KBRT Oak Flat Transmitter SiteKBRT Tower

Since closing on the site in late 2008, we have been working to prepare the FCC and FAA applications and then work through all the local, state and federal regulatory issues that such a project entails. Final planning approval was obtained in October of 2011, and building permits were issued in April of 2012. Work began immediately, starting with bringing in underground power from a location nearly a mile away.

Construction took place in the late spring, summer and fall of 2012, wrapping up in December. Final testing and adjustment of the transmitter and antenna system took place in early January of 2013 and the site went on the air on February 28th, 2013.

The photos on this site chronicle the project, from the first test transmissions to completion of the facility. Click on each photo to view the full-size version.

> Download the Complete Project Narrative written
by Cris Alexander - CBC Director of Engineering (PDF)


Listen as Don Crawford and Cris Alexander join Bottom Line hosts
David Householder and Roger Marsh to discuss the Oak Flat project live on KBRT (02/28/13)


A test antenna was erected and a 1 kW signal was transmitted from the site in October 2010 to measure the ground conductivity of the site and surrounding area. (October 27, 2010)

Underground conduit was installed under Black Star Canyon Road from the National Weather Service NEXRAD radar site almost a mile southwest of the site. (June 20, 2012)

This is the sign adjacent to the gate at the site entrance. Most of the notices thereon are required by law. The rest are required by lawyers. (August 16, 2012)

Grading work began in early July, starting with a biological survey to make sure that there were no nests for endangered species or migratory birds at the site. The site was then mowed and rough grading got underway. (July 11, 2012)

By late July, drilling for the tower base pier and guy anchor caissons was complete and rebar was being installed in preparation for concrete. (July 25, 2012)

Drainage was a big issue with the site and project. Because our site is at the top of the hill, all runoff impacts our downhill neighbors and the watershed below. To keep silt from leaving the property, we constructed a silt dam, complete with standpipe and spillway. The dam works very well. Silt collects in the basin on the uphill side and only clean water enters the standpipe and flows on downstream.
16, 2012)

Base piers and anchor caissons were complete and cured by mid-August, and tower steel was on site ready to stack. (August 16, 2012)

The stubs for the four towers were set first, then the remainder of each tower was stacked to completion. (August 22, 2012)

By August 29, all four towers were complete. What a thrill it was to come up that switchback road and get that first glimpse of towers in the air at the site! (August 29, 2012)

With no power at the site yet, chief engineer Bill Agresta put together solar power systems to run the lights on each tower. This consisted of a 180-watt 36-volt solar panel, charge controller, deep-cycle battery and 400-watt inverter. The lights employ low-energy LED technology. (August 29, 2012)

With rough grading complete and underground conduits installed from the towers and transformer area, forms and rebar were installed for the building foundation. (September 12, 2012)

The prefabricated 12' x 30' building arrived on a flatbed truck in late September. A crane and two smaller stake trucks were on hand to meet it. The building halves were transferred to the stake trucks for transport up the five-mile switchback road to the site some 2,600 feet above. (September 26, 2012)

Onlookers gathered to watch the spectacle of the two building halves and the crane make their way up the mountain. (September 26, 2012)

Each half of the building was craned into place. The front half was bolted down in its permanent location, but the back half was temporarily set with a six-foot gap between the sections so we could get the large pieces of equipment in. (September 26, 2012)

With the equipment inside, the back half was moved into place and the two halves were joined.
26, 2012)

With the building in place, screening/security walls made of foot-thick concrete block began to go up. The voids in the block were filled with concrete, making this wall and those around the tower bases formidable. (October 3, 2012)

With a portable generator supplying power, our engineers were able to begin installing equipment. Here, Bill Agresta (L) and Todd Stickler (R) connect the rigid transmission line to the phasing unit. (October 10, 2012)

CBC president Don Crawford visited the site in mid-October. (October 18, 2012)

Transmission lines from the phasing unit were plumbed through the port to the outside where they were ready for connection to the underground cables to the towers. (October 18, 2012)

Rigid transmission lines from the phasing unit to the egress port. (October 18, 2012)
A project milestone: POWER!! (October 23, 2012)

The antenna tuning units were placed on concrete pads inside the tower base enclosures. A copper grid was installed around the tower bases.
1, 2012)

The screening/security wall was completed around the equipment building and stuccoed, the color blending well into the surrounding hillside. The enclosure adjacent to the building is a stall for a portable generator. (November 1, 2012)

Equipment installation with the phasing unit in the background (blue), main 50,000 watt transmitter (gray) in the middle and the equipment rack on the right (black). The auxiliary transmitter will be brought over from the old site on the island when we are done with it there. (November 7, 2012)

An 11 GHz microwave link connects the Oak Flat site to the studio in Costa Mesa. Here, tower workers install and connect the dish antenna and equipment on the northwest tower. (November 15, 2012)

Ground radials are plowed in starting at the tower bases, planted deep to make them difficult if not impossible for copper thieves to remove.
15, 2012)

Tall chain-link fences enclose the area around each tower base to keep workers and trespassers from entering any areas with hazardous RF fields.
(November 15, 2012)

An array of security cameras that provide color images during the day and infrared images at night cover each of the tower bases, the gate and the equipment building/compound. Doppler radar long-range motion sensors, photosensors and other devices cover every inch of the property. Armed guards make random patrols of the site and respond to alarms from a location near the bottom of the hill.
12, 2012)

High-power sirens and strobe lights activate at each tower base area and the building compound, filling the basin with blinding, flashing light and ear-splitting sound when an intruder is detected. The images from all the cameras are displayed automatically in the monitoring center, and a high-resolution steerable, zoomable camera can zero in on areas of interest. The security agency is then notified for armed response as appropriate. (December 12, 2012)

The first signal! KBRT operated at 5 kW non-directional from the Oak Flat site in early December for a brief period for testing. Signal reports, even at 10% power, were good. (December 12, 2012)

Cris Alexander adjusts a circuit model as he calibrates the antenna model to measured data from the site on January 7. Moment-method modeling and nodal analysis are used to determine the correct operating parameters for the directional antenna.  (January 7, 2013)

Adjusting the networks in the phasor and coupling system is part of the tune-up process. The objective is to produce RF with the correct current and phase at each tower, which in turn will produce the desired directional pattern.  (January 7, 2013)

All ready to go on January 9. There are still a number of pieces of ancillary equipment that will come over from the Catalina Island site and populate the empty slots in the equipment rack, but the site is fully operational and ready to go on the air.
(January 9, 2013)

The user interface on the main transmitter shows 52.7 kW output power during testing on January 9.
(January 9, 2013)

Cris Alexander talks with Bill Agresta and Don Crawford in front of tower #3.
(February 28, 2013)

Don Crawford and Cris Alexander at the high point of the site looking down on the antenna field.
(February 28, 2013)

Don Crawford looks over the antenna field.
(February 28, 2013)

Don Crawford presses the RF ON button on the main transmitter at the new site.
(February 28, 2013)

(February 28, 2013)

(L-R) Todd Stickler, Don Crawford, Cris Alexander and Bill Agresta in the new transmitter building.
(February 28, 2013)

(clockwise from the left) Bottom line hosts David Householder and Roger Marsh and guests Cris Alexander and Don Crawford in the KBRT talk studio.
(February 28, 2013)

Cris Alexander stands next to a plaque honoring him for his part in the new KBRT site.
(February 28, 2013)




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