Why not? All you need is conduit, flashing, and a small weatherhead. Normal everyday stuff.
Last one I did was through my cabin roof, using a marine cable fitting:
http://www.shakespeare-marine.com/connectorshow.asp?menupick=4184
Before that, years ago, I installed a wood stove pipe, triple-wall insulated class A chimney pipe. Took a little longer 😉
Follow the instructions .. it'll be OK.
From a technical point of view elevated radials will work because they provide a method by which current can be returned to the transmitter. This is necessary so the transmitter can provide current to the radiating antenna element. Think of the combination of the radials and radiating antenna as forming a complete circuit for the current.
If the radials are not to radiate they will have to be installed equal length in pairs of 180 degree separation. In this manner the currents in the radials produce fields which cancel and therefore do not produce net radiation.
The so called protective ground if run vertically does not provide a means to cancel the field produced by the current in this conductor and it will produce radiation. The authors of 15.219 knew this and hence the inclusion of the ground lead in the 3 meter limit.
So, to have the benefit of radials and a protective ground it would make sense to place the transmitter at earth level with the radials and the protective ground installed. If not done this way, even if the argument about the elevated radials is accepted by an inspector the protective ground lead can still be questioned.
Neil
The phasing strategy for balancing the radials to eliminate radiation is a great pull and will really help show the full scope of options - awesome!
One of the most ancient roofing materials has been sod. In fact, there is a brand new energy efficient home recently finished here on the island ... they had weekend open house all during May. A major portion of the roof is a garden, actually grows herbs and other plants, has a deer guard where it meets with the upper entry to keep the deer off the roof.
I'll see if I can find a photo.
So, how 'bout it? If one built a house with a turf roof, could it have buried ground radials and still meet the criteria? Chicago's City Hall has a giant roof garden. Such green roofs are gaining popularity for apartment buildings as well.
Interesting.... Verrrrry interesting, Ken.
Here on San Juan Island:
http://www.flickr.com/photos/naturalbalancehouse/5394281665/in/photostream/
Chicago City Hall:
http://explorechicago.org/city/en/about_the_city/green_chicago/Green_Roofs_.html
Apartment building:
http://www.thekitchn.com/thekitchn/gardening/nyc-event-how-to-create-a-green-roof-garden-050324
Most of them have water retention systems ... couldn't do anything but help.
The rooftop water retentive garden, seemingly an ideal grounding plane, reminds me of a long ago note here on the site asking about "water features" in landscape gardening. Something seen a lot on public television garden shows.
We should start a few experimental tryouts.
You do your roof, I'll do the back yard.
This is not a joke. My roof is all slanty so it wouldn't work, but the backyard would be perfect for a pond beneath a 10-foot pole.
Wading boots or a raft would allow transmitter care.
Wading boots? How about stepping stones ... the big one in the middle will be your pedestal for mounting the system ... 😉
Here is where my point comes in to hit everyone in the face regarding different techniques will be required form one location to another.
For some the "floating" ground radials up on a roof performs better than attaching that grid to an earth ground, and others attaching that elevated ground grid to an earth ground below works.
There is no "one way is the only way" to any of this.
Some will swear and bang tables about one method and insist this is it no other method will work stick to tradition blah blah blah (BAHH!!!)..leaving you thinking that there is no way to improve performance. I say pay no attention to that man behind the curtain. Be creative, be adventurous, and be safe about it too..but also expand your horizons and experiment with different configurations and find the one that works best. When you do find the right method and approach, tell us all about it so others can have another angle of attack to perhaps improve their setup.
We can acknowledge tradition and established methods...and continue to ride horses and buggies, or advance and find unique and better ways for the horseless carriage too.
Good luck and never throw up a wall around discovery.
RFB
RFB ... yeah ... here's an example:
http://www.public.navy.mil/spawar/Pacific/TechTransfer/ProductsServices/Pages/SeaWaterAntennaSystem.aspx
i just want to weigh in with my own anecdotal results. i just finished the semi-permanent install for my amt3000 at my studio. it is in a stripmall building with a flat roof made of corrugated metal (aluminum? steel?) covered in tar paper. i had to drill a hole through the metal roof to route my audio and power inputs. with no ground plane i got rather poor performance and had difficulty getting a high peak voltage. i attached a short wire from the transmitter ground to the metal roof (using the hole i had cut) and suddenly i was getting massively higher peak voltage (30V!). i had assumed that the power supply would limit the peak voltage to 16V but maybe that is wrong? what exactly is the peak voltage representing?
transmitter performance seemed to be pretty good. i was able to pick up the signal decently at about 300m from antenna and could faintly detect it at 500m.
my studio is near a light rail station and the tracks run parallel to my building one block over. i think the 3rd rail for the trains is causing interference which prevents better performance. when i approach the tracks i hear a high pitched noise interfering with my signal which gets strong the closer i get to the track.
These are great for VHF and above.
However for the HF and lower bands, I would just use a filled garden hose capped at each end and then passed through the coupler.
Save on the water bill!
Its just a variant of inductive coupling technique.
RFB