Because they don’t know the words…..
Yeah that was a terrible joke I know, you know what else is terrible?? Hum on an otherwise clean sounding AM CC signal. I am trying to find the cause.
Because they don’t know the words…..
Yeah that was a terrible joke I know, you know what else is terrible?? Hum on an otherwise clean sounding AM CC signal. I am trying to find the cause.
What i have tried so far: replaced the jumper behind the L + R audio inputs that bypasses grounding through the power supply, tried a different audio cord and different inductor settings.
I was able to reduce the hum but not eliminate it.
The next thing to try i guess is the double extension cords RFB mentioned.
We do not have an extra 220 v outlet here otherwise i would try what Radio8z mentioned. The only 220v lines here are the water heater,stove and clothes dryer.
And i just thought about this, perhaps i should try a different music source as well, since the computer i use for automation is on the same line as the extension cord but on separate outlets.
Signal strength?? Sounds strong here in the house but i have not had a chance to try it outside away from the house. Maybe tomorrow.
Continued from http://www.part15.us/node/3186
AM humming bird
You might have a “ground loop”. You can get a ground loop eliminator at “The Shack” or other places, or you can get audio cables with small transformers built into them that work too. Happy hunting!
Right on the mark
Rlkocher,
Your exactly right it is a ground loop.
I tried removing the audio cord and as soon as i unplugged the cable from the audio out on the computer the hum was gone.
Plugging the same cord into my Android tablet pc confirmed this. The Android doesn’t use an AC adapter unless your recharging it so it was on battery power when i tried this experiment.
So it looks like i need to look into a ground loop eliminator.
Well as you can see it is late and cold so i didn’t drive around or walk around the park to get a signal report but i did go out to my minivan and was able to hear my CC signal mixed with CKLW 800 am. By day you can’t hear CKLW but by night it is almost the loudest station on 800 AM. My minivan is parked about 4 feet from the house.
So i am on the right track here. We will see maybe tomorrow.
RF Return Path
What are you using for the RF ground return path?
In mobile home situations, it is often difficult to find a good return path that is isolated. Most situations the cold water pipe is a good choice by connecting at the pipe right at the point where it sticks out of the ground. Usually piping from that point is the non-conductive flex hose so that provides the isolation you need.
One crucial point regarding the return path. It must be as short as possible! Two reasons for this. 1 – Prevent the return path lead from becoming the radiator. 2 – Provide the shortest possible return path back to the coupler or TX’s ground point which increases coupling efficiency onto the power lines and increases down-range signal induction…IE the signal will travel further down the lines.
Since the goal here is to cover the park parameter, and your working with the 100mW level, there may be more than one return path technique that can be used here without having to dig up the ground or slam a bunch of ground rods into the dirt.
Look for a ground rod somewhere near the utility meter box. There should be a grounding wire coming from that meter box and connecting to a ground rod. This is the power grid service drop Earth ground which will be directly connected to the neutral buss inside the meter box, or at the primary breaker just below that meter box…NEC code.
Once that is located, check for continuity between that ground and the cold water pipe where it comes out of the ground. If you get no continuity reading between these two points, you have it made and the cold water pipe will serve as an excellent isolated return path for the signal, and since that cold water pipe will run all over the park grounds several feet below the surface, that will create a very large ground “footprint” below the surface which will “grab” more of the signal to complete the RF circuit path, and ensure the signal has a good return path anywhere in the park.
Portables should not have any problem picking up the signal within the park grounds. With formula in hand (157,000/f) the maximum distance away from the park grounds (outside the park parameter) is 196.25 feet. If you need to adjust this, simply reduce the number of turns wrapped around the extension cord to “loosen” the coupling a bit. Or you can install a TX with a power adjustment and control the signal level that way.
Operation in this configuration falls under 15.221 and 15.209 for spurious.
With the 100mW transmitter as the source, I doubt there will be any need to adjust that signal level at all. And don’t panic if the signal reaches a little beyond 196 feet outside the park parameter. Even if your signal couples and travels along the power lines outside the park, as long as that signal does not exceed 15uV at 196 feet off ANY line carrying your signal, your perfectly fine. And trust me, if that signal is 16uV or even 50uV the FCC is not going to frown at that. If anything they will be impressed, sit and chat with you for a bit and go on to their next “bigger” fish to fry.
So if your signal travels down the power lines 5 blocks or 5 miles, it cannot travel off those wires any farther than the calculated distance for your operating frequency. Someone with a radio will be within 196 feet of that power line somewhere, be it a portable, car radio or a radio plugged into the power outlet.
Keep us updated on your progress!
RFB
CCAM/CCFM Question
Since I’m on CCFM what is the maximum signal limit for CCFM On 92.3 Megacycles?
CCFM
“Since I’m on CCFM what is the maximum signal limit for CCFM On 92.3 Megacycles?”
The same limit applies…250uV/m @ 3 meters from the antenna, leaky coax or power line.
There isn’t a specific field strength at a given distance based on frequency in the FM rules…just 250uV/ @ 3 meters from the radiating element.
Just out of curiosity, how are you confirming that FM signal is actually traveling down the power lines and not just radiating from a conduit or other section of metal in and around your coupling point? Have you checked for the signal at a power pole or another home some distance from the TX point to make sure its actually traveling down the lines?
I ask this because for VHF signals above about 50 Mhz it takes quite a bit of power and special coupling to shove that signal down the lines where it usually ends up being absorbed rather quickly within a short distance along the lines.
RFB
i have checked the power lines
i have checked the power lines it travels down the power line i have checked it and i am sure of it.
Rare Surprises
“i have checked the power lines it travels down the power line i have checked it and i am sure of it.”
On some grid systems you can luck out on both CC AM and CC FM easily without much difficulty. Perhaps in your case ABM, you hit the lucky number!
RFB
vertical and cc AM
I need to consider trying both Carrier Current and a vertical antenna.
Since i have a sstran and talking house both, i could use the TH for a vertical antenna and the sstran for carrier current.
Carl gave me an idea a while back, we have a small flower bed here about 2 1/2 feet deep by 10 feet long. There should be enough room there to mount the vertical and perhaps lay down some type of metal for a ground plane just under the soil.
Now the odd shape of the flower bed would probably make my signal a bit directional and being that the flower bed is right in front of the house the siding on the home might cause some refection back towards the antenna, but considering i am having trouble with the CC AM it might be nice to have a back up signal to put out there with a vertical.
That flower bed is the only place we can dig in.
Edit: if it seems that i am all over the place, then you’ve made a good observation. I am bored and in the mood to tinker. I get like this around the Winter months. I am just try to keep myself busy.
CCFM Coverage
the coverage for my station is about 80-120 households w/Average 3 to 4 people per household so it serves about 360 people on an average day.
whether its CCAM Or CCFM if you have the transmitter coupler and ground in a good spot of your household and you’ve tested the frequency works best for you. you will hit the lucky number like me
At One Time
I had a CCFM station back in Texas, Odessa specifically. Out there finding a good ground is like a knat in a tornado, a fight all the way. There is a very hard rock substance under the soft dirt, which can be a few inches to a few feet, called “Caleche” and is not by any sense material good for a even a poor ground conductivity factor. I had to use 5 ground rods clustered together just to get a semi-decent ground.
The FM signal covered all of West Odessa and about 6 blocks into Odessa proper. The AM covered the whole area.
But finding that good ground was a nightmare.
Frequencies were 95.5 and 107.7 and 1670.
RFB
Rain Delays Radio Work
Need i say more?? Would be nice if it was snow.
Happy Holidays
PVC Everywhere
RFB,
It would appear using the cold water pipes for ground would be out of the question, that is pvc from the meter by the road to the where it comes up out of the ground under the mobile home.
What is sticking up out of the ground is basically an “L” shaped piece of metal pipe.
As for the ground rods, in some counties in Kentucky the Electrical Codes differ. One county i lived in required three ground rods 6 feet apart for a mobile home. The county i am in now 2 ground rods 6 feet apart are acceptable.
After looking for at least an hour i was unable to find the ground rods. But they must be close to the meter base which in this case holds two meters, one for my house and one for the neighbors.
The meter base is at least 50 feet from where my sstran is located in the living room.
In the end, i see my sstran being moved closer to the corner of the house closest to the meter base for grounding. Last night was sort of a test run just to see if i could get a decent ground using the cable outlet in the living room. The ground wire was just too long .
Just to give a better idea of what i am dealing with here, i will include some photo’s of the meter base and cable. I know this CC AM should work, considering i used to run a Talking House on the indoor antenna and could hear the station 1/3 of a mile out and louder at certain intersections with power lines on each corner.
One area the signal jumped out of the noise like i was sitting in front of the house. So we know some kind of coupling to the power lines is taking place.
First things first, i need as RFB said, a short run to a good ground. That looks like it will be my biggest challenge.
Challenge
“a short run to a good ground. That looks like it will be my biggest challenge.”
Establishing a good isolated ground return path for CC IS indeed a challenge even with a coupler like a TCU-30. Then again same is true for a 3 meter stick. Without a decent ground it doesn’t work too well.
The “L” shaped metal pipe might be the spot to connect for ground.
RFB