Hello All,
I recently wrote up a primer for a group who are interested in setting up Part 15 AM radio stations in isolated communities in rural Alaska. It may be of use to those on this board, so I have reproduced it below.
The AM1000 Rangemaster www.am1000rangemaster.com , Talking House www.talkinghouse.com , and TalkingSign www.talkingsign.com Part 15 AM transmitters can, if properly installed outdoors, *legally* achieve a broadcast range of 2 miles - 3 miles. The problem is that the villages may need different types of installations depending on their geography, which could lead to installation delays and higher unit prices due to the custom fabrication work and its associated labor costs. The solution is to devise one or more standard outdoor transmitter installations that would fulfill the villages' needs. I have a few ideas regarding this that I wanted to offer to you.
James R. Cunningham's book "Low Power Radio Broadcasting," covers Part 15 AM broadcasting in detail. He built systems in which the 100 milliwatt Part 15 AM transmitter with an 8' - 10' whip antenna (the book dates to 1990, before the 3 meter [9.84'] length was adopted) was mounted atop a 35 foot tall wooden pole. These installations achieved ranges of 2 miles - 3 miles! He used no illegal gimmicks such as radiating ground lead wires, but instead relied entirely upon the antenna's elevated feed point and line-of-sight signal propagation to achieve the long broadcast ranges. The 100 milliwatt TalkingSign, Talking House, and Rangemaster Part 15 AM transmitters would give similar results in similar installations.
Information Station Specialists (ISS) www.theradiosource.com offers its ALERT AM and AM Travelers Information Station (TIS) systems with three different antenna/RF ground system installation options--roof, yard, and isolated. I propose three Part 15 AM transmitter outdoor installation options that are analogous to the ALERT AM and TIS antenna/RF ground system installation options, and I have described them below:
[1] --Roof Mounted-- The Talking House or TalkingSign transmitter is installed inside a weatherproof box. [The 14” X 10” X 4” NEMA ABS Plastic Weatherproof Enclosure, Model Number NBP141004-100 (HIC-NB6), available from www.hyperlinktech.com/web/weatherproof_wireless_enclosure.php , would be perfect for this and the other outdoor installations.] The box is affixed to a weather-proofed wooden pole which extends 3 meters above the box and a short distance below it. The bottom of the pole is bolted to a roof tripod, which in turn is secured to the roof in the geometric center of the roof. The 3 meter wire antenna (made of either stranded wire or solid wire with UV-resistant outdoor insulation) is attached to the pole above the box using stand-off insulators of the type used on electric fences. If an AM1000 Rangemaster transmitter is used, the transmitter (in its weatherproof box with its 102" whip antenna on top) can simply be bolted atop the roof tripod. The 120 volt AC power and audio lines are routed to the transmitter box in a weatherproof conduit. If the roof is metal, it will still act as a counterpoise for the antenna via capacitive coupling (and thus increase the antenna's radiation) even though there is no directly-wired connection between the roof and the transmitter. If the roof is wood, concrete, or asphalt, a PowerPlane (tm) AM radial wire ground plane (available from ISS) installed on the roof below the transmitter box (but *NOT* electrically connected to the transmitter in any way) would also act as a capacitively-coupled counterpoise.
[2] --Pole Mounted (Tall)-- The TalkingSign transmitter in its outdoor box is affixed to a 20' - 40' tall wooden pole (such as a telephone pole), with the top of the transmitter box being 3 meters below the top of the pole. The 3 meter wire antenna (made of either stranded wire or solid wire with UV-resistant outdoor insulation) is attached to the pole above the box using stand-off insulators of the type used on electric fences. If an AM1000 Rangemaster transmitter is used, the transmitter (in its weatherproof box with its 102" whip antenna on top) can simply be bolted to a length of TV antenna mast tubing, which in turn is bolted or strapped to the wooden support pole. The 120 volt AC power and audio lines are routed up the pole to the transmitter box in a weatherproof conduit.
[3] --Pole Mounted (Short)-- This installation is the same as [2] except that the wooden pole is much shorter, being only tall enough to accomodate the 3 meter wire antenna above the transmitter box and 3' - 10' of the 120 volt AC power and audio lines (in a weatherproof conduit) running up the pole to the transmitter box. An AM1000 Rangemaster transmitter could be mounted to the short support pole in the same way as in [2]. If installed on a hilltop, this short pole installation could also achieve multi-mile range. If desired, a PowerPlane (tm) AM radial wire ground plane (available from ISS) installed at the base of the pole below the transmitter box (but *NOT* electrically connected to the transmitter in any way) would act as a capacitively-coupled counterpoise that could be beneficial in areas with poor soil conductivity.
If Talking House or TalkingSign transmitters are used, there is also another antenna option that could be implemented as part of the standard Part 15 AM transmitter outdoor installation plans that I described above.
To get the maximum usable height (and thus broadcast range) from a support pole, a 102" (8.5' or 2.59 meter) steel or fiberglass CB whip antenna could be mounted atop the pole and be connected to the transmitter in its outdoor box using a lead wire. This lead wire could be up to 0.41 meters (41 cm or 16-1/8") long and remain within the 3 meter length limit. Using a whip antenna atop even a short support pole would increase the broadcast range by putting the whip antenna up higher and "in the clear," and it would also permit the transmitter box to be mounted higher on the pole (out of reach of children or the curious) if the transmitter user desires.
I have used Radio Shack part numbers in the description so that you can see what the parts look like on their web site www.radioshack.com . These same parts are, of course, available from many other vendors. The CB whip antenna mount could be a flat-bumper mount (940-0905), a mirror or luggage rack mount (21-937), or a ball mount (21-1115). These would be fastened to the top of the wooden pole (either in the center or on the side, depending on each mount's configuration) using long wood screws. (The ball mount would require an additional small, flat metal stand-off plate due to the location of its coaxial cable connector.)
The CB whip antenna lead wire could be made of #16 gauge stranded outdoor speaker wire with UV-resistant insulation (278-1117). Radio Shack sells this two-conductor outdoor "zip cord" in 100' lengths; peeling the two conductors apart will yield 200', enough for scores of outdoor TalkingSign installations. For the lead wire, I would cut a 35 cm (13-3/4") length (to take into account the length of the CB antenna mount). I would solder one end of the wire to the center (pin) connector of an RCA (Phono) plug and then solder the other end to the center (pin) connector of a PL-259 plug. (The TalkingSign transmitter uses an RCA [Phono] plug as an antenna plug, while the Talking House transmitter uses a spring-loaded wire clip inside the cabinet to connect to the end of the antenna wire.)
I would weather-proof the soldered connections with epoxy (64-2313), silicone rubber sealant (64-2314), or UV-resistant heat-shrink tubing. Where the wire passes into the transmitter box, a rubber grommet may or may not be necessary (a small drilled hole could be sealed around the wire using silicone rubber sealant). After the epoxy or silicone rubber sealant has cured, all you need to do is plug the RCA (Phono) plug into the TalkingSign transmitter (or feed the bare end of the wire into the Talking House's internal antenna wire clip), screw the PL-259 plug onto the CB antenna mount, screw the 102" CB whip antenna into the socket on the antenna mount, and you're ready to broadcast!
I hope this information will be helpful.
-- Black Shire
I recently wrote up a primer for a group who are interested in setting up Part 15 AM radio stations in isolated communities in rural Alaska. It may be of use to those on this board, so I have reproduced it below.
The AM1000 Rangemaster www.am1000rangemaster.com , Talking House www.talkinghouse.com , and TalkingSign www.talkingsign.com Part 15 AM transmitters can, if properly installed outdoors, *legally* achieve a broadcast range of 2 miles - 3 miles. The problem is that the villages may need different types of installations depending on their geography, which could lead to installation delays and higher unit prices due to the custom fabrication work and its associated labor costs. The solution is to devise one or more standard outdoor transmitter installations that would fulfill the villages' needs. I have a few ideas regarding this that I wanted to offer to you.
James R. Cunningham's book "Low Power Radio Broadcasting," covers Part 15 AM broadcasting in detail. He built systems in which the 100 milliwatt Part 15 AM transmitter with an 8' - 10' whip antenna (the book dates to 1990, before the 3 meter [9.84'] length was adopted) was mounted atop a 35 foot tall wooden pole. These installations achieved ranges of 2 miles - 3 miles! He used no illegal gimmicks such as radiating ground lead wires, but instead relied entirely upon the antenna's elevated feed point and line-of-sight signal propagation to achieve the long broadcast ranges. The 100 milliwatt TalkingSign, Talking House, and Rangemaster Part 15 AM transmitters would give similar results in similar installations.
Information Station Specialists (ISS) www.theradiosource.com offers its ALERT AM and AM Travelers Information Station (TIS) systems with three different antenna/RF ground system installation options--roof, yard, and isolated. I propose three Part 15 AM transmitter outdoor installation options that are analogous to the ALERT AM and TIS antenna/RF ground system installation options, and I have described them below:
[1] --Roof Mounted-- The Talking House or TalkingSign transmitter is installed inside a weatherproof box. [The 14” X 10” X 4” NEMA ABS Plastic Weatherproof Enclosure, Model Number NBP141004-100 (HIC-NB6), available from www.hyperlinktech.com/web/weatherproof_wireless_enclosure.php , would be perfect for this and the other outdoor installations.] The box is affixed to a weather-proofed wooden pole which extends 3 meters above the box and a short distance below it. The bottom of the pole is bolted to a roof tripod, which in turn is secured to the roof in the geometric center of the roof. The 3 meter wire antenna (made of either stranded wire or solid wire with UV-resistant outdoor insulation) is attached to the pole above the box using stand-off insulators of the type used on electric fences. If an AM1000 Rangemaster transmitter is used, the transmitter (in its weatherproof box with its 102" whip antenna on top) can simply be bolted atop the roof tripod. The 120 volt AC power and audio lines are routed to the transmitter box in a weatherproof conduit. If the roof is metal, it will still act as a counterpoise for the antenna via capacitive coupling (and thus increase the antenna's radiation) even though there is no directly-wired connection between the roof and the transmitter. If the roof is wood, concrete, or asphalt, a PowerPlane (tm) AM radial wire ground plane (available from ISS) installed on the roof below the transmitter box (but *NOT* electrically connected to the transmitter in any way) would also act as a capacitively-coupled counterpoise.
[2] --Pole Mounted (Tall)-- The TalkingSign transmitter in its outdoor box is affixed to a 20' - 40' tall wooden pole (such as a telephone pole), with the top of the transmitter box being 3 meters below the top of the pole. The 3 meter wire antenna (made of either stranded wire or solid wire with UV-resistant outdoor insulation) is attached to the pole above the box using stand-off insulators of the type used on electric fences. If an AM1000 Rangemaster transmitter is used, the transmitter (in its weatherproof box with its 102" whip antenna on top) can simply be bolted to a length of TV antenna mast tubing, which in turn is bolted or strapped to the wooden support pole. The 120 volt AC power and audio lines are routed up the pole to the transmitter box in a weatherproof conduit.
[3] --Pole Mounted (Short)-- This installation is the same as [2] except that the wooden pole is much shorter, being only tall enough to accomodate the 3 meter wire antenna above the transmitter box and 3' - 10' of the 120 volt AC power and audio lines (in a weatherproof conduit) running up the pole to the transmitter box. An AM1000 Rangemaster transmitter could be mounted to the short support pole in the same way as in [2]. If installed on a hilltop, this short pole installation could also achieve multi-mile range. If desired, a PowerPlane (tm) AM radial wire ground plane (available from ISS) installed at the base of the pole below the transmitter box (but *NOT* electrically connected to the transmitter in any way) would act as a capacitively-coupled counterpoise that could be beneficial in areas with poor soil conductivity.
If Talking House or TalkingSign transmitters are used, there is also another antenna option that could be implemented as part of the standard Part 15 AM transmitter outdoor installation plans that I described above.
To get the maximum usable height (and thus broadcast range) from a support pole, a 102" (8.5' or 2.59 meter) steel or fiberglass CB whip antenna could be mounted atop the pole and be connected to the transmitter in its outdoor box using a lead wire. This lead wire could be up to 0.41 meters (41 cm or 16-1/8") long and remain within the 3 meter length limit. Using a whip antenna atop even a short support pole would increase the broadcast range by putting the whip antenna up higher and "in the clear," and it would also permit the transmitter box to be mounted higher on the pole (out of reach of children or the curious) if the transmitter user desires.
I have used Radio Shack part numbers in the description so that you can see what the parts look like on their web site www.radioshack.com . These same parts are, of course, available from many other vendors. The CB whip antenna mount could be a flat-bumper mount (940-0905), a mirror or luggage rack mount (21-937), or a ball mount (21-1115). These would be fastened to the top of the wooden pole (either in the center or on the side, depending on each mount's configuration) using long wood screws. (The ball mount would require an additional small, flat metal stand-off plate due to the location of its coaxial cable connector.)
The CB whip antenna lead wire could be made of #16 gauge stranded outdoor speaker wire with UV-resistant insulation (278-1117). Radio Shack sells this two-conductor outdoor "zip cord" in 100' lengths; peeling the two conductors apart will yield 200', enough for scores of outdoor TalkingSign installations. For the lead wire, I would cut a 35 cm (13-3/4") length (to take into account the length of the CB antenna mount). I would solder one end of the wire to the center (pin) connector of an RCA (Phono) plug and then solder the other end to the center (pin) connector of a PL-259 plug. (The TalkingSign transmitter uses an RCA [Phono] plug as an antenna plug, while the Talking House transmitter uses a spring-loaded wire clip inside the cabinet to connect to the end of the antenna wire.)
I would weather-proof the soldered connections with epoxy (64-2313), silicone rubber sealant (64-2314), or UV-resistant heat-shrink tubing. Where the wire passes into the transmitter box, a rubber grommet may or may not be necessary (a small drilled hole could be sealed around the wire using silicone rubber sealant). After the epoxy or silicone rubber sealant has cured, all you need to do is plug the RCA (Phono) plug into the TalkingSign transmitter (or feed the bare end of the wire into the Talking House's internal antenna wire clip), screw the PL-259 plug onto the CB antenna mount, screw the 102" CB whip antenna into the socket on the antenna mount, and you're ready to broadcast!
I hope this information will be helpful.
-- Black Shire