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FCC response to Part 15.219 3 meter rule

R

radiopilot

Ok fellows, last week after all the posts regarding what is legal or not, I posted this hypothetical installation to the FCC Office of Engineering and Technology in Washington, D.C., same office that said the 'kits' were legal... anyway this is the response, doesn't mean everyone's installation doesn't meet the Part 15.219 (b) rule, just be aware that if you have the transmitter attached to a metal tower, metal pole, etc. of any significant length you may have a problem... I will be correcting my transmitter mount accordingly.




"----- Original Message -----
From: Generic Office of Engineering Technology
To: [email protected]
Sent: Monday, January 09, 2006 1:22 PM
Subject: Response to Inquiry to FCC (Tracking Number 670631)



Inquiry:

I have a Part15 compliant AM transmitter to the Part15.219 rule... The transmitter is 30 feet high mounted on a metal pole, the 3 meter total antenna including 3 inches of ground lead is attached to the metal pole (30 feet long) mounted to the ground (elevated ground), attached to the pole is 64 radials, each radial 25 feet long in a spiral from the pole... the input to the transmitter is 100mw... is this legal in the FCC rules? Am I violating any Part15 rule by mounting the transmitter 30 feet high? Is the pole radiating any RF outside the 3 meter antenna? Would an FCC inspector disaprove this installation? Should I have this installation inspected prior to operating if all the Part15 rules are adhered to, ie. no interference, no harmonics, no complaints from neighbors or licensed broadcasters? I have pasted the Part15.219 rule for antenna and power requirement for reference.

Thank you.

PART 15--RADIO FREQUENCY DEVICES--Table of Contents Subpart C--Intentional Radiators 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.

Response:
1) No, but connecting the ground lead to a 30 feet metal pole is a violation.
2) The pole can not radiate at all.
3) Yes, this transmitter will not be approve by an FCC inspector.
4) You may not install this transmitter as describe."


I then posed this question regarding some installations as seen on various websites and discussions here on this board and others, again the FCC believes it does not meet the rule if done as described or similar and having a certified transmitter or not doesn't make a difference according to them, of course each
FCC field office will respond differently.



"----- Original Message -----
From: Generic Office of Engineering Technology
To: [email protected]
Sent: Monday, January 09, 2006 2:50 PM
Subject: Response to Inquiry to FCC (Tracking Number 670631)


---Reply from Customer on 01/09/2006---

These installations are currently being approved by field agents and the transmitter manufacturers is advising to install these AM transmitter in this fashion and have been operating for years in this manner. Please see the attached website for the manufacturer as reference and please indicate why my installation would be any different?

I believed that the 3 meter antenna/ground rule was only to the attach point of the 'true ground' and clipping the 3 inch ground lead to a pipe, ground rod, heavy gauge wire to ground rod, or metal pole was sufficient as the AM transmitter needs the ground to complete the circuit? Thank you.


Response:
This is not legal per Section 15.219(b). We can not approve this installation as
you describe. Please contact FCC Enforcement Bureau (EB) if you have any additional
questions. The website for (EB) is: http://www.fcc.gov/eb/
______________________________________________________________________
1) No, but connecting the ground lead to a 30 feet metal pole is a violation.
2) The pole can not radiate at all.
3) Yes, this transmitter will not be approve by an FCC inspector.
4) You may not install this transmitter as describe.


Do not reply to this message. Please select the Reply to an Inquiry Response link from the OET Inquiry System to add any additional information pertaining to this inquiry."



Please, let's be civil regarding this, I didn't want to post this, but thought I'd be helping my fellow part15 broadcasters avoid any issues with the FCC....

Thanks,

Radiopilot
 
I must agree with this FCC office and rfry on this one. The counterpoise must not radiate any signal--only the 3 meter antenna plus ground lead (3 m total length) may radiate. (Yes, I know some individual FCC Field Agents do "pass" such "whip and mast" installations, but we're taking pot luck.)

This is not as bad as it sounds. For ground-mounted installations, geometrically symmetrical (non-radiating) radial wire systems or copper mesh grids will greatly reduce ground losses and increase the fraction of power that is radiated by the antenna/ground lead.

For above-ground installations such as on building rooftops, any horizontal wire or wires (either elevated or lying on the roof) could serve as a ground plane. As long as the wire or wires is/are geometrically symmetrical with respect to the antenna and non-radiating, this should also pass muster with the FCC. The simplest installation of this type would be a single wire running across a roof, with the transmitter/antenna mounted in the middle and the ground lead connected to the center of the wire. -- JasonW

> Ok fellows, last week after all the posts regarding what is
> legal or not, I posted this hypothetical installation to the
> FCC Office of Engineering and Technology in Washington,
> D.C., same office that said the 'kits' were legal... anyway
> this is the response, doesn't mean everyone's installation
> doesn't meet the Part 15.219 (b) rule, just be aware that if
> you have the transmitter attached to a metal tower, metal
> pole, etc. of any significant length you may have a
> problem... I will be correcting my transmitter mount
> accordingly.
>
>
>
>
> "----- Original Message -----
> From: Generic Office of Engineering Technology
> To: [email protected]
> Sent: Monday, January 09, 2006 1:22 PM
> Subject: Response to Inquiry to FCC (Tracking Number 670631)
>
>
>
>
> Inquiry:
>
> I have a Part15 compliant AM transmitter to the Part15.219
> rule... The transmitter is 30 feet high mounted on a metal
> pole, the 3 meter total antenna including 3 inches of ground
> lead is attached to the metal pole (30 feet long) mounted to
> the ground (elevated ground), attached to the pole is 64
> radials, each radial 25 feet long in a spiral from the
> pole... the input to the transmitter is 100mw... is this
> legal in the FCC rules? Am I violating any Part15 rule by
> mounting the transmitter 30 feet high? Is the pole radiating
> any RF outside the 3 meter antenna? Would an FCC inspector
> disaprove this installation? Should I have this installation
> inspected prior to operating if all the Part15 rules are
> adhered to, ie. no interference, no harmonics, no complaints
> from neighbors or licensed broadcasters? I have pasted the
> Part15.219 rule for antenna and power requirement for
> reference.
>
> Thank you.
>
> PART 15--RADIO FREQUENCY DEVICES--Table of Contents Subpart
> C--Intentional Radiators 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.
>
> Response:
> 1) No, but connecting the ground lead to a 30 feet metal
> pole is a violation.
> 2) The pole can not radiate at all.
> 3) Yes, this transmitter will not be approve by an FCC
> inspector.
> 4) You may not install this transmitter as describe."
>
>
> I then posed this question regarding some installations as
> seen on various websites and discussions here on this board
> and others, again the FCC believes it does not meet the rule
> if done as described or similar and having a certified
> transmitter or not doesn't make a difference according to
> them, of course each
> FCC field office will respond differently.
>
>
>
> "----- Original Message -----
> From: Generic Office of Engineering Technology
> To: [email protected]
> Sent: Monday, January 09, 2006 2:50 PM
> Subject: Response to Inquiry to FCC (Tracking Number 670631)
>
>
>
> ---Reply from Customer on 01/09/2006---
>
> These installations are currently being approved by field
> agents and the transmitter manufacturers is advising to
> install these AM transmitter in this fashion and have been
> operating for years in this manner. Please see the attached
> website for the manufacturer as reference and please
> indicate why my installation would be any different?
>
> I believed that the 3 meter antenna/ground rule was only to
> the attach point of the 'true ground' and clipping the 3
> inch ground lead to a pipe, ground rod, heavy gauge wire to
> ground rod, or metal pole was sufficient as the AM
> transmitter needs the ground to complete the circuit? Thank
> you.
>
>
> Response:
> This is not legal per Section 15.219(b). We can not approve
> this installation as
> you describe. Please contact FCC Enforcement Bureau (EB) if
> you have any additional
> questions. The website for (EB) is: http://www.fcc.gov/eb/
>
__________> ____________________________________________________________
>
> 1) No, but connecting the ground lead to a 30 feet metal
> pole is a violation.
> 2) The pole can not radiate at all.
> 3) Yes, this transmitter will not be approve by an FCC
> inspector.
> 4) You may not install this transmitter as describe.
>
>
> Do not reply to this message. Please select the Reply to an
> Inquiry Response link from the OET Inquiry System to add any
> additional information pertaining to this inquiry."
>
>
>
> Please, let's be civil regarding this, I didn't want to post
> this, but thought I'd be helping my fellow part15
> broadcasters avoid any issues with the FCC....
>
> Thanks,
>
> Radiopilot
>
 
> Ok fellows, last week after all the posts regarding what is> legal or not, I posted this hypothetical installation to the> FCC Office of Engineering and Technology in Washington,> D.C., same office that said the 'kits' were legal... anyway> this is the response, doesn't mean everyone's installation> doesn't meet the Part 15.219 (b) rule, just be aware that if> you have the transmitter attached to a metal tower, metal> pole, etc. of any significant length you may have a> problem... I will be correcting my transmitter mount> accordingly.> > > > > "----- Original Message ----- > From: Generic Office of Engineering Technology > To: [email protected] > Sent: Monday, January 09, 2006 1:22 PM> Subject: Response to Inquiry to FCC (Tracking Number 670631)> > > > > Inquiry:> > I have a Part15 compliant AM transmitter to the Part15.219> rule... The transmitter is 30 feet high mounted on a metal> pole, the 3 meter total antenna including 3 inches of ground> lead is attached to the metal pole (30 feet long) mounted to> the ground (elevated ground), attached to the pole is 64> radials, each radial 25 feet long in a spiral from the> pole... the input to the transmitter is 100mw... is this> legal in the FCC rules? Am I violating any Part15 rule by> mounting the transmitter 30 feet high? Is the pole radiating> any RF outside the 3 meter antenna? Would an FCC inspector> disaprove this installation? Should I have this installation> inspected prior to operating if all the Part15 rules are> adhered to, ie. no interference, no harmonics, no complaints> from neighbors or licensed broadcasters? I have pasted the> Part15.219 rule for antenna and power requirement for> reference. > > Thank you.> > PART 15--RADIO FREQUENCY DEVICES--Table of Contents Subpart> C--Intentional Radiators 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.> > Response: > 1) No, but connecting the ground lead to a 30 feet metal> pole is a violation. > 2) The pole can not radiate at all. > 3) Yes, this transmitter will not be approve by an FCC> inspector. > 4) You may not install this transmitter as describe."> > > I then posed this question regarding some installations as> seen on various websites and discussions here on this board> and others, again the FCC believes it does not meet the rule> if done as described or similar and having a certified> transmitter or not doesn't make a difference according to> them, of course each > FCC field office will respond differently.> > > > "----- Original Message ----- > From: Generic Office of Engineering Technology > To: [email protected] > Sent: Monday, January 09, 2006 2:50 PM> Subject: Response to Inquiry to FCC (Tracking Number 670631)> > > > ---Reply from Customer on 01/09/2006---> > These installations are currently being approved by field> agents and the transmitter manufacturers is advising to> install these AM transmitter in this fashion and have been> operating for years in this manner. Please see the attached> website for the manufacturer as reference and please> indicate why my installation would be any different? > > I believed that the 3 meter antenna/ground rule was only to> the attach point of the 'true ground' and clipping the 3> inch ground lead to a pipe, ground rod, heavy gauge wire to> ground rod, or metal pole was sufficient as the AM> transmitter needs the ground to complete the circuit? Thank> you.> > > Response: > This is not legal per Section 15.219(b). We can not approve> this installation as > you describe. Please contact FCC Enforcement Bureau (EB) if> you have any additional > questions. The website for (EB) is: http://www.fcc.gov/eb/ > __________> ____________________________________________________________> > 1) No, but connecting the ground lead to a 30 feet metal> pole is a violation. > 2) The pole can not radiate at all. > 3) Yes, this transmitter will not be approve by an FCC> inspector. > 4) You may not install this transmitter as describe. > > > Do not reply to this message. Please select the Reply to an> Inquiry Response link from the OET Inquiry System to add any> additional information pertaining to this inquiry."> > > > Please, let's be civil regarding this, I didn't want to post> this, but thought I'd be helping my fellow part15> broadcasters avoid any issues with the FCC....> > Thanks,> > Radiopilot> Nick, this is good information to repost.This is why I have always said to sit your antenna in the ground. I always had best luck this way, anyway. The antenna ground lead, at that point, leaves little to measure, but, in placing the tx as high as you can on a pole, you are leaving that pole as an extension of the ground...because the pole feeds the ground system.<P ID="signature">______________
[email protected], [email protected],[email protected]</P>
 
Re: FCC response to Part 15.219 3 meter rule-MORE!

Sorry your "New" antenna system was not approved by the FCC.
A counterpoise or other ground system would have to be connected to the ground of the transmitter (allowing a return RF path for current) in order to be effective. Otherwise you might just as well save yourself the trouble and expense of a counterpoise. According to your posting, a counterpoise or ground plane would then become part of the antenna system, and be subject to and a part of the 3 meter limitation.
Who was the "manufacturer" you referred to in your posting to the FCC?
Ramsey?
Rangemaster?
SStran?


> I must agree with this FCC office and rfry on this one. The
> counterpoise must not radiate any signal--only the 3 meter
> antenna plus ground lead (3 m total length) may radiate.
> (Yes, I know some individual FCC Field Agents do "pass" such
> "whip and mast" installations, but we're taking pot luck.)
>
> This is not as bad as it sounds. For ground-mounted
> installations, geometrically symmetrical (non-radiating)
> radial wire systems or copper mesh grids will greatly reduce
> ground losses and increase the fraction of power that is
> radiated by the antenna/ground lead.
>
> For above-ground installations such as on building rooftops,
> any horizontal wire or wires (either elevated or lying on
> the roof) could serve as a ground plane. As long as the
> wire or wires is/are geometrically symmetrical with respect
> to the antenna and non-radiating, this should also pass
> muster with the FCC. The simplest installation of this type
> would be a single wire running across a roof, with the
> transmitter/antenna mounted in the middle and the ground
> lead connected to the center of the wire. -- JasonW
>
> > Ok fellows, last week after all the posts regarding what
> is
> > legal or not, I posted this hypothetical installation to
> the
> > FCC Office of Engineering and Technology in Washington,
> > D.C., same office that said the 'kits' were legal...
> anyway
> > this is the response, doesn't mean everyone's installation
>
> > doesn't meet the Part 15.219 (b) rule, just be aware that
> if
> > you have the transmitter attached to a metal tower, metal
> > pole, etc. of any significant length you may have a
> > problem... I will be correcting my transmitter mount
> > accordingly.
> >
> >
> >
> >
> > "----- Original Message -----
> > From: Generic Office of Engineering Technology
> > To: [email protected]
> > Sent: Monday, January 09, 2006 1:22 PM
> > Subject: Response to Inquiry to FCC (Tracking Number
> 670631)
> >
> >
> >
> >
> > Inquiry:
> >
> > I have a Part15 compliant AM transmitter to the Part15.219
>
> > rule... The transmitter is 30 feet high mounted on a metal
>
> > pole, the 3 meter total antenna including 3 inches of
> ground
> > lead is attached to the metal pole (30 feet long) mounted
> to
> > the ground (elevated ground), attached to the pole is 64
> > radials, each radial 25 feet long in a spiral from the
> > pole... the input to the transmitter is 100mw... is this
> > legal in the FCC rules? Am I violating any Part15 rule by
> > mounting the transmitter 30 feet high? Is the pole
> radiating
> > any RF outside the 3 meter antenna? Would an FCC inspector
>
> > disaprove this installation? Should I have this
> installation
> > inspected prior to operating if all the Part15 rules are
> > adhered to, ie. no interference, no harmonics, no
> complaints
> > from neighbors or licensed broadcasters? I have pasted the
>
> > Part15.219 rule for antenna and power requirement for
> > reference.
> >
> > Thank you.
> >
> > PART 15--RADIO FREQUENCY DEVICES--Table of Contents
> Subpart
> > C--Intentional Radiators 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.
> >
> > Response:
> > 1) No, but connecting the ground lead to a 30 feet metal
> > pole is a violation.
> > 2) The pole can not radiate at all.
> > 3) Yes, this transmitter will not be approve by an FCC
> > inspector.
> > 4) You may not install this transmitter as describe."
> >
> >
> > I then posed this question regarding some installations as
>
> > seen on various websites and discussions here on this
> board
> > and others, again the FCC believes it does not meet the
> rule
> > if done as described or similar and having a certified
> > transmitter or not doesn't make a difference according to
> > them, of course each
> > FCC field office will respond differently.
> >
> >
> >
> > "----- Original Message -----
> > From: Generic Office of Engineering Technology
> > To: [email protected]
> > Sent: Monday, January 09, 2006 2:50 PM
> > Subject: Response to Inquiry to FCC (Tracking Number
> 670631)
> >
> >
> >
> > ---Reply from Customer on 01/09/2006---
> >
> > These installations are currently being approved by field
> > agents and the transmitter manufacturers is advising to
> > install these AM transmitter in this fashion and have been
>
> > operating for years in this manner. Please see the
> attached
> > website for the manufacturer as reference and please
> > indicate why my installation would be any different?
> >
> > I believed that the 3 meter antenna/ground rule was only
> to
> > the attach point of the 'true ground' and clipping the 3
> > inch ground lead to a pipe, ground rod, heavy gauge wire
> to
> > ground rod, or metal pole was sufficient as the AM
> > transmitter needs the ground to complete the circuit?
> Thank
> > you.
> >
> >
> > Response:
> > This is not legal per Section 15.219(b). We can not
> approve
> > this installation as
> > you describe. Please contact FCC Enforcement Bureau (EB)
> if
> > you have any additional
> > questions. The website for (EB) is:
> http://www.fcc.gov/eb/
> >
> __________>
> ____________________________________________________________
>
> >
> > 1) No, but connecting the ground lead to a 30 feet metal
> > pole is a violation.
> > 2) The pole can not radiate at all.
> > 3) Yes, this transmitter will not be approve by an FCC
> > inspector.
> > 4) You may not install this transmitter as describe.
> >
> >
> > Do not reply to this message. Please select the Reply to
> an
> > Inquiry Response link from the OET Inquiry System to add
> any
> > additional information pertaining to this inquiry."
> >
> >
> >
> > Please, let's be civil regarding this, I didn't want to
> post
> > this, but thought I'd be helping my fellow part15
> > broadcasters avoid any issues with the FCC....
> >
> > Thanks,
> >
> > Radiopilot
> >
>
<P ID="edit"><FONT class="small">Edited by SuperSound on 01/14/06 09:03 AM.</FONT></P>
 
Elevated Ground Planes

> A counterpoise or other ground system would have to be
> connected to the ground of the transmitter (allowing a
> return RF path for current) in order to be effective.
> Otherwise you might just as well save yourself the trouble
> and expense of a counterpoise. According to your posting, a
> counterpoise or ground plane would then become part of the
> antenna system, and be subject to and a part of the 3 meter
> limitation.
__________________

That is an assumption, and not supported by Physics.

A normal elevated ground plane might consist of two straight horizontal wires 90 degrees to each other, connected together at their midpoints. A short wire connects the junction of the ground plane wires to the chassis of the Part 15 AM tx, which is located just above the junction of the radial wires.

But because equal r-f currents flow in opposing directions in elevated radial wires, an elevated ground plane does not radiate -- so it does not add to the field of the ~3-meter vertical section above it. In this situation only the short vertical wire connecting the tx to the ground plane junction, and the ~3-meter section connected to the tx r-f output connector will function as an antenna.

There is no particular reason, then, to elevate such a Part 15 system, because it will have no more gain or "coverage" then, than if it was mounted near the ground, and connected to a good system of buried radials. Possibly even LESS gain.

Also, installing the tx system near ground level makes it much easier to optimize (loading coil adjustment, etc).

//
 
Re: FCC response to Part 15.219 3 meter rule-MORE!

> Sorry your "New" antenna system was not approved by the FCC.
>
> A counterpoise or other ground system would have to be
> connected to the ground of the transmitter (allowing a
> return RF path for current) in order to be effective.
> Otherwise you might just as well save yourself the trouble
> and expense of a counterpoise. According to your posting, a
> counterpoise or ground plane would then become part of the
> antenna system, and be subject to and a part of the 3 meter
> limitation.
> Who was the "manufacturer" you referred to in your posting
> to the FCC?
> Ramsey?
> Rangemaster?
> SStran?
>
>

Supersound,

Not sure if you are talking to JasonW or me, but here goes...

The above installation is not mine but a 'theoretical' installation to get the FCC to respond. My installation is mounted on the roof of my house attached to my chimmney, it is then routed to the radials from that point. the transmitter I used for the question in the FCC contact was a Rangemaster and had asked if the Rangemaster being certified would mean it stood a better chance at getting a better response... I got it twice from them indicating it didn't matter if the transmitter was certified or not, it did not meet the rules for Part 15.219(b)... But what I don't understand is how the FCC agent came out and seen my installation 2 years ago and said they could see nothing wrong with what I had, in fact congratulating on a neat installation and very nice studio set up? So go figure!

At this point the only way to use an elevated ground is to 'hide' the ground wire somehow, maybe 'inbed' the ground wire into wood, into a pvc pipe, or whatever means to avoid having the ground wire being percieved as being larger than the 3 meter antenna above it... Sure it'll radiate but nothing will be seen unless the FCC agent were to have you dismantle it? I don't know....

Radiopilot
 
Re: Elevated Ground Planes

> > A counterpoise or other ground system would have to be> > connected to the ground of the transmitter (allowing a> > return RF path for current) in order to be effective.> > Otherwise you might just as well save yourself the trouble> > > and expense of a counterpoise. According to your posting,> a> > counterpoise or ground plane would then become part of the> > > antenna system, and be subject to and a part of the 3> meter> > limitation.> __________________> > That is an assumption, and not supported by Physics.> > A normal elevated ground plane might consist of two straight> horizontal wires 90 degrees to each other, connected> together at their midpoints. A short wire connects the> junction of the ground plane wires to the chassis of the> Part 15 AM tx, which is located just above the junction of> the radial wires.> > But because equal r-f currents flow in the radial wires in> opposing directions, the ground plane does not radiate -- so> it does not add to the field of the ~3-meter vertical> section above it. In this situation only the short vertical> wire connecting the tx to the ground plane junction, and the> ~3-meter section connected to the tx r-f output connector> will function as an antenna. > > There is no particular reason, then, to elevate such a Part> 15 system, because it will have no more gain or "coverage"> then, than if it was mounted near the ground, and connected> to a good system of buried radials. Possibly even LESS> gain.> > Also, installing the tx system near ground level makes it> much easier to optimize (loading coil adjustment, etc).> > //> Mr. Fry is now saying what I have been saying since I've been building part 15 antennas: place it in the ground.While there are real physical differences between very low power AM radio (part 15, with an electrically short antenna) and commercial radio, I always believed that the best installation will mimic type-accepted antennas/towers as best we can under the circumstances........A 3-meter antenna mounted close to the ground is not only easier to tune (and re-tune!), but mirrors more exactly a ground radial system. Your aim in AM radio is to shoot as great a signal as you can into the ground, and have those ground radials carry it...(simply put).,,,at this power, with an antenna mounted 10's of feet above ground, even if your ground wire radiates a bit, it isn't putting anything into your ground system. Your antennna is too far away from your ground system....a very small mast pipe (a foot long) mounted in the ground with cement, the antenna mounted on top of that, and a ground system buried surrounding that mast pipe, to me is the best installation I have come up with in my many tests.But thanks guys for coming thru with some real information that can be used....Carl<P ID="signature">______________
[email protected], [email protected],[email protected]</P>
 
Re: Elevated Ground Planes

> Your aim in AM radio is to shoot as great a
> signal as you can into the ground, and have those ground
> radials carry it...(simply put).,,,at this power, with an
> antenna mounted 10's of feet above ground, even if your
> ground wire radiates a bit, it isn't putting anything into
> your ground system. Your antennna is too far away from your
> ground system.
______________

This concept is inaccurate, sorry. An elevated Part 15 AM tx with its ~3-meter section above it, plus its long conducting path to "real" earth ground is the electrical equivalent of installing the tx at ground level, and connecting it to a long vertical radiator reaching the same elevation above that same ground connection as the elevated ~3-meter section did.

Also -- the path to ground in an elevated 3-meter tx+antenna radiates more than "a bit." It easily can radiate many times more field strength than the 3-meter section above it.

And... the impedance of the ground system is equally important to the fields that the antenna system can generate, no matter what is its configuration. Here is a link to one of my previous posts on the function of MW ground systems:

http://www.radio-info.com/mods/board?Post=607449&Board=community

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Re: FCC response to Part 15.219 3 meter rule-MORE!

> At this point the only way to use an elevated ground is to
> 'hide' the ground wire somehow, maybe 'inbed' the ground
> wire into wood, into a pvc pipe, or whatever means to avoid
> having the ground wire being percieved as being larger than
> the 3 meter antenna above it... Sure it'll radiate but
> nothing will be seen unless the FCC agent were to have you
> dismantle it? I don't know....
>
> Radiopilot
>
The FCC agent will be able to tell what is and is not radating by bringing a field intensity meter near the wooden or PVC mast, because it will most likely pin the meter. These people are not stupid...
 
Re: FCC response to Part 15.219 3 meter rule-MORE!

> > At this point the only way to use an elevated ground is to
>
> > 'hide' the ground wire somehow, maybe 'inbed' the ground
> > wire into wood, into a pvc pipe, or whatever means to
> avoid
> > having the ground wire being percieved as being larger
> than
> > the 3 meter antenna above it... Sure it'll radiate but
> > nothing will be seen unless the FCC agent were to have you
>
> > dismantle it? I don't know....
> >
> > Radiopilot
> >
> The FCC agent will be able to tell what is and is not
> radating by bringing a field intensity meter near the wooden
> or PVC mast, because it will most likely pin the meter.
> These people are not stupid...
>


Yet, WNAR was approved by the FCC office and inspected? How about the Rangemaster installations that many have that go far beyond what I suggest or the many installations that do not conform to the 3 meter rule?

No one here sugggests that any FCC agents are stupid, just that some installations pass the mustard while others don't.

Have you been to the Rangemaster site and seen what it suggest for the 'typical' installation?

Radiopilot
 
Re: FCC response to Part 15.219 3 meter rule-MORE!

> Yet, WNAR was approved by the FCC office and inspected?

You might want to check with Dave McCrork about that. I believe he only spoke to someone in an FCC field office about his setup, and that no on-site inspection was made. Any answer he would get that way would be subject to the system description the FCC office was given, as well as the way the FCC contact understood it, and Part 15 limits. It is not highly advisable to use such "anecdotal" accounts to establish Part 15 compliance of the WNAR-type, elevated antenna system.

> Have you been to the Rangemaster site and seen what it
> suggest for the 'typical' installation?

A drawing recently downloaded from the Rangemaster site shows a Part 15 AM tx+antenna installed on a tower top, with a long (radiating) conductor from the tx to two ground rods. The drawing suggests 25-30 foot elevation for the tx + 3-meter section. Recently posted emails here from the FCC have stated that such systems are non-compliant, so perhaps Keith Hamilton will change his on-line drawing so as not to suggest something to his Rangemaster customers that the FCC objects to.

//
 
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