TheLegacy pondered: "Keeping these things in mind when pondering on that petition and since we're talking about ground and elevated transmitter these are all things to ponder upon."
On Golden Ponder.
DHR said the radials needn't be longer than the radiator. That would make it very similar to the CB ground plane antenna of yesteryear.
That would be quite manageable. Just find an old CB ground plane antenna, cut the radiator at the base and insert a loading coil.
After sifting these conversations about "long ground leads" over the years, I would like to propose that no one as yet has actually reduced the conversation to its most basic components.
Allow me.
An elevated AM 3-meter antenna with a vertical wire attached to the transmitter ground and stretching down to the earth is a very unbalanced dipole antenna.
It is unbalanced in three ways.
Being by definition a balanced circuit, a dipole antenna is mismatched to the transmitter which typically has an unbalanced RF output.
The technically proper way to match an unbalanced RF output to a balanced dipole antenna would be the use of a transformer,
If the transmitter were raised 3-meters off the ground with a 3-meter wire attached to the ground side of the transmitter and reaching to the ground and had a 3-meter antenna rising vertically above the transmitter the dipole would be balanced through being symetrical, but the total antenna length would become 6-meters, violating 15.219. Attaching the earth end of the dipole to a ground rod would extend the lower reach of the antenna another 8-feet into the earth, accomplishing another form of mismatch to the antenna.
There is no proper dipole antenna that sinks one end into the earth.
The best one could do with a dipole under 15.219 would be 1.5-meter vertical wire on the ground side of the transmitter and a 1.5-meter vertical wire on the antenna. Mounting at any altitude would be possible with no electrical earth ground.
Now that the topic of elevating an AM transmitter has been beaten to death once again how about the other part of the OP's post regarding wireless STL to the transmitter? I know some of us have done this and could comment so how about it?
I use a three conductor thermostat wire to feed my outdoor transmitter with power and audio. The RF outlput is isolated from the transmitter with a transformer to prevent a ground loop yet provide an earth and radial ground for RF on the secondary. I, personally, do not want to mess with another transmitter and receiver just to make a STL to go 40 feet so I use wire.
Neil
I put an Internet Radio (Receiver) inside a weatherproof box, with the transmitter also inside. AC power was nearby, so that wasn't an issue, but I could have gone solar. The Internet Radio picked up a dedicated, fairly high bit rate stream and fed it to the transmitter.
Worked like a charm. This is expandable to greater distances than a simple FM feeder system could be (its limit is probably 100-200 feet), as you're allowed better antennas and more power (1 watt) for Part 15 wireless.
I use Belden 5302 18 Ga 4 conductor shielded. Two conductors are +/- power and the other two are +/- balanced audio. The outer shield drain wire is terminated at one end.
Now for the LPFM we use Barix via a dedicated internet stream.
I've had very good luck using the Nyrus 5Ghz Wireless Video senders, though now I just use a direct wire connection. In the past I have also used an FM Transmitter and radio to feed the AM.
That there are some cases where the agents had no problems. Often much has to do with how nice you are to the agents, same as dealing with other law enforcement persons.
yes, the old cooperation argument.
Has anyone tested out any Part 15 rule splitting in court? I'm referring to somebody with intent to comply and was found by an inspector to be non-compliant, not a 'pirate'.
FCC agents know the difference between arrogant non-compliance and someone who is actually trying to comply. Case in point was the guy in Oregon. The more he dug in, the more the agent dug in.
OK here is where I am confused. I'm fairly new at this and only know what I read, and no doubt I need to read alot more, BUT, I've read that if I install my AMT-5000 indoors and use the 118" antenna as the antenna, and run the black ground lead to the ground terminal on my electrical outlet, where it could possibly run 150 to 300 feet through the building to reach earth ground, that that is perfectly fine and legal. So why would the ruling be different if the ground lead was terminated to the same type of ground terminal on an outdoor outlet???
I'll have no problem remembering that! Years ago when I was in the meat business and the local weights and measures inspector would come around, he would weigh the same package dozens of times, and due to the normal vibrations in the store, suich as compressors kicking on and off, the weight might vary by 0.001lbs. He would just keep weighing them and the same thing would keep happening. Then I found the answer. He wanted a 5lb. can of Maxwell House coffee then all was well! In another county I just had to give him 10 lbs. of pepperoni then I was golden. Pissed me off at first because I wasn't cheating anyone, but that's business!
.... why would the ruling be different if the ground lead was terminated to the same type of ground terminal on an outdoor outlet???
Answer: It will not be different as far as its abillty to generate electromagnetic fields (radio waves).
- Radio waves are generated whenever r-f current flows along a conductor.
- Radiation occurs whether or not such a conductor is attached to the earth at one end.
- The r-f current needed for the 3-m whip to radiate flows along the "ground" conductor connected to the r-f ground terminal or chassis of the transmitter.
- Therefore the "ground" conductor radiates for the same reason that the 3-m whip radiates.
- Longer ground conductors produce more radiation than shorter ones even though the same amount of r-f current flows on both such lengths.
Below is an illustration of these principles, using antenna engineering software:
