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Post by End80 on Mar 5, 2019 1:54:48 GMT
I know I had asked this on some forum somewhere, some years before, but now can't find it again. It is my understanding that the ground lead is simply an extension of the antenna until the point when it reaches actual ground... But I'm not actually certain so asking again.
With something like a Rangemaster, is there really any difference between the whip on top or a ground lead of equal length below it? - or if you employed about 48" antenna with a 48" ground lead, would that not perform equally to a ground mounted install with just a 96" whip?
Seems the last time I asked the conclusion was there really is no technical difference.. But is there?
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Post by mark on Mar 5, 2019 5:56:51 GMT
If you read this....http://lowpowerradio.blogspot.com/2012/05/low-power-am-broadcasters-can-improve.html You will have your answer.
According to this the answer to your question is YES, a ground lead not under ground will radiate and be like extending the antenna. That's why the FCC has the ground lead rule as part of the total length you can have(antenna and ground lead above ground)
When the ground lead is buried it can't radiate as EMR can't travel through the earth to radiate in the atmosphere but causes the antenna to radiate more without increasing it's length if the ground conductivity is good.
They also do nuclear tests underground for this very reason.
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Post by End80 on Mar 5, 2019 13:05:00 GMT
Thanks Mark, but that's not exactly what I meant, but it does better illustrate the question.. an exposed vertical ground lead certainly radiates just like the antenna does - So the question is does that make them both to be indeed technically the same thing? A rose by any other name..
Maybe I'd be better to ask does a ground lead radiate with the same degree of efficiency the antenna does? -Is there any difference between the conductor extending from the ground lead and the conductor extending from the antenna connector?
Or better yet: If you have a 102 inch whip antenna and a 4 inch ground lead, would that perform equally to a 102" ground lead and a 4" antenna?
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Post by station8 on Mar 5, 2019 13:07:24 GMT
Howdy Guys: I'll put my 2 cents in. Everyone knows that i do real world testing in florida.
This test was conducted :
0) Transmitters used in test a rangemaster 1000 & procaster am transmitter. A) Orginal antenna that came with the tx where used in test.
1) The tx was 6 feet off ground level.
2) Used 25 feet of 12 AWG solid copper wire with insulation on wire.
3) Ground rod in test. 4) Both tx where mounted in same location.
First test:
rangemaster 1000
I used a ground rod & the 25 feet of 12 AWG solid copper wire.
The results where 1/2 mile range with an automobile radio.
procaster
I used a ground rod & the 25 feet of 12 AWG solid copper wire.
The results where 1/2 mile range with an automobile radio.
Second test:
Rangemaster 1000.
I used 25 feet of 12 AWG solid copper wire laying on top of gnd. The result where 1/2 mile range with an automobile radio.
Procaster I used 25 feet of 12 AWG solid copper wire laying on top of gnd. The results where 1/2 range with an automobile radio.
CONCLUSION:
All i can say is this is the results that i got here in my area It could be different in other area's by how much i have NO clue
Except a educational quess.
You guy's won't know the real answer unless you do the test Where you live and post it here. I hope this give you an idea of real world test results
Happy tx
Station 8
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Post by End80 on Mar 5, 2019 14:14:35 GMT
That's cool Station8, liked hearing the real world report, however it still doesn't answer my question..
But would like to address what you just described anyway for some clarification..
First off, I'm presuming you mean your range was 1/2 mile from your transmitter, so, about a mile radius range - correct? That is about the same I was able to achieve when I lived out in the country (about 60 miles inland from where I am now in Georgia) with the Rangemaster about 10ft off the ground (on top of a mobile home grounded with #12 solid copper bare wire angled about 30 degrees and connected to a buried 4 foot(?) ground rod.
I don't understand the difference between your test #1 and #2, - You specify both test involved a six foot elevation with 25 foot of lead - I don't understand. Test 2 says the lead was laying on the ground.. ok, but then how was the lead in test 1? How can you have 25 foot of lead with only a six foot height install?
EDIT: Oh!.. I see, test 2 did not utilize a ground rod at all.. But I still don't understand what the additional 19 foot of ground lead was doing in test 1.. it would have to be semi-vertical to have any real effect, which kind of explains why the two configurations had equal results. Why so much lead for a six foot install? The excess must have been just laying on the ground for both test.. I don't get it.. kind of defeats the purpose of the test doesn't it?
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Rich
Full Member
RF Systems Engr (retired)
Posts: 112
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Post by Rich on Mar 5, 2019 14:55:45 GMT
... Maybe I'd be better to ask does a ground lead radiate with the same degree of efficiency the antenna does? ...
The conducting path(s) leading from the transmitter circuit board common bus and/or its r-f ground terminal can radiate more r-f energy than the ~3-m whip attached to the transmitter that is considered to be "the antenna."
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Post by station8 on Mar 5, 2019 14:57:23 GMT
Howdy All: Let see if i can explain in another way. 1) I had to use the 25 feet of 12 awg wire do to where the placement of the tx
Thats where are septic line is so i had to place my ground some where Else so i did NOT damage the towns septic line as well as the home line!. 2) The 1/2 mile range was the actually range i got from the tx site to A straight line out from the tx location.
3) If you look at the results in both test It did not make a difference at all with a ground rod system
Or where you had above ground system without a ground rod They both showed the same range in the test
It did NOT make a difference at all if my ground wire was in A vertical or horizontal position layout in the test.
So this tells you that in my test that above ground system did NOT
Radiate at all!.
Keep in mind if my above ground did radiate theoretically i would Had some range,But i did not have anymore range.
I hope this clear some thing up Have a great day
Station 8
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Rich
Full Member
RF Systems Engr (retired)
Posts: 112
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Post by Rich on Mar 5, 2019 15:03:47 GMT
So this tells you that in my test that above ground system did NOT Radiate at all!.
I hope this clear some thing up However the FCC has issued citations to several unlicensed AM setups after proving in their field inspections that the long ground conductor in use there contributed a substantial amount of the field strength that the FCC measured from that installation.
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Post by station8 on Mar 5, 2019 15:11:25 GMT
Howdy All: When i do testing what you guys DON'T knowknow about me.
I talk to the Fcc about what I'm doing at times
They know me and my back ground so when i talk
To the fcc agent they don't have an issue with me at all And what I'm doing.
I have enough common sense to get permission first
I hope this clears some confusion up Station 8
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Post by mark on Mar 5, 2019 16:53:06 GMT
Thanks Mark, but that's not exactly what I meant, but it does better illustrate the question.. an exposed vertical ground lead certainly radiates just like the antenna does - So the question is does that make them both to be indeed technically the same thing? A rose by any other name..
Maybe I'd be better to ask does a ground lead radiate with the same degree of efficiency the antenna does? -Is there any difference between the conductor extending from the ground lead and the conductor extending from the antenna connector?
Or better yet: If you have a 102 inch whip antenna and a 4 inch ground lead, would that perform equally to a 102" ground lead and a 4" antenna?
This I don't know. Can't find info on this in particular.
Maybe Rich knows?..................Rich?
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Rich
Full Member
RF Systems Engr (retired)
Posts: 112
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Post by Rich on Mar 5, 2019 18:24:42 GMT
If you have a 102 inch whip antenna and a 4 inch ground lead, would that perform equally to a 102" ground lead and a 4" antenna? This I don't know. Can't find info on this in particular. Maybe Rich knows?..................Rich?
The output signal of a radio transmitter is an a-c waveform. Energy appearing at its "antenna" connector and its "ground" connector are identical, except for being 180° out of phase with each other.
In free space it doesn't matter to the performance of that system configuration as to which of the two output terminals of the transmitter connects to a 4" wire called "the antenna" and the other to a 102" wire called "ground," or with the wires reversed.
Remember the old days before polarized a-c power plugs were required? A radio then could be plugged into a wall socket no matter which way the plug was inserted, and the radio worked fine either way (not OSHA safe, but it worked). Same principle.
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Rich
Full Member
RF Systems Engr (retired)
Posts: 112
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Post by Rich on Mar 5, 2019 18:56:16 GMT
... It did not make a difference at all with a ground rod system. Or where you had above ground system without a ground rod. They both showed the same range in the test. ...
The exact details of your test are not clear, but its results apparently defy physics.
You might be interested in the findings of the FCC when they tested a Part 15 AM system with and without a 20-foot "ground" conductor (see the second paragraph in the link below).
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Post by End80 on Mar 5, 2019 22:12:06 GMT
... Maybe I'd be better to ask does a ground lead radiate with the same degree of efficiency the antenna does? ...
The conducting path(s) leading from the transmitter circuit board common bus and/or its r-f ground terminal can radiate more r-f energy than the ~3-m whip attached to the transmitter that is considered to be "the antenna." That's very interesting.. not sure how to take it though.. When you say the ground lead CAN radiate more than the actual antenna whip, I'm guessing you mean only if the ground lead was longer than the antenna. But providing both were of equal length then both would have equal radiation - correct?? ..I talk to the Fcc about what I'm doing at times They know me and my back ground so when i talk To the fcc agent they don't have an issue with me at all And what I'm doing.
That further illustrates what I keep saying (in other threads), the FCC has consistently been aware of installs exceeding 3 meters, it's never the true issue and not what leads to a NOUO, it's always the range.. it is only the ground lead rule which is used as justification for the citation, since there is no range limitation rule. That has always been the established common practice of the FCC concerning enforcement of 15.219 (If the official agents handbook was fully viewable there's a probable chance this subject is addressed, and has been so for the last 50 years.
No.. I can point to no publicly available documentation that says that, but it is strongly indicated by part 15.219 historic and present use.
... It did not make a difference at all with a ground rod system. Or where you had above ground system without a ground rod. They both showed the same range in the test. ...
The exact details of your test are not clear, but its results apparently defy physics. You might be interested in the findings of the FCC when they tested a Part 15 AM system with and without a 20-foot "ground" conductor (see the second paragraph in the link below). The reason no observable change in range occurred was probably because both test were already achieving ground via the path of power (and/or audio) cabling. Numerous early 1970s documented experiments of highway departments observed this to be so.
By the way, I suspect if you shortened that 25 feet of lead to correspond with the 6 foot height of your transmitter and then connected it to your ground rod (thus vertical), you might notice an increase in range.
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Rich
Full Member
RF Systems Engr (retired)
Posts: 112
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Post by Rich on Mar 5, 2019 22:51:45 GMT
The conducting path(s) leading from the transmitter circuit board common bus and/or its r-f ground terminal can radiate more r-f energy than the ~3-m whip attached to the transmitter that is considered to be "the antenna." That's very interesting.. not sure how to take it though.. When you say the ground lead CAN radiate more than the actual antenna whip, I'm guessing you mean only if the ground lead was longer than the antenna. But providing both were of equal length then both would have equal radiation - correct?? For practical Part 15 AM setups, the r-f current flowing along the "ground" conductor with its base attached to a ground rod or buried radials is nearly uniform over the length of that conductor. The current on the 3-m vertical whip necessarily drops to about zero at the top of it — there is no metallic path upon which it can flow, above that.
The current magnitude, and the length of the conductor on which it flows determine how much e-m energy is radiated from those conductors.
For those reasons it is quite easy for the radiation from conductors connecting from the transmitter chassis/ground terminal to the buried r-f ground conductors to be significantly more than from the 3-m whip. See the graphic below.
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Post by station8 on Mar 6, 2019 0:25:31 GMT
Howdy All: let see if i can answers your questions
I have done part 15 from the late 1970 to early 1980's
I have done testing more then you guys even know
I design and built my own antennas
I have also done numerous various setups to see how it works
I even done same length of counterpoise as the hot ant
I even done various ground design and setup
I even done even various height setup
I even tried various part 15 am tx at 100 mw
I even seen things that shouldn't worked ,But it did
I even seen in setup what works for one area doesn't mean it will Work in another area
When working on a system i will call the Fcc to see if it's ok to do Because i have NOTHING to hide
When talking to the Fcc the biggest complaint i hear from them is interference Issues and they say DON'T cause any!.
The Fcc likes it when i call and talk to them and tell them what I'm doing!
I had an Fcc agent tell me that he wish allot of you other people do the Same thing that i do by calling in and asking
I give you guy's detail information better then i see you other guy's giving information
I'm not going to write a book like you guys do on these site
And DON'T do time management reading
This is where people get confused
So you guys need to keep you sentences short and sweet like the Fcc laws
It would be easier to talk to you guys on teamspeak, conference calls, etc. Then i could tell you allot more
I hope this gives you some ideas
Have a great day
Station 8
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