Part 15 AM Coverage Capability: Reality Check

[Tom Wells]

My own part 15 AM operates in a densely packed brick structure neighborhood in Chicago, and uses an internal leaky coax through the house, with no intentional radiator.

I realistically could be heard maybe 125 ft away, maybe 2 doors down.

I have carefully read Pt 15 Am and find no specification of "transmitter size".

I propose an output tank circuit at true earth ground and elevation, C at ground level, and L as a large vertical loop.

Alternatively, transmitter at true earth ground and elevation, with tank circuit as close-coupled lumped L and C,
arranged as grounded-end wire to attic, with horizontzal wound long helix?



This becomes not feed line, but then part of the tuning circuit proper.


Not expecting this to compare favorably with "proper" antennas, does anyone think such arrangements might radiate usefully?

How about the legality of a tank circuit of "jumbo proportions"?

If legal, very large tank circuits might give Pt 15 AMs a good grip on groundwave.



I trust Mr Cunningham's hands-on experience more than a bureau, yes.

 

[rfry]

I trust Mr Cunningham's hands-on experience more than a bureau, yes.

The FCC's rules and regulations about MW coverage relate to hands-on, measurable equipment performance determined empirically decades ago by holders of Ph.D. degrees in Electrical Engineering.

Regrettably to some, an objective analysis of your viewpoint about this topic will find that it is based more on faith and hope than on provable science and field experience.
//

 

[wkbam1690]

Apparently, the Commission has recently addressed the ground lead question:

http://www.fcc.gov/eb/FieldNotices/2003/DOC-269883A1.html

 

[Black_Shire]

Mr. Cunningham was a licensed broadcast engineer who dealt in facts, not beliefs, regarding all of the FCC's rules, including the Part 15 rules. He dealt constantly with the FCC during his broadcast engineering career, and he was a stickler for following all of the FCC rules to the letter, including the Part 15 rules.

I couldn't care less for why you have a stick up the posterior regarding Part 15 broadcasting, but I *do* care that you are trying to discourage interested would-be Part 15 broadcasters by posting unsupported assertions based on ZERO Part 15 AM experience on your part. Having installed several Part 15 AM systems myself (for my own pleasure and curiousity), I have far more experience than you do in this area, and Mr. Cunningham had far more Part 15 AM experience (measured in decades) than me. (I've had no difficulty getting 1/3 mile - 1/2 mile ranges with clear reception at 1610 kHz - 1700 kHz [in different directions] on several different AM pocket radios and Walkman receivers, just by elevating a "stock" Talking House Part 15 AM transmitter 6' -10' off the ground.)

Moreover, the successful commercial Part 15 AM radio stations that are operating across the country and have been for years (some with multi-mile ranges) are physical testimony to the erroneousness of your claims. If you don't like Part 15 AM broadcasting that's your right, but don't tell me the "stock" Part 15 AM equipment doesn't perform well when I and many others have real-world experience (as did James Cunningham, as he documented in his Part 15 AM testing) to the contrary.


-- Black Shire

James Cunningham designed and built his Part 15 AM equipment (100 milliwatt intentional radiators, Carrier Current systems, and Part 15 campus rules intentional radiators) and made measurements of their performance using professional-grade test equipment, and then published his test results so that anyone could duplicate the tests for themselves. Until and unless you do the same, your charts and plots are inferior to his real-world data that he obtained on actual, physical transmitters that he built, installed, and tested.

Do you really think that the beliefs of James Cunningham on this topic are superior to those upon which the FCC bases its AM allocations and coverage policies that, for decades of provable field experience have been shown to be accurate?

If your perceptions are correct, and show with scientific accuracy that my statements about Part 15 AM coverage capabilities are wrong, I will publicly say so here with credit to you.

And if your statements are wrong, are you willing to do the same?
//

 

[Black_Shire]

Apparently, the Commission has recently addressed the ground lead question:

http://www.fcc.gov/eb/FieldNotices/2003/DOC-269883A1.html

Yup, you can't use a long ground lead wire as they did. There are no restrictions on the length of the AC power lead or audio input lead to the transmitter, however. Some ground-mounted Part 15 AM transmitters use 30' or longer AC power and audio leads (to get the transmitter and its attached antenna "in the clear" away from trees or buildings). Some users elevate their transmitters, and the elevated antenna's longer line-of-sight combined with capacitively-coupled RF that is radiated by the AC and audio leads legally increases the transmitter's range.


-- Black Shire

 

[Black_Shire]

Heh, heh, Tom, a big kaliotron (spelling?) oscillator, eh? Where the loop conductor and the variable capacitor *are* the tank circuit, with no separate antenna. I don't know if I'd try to push the Part 15 AM definitions with that, though.


-- Black Shire

My own part 15 AM operates in a densely packed brick structure neighborhood in Chicago, and uses an internal leaky coax through the house, with no intentional radiator.

I realistically could be heard maybe 125 ft away, maybe 2 doors down.

I have carefully read Pt 15 Am and find no specification of "transmitter size".

I propose an output tank circuit at true earth ground and elevation, C at ground level, and L as a large vertical loop.

Alternatively, transmitter at true earth ground and elevation, with tank circuit as close-coupled lumped L and C,
arranged as grounded-end wire to attic, with horizontzal wound long helix?



This becomes not feed line, but then part of the tuning circuit proper.


Not expecting this to compare favorably with "proper" antennas, does anyone think such arrangements might radiate usefully?

How about the legality of a tank circuit of "jumbo proportions"?

If legal, very large tank circuits might give Pt 15 AMs a good grip on groundwave.



I trust Mr Cunningham's hands-on experience more than a bureau, yes.

 

[rfry]

Apparently, the Commission has recently addressed the ground lead question:

http://www.fcc.gov/eb/FieldNotices/2003/DOC-269883A1.html

Yup, you can't use a long ground lead wire as they did. There are no restrictions on the length of the AC power lead or audio input lead to the transmitter, however.

To Black_Shire (whoever you are):

Please provide a written citation traceable to an official FCC source to support your belief.

And PLEASE research the physics of this for yourself before you lead more people into possible FCC Part 15 AM citations.

The radiation from any/all radiators (whether they are ground leads, ground wires, flagpoles, towers, billboard steel , power or audio cables or any combination of those) that exceeds the 3-m effective radiating length defined in FCC 15.219 can subject people with such systems to FCC action.

Obviously I have no personal objection to this if you want to do so yourself, but readers of your posts here should understand what risks they might face if they follow your beliefs.
//

 

[Black_Shire]

You seem to have a problem differentiating between what the words "fact" and "belief" mean. But don't worry--I'll help you out. The Part 15.219 rules ( www.part-15.org/fcc/part15/15-219.htm ), under which the 100 milliwatt Part 15 AM transmitters are certified, read thusly:


CATEGORIES

Subpart C -- Intentional Radiators - §15.219 Operation in the band 510-1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.

(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.

(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.


Now, how long do the above rules say the transmitter's AC power lead and/or audio input lead may be? Oh, that's right--the rules don't mention AC power leads or audio input leads *at all*, let alone their allowed lengths or permitted layouts (horizontal or vertical), and that's a *fact*. Since the rules do not even mention AC power leads or audio input leads, the user is as free to mount the transmitter with its 3 meter antenna atop a 35 foot pole as s/he is to paint the transmitter cabinet pink with purple polka-dots, if s/he wishes.


-- Black Shire

Apparently, the Commission has recently addressed the ground lead question:

http://www.fcc.gov/eb/FieldNotices/2003/DOC-269883A1.html

Yup, you can't use a long ground lead wire as they did. There are no restrictions on the length of the AC power lead or audio input lead to the transmitter, however.

To Black_Shire (whoever you are):

Please provide a written citation traceable to an official FCC source to support your belief.

And PLEASE research the physics of this for yourself before you lead more people into possible FCC Part 15 AM citations.

The radiation from any/all radiators (whether they are ground leads, ground wires, flagpoles, towers, billboard steel , power or audio cables or any combination of those) that exceeds the 3-m effective radiating length defined in FCC 15.219 can subject people with such systems to FCC action.

Obviously I have no personal objection to this if you want to do so yourself, but readers of your posts here should understand what risks they might face if they follow your beliefs.
//

 

[rfry]

Now, how long do the above rules say the transmitter's AC power lead and/or audio input lead may be? Oh, that's right--the rules don't mention AC power leads or audio input leads *at all*, let alone their allowed lengths or permitted layouts (horizontal or vertical), and that's a *fact*.

It is also a fact (of physics) that all conductors providing a path to ground from the circuit board ground plane/chassis of an elevated Part AM tx will radiate -- which increases the radiating length of the antenna system beyond the 3-meter limit.
//

 

[Timewarp]

Part 15? Really?

Sounds like a bunch of tricks. Trix are for kids and so is part 15.

 

[RadioMan203]

My only question on this one may be a brain scratcher:

If you were to mount a Part 15 AM transmitter on a metal pole and you were to follow the rules of the National Electrical Code (at least the way it was presented to me in a discussion of several others) that you would need to run a ground lead from the transmitter to earth. If the pole is longer that 10 feet, what then? Can the FCC say they rank over the National Electrical Code with regards to this ground lead? Mind you, I don't have the particular verbage as it was discussed a couple of months ago, but I thought about this and I wondered if someone would have a fighting chance presenting this argument over an appearent FCC violation for a ground lead.

If anyone can provide some light on this it would be appreciated.

 

[Black_Shire]

And I fully agree with you regarding the physics.

But the 3 meter total length limit applies *only* to the antenna, its feed line (if any), and ground lead (if any). The AC power lead and audio input lead are not even *mentioned* in the rules, let alone specified in terms of any allowed lengths.


-- Black Shire

Now, how long do the above rules say the transmitter's AC power lead and/or audio input lead may be? Oh, that's right--the rules don't mention AC power leads or audio input leads *at all*, let alone their allowed lengths or permitted layouts (horizontal or vertical), and that's a *fact*.

It is also a fact (of physics) that all conductors providing a path to ground from the circuit board ground plane/chassis of an elevated Part AM tx will radiate -- which increases the radiating length of the antenna system beyond the 3-meter limit.
//

 

[Black_Shire]

This matter was settled some time ago. As reported in Chapter 7 of the Medium Wave Alliance Antenna Handbook www.geocities.com/raiu_harrison/mwa/skyhooks/chapter7.html , the FCC counts the height of a conductive support as part of the 3 meter antenna + antenna feed line + ground lead total length if the transmitter is grounded to it, so grounding a Part 15 AM transmitter to a metal pole or mast of any height puts it *way* over the 3 meter total length limit!

The AC power lead and audio input lead are not mentioned in the Part 15 AM rules, however, so mounting a Part 15 AM transmitter atop a tall *non-conductive* support and running AC power and audio leads up to it is perfectly legal. (A tall conductive support is also legal as long as the transmitter is *not* electrically connected to it in any way.)


-- Black Shire

My only question on this one may be a brain scratcher:

If you were to mount a Part 15 AM transmitter on a metal pole and you were to follow the rules of the National Electrical Code (at least the way it was presented to me in a discussion of several others) that you would need to run a ground lead from the transmitter to earth. If the pole is longer that 10 feet, what then? Can the FCC say they rank over the National Electrical Code with regards to this ground lead? Mind you, I don't have the particular verbage as it was discussed a couple of months ago, but I thought about this and I wondered if someone would have a fighting chance presenting this argument over an appearent FCC violation for a ground lead.

If anyone can provide some light on this it would be appreciated.

 

[rfry]

But the 3 meter total length limit applies *only* to the antenna, its feed line (if any), and ground lead (if any). The AC power lead and audio input lead are not even *mentioned* in the rules, let alone specified in terms of any allowed lengths.

Audio and/or power conductors leading from an elevated Part 15 AM tx/3-m antenna to other equipment and connections below can serve a dual purpose. They can convey audio or power to the tx, and also they can function as radiating conductors.

Therefore they can extend the functional, radiating length of the 3-m antenna above them, so that total radiating length exceeds the legal, 3-m length defined in 15.219 -- no matter what was the "primary purpose" of those conductors.
//

 

[Black_Shire]

That is all true, but the point is that they don't count the length of AC power leads or audio input leads.

The "stock-out-of-the-box" Talking House and TalkingSign Part 15 AM transmitters come with "wall wart" AC adapters that have 6 foot leads, and they also come with external microphones that have 6 foot leads of their own. That's a total of 12 feet of conductors for each transmitter (in addition to the 3 meter wire antenna) that radiate RF when plugged into the transmitter.

If the transmitter is elevated and the power lead and microphone lead are suspended vertically beneath it, their radiation will indeed be added to that from the 3 meter wire antenna. If more length is required, AC extension cords and longer audio patch cords (usually used to connect the transmitters to audio sources other than microphones) are called for in the instructions. Extended power and audio leads are permitted, while dedicated single-purpose ground wires are not.


-- Black Shire

But the 3 meter total length limit applies *only* to the antenna, its feed line (if any), and ground lead (if any). The AC power lead and audio input lead are not even *mentioned* in the rules, let alone specified in terms of any allowed lengths.

Audio and/or power conductors leading from an elevated Part 15 AM tx/3-m antenna to other equipment and connections below can serve a dual purpose. They can convey audio or power to the tx, and also they can function as radiating conductors.

Therefore they can extend the functional, radiating length of the 3-m antenna above them, so that total radiating length exceeds the legal, 3-m length defined in 15.219 -- no matter what was the "primary purpose" of those conductors.
//

 

[rfry]

If you were to mount a Part 15 AM transmitter on a metal pole and you were to follow the rules of the National Electrical Code (at least the way it was presented to me in a discussion of several others) that you would need to run a ground lead from the transmitter to earth. If the pole is longer that 10 feet, what then?

Good questions. Physics shows that connecting electrically grounded conductors of any kind (ground lead/wire, "lightning" ground, guy wire, "counterpoise wire," metal pole/support, audio and power conductors etc) to the ground terminal/circuit board ground plane of an elevated Part 15 AM transmitter which increase the radiating length of the 3-m section above will mean that the antenna system is functionally non-compliant with 15.219.

Can the FCC say they rank over the National Electrical Code with regards to this ground lead? Mind you, I don't have the particular verbage as it was discussed a couple of months ago, but I thought about this and I wondered if someone would have a fighting chance presenting this argument over an appearent FCC violation for a ground lead.

A Part 15 AM antenna installation where the 3-m radiator is installed indoors, or installed outdoors with its base at ground level will not have much risk from lightning damage. For those who are still concerned, they can cease operation during time of risk, and re-connect the antenna feedpoint to an electrical ground. Other approaches are to install approved lightning/r-f suppression devices in the appropriate conductors connecting the tx/antenna system with the equipment driving it.

There may be conflicts between the rules of various regulating agencies, so due care will be needed to be both safe, and legal. For example, installing a Part15 AM tx+ 3-m antenna 10, 20 or more feet above the earth along with a NEC-approved ground conductor and "ground rod" certainly will result in a radiating length that exceeds the 3-m limit defined by 47 CFR Part 15.219. The same is true for any other conductor with a connection to ground (audio/power cables, metal flagpoles, billboard steel etc).

Note also that the "NEC approved ground" may do little toward protecting an elevated Part 15 AM system from lightning damage unless the antenna output connector of the tx sees a very low impedance to that ground reference (probably not too likely).
//

 

[Black_Shire]

Yes, the elevated Part 15 AM installations are pretty much "lightning targets" no matter what one does. The transmitters are DC grounded (to bleed off static charges to Earth ground) through the third (ground) conductor in the AC power lead.

While installing an AM tower-type "Johnny Balls" air-gap lightning arrestor between the antenna base and the top of a metal support pole (or the top end of a ground lead wire running down to a ground rod) is physically possible (and legal, since there would be no physical, wired connection through the arrestor), it would probably offer no meaningful protection to the transmitter because a lightning strike would jump right down the AC power lead and audio input lead to reach Earth ground, frying the transmitter in the process.

Winding the AC power and audio input leads through ferrite toroid cores can help prevent induced currents from nearby lightning strikes from damaging the transmitter and audio equipment, but short of tilting the mast down and bringing the transmitter indoors, there's really nothing that can protect a Part 15 AM installation from being destroyed by a direct hit by a lightning bolt.


-- Black Shire

If you were to mount a Part 15 AM transmitter on a metal pole and you were to follow the rules of the National Electrical Code (at least the way it was presented to me in a discussion of several others) that you would need to run a ground lead from the transmitter to earth. If the pole is longer that 10 feet, what then?

Good questions. Physics shows that connecting electrically grounded conductors of any kind (ground lead/wire, "lightning" ground, guy wire, "counterpoise wire," metal pole/support, audio and power conductors etc) to the ground terminal/circuit board ground plane of an elevated Part 15 AM transmitter which increase the radiating length of the 3-m section above will mean that the antenna system is functionally non-compliant with 15.219.

Can the FCC say they rank over the National Electrical Code with regards to this ground lead? Mind you, I don't have the particular verbage as it was discussed a couple of months ago, but I thought about this and I wondered if someone would have a fighting chance presenting this argument over an appearent FCC violation for a ground lead.

A Part 15 AM antenna installation where the 3-m radiator is installed indoors, or installed outdoors with its base at ground level will not have much risk from lightning damage. For those who are still concerned, they can cease operation during time of risk, and re-connect the antenna feedpoint to an electrical ground. Other approaches are to install approved lightning/r-f suppression devices in the appropriate conductors connecting the tx/antenna system with the equipment driving it.

There may be conflicts between the rules of various regulating agencies, so due care will be needed to be both safe, and legal. For example, installing a Part15 AM tx+ 3-m antenna 10, 20 or more feet above the earth along with a NEC-approved ground conductor and "ground rod" certainly will result in a radiating length that exceeds the 3-m limit defined by 47 CFR Part 15.219. The same is true for any other conductor with a connection to ground (audio/power cables, metal flagpoles, billboard steel etc).

Note also that the "NEC approved ground" may do little toward protecting an elevated Part 15 AM system from lightning damage unless the antenna output connector of the tx sees a very low impedance to that ground reference (probably not too likely).
//

 

[Neil E.]

Re: Part 15 AM Coverage Capability: Reality Check Ground leads

Hello all,

I have been following this thread with interest and thought I would add a few comments.

First, regarding "ground lead", I have been professionally involved in engineering and electronics for over 42 years and have a good knowledge of the terminology and jargon that goes with this. In an electronic circuit, a ground is understood to be a common point in a circuit whether it is connected to physical earth ground or not. Battery operated devices have a ground as shown on many schematics.

If this circuit ground is extended by means of an audio cable or power cable from a remote transmitter to the audio and power source then the circuit ground has a lead length consisting of these wires and it is included in part 15.219 limits. This is just the common working definition which is well known to those practicing the art. Even if the leads are not earth grounded at the audio and power source end they are still part of the radiating antenna system since they are connected to the transmitter circuit ground and are still, by common understanding, ground leads.

In part 15 AM transmitters, the power ground and the RF ground are the same electrically within the circuit. Some, namely the SSTRAN AMT3000 provide a means to RF isolate the circuit ground on the board from the audio input external ground and the external power leads by means of inductors. Here it appears possible to have audio and power feed which would not count toward the FCC ground lead specification. Others, such as the Ramsey AM-25 do not provide this RF isolation and therefore the power and audio ground leads are included in the 15.219 limitation whether they are earth grounded or not.

A grounded mast provided for lightning protection and connected to the transmitter circuit ground is a ground lead, by commonly accepted useage, as referenced in 15.219 even though it is inches in diameter. Calling it a mast or pipe does not change its action regarding radiating RF.

I believe it best to consider the intent of part 15.219 which is to minimize the potential of interference by limiting the range of part 15 transmitters by limiting the field strength produced by these devices. Since any "ground lead" which contributes to the radiated field it, along with the antenna and transmission line, must be included in the total length requirement to achieve this end. The safest way, in my opinion, to be compliant is to mount the transmitter at ground level with the circuit ground going directly to a stake or buried radials. To radiate effectively, the transmitter needs an RF ground. There is no way to provide an RF ground to an elevated transmitter without counting its length toward the limit.

If the power feed and audio feed are adequately isolated at RF from the circuit ground and it can be demonstrated that they carry no RF current then one can probably defend a statement that they are not part of the transmitter ground and thus are not to be counted in the ground lead limit yet, if true, the transmitter will not have a RF ground to "work against".

This has been discussed all over the net on many boards many times and we now have a FCC action against an AM operator based on excessive ground length as linked a few posts above. We know this can be an issue.

Neil

 

[Black_Shire]

Neither the SSTRAN nor the Ramsey AM-25 (or indeed, any of the Ramsey Part 15 AM transmitters) are FCC Certified. The Talking House www.talkinghouse.com , TalkingSign www.talkingsign.com , and AM1000 Rangemaster www.am1000rangemaster.com are FCC Certified.

I have measured the radiation emitted by the power leads on the Talking House and TalkingSign transmitters using a Micronta Field Strength Meter. Using even a 20 foot extension cord with the transmitters' 6 foot power cords the radiation is very feeble, being barely strong enough to move the needle even a millimeter when the FSM is held 30 cm from the power lead. I got the same results from the 6 foot microphone cord. (The radiation from the 3 meter antenna, by contrast, pegs the needle at that same distance.) These transmitters may have RF chokes to keep the RF out of their power leads and audio input leads (although RF at these low frequencies is pretty hard to block completely).

If one of these transmitters is mounted atop a metal pole or mast and is electrically connected to it, the pole's length is counted as part of the antenna + antenna feed line (if any) + ground lead total length, but it is *not* counted as part of the total length if it is *not* electrically connected to the transmitter.

The Part 15.219 rules ( www.part-15.org/fcc/part15/15-219.htm ) under which the 100 milliwatt Part 15 AM transmitters are certified (I have reproduced them below) don't count the transmitters' power leads or audio input leads as part of the 3 meter antenna + antenna feed line (if any) + ground lead total length. If they did, FCC Certified Part 15 AM transmitters such as the Talking House and TalkingSign wouldn't come with 6 foot power cords but would instead have their AC adapters built right into their cabinets with the three-prong plugs protruding from the back, and they would plug directly into electrical outlets. The same is true for audio input leads--these FCC Certified Part 15 AM transmitters would not have audio input jacks for microphones and audio patch cords (the Talking House and TalkingSign transmitters both have *two* such audio input jacks and come with microphones that have 6 foot leads) if these audio leads were counted as part of the 3 meter total length.


CATEGORIES

Subpart C -- Intentional Radiators - §15.219 Operation in the band 510-1705 kHz.

(a) The total input power to the final radio frequency stage (exclusive of filament or heater power) shall not exceed 100 milliwatts.

(b) The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3 meters.

(c) All emissions below 510 kHz or above 1705 kHz shall be attenuated at least 20 dB below the level of the unmodulated carrier. Determination of compliance with the 20 dB attenuation specification may be based on measurements at the intentional radiator's antenna output terminal unless the intentional radiator uses a permanently attached antenna, in which case compliance shall be demonstrated by measuring the radiated emissions.


-- Black Shire

 

[desert_er]

One thing to keep in mind here is that the interpretation of the part 15 rules is up to the individual field inspector. The violation referenced in the earlier post was regarding an installation with *100'* of ground-lead wire. I'm sure it was apparent to the inspector that this installation was purposefully in violation of the rules. Who's to say if the same inspector would've scrutinized a residential rooftop installation with a 15' lead directly to ground? According to the Hamilton site, such installations have indeed passed an inspection and remained in operation without changes.

Do FCC rules trump the NEC? That really isnt a valid question, considering that it would still be possible to follow code by relocating the transmitter to ground level, or say, using a 1m ground lead, and a 2m antenna. Following the rules of these two regulating bodies is an "and" situation rather than an "or". Both should be taken into consideration for a given installation.

Just because a device is part 15 accepted (i.e. "real-estate" transmitters) doesn't necessarily mean that it is operating within the limits. Read the article in BERadio regarding "part 15" devices on the FM band... Most of them radiate way more than they are "supposed" to. Guess the FCC certification office needs to tighten the slack a bit. NPR is reeling over this, since most part 15 FM transmitters are in the NCE part of the band.

Part 15 transmitters cannot defy the laws of physics. Period. Certainly it can be difficult to calculate the real-world performance of these installations due the the infinite number of variables involved. I was thinkking of this thread earlier this week as I was using an HP signal generator to tune an ATU for an AM facility that I was moving. The generator put *out* 25mW, and the calculated efficiency of the feedline/ATU/ground system/soil conductivity/.225-wave tower was about 76%. This is still more than 10dB higer than a 'ground mounted' part 15. Modulated with 1000Hz tone, I took a drive and set the GPS on the dash. Signal was clear/listenable to about 1km, noisy/somewhat listenable by 2-2.5km, and by 3-3.5km was just barely perceptible or non-existent. I was able to go out to 4km in three directions, and even with the car off was unable to detect the presence of any signal.