The company named “Radio Systems” refer to themselves as “The primary supplier of carrier current equipment,” which suggests that there are other suppliers of carrier current equipment. But no other suppliers of carrier current equipment are known, unless you can mention another supplier.
Radio Systems has only one choice, the TR-6000 30-Watt transmitter and the CP-15 20-Watt coupler, not exactly matched as to power, and not capable of the maximum 50-Watts permitted by Part 15 rules.
And here’s a question about a theoretical carrier current operation that “really travels a long distance” under ideal power line conditions. In such a case, how can the actual transmitting location of the radio station be tracked and found?
If some carrier current stations are able to cover large areas, why don’t we see more carrier current radio stations in operation?
Not as many
Theres likely not as many Carrier Currents because it takes more technical skill to setup properly.
Carrier Current Systems are also much more expensive.
Not Well Documented
In the spec sheets on the Radio Systems website the TR-6000 transmitter is listed at 30-Watts, but here in their Manual it’s a 10-Watt Transmitter…
http://www.radiosystems.com/Manuals/TR-6000%20Manual%2010-09.pdf
10
The unit is a 10 watt. I would file it as a typo on the site.
RFB
Some Answers
“And here’s a question about a theoretical carrier current operation that “really travels a long distance” under ideal power line conditions. In such a case, how can the actual transmitting location of the radio station be tracked and found?”
Not all CC stations that achieve wide coverage are using a single point TX. Some will be set up with power splitters and linear amps to continue the signal feed further down the lines, such as bypassing transformers or linking up another building.
It is only on very rare setups that the power grid is wired or bypass capacitors installed at the transformers for things like BPL, would be in place that would allow a single point TX site to cover a large area with just that one transmitter.
Either case, the originating signal source can be found by simply requesting that information from the operator/owner, which would be wise to document and keep on record every single location of repeater linear, splitter and primary location of the main TX.
The FCC uses direction finding techniques to locate RF energy sources, including a CC system. The primary TX point within its regulated limit range from the power line will be easier to find and measure simply because as the signal travels down the line, it is attenuated by that line and distance, just like how an RF field reduces its strength the further distance from the antenna.
“If some carrier current stations are able to cover large areas, why don’t we see more carrier current radio stations in operation?”
CC is a limited coverage method of broadcasting. Even loading to the neutral it is still a limited range system.
Let me try to give an example.
Let’s say you want to operate at 600khz. Do the calculation from the formula 157,000/F. The answer is 262 (261.666666–), thus 262 feet. Your signal cannot exceed 262 feet from that power line or neutral line. At the 262 foot marker, it better be in the noise floor (15uv).
Now this does NOT mean your signal has to travel DOWN the power line or neutral only 262 feet. It can travel down that power line or neutral if those lines extended 500 miles. As long as your signal does not emit off those wires beyond 262 feet your fine.
CC systems are not meant to operate like regular antenna systems. They are not meant to radiate large EM fields that need to travel a long distance away from the emitting radiator. CC is meant to “contain” the signal along a set pathway (power wires) so that the signal is more or less as close as possible to the receiver point..ie a power socket or electrical wiring in a building.
Also keep in mind that in most CC setups, it is not needed to run the transmitter at its full power output to achieve good controlled coverage. It is also required to make sure you only use the amount of power needed to obtain good coverage thus you are required to reduce the TX output to the point of good signal coverage and not excessive signal just to make it reach out further from those wires. If you need that signal to go DOWN farther on the lines, this is where power splitters and repeater linear amps come into the mix.
Hope that sheds some light.
RFB
Now Know
Good explaining, RFB, Mr. Carrier Current.
Yes, your description registers in my understanding and I want to start but have to wait until the right parts become available, probably on e-bay someday.
About the location issue, of course it can be found by professional sniffing methods, but other than that, since there is no rule requiring a part 15 station to identify itself with an announcement, it would therefore be legal to say, “Broadcasting from a very secret location extremely far away, this is Radio 560.”
Already Question
I’m already back with another question.
Yes, I understand what you said about transmitter power with carrier current…. the only reason for the allowed power range is to use only the power needed to meet the field radiation limits for the frequency being used….. which can vary also with different power line situation since power lines are not the same everywhere.
But since 50-Watts is the absolute highest power transmitter allowed (if needed), when would so much power be needed? What kind of power wiring would be so different that all 50-Watts would be needed?
Power..Who Needs Power?!
“But since 50-Watts is the absolute highest power transmitter allowed (if needed), when would so much power be needed? What kind of power wiring would be so different that all 50-Watts would be needed?”
I have yet to run into a CC system where a full 50 watts was needed to be injected onto the wiring. Although I have heard of such installs in very large buildings like a MCM Grand or 150 level apartment building and such.
In these large installations, the coupling is done at the primary AC service entry point. This wiring will be quite hefty in size, as well as it being connected to all the other wiring in the large building, creating a tremendous load the coupler must match to. Sometimes that load impedance will drop all the way down to less than 1 ohm.
In such cases, since the load is so low in impedance, it takes a lot more power to inject the signal onto that very low impedance load so that the signal is not absorbed the second it leaves the coupler.
Even with those setups, you don’t want to overload the receivers close to the coupling point…ie first floor or two of apartments, and the rest above are getting a weaker signal. So to overcome this, power splitters and repeater linear amps and added couplers save the day.
More power is also required when operating in the lower portion of the band because of the longer wavelength and overall load impedance of the grid or building wiring presented to the transmitter and coupler.
It is all a balancing act. Except there is no safety net below you.
During the summer months, my CC station operates on 1670Khz, and to achieve good coverage with a decent signal, the transmitter is set to run between 6 and 15 watts, depending upon the environment conditions at the time, such as if it rains or is a very dry day. When the ground is wet after a good rain, that power can be as low as 3 watts and cover the area with a clean signal. On the dry hot days, that power has to be turned up a bit to as much as 15 to get the same signal coverage..all while maintaining the field strength limit at the given frequency..which in the case for 1670Khz is 93 feet.
During the winter my CC station operates on 3 possible frequencies…all in the low portion of the band. 630Khz, 680Khz or 710Khz. The reason for moving from the upper band to the lower band is that during the winter months around here, we get a good amount of snow and moisture..adding to the ground conductivity factors. The snow and ice build up on the power lines like they do on any wire sticking in the air. This changes the already very low impedance to an even lower amount..so much that at 1670, it takes about 45 watts just to get about 2/3 the coverage area than I get during the summer with 6 watts. The iced up lines, snow covered lines tend to absorb that signal rather quickly at the upper portion of the band.
At the low end however, all the ice and snow seem to aid in getting the signal down the lines. And it takes about 15 to 25 watts, from a dry winter day to a wet, nasty snow covered ground day to maintain the signal coverage.
Either end of the dial, it can vary from one day to the next, and even within a 24 hour period due to the loading factors on the power lines by customers turning on their AC’s and lights and such. Same is true during the winter months..perhaps a bit more where there would be heavy loading on the grid by the use of more electricity and the sun setting earlier, meaning heaters come on sooner, more lights come on sooner etc.
I check my coupler every single day to see if the VSWR has changed due to the loading changes on the lines. When the changes do happen, it is not a wild swing in VSWR, but enough to see the difference on the meter. Usually it just takes one selection over on the 100pf capacitor knob to return the VSWR to its lowest point, which really is not that much of a difference. But it is an example of how suddenly and how often the grid changes due to loading from one part of the day to the next.
Also I move to the lower part of the band because during the winter when the ground out here is covered in snow for miles, sometimes state wide, that aids in allowing sky wave to occur at much earlier times, even before the sun has set completely. I would pick up stations I never knew where there if it was the summer time, but when winter comes..so do those out of nowhere stations! The lower part of the band is clearer during the winter months and less stations coming in from skip.
RFB
So Interesting
So every day you need to monitor and correct your CC coupling, it is not something you can do once and ignore.
How do you notify your audience that you will be changes frequencies?
Daily Checks
Well even an engineer for a licensed station checks things often, maybe not on a day to day basis, but checking and tweaking and peaking is the engineer’s whole purpose in life!! Well so it seems anyway…a lot of the devices today are so incredibly reliable and stable us engineers no longer carry around the pocket protector with the “greenie”.
My daily checks are just out of habit being in the engineering industry for so long..it has become routine. There is not a day that goes by that I do not glance at the temperature reading on the thermostat in the house, or glance at plumbing fixtures under the sink, or listen for odd sounds out of the household items like the ice box or the AC/Heater.
Usually the changes that do take place are small and really does not require any re-adjustment..but I like to see the VSWR meter always be at the 1:1 notch. 🙂
There are days though when the change is so great, that the VSWR will rise to about 1:8, sometimes into 2:1, but not often. I have developed a check schedule based on observation over the last 3 years and noting the environment conditions when the changes took place and what amount of adjustment was required. Overall, the adjustment for both ends of the band when the loading characteristics change on the power grid is still minor and usually just one turn of the 100pf cap knob is all that is needed.
As to notifying the audience about the frequency change, I have audio announcements I run prior to the change that announces the date of the change and to what frequency, giving listeners plenty of heads up time to know where to tune.
RFB
CC Coverage area
RFB,
How many miles coverage do you get from your CC system on AM 1670/lower band frequencies?
In addition, what is the general cost difference between CCAM and part15 AM?
-Travis