Ground Losses

[rfry]

Supersound wrote:
> Experimental evidence shows elevating the entire antenna
> above ground, reduces ground losses, so that a marginal
> ground system, introduces less loss. This is only logical
> since the induced current in the (soil) ground is less. The
> farther away from the antenna, the less loss.
________________

Engineering analysis shows that radiation from an elevated 3-meter Part 15 AM antenna is not confined to the ~3-meter section above the tx.

The entire length of the conducting path ("ground lead" + "ground wire" and/or flagpole/tower/whatever) from the tx chassis to the ground plane at physical earth carries the same maximum r-f current present at the bottom of the 3-meter section. And because the conducting path to the ground plane typically is longer than 3 meters, it produces more radiation than the 3-meter section above it. This can be confirmed in any good antenna engineering textbook.

The r-f current is almost uniform in the conducting path from the tx chassis to the ground plane at physical earth. And so elevating the tx and the 3-meter section has not reduced radiation toward the ground, it has increased it. The belief that an elevated Part 15 tx+antenna system has lower ground losses than one mounted on the ground is the opposite of physical reality.

Elevated Part 15 AM systems do radiate greater fields than those at ground level, but the reason is not due to reduced ground loss -- it is because the effective length of the antenna system, then, is longer than 3 meters.
--
(I keep repeating this information here because of continuing posts showing the need for it.)

//

 

[radiopilot]

Rfry,

If you follow the below to the rule.. you will see that 'unintentional radiation'.... such as elevated ground lead radiation is permissible under the rules if it's not intended to doing so when radiating using an 'intentional radiator'....


[Code of Federal Regulations]
[Title 47, Volume 1, Parts 0 to 19]
[Revised as of October 1, 2000]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.3]

[Page 676-679]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15--RADIO FREQUENCY DEVICES--Table of Contents

Subpart A--General

Sec. 15.3 Definitions.
........
(z) Unintentional radiator. A device that intentionally generates
radio frequency energy for use within the device, or that sends radio
frequency signals by conduction to associated equipment via connecting
wiring, but which is not intended to emit RF energy by radiation or
induction.
......

So that basically washes anything you say as far as elevated grounds... I posted this below in response to SuperSound also....

Radiopilot

 

[LeeSmith]

Richard:

I've been a HAM op for about 35 years. I have some very dim recollection that you wrote a few articles in various magazines a long time ago. Am I correct?

73 de
Lee
VE4ANC

 

[rfry]

> I've been a HAM op for about 35 years. I have some very dim
> recollection that you wrote a few articles in various
> magazines a long time ago. Am I correct?
_______________

Lee: I have written technical articles that have been published in Radio World both before and after I retired about 7 years ago. Some of them I posted on my website http://rfry.org .

I was an active ham op in junior high/high schools days long ago, but I let my ham license lapse when I got my 1st Class Radiotelephone License in 1959, and began working in the industry.

//

 

[rfry]

Unintentional Radiators

> So that basically washes anything you say as far as elevated
> grounds... I posted this below in response to SuperSound
> also.... Radiopilot
________________

The Part 15 text that you posted _defines_ an unintentional radiator, but does not authorize its use without limits for Part 15 AM.

Below is a quote from Part 15, Section 3. Note especially paragraphs (b) and (c).

+ + +

Authority: 47 U.S.C. 154, 302a, 303, 304, 307, 336, and 544a.

Source: 54 FR 17714, Apr. 25, 1989, unless otherwise noted.

(a) This part sets out the regulations under which an intentional,
unintentional, or incidental radiator may be operated without an
individual license. It also contains the technical specifications,
administrative requirements and other conditions relating to the
marketing of part 15 devices.
(b) The operation of an intentional or unintentional radiator that
is not in accordance with the regulations in this part must be licensed
pursuant to the provisions of section 301 of the Communications Act of
1934, as amended, unless otherwise exempted from the licensing
requirements elsewhere in this chapter.
(c) Unless specifically exempted, the operation or marketing of an
intentional or unintentional radiator that is not in compliance with the
administrative and technical provisions in this

[[Page 752]]

part, including prior Commission authorization or verification, as
appropriate, is prohibited under section 302 of the Communications Act
of 1934, as amended, and subpart I of part 2 of this chapter. The
equipment authorization and verification procedures are detailed in
subpart J of part 2 of this chapter.
//

 

[radiopilot]

Re: Unintentional Radiators

Please read between the lines...


> > So that basically washes anything you say as far as
> elevated
> > grounds... I posted this below in response to SuperSound
> > also.... Radiopilot
> ________________
>
> The Part 15 text that you posted _defines_ an unintentional
> radiator, but does not authorize its use for Part 15 AM.
>
> Below is a quote from Part 15, Section 3. Note especially
> paragraphs (b) and (c).
>
> + + +
>
> Authority: 47 U.S.C. 154, 302a, 303, 304, 307, 336, and
> 544a.
>
> Source: 54 FR 17714, Apr. 25, 1989, unless otherwise
> noted.
>
> (a) This part sets out the regulations under which an
> intentional,
> unintentional, or incidental radiator may be operated
> without an
> individual license. It also contains the technical
> specifications,
> administrative requirements and other conditions relating to
> the
> marketing of part 15 devices.
> (b) The operation of an intentional or unintentional
> radiator that
> is not in accordance with the regulations in this part must
> be licensed
> pursuant to the provisions of section 301 of the
> Communications Act of
> 1934, as amended, unless otherwise exempted from the
> licensing
> requirements elsewhere in this chapter.



Not in accordance if over these limites for AM...

Sec. 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 deomonstrated by measuring
the radiated emissions.



> (c) Unless specifically exempted, the operation or
> marketing of an
> intentional or unintentional radiator that is not in
> compliance with the
> administrative and technical provisions in this
>
> [[Page 752]]
>
> part, including prior Commission authorization or
> verification, as
> appropriate, is prohibited under section 302 of the
> Communications Act
> of 1934, as amended, and subpart I of part 2 of this
> chapter. The
> equipment authorization and verification procedures are
> detailed in
> subpart J of part 2 of this chapter.
> //
>


The technical requirements one must meet are these:

Sec. 15.15 General technical requirements.

(a) An intentional or unintentional radiator shall be constructed in
accordance with good engineering design and manufacturing practice.
Emanations from the device shall be suppressed as much as practicable,
but in no case shall the emanations exceed the levels specified in these
rules.
(b) An intentional or unintentional radiator must be constructed
such that the adjustments of any control that is readily accessible by
or intended to be accessible to the user will not cause operation of the
device in violation of the regulations.
(c) Parties responsible for equipment compliance should note that
the limits specified in this part will not prevent harmful interference
under all circumstances. Since the operators of part 15 devices are
required to cease operation should harmful interference occur to
authorized users of the radio frequency spectrum, the parties
responsible for equipment compliance are encouraged to employ the
minimum field strength necessary for communications, to provide greater
attenuation of unwanted emissions than required by these regulations,
and to advise the user as to how to resolve harmful interference
problems (for example, see Sec. 15.105(b)).


Other than the other rules for emissions and field strength... that's it... over with... We all understand rules already!

Radiopilot

 

[radio8z]

> Rfry,
>
> If you follow the below to the rule.. you will see that
> 'unintentional radiation'.... such as elevated ground lead
> radiation is permissible under the rules if it's not
> intended to doing so when radiating using an 'intentional
> radiator'....
>
>
> [Code of Federal Regulations]
> [Title 47, Volume 1, Parts 0 to 19]
> [Revised as of October 1, 2000]
> From the U.S. Government Printing Office via GPO Access
> [CITE: 47CFR15.3]
>
> [Page 676-679]
>
> TITLE 47--TELECOMMUNICATION
>
> CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION
>
> PART 15--RADIO FREQUENCY DEVICES--Table of Contents
>
> Subpart A--General
>
> Sec. 15.3 Definitions.
> ........
> (z) Unintentional radiator. A device that intentionally
> generates
> radio frequency energy for use within the device, or that
> sends radio
> frequency signals by conduction to associated equipment via
> connecting
> wiring, but which is not intended to emit RF energy by
> radiation or
> induction.
> ......
>
> So that basically washes anything you say as far as elevated
> grounds... I posted this below in response to SuperSound
> also....
>
> Radiopilot
>
Hi,

If the elevated ground is considered an unintentional radiator, then it is subject to radiation limits also. If it is an intentional radiator then it is part of the antenna system and also subject to the 3 meter rule.

Either way, the rules set limits on radiated field strength. I would predict that the elevated ground exceeds the unintentional radiator limits on part 15 AM.

Neil

 

[rfry]

Re: Unintentional Radiators

Radiopilot writes these clips:
> Not in accordance if over these limites for AM...
> (b) The total length of the transmission line, antenna and ground
> lead (if used) shall not exceed 3 meters.
and
> Other than the other rules for emissions and field strength...
> that's it... over with. We all understand rules already!
___________

Not so sure we ALL do.

My post from Part 15.1 included this: “(c) Unless specifically exempted, the operation or marketing of an intentional or unintentional radiator that is not in compliance with the administrative and technical provisions in this part, including prior Commission authorization or verification, as appropriate, is prohibited under section 302 of the Communications Act of 1934, as amended, and subpart I of part 2 of this chapter”

So no radiator may be used with a Part 15 device that does not meet the provisions of the Rules for such radiators. And you, yourself quoted the Rule that limits the radiator (antenna) length for Part 15 AM systems to 3 meters.

Part 15.1 says that that whether the radiator used with a Part 15 AM tx is intentional (a ~3-meter “whip” on a tx r-f output connector), unintentional (the radiating, conductive path leading from the tx chassis to the ground plane at physical earth, even if through a grounded flagpole/tower/billboard/whatever), or some combination of these, the total radiating length must be 3 meters or less.

//

 

[radiopilot]

Re: Unintentional Radiators

Read between the lines...please!

> Radiopilot writes these clips:
> > Not in accordance if over these limites for AM...
> > (b) The total length of the transmission line, antenna and
> ground
> > lead (if used) shall not exceed 3 meters.
> and
> > Other than the other rules for emissions and field
> strength...
> > that's it... over with. We all understand rules already!
>
> ___________
>
> Not so sure we ALL do.
>
> My post from Part 15.1 included this: “(c) Unless
> specifically exempted, the operation or marketing of an
> intentional or unintentional radiator that is not in
> compliance with the administrative and technical provisions
> in this part, including prior Commission authorization or
> verification, as appropriate, is prohibited under section
> 302 of the Communications Act of 1934, as amended, and
> subpart I of part 2 of this chapter”
>


So using that same logic... a Rangemaster or LPB or whatever certified transmitter would be in compliance if used with a ground lead over 3 meters in length not including the whip? Is this what the FCC certified these transmitters to? The compliance of any transmitter that meets the part15.219 only states 100mw, 3 meter antenna and ground lead... you are adding your 'own' interpretation to justify something that is not there!



> So no radiator may be used with a Part 15 device that does
> not meet provisions of the Rules for such radiators. And
> you, yourself quoted the Rule that limits the radiator
> (antenna) length for Part 15 AM systems to 3 meters.
>
> Part 15.1 says that that whether the radiator used with a
> Part 15 AM tx is intentional (a 3-meter “whip” on a tx r-f
> output connector), unintentional (the radiating, conductive
> path leading from the tx chassis to the ground plane at
> physical earth, even if through a grounded
> flagpole/tower/billboard/whatever), or some combination of
> these, the total radiating length must be 3 meters or less.
>
> //
>


That is your interpretation and you are entitled to anything you wish!

Radiopilot

 

[rfry]

Re: Unintentional Radiators

> So using that same logic... a Rangemaster or LPB or whatever
> certified transmitter would be in compliance if used with a
> ground lead over 3 meters in length not including the whip?
____________

That's not MY logic or statement. If you re-read my post that prompted your clip above, it says that the _total length_ of whatever is attached to the tx r-f output connector (the intentional radiator), plus whatever conductor connects the tx to the ground plane at physical earth (the unintentional radiator) together form the antenna for the Part 15 AM tx, and that such total length is limited by Part 15 to 3 meters.

//

 

[radiopilot]

Re: Unintentional Radiators

> > So using that same logic... a Rangemaster or LPB or
> whatever
> > certified transmitter would be in compliance if used with
> a
> > ground lead over 3 meters in length not including the
> whip?
> ____________
>
> That's not MY logic or statement. If you re-read my post
> that prompted your clip above, it says that the _total
> length_ of whatever is attached to the tx r-f output
> connector (the intentional radiator), plus whatever
> conductor connects the tx to the ground plane at physical
> earth (the unintentional radiator) together form the antenna
> for the Part 15 AM tx, and that such total length is limited
> by Part 15 to 3 meters.
>
> //
>


I only point out the Rangemaster or LPB as a basis of a certified transmitter for AM under the FCC which approved such units knowing full well the 3 meter whip and ground lead would be over 3 meters or more or am I the only one understanding that? Why not go to the Rangemaster or LPB site to see what they propose to do with those transmitters, surely no one is buy these transmitters to plant them in the ground like a flowerpot and a 3 meter whip!

Radiopilot

 

[SuperSound]

Re: Unintentional Radiators-Rich's Reply

I agree. The ground lead is the wire connecting the transmitter to the closest ground conductor. In the WNAR-AM case this is only inches.
See picture link:
http://www.wnar-am.com/images/1620 WITH FLAG.jpg

Is the length of the ground stake also to be included in the calculation of antenna length?
If I use a one foot ground stake, does that one foot count toward the antenna length?
Suppose the ground stake is longer?
Clearly it is intended that these transmitters can be operated more then 3 feet from an actual physical earth ground (and often are approved to do so), and still have a 3 foot antenna.
What about the case where the transmitter uses a 3 wire grounded plug. Does the entire AC ground wire length of the building also count as part of the antenna length?
The AC wireing may certainly may radiate or re-radiate. So should the length of the AC wireing also be deducted from the 3 ft. antenna length?
The ground lead from the transmitter, goes from the transmitter to the closest existing grounded conductor. This indeed is the case with the WNAR-AM transtenna.
-Rich
> > > So using that same logic... a Rangemaster or LPB or
> > whatever
> > > certified transmitter would be in compliance if used
> with
> > a
> > > ground lead over 3 meters in length not including the
> > whip?
> > ____________
> >
> > That's not MY logic or statement. If you re-read my post
> > that prompted your clip above, it says that the _total
> > length_ of whatever is attached to the tx r-f output
> > connector (the intentional radiator), plus whatever
> > conductor connects the tx to the ground plane at physical
> > earth (the unintentional radiator) together form the
> antenna
> > for the Part 15 AM tx, and that such total length is
> limited
> > by Part 15 to 3 meters.
> >
> > //
> >
>
>
> I only point out the Rangemaster or LPB as a basis of a
> certified transmitter for AM under the FCC which approved
> such units knowing full well the 3 meter whip and ground
> lead would be over 3 meters or more or am I the only one
> understanding that? Why not go to the Rangemaster or LPB
> site to see what they propose to do with those transmitters,
> surely no one is buy these transmitters to plant them in the
> ground like a flowerpot and a 3 meter whip!
>
> Radiopilot
>

 

[SuperSound]

Free speech. Use it, or loose it!

> Richard:
>
> I've been a HAM op for about 35 years. I have some very dim
> recollection that you wrote a few articles in various
> magazines a long time ago. Am I correct?
>
> 73 de
> Lee
> VE4ANC
>
<P ID="edit"><FONT class="small">Edited by SuperSound on 01/06/06 09:41 AM.</FONT></P>

 

[rfry]

Re: Unintentional Radiators-Rich's Reply

> The ground lead is the wire connecting the
> transmitter to the closest ground conductor.
> In the WNAR-AM case this is only inches.

If you acknowledge that the "ground lead" (your definition) is counted as part of the antenna length, what is the electrical characteristic showing that the conductors in series with it which lead to the ground plane at physical earth are not carrying the same current as the ground lead, and therefore also functioning as part of the radiating elements of the antenna?

> Is the length of the ground stake also to be included in the
> calculation of antenna length? If I use a one foot ground stake,
> does that one foot count toward the antenna length?
> Suppose the ground stake is longer?

A buried conductor does not function as a radiator. And the more conductors that are buried and connected (in the right places) around an AM vertical antenna, the more efficient they will be in collecting the induced r-f ground currents around the antenna, which improves system efficiency. See my earlier post on MW grounds.

> Clearly it is intended that these transmitters can be
> operated more then 3 feet from an actual physical earth
> ground (and often are approved to do so), and still have a 3
> foot antenna.

Probably you meant "meters." The practice you describe/use appears to be common, because it produces higher field strengths for the reasons I've been posting. But did the FCC intend for this to be the case? Why in Part 15 would the FCC limit power, and limit the antenna length to 3 meters? Answer: they intend to limit the fields produced. And as using elevated Part 15 systems with long conducting paths to earth ground permits radiation that exceeds those fields, does that match the FCC's intent?

> What about the case where the transmitter uses a 3 wire
> grounded plug. Does the entire AC ground wire length of the
> building also count as part of the antenna length?

Any wire connected to the tx itself can become a part of its antenna system if r-f current is allowed to flow on it. But there are techniques of controlling this, such as ferrite chokes and r-f decoupling networks.

> The AC wireing may certainly may radiate or re-radiate. So
> should the length of the AC wireing also be deducted from
> the 3 ft. (meter?) antenna length?

This is not a driven part of the antenna system, that is, it has no direct connection to the parts of the tx producing r-f current.

> The ground lead from the transmitter, goes from the
> transmitter to the closest existing grounded conductor.
> This indeed is the case with the WNAR-AM transtenna.

Not really. Electrical conditions at the top of whatever your short "ground lead" connects to are not the same as at the bottom, where it connects to something buried in the ground. If they were, that conductor (ground "wire"/flagpole/tower/whatever) would not radiate, and would not add to the fields of the 3-meter section above the tx -- which field improvement is provably true.
//