My Isotron does not use a long ground wire and it works better than the 3 meter vertical over a radial system.
My Isotron has a 2 inch long ground wire connecting the bottom ground plate to the support mast which is 1 meter in height off the ground. Then another 2 inch long ground wire attaches to the mast and then to an 8 foot long ground rod.
The Isotron itself is just under 2 meters in length. The whole thing is just under 3 meters.
The tuning was really not that big of a deal at all, though it did take more time to peak up than the ultimate loading coil with a capacitor, but once it was tuned that thing shot the signal out about 30 percent farther than the standard vertical stick.
In the winter when its foggy or snowing or during the warm seasons when it rains, that throws off the resonance a bit, as expected to any L circuit when conductive objects are placed near the circuit or stray inductance, both causing the L circuit to go off resonance.
In other words, the Isotron is far more sensitive to environmental conditions and changes than the standard 3 meter loaded vertical.
RFB
can you shed some light on what makes it perform better than a traditional base loaded vertical?
I would say that the Isotron performs better because there is nothing robbing power from it, like that encountered with the loaded vertical and the loading coil.
But in essence the standard vertical stick with a loading coil would basically be the same thing as an Isotron if the vertical stick had a cap hat on top and a ground cap at the bottom at the ground contact point.
What can I say..it just works better but the reverse to that better performance is the fact the Isotron is far more sensitive to influences which will change its resonance, more so than the vertical stick. If you enjoy peaking and tweaking often this is your puppy. It may keep you busy, but the performance will also make you smile.
RFB
My Isotron does not use a long ground wire and it works better than the 3 meter vertical over a radial system... .. once it was tuned that thing shot the signal out about 30 percent farther than the standard vertical stick.
I of course know little about the Isotron, but the 'long ground' and touchy tuning references were in relation to installing on a roof.
But as for the 30% increase in range - is that while still staying within the field strength limit?
BZZZTTTT Foul on RichPowers
There is no Field Strength Limit for AM!
This isn't Carrier Current!
under part 15.219 there is no f/s limit. the better question is will an inspecting agent allow that to pass under part 15.219? especially if being used with a kit built tx like the amt5k. and you have a long path to ground via power and audio wires, unless the whole rig is setup up on battery/solar with a wireless receiver feeding the audio all placed with tx. even if it has a GP under ir up on the roof your audio and power leads are still acting as a counterpoise to the isotron.
"path to ground via power and audio wires, unless the whole rig is setup up on battery/solar with a wireless receiver feeding the audio all placed with tx. even if it has a GP under ir up on the roof your audio and power leads are still acting as a counterpoise to the isotron."
Isn't it the same thing with a standard 3 meter stick with everything packed into the puppy hut being fed with power and audio wires even if under a ground plane up on a roof, those direct connected wires of power and audio still provide a ground path for RF.
Then even with the setup of everything packed into the puppy hut powered by battery/solar panel and wireless audio linking, there is the National Electric Code for proper grounding of masts on rooftops for lightning protection, which that means the whole thing MUST be directly connected to ground, be it through it's own long ground wire or short ground wire to a nearby known ground point on the roof.
One way or the other, there is going to be a ground path in the rooftop situations be it through audio/power wires or lightning ground path.
I say let the FCC and NEC hammer that one out.
RFB
yes anytime there are leads power, audio or ground going from an elevated location those leads radiate.
now i do agree with fry on this fact and always have, i just did not agreed on the definition (and still don't) of "ground lead".
to me "ground lead" is the short piece of wire going to a ground termination point. whether that point is elevated as is on a roof or pole or whether that lead is at dirt level.
but it would appear field agents have sided with fry on this issue.
Everything I start to think I've learned something I end up getting BZZZTTTTed!....
I'm not searching it out right now, but I thought there was a maxium feild stregth taken at a particular distance reading...
I'll get it straight eventually.
.. and then get it mixed up again
under 209 and 221 there is. under 219 there isnt.
"to me "ground lead" is the short piece of wire going to a ground termination point. whether that point is elevated as is on a roof or pole or whether that lead is at dirt level."
I agree with that as well.
"but it would appear field agents have sided with fry on this issue."
Well the longer conductive object making the ground path between the ground lead connection point at the top and the dirt below would resonate and resonate with greater effect than the intended radiator at the top.
The rules are not specific about this ground lead thing and the back and forth debates have gone on since the act. I doubt things will be clarified anytime soon but they should be in my opinion.
RFB
The rules are not specific about this ground lead thing and the back and forth debates have gone on since the act. I doubt things will be clarified anytime soon but they should be in my opinion.
Ain't that the truth! It's a very frustrating topic.
Incidentally, earlier this year I had emailed Keith Hamilton concerning a topic on the Rangemaster site in which tips for specifically "Avoiding a radiating ground" is provided; in which it actually suggest:
"If you are connected to a ground that looks like an antenna , then you are going to get radiation from the system. Design the ground so that will not radiate, or does not function as an antenna. For example a pole grounded at the base with a short "ground lead" connected from the top of the pole to the transmitter has been shown to be a solution." ( http://www.am1000rangemaster.com/radiate.html)
When I sent the following email in reference to the above:
"Just a heads up on something you may have missed during past re-editing of your website.. this appears to drastically contradict itself in this statement.. Unless I am ignorantly misreading it.."
His reply to me was: "Sorry, I’m not getting your point."
My response said: " Well, maybe I'm misreading it. It sounds to me like it's saying to attach the transmitters ground lead to the top of the pole.. But to do that would just cause the pole to become a radiating conductor, -- and that contradicts the whole subject of the article, which is; to avoid a radiating ground - right? What am I missing?"
His reply was simply "FCC agents have been passing transmitters on poles after testing them for ground radiation."
Needless to say, I was speechless. But as part15 a manufacturer he's not alone with suggesting this method. The Procaster emphasizes a diagram using a long radiating ground on the front page of it's website!
After going round and round with this problem in my own situation.. I guess I'm just going to have to go with it.. because, quite frankly, I see no other viable option whatsoever - other than to not ground the transmitter at all.
His reply was simply "FCC agents have been passing transmitters on poles after testing them for ground radiation."
Well that reply does not tell us or answer the question of how tall were those poles the transmitters were mounted to and tested for ground radiation and passed. The reply could mean transmitters sitting on a stub 1 foot off the dirt.
Interesting response though..considering who it is and what they got tagged for!
As long as the ground lead issue is not clarified the question will never get answered.
RFB
I think I'm going have an outdoor power outlet installed on the roof (or do it myself) and then simply ground the Rangemasters to the ground of the power outlet.. This is method used to install the indoor unit is installed.
I emailed Keith asking if there was any problem with this method, and he said Actually that is a good way to go, because many transmitters use the electrical ground of the wall socket. Talking house uses the wall socket for it’s grounding & there are thousands of them in operation.
The only possible problem is if the building has a poor ground.
I hope this can be a solution to having an legal install on the roof.
In relation to that ground, there's noting to say you can't cheat a little and hide a ground wire in that outdoor electrical box, attached to that center screw, running inside the PVC then exiting at ground level where you secretly install some ground radials underground.
In Fact, here's a diagram on how this could be accomplished.
