It might help to see the site - I live in one of the 1 story, WW2 era homes built for Moffet Field here: http://goo.gl/maps/oKHhk
The yard is small, there are trees and power lines all over.
I have tried the following:
1) Transmitter/Antenna on the roof (one story house) with ground running to the house ground.
2) Transmitter/Antenna on the ground (3 feet above dirt), with a 8' ground rod and a 20x20 area covered in chicken wire
3) Transmitter/Antenna on the roof connected with a long wire to the before mentioned chicken wire setup.
4) Transmitter/Antenna on the roof connected to both house and ground plane setup.
The roof installs were the best - I didn't see any difference in the grounding options when I connected them.
I am wondering if it is worth moving the chicken wire to the roof?
Once up there, is it worth grounding the chicken wire to the house or to the earth ground rod?
I think if I stick the TX on the roof with the ground plane up there, mount the antenna/tx directly to the pooper vent, then I can remain legal, yet still get my good grounding.
This is my second favorite AM antenna problem, a very limited outdoor area to try to maximize as much as possible.
I am looking forward to what people say about the situation, as I have not had any experience with elevated AM installations.
In fact, I'm only now building my first outdoor AM pole.
My first-favorite antenna problem is the indoor transmitting antenna, for those folks who have no choice.
I have a neverending stream of fun problems 🙂 I am happy to provide endless entertainment! Wheeee!
What transmitter(s) did you use?
And did you attempt to transmit with an elevated transmitter and no ground connected?
The ideal elevated install is just above a metal roof - you don't even need to connect a ground wire, the metal roof acts as a counterpoise/ground.
For your situation, I think I would try 90 degree radials on the roof (i.e., lying flat along the roof perpendicular to the antenna). They shouldn't radiate (assuming that you place them opposite each other with the same lengths) and they don't add anything to your antenna length vis a vis Part 15.
I always wanted to try 4 10' thin copper pipes, mounted 90 degrees apart, as radials. Now I can't, as I'm in an apartment. I hope to eventually post the trials and tribulations of getting my station back up, once it's actually back up to my satisfaction.
This was with the Procaster and the SSTran 5000; Regarding the 10' radials: I may give that a shot. I have the weekend to tinker.. I'll also be trying the ATU on the Talking House..
Someone mentioned that anything more than 8 radials was diminished return..
Also: my roof has a slight pitch to it; its mostly flat.. maybe a 15degree incline... is this going to have an effect on the radial?
And if an elevated antenna does not really need the ground, maybe i just drill a hole in the mast and stick the grounding strap to that. The mast is loosely attached to the pooper vent...
To avoid exceeding the total 3-meter length allowance of 15.219, ground radial wires must be designed so they will not radiate.
This can be confusing, because the purpose of the radials is to improve the radiated signal coming from the 3-meter vertical antenna.
But in fact the radials do not add to the radiated signal strength, they serve to complete the circuit established between air and ground, allowing the radiated signal to become coupled with the earth-plane-atmosphere, which increases the effective radiated field.
Perhaps others can better express what takes place and why, but let me get back to radials.
32 to 64 ground radials at least 30-feet long is the recommended minimal setup for Part 15 AM according to design engineer PhilB
I will be back for Part 2
To continue on with Carl's thoughts, sloping radials will radiate. You need to get them level somehow.
And while the ideal may be 32 to 64, 4-8 will still help a lot.
Read and print out the excellent posting from PhilB on the science of Part 15 AM Radials. That is serious text book information. And the response from Radio8Z gives good reason to believe that your limit of 10-foot radial lengths offer worthwhile hope.
I was surprised to read that you are letting go of your AMT5000, it would be my first choice for a Part 15 install, but it will be a good buy for someone who wants one.
I have thought about what words I can use to best express what I want to say about ground radials, so here goes:
I will use your length of 10-feet, so you don't need to re-do the numbers.
A minimal radial set would consist of a 20-foot horizontal wire laid flat and straight, aligned (let's say) north-to-south, with the transmitter grounded to the exact center of that length of horizontal wire. The 10-feet of radial wire north of the transmitter ground point would be out-of-phase with the 10-foot length of wire pointing south from transmitter ground. The two halfs of this radial wire count as TWO radials. If the transmitter is grounded off-center on this 20-foot length of wire, the longer length WILL radiate and be non-compliant with 15.219.
If you only had one 10-foot radial length, it would radiate, and would be in violation of 15.219, because it would increase the total radiating wire to 20-feet (antenna + 1-ground radial wire).
The two 10-foot halfs comprising the two radial wires, still being a single 20-foot length of horizontal wire, could reasoanble be called a shunted dipole (shunted meaning shorted).
All additional radials would be the exact same design, but pointing in all directions on the compass.
Each shunted dipole, or pair of ground radials, adds to the earth bonding but each one is out-of-phase and does not contribute to radiation.
The total number of radials wires MUST be an even number, because an odd numbered radial would contribute radiation and therefore violate 15.219.
This is probably confusing, but I don't know how to make it simpler.
By the way, I tried to get a good look at your location on the Goggle Map, and it looks like you live at a Seven-Eleven store.
Re: 7-11 ha! It's a block from my house. I'm in one of the little 1000sf things with tiny yard ( you should check trulia.com and see what these pathetic things are selling for... And I live in the ghetto of Silicon Valley).
Re: your explanation of radials - woot!!! Finally I get it! Thank you.