Help: Ready to put a part 15 am on air, Now what to do next.

[lilburncommunityradio]

Hi to one and all ! We are ready to put a new pt 15 am trans on air.
We have all the pieced together equipment in place, and yet to build a
counter and such for it to be placed on... But what kinda of transmitter,
and we live in a two bedroom duplex apt, So is a part 15 am setup even
feasable. We have a fm already broadcasting, but the am is what were
shooting for! If any of you have any information, or suggestions about
this endeavor then let us know.. Were unsure of what kind of am transmitter is
best, and e.t.c. We dont need anywhere near the most expensive, but we need
something to get some coverage.. Thanks in advance. J&M Lilburn Community Radio

 

[JasonW]

Hi to one and all ! We are ready to put a new pt 15 am trans on air.
We have all the pieced together equipment in place, and yet to build a
counter and such for it to be placed on... But what kinda of transmitter,
and we live in a two bedroom duplex apt, So is a part 15 am setup even
feasable. We have a fm already broadcasting, but the am is what were
shooting for! If any of you have any information, or suggestions about
this endeavor then let us know.. Were unsure of what kind of am transmitter is
best, and e.t.c. We dont need anywhere near the most expensive, but we need
something to get some coverage.. Thanks in advance. J&M Lilburn Community Radio

The very best Part 15 AM transmitter is the Hamilton PCB AM1000 Rangemaster www.am1000rangemaster.com . If its price is too steep for you at this time (it's the Cadillac of transmitters and is priced accordingly, but is well worth it), the TalkingSign ( www.talkingsign.com ) and Talking House (www.talkinghouse.com and www.actradio.com ) realty transmitters are good, lower-priced alternatives.

Talking House TH II transmitters (the black, metal-cased model) are constantly available on eBay for ~$100 to ~$250. Both the Talking House and TalkingSign have provision for using a special outdoor antenna tuning unit (ATU) with a stock 8.5' (2.59 m) fiberglass CB whip antenna. The ATUs and whip antennas are available from the transmitters' manufacturers.

I hope this information will be helpful. -- Jason

 

[lilburncommunityradio]

Ok, question is though, With a talking house trans, is there a way to bypass the digital chip recorder, to keep a stream going thru it live? Help? Anyone?

 

[PaulBWalkerJr]

Yup.. there sur eis. There's a switch on the back that should by pass it.

Email me offlist, I can still do those liners for you.

 

[JasonW]

Ok, question is though, With a talking house trans, is there a way to bypass the digital chip recorder, to keep a stream going thru it live? Help? Anyone?

The Talking House ( www.talkinghouse.com ) automatically shuts down the chip recorder and picks up the live audio feed as soon as you plug the audio feed cable into the "LIVE AUDIO" jack. Older Talking House TH IIs have RCA (Phono) audio jacks while the newer ones have 3.5 mm (1/8") jacks.

You can use the chip recorder to your advantage--in case your audio source computer crashes, you can keep a pre-recorded message on the chip recorder ("We are experiencing technical difficulties. Please stand by.") that you can broadcast while re-booting the computer. The audio chip memory is non-volatile, so it is unaffected by power failures.

The TalkingSign ( www.talkingsign.com ) has soft-touch selector switches for "PLAY" (play the chip recorder) and "LIVE" (live audio) on the front of the transmitter cabinet. It uses 3.5 mm (1/8") audio jacks.

If you're going to plug the transmitter and audio source into the same AC outlet or power strip, I'd recommend using a Radio Shack car stereo ground loop isolator (Cat. No. #270-054). It eliminated the 60 Hz ground loop hum in my transmitters.

-- Jason

 

[Grrrradio]

Do you have any way at all of "grounding" the antenna? Getting the perfect match requires some rather precise calculations, but in my (limited) experience with low-power AM, any contact at all with the ground can help your coverage tremendously. I was using a Ramsey 100-mW AM unit and transmitting into a car rx antenna (detached from the car, of course)... when I ran a simple copper wire down from the antenna to the metal handicap support rail in the ground outside my building, my copyable distance on a portable radio jumped from 200' to 800'.

 

[JasonW]

Do you have any way at all of "grounding" the antenna? Getting the perfect match requires some rather precise calculations, but in my (limited) experience with low-power AM, any contact at all with the ground can help your coverage tremendously. I was using a Ramsey 100-mW AM unit and transmitting into a car rx antenna (detached from the car, of course)... when I ran a simple copper wire down from the antenna to the metal handicap support rail in the ground outside my building, my copyable distance on a portable radio jumped from 200' to 800'.

Except when using a Folded Unipole antenna or a shunt-fed tower antenna (neither of which is practical for Part 15 AM), you don't ever want to ground an antenna because the signal will simply flow into the ground instead of being radiated.

Your ground wire to the support rail is acting as the other half of a dipole antenna and is radiating, which is why your transmission range has increased. Unfortunately this is illegal, as the combined length of the antenna, antenna feed line (if any), and ground lead can be no greater than 3 meters. Also, the Ramsey transmitters are illegal because they aren't FCC Certified. Only the Rangemaster, AM2000, Talking House, and TalkingSign Part 15 AM transmitters are FCC Certified.

However, you *can* legally ground a Part 15 AM transmitter directly to a large metal object such as a ground rod, a railing, a fence, or a car. This will boost your signal, and as long as the antenna plus ground lead are 3 meters long or less, it's legal.

-- Jason

 

[rfry]

Do you have any way at all of "grounding" the antenna?

From an engineering point of view, you could connect the antenna output of your tx to the loading coil input of a ~3 meter vertical radiator, and connect the ground terminal of the tx directly to the center of a straight, horizontal wire of ~ 6 meters or so that is insulated from ground. The total, radiating length of this system will include the ~3-meter vertical and coil plus the length of the conductor from the tx to the center of the horizontal wire. There must be no conducting path from any of this system to a "building," AC, or earth ground.

This installation may cause some controversy to those who believe that the horizontal wire is radiating, and should be counted in the 3-meter radiating length. This may include FCC inspectors, so be careful. But the radiation from each half of the horizontal wire cancels the radiation from the other half, so the net useful radiation from it is (theoretically) zero.

The loading coil inductance needed will be rather unpredictable, because the input capacitance (and radiation pattern) of the antenna will be affected by the building steel, AC wiring, other nearby conductors, and how far it is above the earth.
//

 

[JasonW]

Do you have any way at all of "grounding" the antenna?

From an engineering point of view, you could connect the antenna output of your tx to the loading coil input of a ~3 meter vertical radiator, and connect the ground terminal of the tx directly to the center of a straight, horizontal wire of ~ 6 meters or so that is insulated from ground. The total, radiating length of this system will include the ~3-meter vertical and coil plus the length of the conductor from the tx to the center of the horizontal wire. There must be no conducting path from any of this system to a "building," AC, or earth ground.

This installation may cause some controversy to those who believe that the horizontal wire is radiating, and should be counted in the 3-meter radiating length. This may include FCC inspectors, so be careful. But the radiation from each half of the horizontal wire cancels the radiation from the other half, so the net useful radiation from it is (theoretically) zero.

The loading coil inductance needed will be rather unpredictable, because the input capacitance (and radiation pattern) of the antenna will be affected by the building steel, AC wiring, other nearby conductors, and how far it is above the earth.
//

Any purposely-built symmetrical horizontal (non-radiating) ground seems to be "Kosher" with the FCC. Information Station Specialists offers a 20' diameter "wagon wheel" copper wire radial system for use with the outdoor Antenna Tuning Unit/8.5' whip antenna of their InfoMAX (a.k.a. Talking House) Part 15 AM transmitter.

Each of the 10' radials (doubled bare wires soldered to the central ring wire) can be cut and extended to 20' (for a 40' total radial system diameter) for greater efficiency at frequencies below 1000 kHz. The ATU is mounted just above the center of the "wagon wheel."

When using existing metallic structures as grounds, there are no limits on size. Metal billboards make great RF grounds for the whip antennas to "work against," as 'talking billboard' advertisers have happily discovered. Metal roofs and metal towers make the best RF grounds, and metal car bodies also work well for mobile Part 15 AM broadcasting.

-- Jason

 

[rfry]

Any purposely-built symmetrical horizontal (non-radiating) ground seems to be "Kosher" with the FCC. ... When using existing metallic structures as grounds, there are no limits on size. Metal billboards make great RF grounds for the whip antennas to "work against," as 'talking billboard' advertisers have happily discovered. Metal roofs and metal towers make the best RF grounds, and metal car bodies also work well for mobile Part 15 AM broadcasting.

Jason, could you please explain the technical/legal basis for your post?

True r-f grounds do not radiate. They only reduce antenna system losses, so that an electrically short (3 meter radiating structure by the FCC definition) can radiate more of the power that the Part 15 AM tx legally can produce.

But billboard steel, a slanted metal roof, a tower, a flagpole and an auto body increase Part 15 AM field strength because each of them comprises a RADIATING section of the antenna -- not because they provide the characteristics of true (non-radiating) r-f ground.

It doesn't matter to Part 15 or antenna/radiation physics whether any of those structures was purpose-built, or not, does it?
//

 

[JasonW]

Any purposely-built symmetrical horizontal (non-radiating) ground seems to be "Kosher" with the FCC. ... When using existing metallic structures as grounds, there are no limits on size. Metal billboards make great RF grounds for the whip antennas to "work against," as 'talking billboard' advertisers have happily discovered. Metal roofs and metal towers make the best RF grounds, and metal car bodies also work well for mobile Part 15 AM broadcasting.

Jason, could you please explain the technical/legal basis for your post?

True r-f grounds do not radiate. They only reduce antenna system losses, so that an electrically short (3 meter radiating structure by the FCC definition) can radiate more of the power that the Part 15 AM tx legally can produce.

But billboard steel, a slanted metal roof, a tower, a flagpole and an auto body increase Part 15 AM field strength because each of them comprises a RADIATING section of the antenna -- not because they provide the characteristics of true (non-radiating) r-f ground.

It doesn't matter to Part 15 or antenna/radiation physics whether any of those structures was purpose-built, or not, does it?
//

Information Station Specialists (ISS) www.theradiosource.com produces, markets, installs, and services transmitters and antenna/ground systems for FCC Part 90 licensed Travelers Information Station (TIS) and Highway Advisory Radio (HAR) systems and FCC Part 15 unlicensed radio systems, for both government and commercial clients.

They work closely with the FCC when helping their clients plan these Part 90 and Part 15 AM radio stations (conducting open frequency searches, doing site selection, etc.). They've been in this business for 23 years, and if the FCC had had any problems with these types of Part 15 AM installations on billboards or metal roofs or using the "wagon wheel" radial system (called the "PowerPlane" ground plane system by ISS), they would have made it known to the company long before now.

-- Jason

 

[rfry]

Information Station Specialists (ISS) www.theradiosource.com produces, markets, installs, and services transmitters and antenna/ground systems for FCC Part 90 licensed Travelers Information Station (TIS) and Highway Advisory Radio (HAR) systems and FCC Part 15 unlicensed radio systems, for both government and commercial clients.

The FCC Rules for TIS/HAR systems are different than for Part 15 AM.

...and if the FCC had had any problems with these types of Part 15 AM installations on billboards or metal roofs or using the "wagon wheel" radial system (called the "PowerPlane" ground plane system by ISS), they would have made it known to the company long before now.

Non-radiating r-f grounds such as the wagon wheel design shouldn't concern the FCC for Part 15 AM systems, because they do not form any part of the legal 3-meter radiating length allowed by the FCC for Part 15 AM systems.

No matter what the non-radiating r-f ground termination consists of, or even if it exists at all, a long "ground lead + ground wire," billboard steel, a slanted metal roof, a tower, a metal flagpole, and even an auto body can increase Part 15 AM field strength beyond what Part 15 permits, because all of these conductors comprise a RADIATING section of the antenna that can produce higher fields than permitted, even with an otherwise legal tx having 100 mW DC input power.
//

 

[JasonW]

R. Fry wrote:

<The FCC Rules for TIS/HAR systems are different than for Part 15 AM.>

Obviously. The point is that a company such as Information Station Specialists (ISS), whose livelihood depends on complying with the FCC's rules, wouldn't install Part 15 AM systems the way that they do (on billboards, etc.) unless the FCC approved of them.

<Non-radiating r-f grounds such as the wagon wheel design shouldn't concern the FCC for Part 15 AM systems, because they do not form any part of the legal 3-meter radiating length allowed by the FCC for Part 15 AM systems.>

Yup.

<No matter what the non-radiating r-f ground termination consists of, or even if it exists at all, a long "ground lead + ground wire," billboard steel, a slanted metal roof, a tower, a metal flagpole, and even an auto body can increase Part 15 AM field strength beyond what Part 15 permits, because all of these conductors comprise a RADIATING section of the antenna that can produce higher fields than permitted, even with an otherwise legal tx having 100 mW DC input power.>

*Shrug* The FCC isn't concerned about this, or they would have let ISS know years ago. They've done many billboard, roof, and seaside Part 15 AM installations over the years. If it doesn't bother the FCC, it doesn't bother me.

-- Jason

 

[rfry]

Information Station Specialists (ISS) www.theradiosource.com produces, markets, installs, and services transmitters and antenna/ground systems for FCC Part 90 licensed Travelers Information Station (TIS) and Highway Advisory Radio (HAR) systems and FCC Part 15 unlicensed radio systems, for both government and commercial clients.

They've been in this business for 23 years, and if the FCC had had any problems with these types of Part 15 AM installations on billboards or metal roofs or using the "wagon wheel" radial system (called the "PowerPlane" ground plane system by ISS), they would have made it known to the company long before now.

Jason and all - ISS does not support the use of radiating lengths greater than 3 meters for their equipment used for Part 15 AM.

To confirm, please read their statement about this in the response to question #2 in the FAQs on their website. Here is a partial quote from it. "In other words, ISS does not recommend that the groundlead be connected to a roof, groundplane, metal pole, tower or other conducting material of any length; nor does the FCC condone it."

The ISS statement does not support your earlier posts, Jason.

Here is a link to the full text: http://www.theradiosource.com/faqs-am.htm
//

 

[JasonW]

Information Station Specialists (ISS) www.theradiosource.com produces, markets, installs, and services transmitters and antenna/ground systems for FCC Part 90 licensed Travelers Information Station (TIS) and Highway Advisory Radio (HAR) systems and FCC Part 15 unlicensed radio systems, for both government and commercial clients.

They've been in this business for 23 years, and if the FCC had had any problems with these types of Part 15 AM installations on billboards or metal roofs or using the "wagon wheel" radial system (called the "PowerPlane" ground plane system by ISS), they would have made it known to the company long before now.

Jason and all - ISS does not support the use of radiating lengths greater than 3 meters for their equipment used for Part 15 AM.

To confirm, please read their statement about this in the response to question #2 in the FAQs on their website. Here is a partial quote from it. "In other words, ISS does not recommend that the groundlead be connected to a roof, groundplane, metal pole, tower or other conducting material of any length; nor does the FCC condone it."

The ISS statement does not support your earlier posts, Jason.

Here is a link to the full text: http://www.theradiosource.com/faqs-am.htm
//

Information Station Specialist's ACTIONS *fully* support my earlier posts. They continue to install Part 15 AM transmitters on metal billboards (Honda recently used the "talking billboards" in one of their ad campaigns), and ISS offers weather-resistant metal transmitter enclosures that are bolted to the billboards to form good ground connections. Cadillac uses these "talking billboards" rather often in their "Radio Cadillac" ad campaigns, and they've done so for at least ten years. If the FCC really cared about this, they would have long ago shut down every "talking billboard" Part 15 AM station and raided Information Station Specialists, just as they've raided Ramsey Electronics several times for selling non-compliant Part 15 FM transmitters.

-- Jason

 

[rfry]

Information Station Specialist's ACTIONS *fully* support my earlier posts. They continue to install Part 15 AM transmitters on metal billboards (Honda recently used the "talking billboards" in one of their ad campaigns), and ISS offers weather-resistant metal transmitter enclosures that are bolted to the billboards to form good ground connections. (etc)

Thanks for your reply. But I expect that your statements/beliefs apply only to licensed TIS/HAR installations -- which are defined by field strength values, and which under Part 90 do not preclude elevated antennas and lengthy, radiating "ground" conductors.

Unlicensed Part 15 AM systems are a different story, aren't they?

//

 

[JasonW]

Information Station Specialist's ACTIONS *fully* support my earlier posts. They continue to install Part 15 AM transmitters on metal billboards (Honda recently used the "talking billboards" in one of their ad campaigns), and ISS offers weather-resistant metal transmitter enclosures that are bolted to the billboards to form good ground connections. (etc)

Thanks for your reply. But I expect that your statements/beliefs apply only to licensed TIS/HAR installations -- which are defined by field strength values, and which under Part 90 do not preclude elevated antennas and lengthy, radiating "ground" conductors.

Unlicensed Part 15 AM systems are a different story, aren't they?

//

Here are links to two pictures of a Honda "Talking Billboard," taken by dbdigital in April of this year:

http://home.gci.net/~gida/hondatx1.JPG
http://home.gci.net/~gida/hondatx2.JPG

This is the standard InfoMAX (a.k.a. Talking House) weatherproof outdoor enclosure offered by Information Station Specialists, topped by the standard 8.5' Part 15 AM whip antenna (a CB whip).

-- Jason

 

[SUPERCASTER]

Reply to R. Fry:

But the radiation from each half of the horizontal wire cancels the radiation from the other half, so the net useful radiation from it is (theoretically) zero.

Why would opposite oriented ground radials below a verticle monopole antenna cancel?
There is no reason why they should do so. They are not out of phase, but IN PHASE.
Since the return currents form the various ground radials (or counterpoise) are in phase they add together to form the return current. That is how a ground system or counterpoise operates below a verticle antenna. An RF ammmeter placed in series between the ground system and transmitter ground will prove this. The more radials the more efficiency and greater the in phase return RF current.
There is no reason why the RF from a single verticle radiator should be out of phase at equal distances from either side of a verticle antenna or in the individual or combined center connected ground radials.

 

[rfry]

Why would opposite oriented ground radials below a verticle monopole antenna cancel?

These are not "ground" radials, as in the type buried in the ground. They are elevated above the ground, and they behave differently than buried radials because of that.

Following are links to two graphics of this antenna system made using NEC-2 (antenna modeling software). They show the current distribution on the three wires, and the shape of their net radiation pattern above a perfect earth.

You will see that there is no useful radiation from the horizontal wire. If there was, it would be maximum at a right angle to the wire. But instead, total radiation in that direction is zero (as expected from a vertical radiator). And of course, a horizontal wire cannot generate vertically-polarized radiation in the horizontal plane, anyway.

Please refer to antenna engineering textbooks to confirm this.

http://i62.photobucket.com/albums/h85/rfry-100/CurrentDistr.gif

http://i62.photobucket.com/albums/h85/rfry-100/Part15AptAntennaSurfacePattern.jpg

//

 

[rfry]

Here are links to two pictures of a Honda "Talking Billboard," .... This is the standard InfoMAX (a.k.a. Talking House) weatherproof outdoor enclosure offered by Information Station Specialists, topped by the standard 8.5' Part 15 AM whip antenna (a CB whip).

The 8.5 foot whip in those photos is a "standard" Part 15 AM whip only if it, plus any other radiating source is 3 meters or less in length. But in these photos it is likely that the tx "ground" terminal is connected to the steel frame of the billboard. As the billboard frame is longer (higher) than the whip, it would radiate more r-f than the whip itself, and certainly mean that the radiating length in this system was greater than 3 meters.

This reality of physics either isn't being recognized, or it is being ignored by ISS (if they support it), "Part 15" operators, and, according to these boards -- even the FCC.
//