Take a portable and go to the 2.5 drop point, walk up to a power pole near that drop point and put the portable right up to the ground wire running down the pole. Should be able to pick up the signal, which verifies the signal is staying where it should be..on the wire traveling down the wire into every drop and into homes/businesses.
If it is not detectable at that point, the 2.5 block drop point is where the grid separates onto another grid. A repeater or bypassing would be needed to continue on to the next grid and so on.
RFB
While still transmitting at 970kHz we tried to up the power from 2 to 3-Watts, and the meters pinned and the AM band started chattering like a radiation detector. This was expected behavior and I'll explain why.
RFB had used his own LPB equipment to simulate my situation, he ran his "low band" transmitter at 970kHz (my frequency of choice) and found it could be done, if 5-Watts was not exceeded. What's going on?
Look at the LPB specs. The AM band is sliced into 3-parts, each requiring a different low pass filter in the output section:
Low = 530-830 kHz
Mid = 830-1270 kHz
High = 1270-1710 kHz
By running a low band transmitter in mid-band the filter is not correct and the transmitter becomes unstable above a certain level, in my case 3-Watts.
Designing a mid-band filter is half explained by available LPB information, but there are some details that will need to be found in the absence of official information.
To avoid stressing the transmitter I have moved to 670 kHz (low band) and am running at 3-Watts.
More power will not get you any further range. Remember CC works by near field induction and not far field radiation.
At most, with more power applied, what will happen is a much stronger near field and over-saturated receivers..not to mention exceeding the 157,000/F 15uV@30m specification. (221)
Expecting results like that from a center point radiator such as a 3 meter antenna won't happen. CC is a "wired" wireless form of radio transmission and our goal here is to keep the signal on the wire being coupled to. We want the signal to continue down the length of that wire for as far as it goes. Beyond that, requires another coupling point.
Where your 3 meter antenna signal cannot penetrate, the CC system does by delivering the signal right into the power outlets. The signal need not even be a half watt ERP off that wire and still provide a clear signal at the furthest reaches of the wire's length. What does emit off the wire must be limited to the specification called for in 15.221 and no further off that wire..ie distance from the wire, not down the length of the wire.
As I pointed out, running the TX at 970 with a lower 3rd filter is tricky and should not be done at excess power levels, and is why your TX went into oscillations and spitting splatter everywhere.
Reason why yours sputtered at 3 watts and mine didn't even sweat at 5 watts plus is because of component tolerance between the two TX's. at 10 watts my TX will sputter just like yours did at 3. Either case, both instances with both TX's demonstrated the use of incorrect LPF, which creates an
internal mismatch between the output toroid and the input of the LPF.
It all makes for excellent self teaching lessons, and the adventure has barely begun!
RFB
This morning at 8 the LPB was set at 670kHz, 3-Watts, with a VSWR of 1.5:1
This afternoon at 5 it was checked and found to have changed on its own. The new power reading is 2-Watts. The VSWR remained at 1.5:1
What is?
The bias circuit in the final amplifier adjusts itself to surrounding temperature changes. Makes sense that at 8am when it's cooler, the bias sets itself for that temperature range, then as the day goes on into the warmer temps of the afternoon, the bias will adjust itself and lower that voltage, in turn lowering the final amplification a bit.
It's working like it is supposed to, protecting that amp from over-heating.
The time to worry is when it bounces from a setting of 2 or 3 watts and jumps out to 10 or more on its own..then there is a real problem to investigate and solve.
Imagine what would happen if that amp did not have a temperature compensating bias. The amp would thermally run away and POOF..especially in an environment where air circulation lacks.
RFB
Everything recommended by RFB has worked. Everything predicted by RFB has proven true. I believe this man should consider becoming the national carrier current consultant, and I very much believe that carrier current is a remarkable and fascinating mode of putting radio on the AM dial.
This morning I set up on 570 kHz, first at 2 Watts. Then I checked every radio in the house especially to observe nearby stations at 550 and 590. I wanted to minimize the risk of covering either station, especially on cheap radios.
By the time I had those two frequencies clear of interference, I was transmitting at 1/2 Watt, with a very low VSWR, just above 1:1
Later we'll do the drive bit to see how the range compares to the best of before, which was 2.5 blocks eastbound.
Took a ride with 570 playing on the dashboard, 1/2 Watt into the neutral carrier current system. Let me describe the result by listing comparative readings over the past several days on two different frequencies:
1. 2-Watts at 970kHz has a strong signal on the auto radio for 2.5 blocks, then fades out fast;
2. 1-Watt at 870 is strong for 1.5 blocks, then becomes weak but listenable for 1 more block, then gone;
3. 1/2 Watt at 570kHz is exactly between the two results at 970. Not as strong as No. 1, but not as weak as No. 2.
Of course the drive is right along the poles carrying the neutral wire up in the air, probably 40-feet from the car.
Remember, that at the lower frequencies, it requires a bit more power to equal the same clear coverage range than what is necessary at the higher frequencies.
Since your operating between two other stations, you were wise to ensure your CC signal was not over-lapping onto their channels by adjusting the power output level for adequate coverage. In fact, that is the exact procedure once a CC system is set up, to adjust the power level only to a point where good clean coverage is obtained.
More power will not increase range, it will only increase the near field intensity and overload nearby receivers, and overlap co-channel stations.
Your doing fine and doing all the right steps in your journey through the CC world.
RFB
Hi Carl,
Your foray into CC is much appreciated. Wish I could find some gear I can afford.
Block lengths vary from town to town. How long are yours? Can you give us a more accurate range?
Can you find a frequency which won't interfere so you can pump up the power?
I would much like to try it here some day, but I get much more than 2.5 blocks (well, unless your blocks are very long) with a stick on my boat.
If I didn't have that advantage I'd try for the roof of a local hardware store, which is all metal, maybe 15000 sq. ft.
"I would much like to try it here some day, but I get much more than 2.5 blocks (well, unless your blocks are very long) with a stick on my boat."
Yes indeed! Neat thing about CC...if the frequency is open and even fairly clean of noise, Carl's 2.5 blocks will be rock solid and potentially beyond 2.5 with a radio plugged into the AC power grid. Keep in mind his field tests were with a vehicle radio and it's picking up the stronger inductive field (near field) up to the point of the change to the far field, and the signal drops...as it's supposed to.
Its a good chance that at the next nearest pole from the 2.5 block drop point, a decent portable held up to the utility pole's ground wire, will pick up the signal and may pick it up within a foot or two before that.
CC is an inductive system. At night when skywave slams 3 meter sticks, on dirt or water doesn't matter, the CC system will transmit a strong clean clear signal.
But the really neat thing with your situation Ken, is that you do indeed have one fine isolated Earth ground out there! Even for a CC system! You think that 3 meter stick on the boat does wonders...try a CC coupling netural with the return path being that same water ground system..lucky whale you! 😉
RFB
The surveyors or architects who sketched this area decided that nothing would be rectangular or level. Every square inch is at an uphill/downhill angle, the streets are based on curves and triangles, and cross streets are either very close together or very far apart.
When I did the comparative tests between the new AMT5000 and the original AMT3000 I used a measuring wheel to get accurate footage, but one day while I was skimming the sidewalk a town official drove past in his shiny black upscale car paid for with tax money, and he almost drove off the road when he saw that a civilian was doing something out of the ordinary. Before he could turn around and swing by again or call for back-up, I disappeared using a technique learned on the old "The Shadow" radio program.
We are living in a time when even the smallest bureaucrat dreams of being the next Adolf. "If you see anything, say anything."
When RFB suggested I walk up to a pole and press a portable radio against the drop wire I could just hear the "neighborhood watch" ladies on their cell phones reporting to Homesick Security.
How can a simple and honest street measurement be made? I have a plan. I am going to disguise the measuring device as a baby carriage or a dog-on-leash; an entire army could pass through the neighborhood if they used those two disguises.
We are living in a time when even the smallest bureaucrat dreams of being the next Adolf. "If you see anything, say anything."
The result of SS Engineering, or Super Social Engineering. After 10 years of media pounding fear this, fear that, suspect this and suspect that, boogie man here, boogie man there and under your bed, is it any wonder why!
Why should it be a shock that things are the way they are? Isn't that what the public wants..rights stripped away and every individual is a potential terrorist?
"How can a simple and honest street measurement be made? I have a plan. I am going to disguise the measuring device as a baby carriage or a dog-on-leash; an entire army could pass through the neighborhood if they used those two disguises."
NO..the baby carriage would still be searched, the dog on the leash would be considered as aiding and abetting, and the individual a re-incarnated Bin Laden.
But hey..you still have your choice of being back scattered irradiated or groped and grabbed. Even little Jr will get his first wonderful exposure in front of hundreds of complete strangers.
War on Tourism, War on Society, War on Freedom, War on Rights. And terrorism is the thing to be worrying about???
Wait..be right back...my kitchen sink faucet is dripping one drop every 20 seconds. Better fix it before the green police show up and haul me off to some foreign land with no right to counsel or trial or even be charged with anything.
Ain't life grand!
Pack lightly.
RFB
I can't pack lightly because the LPB2-20 Transmitter weighs about 50-pounds. I may have to stay behind. I won't abandon it!
At around 8 PM, now dark outside, I checked KDX CC, the name I will use for my carrier current station that is currently broadcasting at 2-Watts with no IDs, since the part 15 rules don't require any. Everything was fine at 670kHz, the temporary frequency being used until I build a Low Pass Filter for the permanent home at 970kHz.
One notch higher, 680, was completely blank, and another notch, 690kHz, the 1kW daytime power of the local station was now switched down to night power of 17.6-Watts, and it was coming in weakly, as usual for the low power.
Going down a notch, 660kHz was blank, but something interesting happened on 650kHz. I was hearing WSM, Nashville, TN, 50kW, almost as clearly as if it were local. But I was ALSO hearing KDX CC at about the same level but with a very noticeable "echo" effect, as if it was a reflection being bounced back from down-line somewhere.
I deliberately avoided being on 660, which otherwise would have been better than 670, because I didn't want to crowd WSM. But now it appears I may be conflicting with them anyway and wonder what you all think or suggest about this observation (?)
670 and 650 are 20Khz apart. And your wondering why your hearing a bit of the CC on 650 while operating on 670?
The 690 signal, though local, is so weak there is no intermixing going on. Obviously the 650 blaring in at night is stronger so your going to hear some intermixing going on. However that is going to be highly localized and most likely only apparent within your location.
I wouldn't worry about it since your going to be operating on 970 in the long run. But if you are worried, then drop the power level to 1.5 or lower.
RFB