want to ponder that, and get back
to me, that would be OK. But don't sweat it,
because there may not be an answer to this
question.
In the meantime, as you're servicing all of this
stuff in this wide area, be safe and
(I'm not a religious man, but) Godspeed RFB!
Bruce, DOGGRADIO STUDIO 2
Godspeed is faster than radar so not to worry.
Good question about carrier current messing with electric billing methods.
Maybe it will register as "No Electric Usage."
Yeah, RFB is servicing radio
stations - as you know.
All that driving and unexpected
stuff that you could find when
you go into a station. I've heard
a lot of stories from my friends
in the business. Imagine finding
a major problem after driving 300
miles...
Wouldn't that be great if "CC/utility
measuring thing" had the result that you
mentioned. Carl Blare humor. I wish
you could bottle it and sell it.
Everywhere.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2
Our city switched to Automatic Meter Reading a couple years ago. Not all but most meters have been replaced.
The electric and water meters have data transmitters which are received by neighborhood collection receivers, about 30 citywide. These collectors retransmit the data to central collecting receivers, 3 at key points. From there the data is transfered over fiber to the city Utility Billing office.
The system uses frequencies in the gigahertz range. So far there's been no noticable interference to or from the meter system. Most likely your system uses similar frequencies so interference shouldn't be a problem.
670kHz CC is on its last days while we watch for UPS with the parts for the permanent move to 970kHz. We are running 2.5Watts and the signal radiates out to about 200-ft from the powerline, close to the 238-ft limit stated by RFB (by memory).
We have found that neutral injection maintains very stable settings, the SWR never needs to be re-adjusted. Readings are taken in the morning and evening.
Most of the time the SWR is 1:1.5, although once following a heavy rain it went to 1:1.75, but could not be adjusted any lower.
RFB forecast that with hot-side coupler connection the SWR needs to be re-adjusted several times a day and requires silent carrier, which can be a real chore for a station that feeds several transmitters and a stream, but with neutral injection that is not an issue/
Thank you MRAM, that is a comfort to me.
And Carl, your CC is doing great! It's a
major accomplishment.
I'll be back.
Bruce, DRS2
Last Tuesday the temporary CC operation, 2.5Watt on 670kHz, shut down while we prepare to convert the transmitter for its permanent home at 970kHz. But life without CC is like trying to get by after the favorite dog runs away. I re-installed it for a Second Temporary Life.
This time we are doing 1Watt at 570kHz, with only one guard band on either side. The SWR is 1.75:1
Now life is wholesome again and I don't need to go to church; this IS church with towers, antennas, glowing lights and mysterious signals in the night.
You really need to find yourself a decent FIM or something to measure with. At 570 on 1 watt your lucky if that signal is reaching the previous drop off point simply because the lower frequencies require a lot of juice to shove down the line.
Radio receivers with S meters don't tell you the real story, nor does driving around. Start hunting for a used IFR or other, hook it up and you will see what I mean.
RFB
Because I am in this thing for real and love the combined thrill of air radiation and powerline transmission, I accept and appreciate your advice to begin assembling the test array needed to know and control what is actually happening.
Part of the pleasure of low power life is the building of the system and the improvement of the component parts.
Perhaps tonight after dark I shall boost the power to 2Watts at 570kHz just for the night.
Today the "testing" is being done by checking several house radios to make sure that the neighbor frequencies are not being interfered with.
Too lazy to drive anywhere, too shy to walk around with a portable.
EXCEPT THAT THIS IDEA JUST POPPED UP FOR FUTURE FIELD BEHAVIOR:
The way to "blend in" and appear to be official and not suspicious is to wear a yellow orange safety vest with a white hard-hat and get out in the street with meters. Maybe even some orange safety-cones.
Using the various radios as a general guide to ensure neighborly manners to co-channel located stations is great on your part. If you do intend to use a radio receiver with an S meter or modify one to have an S meter, when you have the CC system verified have the tech give you their field strength reading at the 157k/f point and note your radio's S meter position as well as the radio's physical position etc.
Then care for that radio like you would that transmitter because that radio will be your referencing base as to what the system is doing.
Just like the steady patience you had to obtain CC gear, the opportunity to obtain a decent FS or coms analyzer will come around too!
RFB
Overnight the 570kHz temporary transmission went out as planned with 2Watts, then at daylight the power went back to 1Watt. Keeping the flame low to avoid messing with nearby stations.
Something interesting, while studying the rules, noticed 15.113 Power Line Carrier Systems. This section describes the technology for power companies to use carrier current for controlling their own system, and specifies the range from 9kHz to 490kHz, using "the minimum power possible to achieve the objective."
Of note is that 15.113 is in the section "Unintentional Radiators" whereas the AM CC rules, 15.221, is under "Intentional Radiators." I am not sure I understand the logic for this difference,