traveler's info stations AM or FM

[menotti1]

my understanding is anything over part 15 am or fm has to be licensed by the fcc.i know you can set up a network of these.
part 15's.but for example a 10 watt am or fm would have to be a licensed facility, is that not correct.??i've seen these things along the highway but have actually never dialed one in..someone ask me about this today from the tourism center,i don;t think the fcc has special rules for these stations.

 

[tomservo]

The FCC does have a special status, if that's what it's called, for TIS stations on AM. See this link for information and a search feature.

It's a viable option for coverage of a small area. They're used at some spots along the Natchez Trace Parkway, with coverage about 1 mile out in all directions.

Getting an LPFM license is also an option for a non-profit organization. Tuscaloosa, Alabama has one (WTUS-LP) perched atop a hill on the south side of town. It puts a good signal over about 75% of town, covering all three of the "major" interstate exits.

I'm not sure the part 15 network thing is legal. Someone else can clairify that. A single part-15 transmitter is great -- if you want to cover a parking lot.

 

[pianoplayer88key]

The FCC does have a special status, if that's what it's called, for TIS stations on AM. See this link for information and a search feature.

It's a viable option for coverage of a small area. They're used at some spots along the Natchez Trace Parkway, with coverage about 1 mile out in all directions.

From my home in the Mt Helix area (east of La Mesa, south of El Cajon) of San Diego County, I can faintly hear a TIS on 1620 from San Ysidro, and on 530 from LAX airport.

 

[PaulBWalkerJr]

A Part 15 AM Network IS LEGAL as the only thing really regulated under Part 15 on the AM side is the POWER OUTPUT of a SINGLE transmitter. As long as your ERP(Effective Radiated Power) of any one transmitter doesnt exceed 100 milliwatts, it is legal to synch/slave several units together in one location for a strong, more dense local signal.. or spread them out for a wider, yet not as strong signal.

You can't do this on FM, as THAT IS regulated to power output, but more so.. field strength, 250 mv/3m.

 

[Neil E.]

Paul,

You might want to clairify this a bit. Part 15.219 as it applies to AM limits the input power to the final amplifier to 100 mW. and does not address the power output nor the ERP. If operated under Part 15.209, then the limit is expressed as a field strength at a distance.

Part 15 FM is not restricted to power input nor output, rather it is restriced to a maximum field strength in any direction of 250 uV/m at 3 meters. The rules do not mention power for FM operation but it is worth noting that a power output of tens of nanowatts can produce the maximum legal field even with a simple whip antenna.

For AM TIS stations, my understanding is that they are limited on bandwidth and what can be transmitted (such as no music), power, and antenna height. Despite this, the TIS in my community can be heard on my car radio loud and clear 17 miles from the transmitter. I assume they are operating within the rules but I don't know that for certain.

Neil

 

[Tom Wells]

Paul,

You might want to clairify this a bit. Part 15.219 as it applies to AM limits the input power to the final amplifier to 100 mW. and does not address the power output nor the ERP. If operated under Part 15.209, then the limit is expressed as a field strength at a distance.

Part 15 FM is not restricted to power input nor output, rather it is restriced to a maximum field strength in any direction of 250 uV/m at 3 meters. The rules do not mention power for FM operation but it is worth noting that a power output of tens of nanowatts can produce the maximum legal field even with a simple whip antenna.

For AM TIS stations, my understanding is that they are limited on bandwidth and what can be transmitted (such as no music), power, and antenna height. Despite this, the TIS in my community can be heard on my car radio loud and clear 17 miles from the transmitter. I assume they are operating within the rules but I don't know that for certain.

Neil

The TIS station in Corpus Christi has a music bed that is faded up and down during the announcements, maybe the ONLY time I've ever heard music on a TIS.

A "talking billboard" in Chicago on 1550, which is now thankfully silent, used to broadcast "Old Navy" advert loops, and then was
"Radio Cadillac", touting the Cadillac Escalade. Both had music elements. Both sounded just AWFUL, far worse than telephone.
I never had the time to fox hunt the billboard, but I'm sure it was along the 90/94 expressway north of the city.
Most of these sound as though the audio was recorded remotely over a telephone land-line.

 

[Black_Shire]

The Hamilton AM1000 Rangemaster www.am1000rangemaster.com Part 15 AM transmitter is FCC Certified and has provision for synchronizing several of them together.

Regarding music on TISs, it is permitted as long as the music either isn't copyrighted *or* the artist gives written permission for it to be broadcast on the TIS, and in either circumstance the music has to be part of a non-commercial message (as the intro, background music for it, etc.).


-- Black Shire

Paul,

You might want to clairify this a bit. Part 15.219 as it applies to AM limits the input power to the final amplifier to 100 mW. and does not address the power output nor the ERP. If operated under Part 15.209, then the limit is expressed as a field strength at a distance.

Part 15 FM is not restricted to power input nor output, rather it is restriced to a maximum field strength in any direction of 250 uV/m at 3 meters. The rules do not mention power for FM operation but it is worth noting that a power output of tens of nanowatts can produce the maximum legal field even with a simple whip antenna.

For AM TIS stations, my understanding is that they are limited on bandwidth and what can be transmitted (such as no music), power, and antenna height. Despite this, the TIS in my community can be heard on my car radio loud and clear 17 miles from the transmitter. I assume they are operating within the rules but I don't know that for certain.

Neil

The TIS station in Corpus Christi has a music bed that is faded up and down during the announcements, maybe the ONLY time I've ever heard music on a TIS.

A "talking billboard" in Chicago on 1550, which is now thankfully silent, used to broadcast "Old Navy" advert loops, and then was
"Radio Cadillac", touting the Cadillac Escalade. Both had music elements. Both sounded just AWFUL, far worse than telephone.
I never had the time to fox hunt the billboard, but I'm sure it was along the 90/94 expressway north of the city.
Most of these sound as though the audio was recorded remotely over a telephone land-line.

 

[menotti1]

quick check on the rules,10 watts max on AM,Max ant.height 15 meters(49.5FT)LPFM would work and as you know some states are using them for this purpose, but with no current window that would be moot.got a 4 story bldg in mind that should work very nicely.10
watts at this height should work fine for this purpose.

 

[rfry]

quick check on the rules,10 watts max on AM,Max ant.height 15 meters(49.5FT)LPFM would work and as you know some states are using them for this purpose, but with no current window that would be moot.got a 4 story bldg in mind that should work very nicely. 10 watts at this height should work fine for this purpose.

You might want to check further on this. Selected quotes from Part 90.242 (bold attribute is mine)...

\\ (4) For a station employing a conventional radiating antenna(s) (ex.
vertical monopole, directional array) the following restrictions apply:
(i) The antenna height above ground level shall not exceed 15.0
meters (49.2 feet).
(ii) Only vertical polarization of antennas shall be permitted.
(iii) Transmitter RF output power shall not exceed 10 watts to
enable the user to comply with the specified field strength limit.
(iv) The field strength of the emission on the operating frequency
shall not exceed 2 mV/m when measured with a standard field strength
meter at a distance of 1.50 km (0.93 miles) from the transmitting
antenna system. //

This requires that the TIS tx power must be adjusted downward from 10 watts if needed to keep the field at 1.5 km at 2mV/m or less.

Regarding music on TISs, it is permitted as long as the music either isn't copyrighted *or* the artist gives written permission for it to be broadcast on the TIS, and in either circumstance the music has to be part of a non-commercial message (as the intro, background music for it, etc.).

\\ (7) Travelers Information Stations shall transmit only noncommercial
voice information pertaining to traffic and road conditions, traffic
hazard and travel advisories, directions, availability of lodging, rest
stops and service stations, and descriptions of local points of
interest.

(8)Each transmitter in a Travelers Information Station shall be
equipped with an audio low-pass filter. Such filter shall be installed
between the modulation limiter and the modulated stage. At audio
frequencies between 3 kHz and 20 kHz this filter shall have an
attenuation greater than the attenuation at 1 kHz by at least:

60 log<INF>10</INF> (f/3) decibels.

where ``f'' is the audio frequency in kHz. At audio frequencies above 20
kHz, the attenuation shall be at least 50 decibels greater than the
attenuation at 1 kHz. //

 

[Neil E.]

Well, I did quick check the rules and found from 47 CFR 90.242:

(7) Travelers Information Stations
shall transmit only noncommercial
voice information pertaining to traffic...

So how does this allow for "non copyrighted music",etc. since it specifically mentions voice information? It appears that some are reading a different set of rules than I or are making it up as they go along.

Neil

 

[rfry]

The Hamilton AM1000 Rangemaster www.am1000rangemaster.com Part 15 AM transmitter is FCC Certified and has provision for synchronizing several of them together.

In order to do this successfully the carriers of the two (or more) transmitters will need to be frequency/phase locked to each other, and the antenna system will need some serious engineering design.

Locking the carriers together is needed to prevent generating a beat frequency between them in receivers. The physical placement of the antennas with respect to each other and to the desired coverage area, and the r-f phase and amount of r-f power applied to each of them will determine what shape the net radiation pattern will have. The patterns of the individual antennas will reinforce each other in some directions, and tend to cancel out in other directions.

And the modulation polarities of the two transmitters need to be the same for all modulating frequencies.

It's not a simple problem or installation.
//

 

[Black_Shire]

The Hamilton AM1000 Rangemaster www.am1000rangemaster.com Part 15 AM transmitter is FCC Certified and has provision for synchronizing several of them together.

In order to do this successfully the carriers of the two (or more) transmitters will need to be frequency/phase locked to each other, and the antenna system will need some serious engineering design.

Locking the carriers together is needed to prevent generating a beat frequency between them in receivers. The physical placement of the antennas with respect to each other and to the desired coverage area, and the r-f phase and amount of r-f power applied to each of them will determine what shape the net radiation pattern will have. The patterns of the individual antennas will reinforce each other in some directions, and tend to cancel out in other directions.

And the modulation polarities of the two transmitters need to be the same for all modulating frequencies.

It's not a simple problem or installation.
//

The AM1000 Rangemaster transmitter *is* designed to do this (and in several ways), as described on the Hamilton AM1000 Rangemaster web site (specifically, on this page of http://www.am1000rangemaster.com/zerobeat.html ).

 

[rfry]

The AM1000 Rangemaster transmitter *is* designed to do this (and in several ways), as described on the Hamilton AM1000 Rangemaster web site (specifically, on this page of http://www.am1000rangemaster.com/zerobeat.html ).

However that webpage gives no recognition to the siting and engineering effort needed for the separate tx/antenna systems to provide the coverage area(s) desired.

It's not just a matter of supplying synchronous and phase-stable r-f to the various antennas. Those phase relationships need to be calculated, as well as the means to produce them accurately.
//

 

[tomservo]

What's the purpose of the rule limiting bandwidth on the TIS?

 

[rfry]

What's the purpose of the rule limiting bandwidth on the TIS?

TIS is not supposed to compete with commercial broadcast stations, so an audio bandwidth needed for decent transmission of music was not required (or desired).

An audio response to 3 kHz is adequate for the voice announcements that TIS is licensed to provide.
//

 

[Black_Shire]

The AM1000 Rangemaster transmitter *is* designed to do this (and in several ways), as described on the Hamilton AM1000 Rangemaster web site (specifically, on this page of http://www.am1000rangemaster.com/zerobeat.html ).

However that webpage gives no recognition to the siting and engineering effort needed for the separate tx/antenna systems to provide the coverage area(s) desired.

It's not just a matter of supplying synchronous and phase-stable r-f to the various antennas. Those phase relationships need to be calculated, as well as the means to produce them accurately.
//

Then why don't you offer your services as a paid consultant to those Part 15 AM community radio station owners who want to operate multiple synchronized Rangemaster transmitters? The late broadcast engineer James R. Cunningham set up many such multiple-transmitter Part 15 AM radio stations using both Part 15.219 intentional radiators and Part 15.221 Carrier Current systems (both in combination and using multiple units of each type) with great success, and he shared his expertise with these installations in his books.

 

[Black_Shire]

What's the purpose of the rule limiting bandwidth on the TIS?

TIS is not supposed to compete with commercial broadcast stations, so an audio bandwidth needed for decent transmission of music was not required (or desired).

An audio response to 3 kHz is adequate for the voice announcements that TIS is licensed to provide.
//

Agreed. Also, the narrower bandwidth has the effect (whether the rule makers intended it or not, I don't know) of making the signal intelligible at a greater range with the given power than a standard 10 kHz AM signal could be copied.

 

[rfry]

Then why don't you offer your services as a paid consultant to those Part 15 AM community radio station owners who want to operate multiple synchronized Rangemaster transmitters? The late broadcast engineer James R. Cunningham set up many such multiple-transmitter Part 15 AM radio stations using both Part 15.219 intentional radiators and Part 15.221 Carrier Current systems (both in combination and using multiple units of each type) with great success, and he shared his expertise with these installations in his books.

Thanks, but the limit of my interest during retirement is to provide some basic guidelines in an attempt to counter some of the misleading conclusions posted by some, and not to get very specific.

Those who want more maybe can consult the expertise you report is contained in the books of James Cunningham, or (preferably, IMO), standard textbooks on transmission system physics.
//

 

[Neil E.]

Black shire,

When you wrote:

Also, the narrower bandwidth has the effect (whether the rule makers intended it or not, I don't know) of making the signal intelligible at a greater range with the given power than a standard 10 kHz AM signal could be copied.

you perhaps had in mind the equation which predicts noise at a receiver which is

En = SQRT(4*k*T*BW*R)

Intelligibility is related to the signal to noise ratio and this equation predicts that the noise will be reduced by the SQRT of the bandwidth, but unless the bandwidth of the receiver is narrowed, there will be no gain in S/N for a bandwidth limited TIS transmitter as compared to a full bandwidth broadcast AM station. This advantage is a function of the receiver bandwidth and not the transmitter bandwidth.

Perhaps you know of another reason there is an advantage to narrow bandwidth that I missed.

Neil

 

[Black_Shire]

Then why don't you offer your services as a paid consultant to those Part 15 AM community radio station owners who want to operate multiple synchronized Rangemaster transmitters? The late broadcast engineer James R. Cunningham set up many such multiple-transmitter Part 15 AM radio stations using both Part 15.219 intentional radiators and Part 15.221 Carrier Current systems (both in combination and using multiple units of each type) with great success, and he shared his expertise with these installations in his books.

Thanks, but the limit of my interest during retirement is to provide some basic guidelines in an attempt to counter some of the misleading conclusions posted by some, and not to get very specific.

Those who want more maybe can consult the expertise you report is contained in the books of James Cunningham, or (preferably, IMO), standard textbooks on transmission system physics.
//

If you're content to dabble with equations, yes. Those who are more interested in actual Part 15 AM broadcasting would do better to read the works of someone who had decades of actual experience with the hardware and techniques involved in Part 15 AM Community broadcasting, and Mr. Cunningham is that person.