The History of the

Cactus Intertie System

Cactus Intertie, Inc., originally known as Cactus Radio Club, Inc.,, and the Cactus Intertie System began on October 31, 1971, when Alan Burgstahler, WA6AWD, and Robin Critchell, WA6CDR, installed a 440-Mhz repeater at a site on a ridge 7,600 feet above sea level (and nearby terrain) near the southern end of the San Bernardino National Forest, about 20 miles South of Palm Springs, California. The space at the site was, at the time, offered to them at no cost so it was too good to pass up. Robin had been involved in the construction and day-to-day operation of a remote base station (WA6SVC) on a site called Sunset Ridge, near Pomona, California, while Alan had been a user of that and another system. This was their first collaboration on a radio site.

Since the offer of a free site came quickly and they didn't want to lose the offer, a repeater was hastily assembled using some old Motorola tube-based equipment. No control system was installed at first. It was unknown exactly what areas the radio signal from the San Bernardino site would cover. They found out that Robin could talk to the site extremely well from his house and from many places he traveled during his work day, but Alan couldn't hear the repeater at all from where he lived and very intermittently as he was driving to work.

At Robin's house there was a radio link on 420-Mhz from the remote base on Sunset Ridge for the purpose of accessing a phone patch. It was decided to construct a 420-Mhz link from Robin's house to the San Bernardino site and connect it to the 420-Mhz link coming from Sunset Ridge. Since money was tight and enthusiasm was high, the link equipment was made out of modified General Electric Pre-Prog mobile radio, known as an MC-306. All the radios used at the time were wideband deviation, which suited the technical requirements of the linked system, but they were also about the only radios available because the narrowband radios were the state of the art expensive commercial radios. Maintenance was high but for a number of years money wasn't available for solid-state equipment, and the GE tube equipment was used for many of the links that were to come, sometimes with modifications. At one site, one of those modifications was to use a Motorola Motrac solid-state exciter and use the GE tube radio only as the multiplier and amplifier. If they had waited to be able to afford solid-state equipment, the link system would never have been built. Alan had been playing with some control system ideas using touch-tone control and transistor-resistor-capacitor timing circuits to latch and unlatch relays. This crude control system was pressed into service at the San Bernardino site to turn on and off the connection to the 440 Mhz repeater. When the link was connected to the repeater, the 420-Mhz link from the Sunset Ridge remote base allowed communication between the two sites. If the link was off and the telephone was accessed through the link from Sunset Ridge, then the phone patch worked. Sometimes, someone would make a phone call and forget to check if the link to the San Bernardino site was turned on and the phone call would go out through both repeaters.

Since the San Bernardino site now had a control system, crude though it was, it was decided that a two-meter radio would be installed at the site and be connected to the 440 Mhz repeater. An experiment in prior years had shown that the San Bernardino site could talk to some of the mountaintops near Phoenix, Arizona. Among them were Pinal and Towers. It was rather common to talk from Pinal to the San Bernardino site although the propagation was intermittent. Also, a popular two-meter repeater, at that time on 146.34-94 and later on 146.16-76 was operating on Haden Peak in the Hualapai mountains near Kingman, Arizona and covered much of the Colorado River border between California and Arizona and even into Las Vegas, Nevada. Setting up one of the channels in the two-meter station to be able to talk into this repeater meant that communication was possible from the Los Angeles area well into Arizona and Nevada on a combination of UHF and VHF channels. Who knew who else they'd be able to talk to.

Eventually there was enough activity on this crude but operational system that some of the users on the Sunset Ridge remote base started to complain. Their quiet radio was now being used almost exclusively to talk to people to the East of the Los Angeles area through this link system thing. As a result, Robin and Alan procured radio space in an adjacent building on Sunset Ridge and put up a 440-Mhz repeater with its own link to Robin's house on a different frequency than the old phone system link. This new repeater had the sole purpose of accessing the link to the San Bernardino site repeater, which had now become a remote base station in its own right. To differentiate between the two systems on Sunset Ridge, the old remote base was called Sunset One, and the new link access radio was called Sunset Two. Later, an additional remote base was added at Sunset Ridge to give local users another place to talk away from the link system and to have two-meter access in the Los Angeles area. This radio was called, appropriately enough, Sunset Three.

Robin had been talking with Tom Robinson, K6TAZ and the late Gene Nicholson, W6YJO, who had a remote base station installed on Santa Ynez, a 4,300 foot mountain top near Santa Barbara, California. Robin put up another 420 Mhz link at his house in Pomona, California, and Tom & Gene put one at their Santa Barbara site. The path was a long 140 miles and definitely not line-of-sight. The path would fade in and out as conditions changed, but communication was made and excitement was generated. Eventually an intermediate back-to-back relay site was installed at a midpoint ,Saddle Peak near Malibu, and communications became solid.

About this time, Lee Hendrickson (K6LQT) heard about this linked system and became very interested. Lee, Phil Hughes, WA6SWR, and Jim Grimm, WA6OOU, already had built and installed a 440 Mhz and six-meter repeater with a two-meter remote base on Santiago Peak, a 5,796 foot site in Orange County in 1964. Phil had designed a complex control system based on a telephone Stroeger switch (10 by 10 stepper switch). Around the time Lee met Robin and Alan, the system was undergoing reconfiguration as a 440 repeater prior to being moved to the residence of Hank Meyer, W6GGV, on top of the 1,500-foot Palos Verdes Peninsula. A 420 link to Jim's house in Manhattan Beach provided a telephone connection. To link the system to Cactus, it was necessary to completely redesign it (again!) and build a new (third) repeater with a 420 Mhz link to talk to the Cactus system. The new repeater (WA6AXC) consisted of a GE MASTR Pro base station repeater and two 420 link transmitters and receivers. One link pair pointed to Robin's house in Pamona, and the other to Contractor's Peak in the San Fernando Valley where Ron, W6AXC, constructed a system that provided good San Fernando Valley coverage for mobile users. Jim designed the touchtone decoder and other strategic pieces of control and phone patch circuitry. Alan provided the audio switching cards for the controller which the members of Lee's group assembled. A major push ensued by Lee, Jim, Ken Robbins, WA6PYJ, Neil McKie, WA6KLA, the late Gary Briones, WA6KIP, and others to get the system up and on-line only two weeks after Santa Ynez came on-line.

The two-meter activity from the San Bernardino site got the Phoenix area hams all excited. Some of them had constructed remote base stations on their nearby mountain tops also. A site on Towers Mountain, Southeast of Prescott, Arizona had the best path, although it was intermittent. A stacked pair of eleven-element two meter beams and a 20 element broadside array was installed on the San Bernardino site down the east side of the mountain aiming eastward. This east side approach benefitted from having some rocks and dirt between it and the Los Angeles two-meter signals, and also it was on the leeward side of the mountain from all the winter storms. Those beams wouldn't have lasted through the first storm if they had been mounted at the top of the ridge. A new control system had been designed and built by Alan using TTL integrated circuits for the logic switching. This control system also had some relay outputs and one of those was used to switch the two-meter radio between the PD-340 antenna, with all the dipoles pointed northeast, at the top of the ridge and the twin yagis down the East side of the ridge. The use of these yagis made the 2-meter path to Towers Mountain somewhat more predictable, and once in a while a remote base station on Pinal Peak, about 70 miles east of Phoenix, was heard when conditions were right.

As interest to the east grew, a site was procured at Black Peak, near Parker, Arizona. The site was within a few miles of the Colorado River. While access to both Sunset Ridge and the San Bernardino site could normally be achieved in a 2 wheel drive truck, the Black Peak access road was strictly a 4 wheel drive affair. The road was so steep at one place that it had been paved in hand-poured rough concrete to give enough traction to the vehicles going up, and to keep vehicles from sliding off the edge with all four wheels locked tight while going down. Above the paved area the road was loose rock, much of it volcanic, and tire sidewalls and wheel rims suffered as the vehicles ground their way to the top. First time riders up the hill usually turned the air blue with epithets, much to the amusement of seasoned veterans of the trip. This definitely was the worst site road of all.

At Black Peak, the radio system consisted of a 440-Mhz repeater, a multi-frequency two-meter base station, a 420 Mhz link back to the San Bernardino site, and an additional 420 Mhz link to be used for connecting east in the future. All this was connected by another TTL control system built by Alan. The 420 Mhz link path to the San Bernardino site was so poor that the exact antenna location for the 14-element KLM yagis used for the path had to be found by putting the link transmitter at the San Bernardino site into a continuous transmit condition while Robin climbed all over the H-frame tower structure while monitoring received signal strength on a meter. All of this was done at night because during the summer it was so hot during the daytime that a person could not touch any metal in the sun without burning his hands. The entire H-frame tower structure had been installed between midnight and 4 am because of this problem. Once the location for the 420 Mhz link antennas was found, the path was very stable, operating for a number of years with very few fades. This was a 140 mile path that again was definitely not line-of-sight but a forward scatter path. Someone once made a plot of the path and determined that to make it a line-of-sight path, it would have had to have gone 1000 feet below the terrain in the center of the path. This site was later removed and a new site closer to Interstate 10 was installed, Guadalupe Peak near Quartzite. About this time an 11 element two-meter beam was put on Pinal Peak. With the beam pointed at Black Peak, the reliability of communications improved.

At Black Peak there was some interest generated in having a large rotatable antenna system on two meters. Bob Lawson, N6RW, designed and built a rotator control that could be interfaced to Alan's control system. The antennas consisted of two twelve-element phased yagis, vertically polarized, that could be told to point to any numeric direction of the compass. It was quite exciting to stand there at Black Peak and watch as someone in Los Angeles or Phoenix would enter some touch-tone digits into their transmitter and the antenna at Black Peak, miles away from them, would point to the direction they had entered.

The Black Mountain site had much better two-meter coverage deep into Arizona than did the San Bernardino site. Contact could now be made with two-meter repeaters in the Phoenix area. The group that ran the remote base on Pinal Peak became very interested in building a link to Black Peak and they procured a site called Smith Peak, partway between the two sites. A simple back-to-back 420 Mhz relay station was installed and people in the Phoenix and Tucson areas could talk on 440 Mhz into Pinal Peak and communicate on a solid basis with the people operating in Los Angeles and Santa Barbara, and anywhere in between that there was a 440 Mhz radio connected to the link. Another TTL control system was built by Alan and installed on Pinal Peak to aid in the operation and control of the radio link system. Now people anywhere along the link system, could also operate the two-meter radio on Pinal Peak and talk easily to people on two-meters (including simplex) in the Phoenix and Tucson areas.

Eventually, Alan built another TTL control system and it was placed on Towers Mountain, Southeast of Prescott. This became the intermediate link port between Black Peak and Pinal Peak, and the Smith Peak site was removed. The Towers Mountain radio site included a 440 Mhz repeater and a two-meter radio as well as the link radios.

One of the members of the Pinal Peak group was Milt Jensen, N5IA, who lived just inside New Mexico from the Arizona border. He could talk to the Pinal Peak radio site from his house (with a T-44 and twin 14 element KLM beams) but not from his mobile unit while driving in his area. He and a few friends had procured a radio site at Jack's Peak, northeast of Lordsburg, New Mexico, built their own building at the site, and had been operating a local repeater and a tube type 440 station with a 4 channel tube type 2 meter remote base station. Their controller was single digit DTMF with stepping relays for on/off and frequency selection.

They asked Alan to build another TTL control system. After the Cactus annual meeting in January of 1978, Milt, N5IA, Mike, WB5NQC, and Stan, K7KNP, stayed in Riverside at Alan's home for a week exposing, etching, drilling, stuffing, and soldering the 100+ boards that would comprise the "Burghstahler Super Controller". Five, 14 hour days, with some supervision from Jeff, did the job. Alan spent the summer wiring the four card racks and testing all the boards. The ultimate product utilized over 1,000 ICs and the TTL logic demanded 15 Amps from the 5 Volt supply, plus the positive and negative 12 Volts for the audio.

Alan and Robin made the trip to New Mexico and the controller was installed at the Jack's Peak site over the Labor Day weekend of 1978. The 440 station was a brand new factory fresh GE Mastr II 100 Watt repeater package. It was linked back to Pinal Peak and the Cactus Intertie System was still moving eastward. The radio system at Jacks Peak was somewhat unique in that not only did it have the usual 440 Mhz repeater, but the two-meter FM remote base station consisted of a GE Mastr II with a VHF Engineering synthesizer that provided 19 diode matrix pre-programmed channels plus "Frequency of the Day" selected by the thumb wheels on the synthesizer. Later, a remote programming card was designed and added to this selection. This controller was also unique in that it had three back bone link ports, the N5IA conceived "aux link" port to the 440 radio for the Guthrie Peak and Caballo Mountain sites, six antenna selects for the 2 meter remote, Hi/Lo power selects for the 440, a six meter remote base station on 52.525 Mhz, a ten meter remote base station on 29.6 Mhz, on/off controls for a tower mounted night light, controls for the on-site 2 meter repeater, and an original "Raspberry" sound generator. Two years later the link was extended to a site on Comanche Peak at El Paso, Texas, prepared by the Comanche Remote Amateur Base Society (CRABS). The link system was now connected to four states, all linked on 420-Mhz.

Meanwhile, Mike, N7CK, who had been going to school in Camarillo, California back when Santa Ynez came on line, had become a member of the Pinal group. Larry, W7MCO, who had moved from Oxnard, California to Tucson discovered that the coverage from Pinal to Tucson wasn't all that great, so they formed the Cholla Amateur Remote Base Association (CARBA) and built a new site using GE Progress Line radios in Larry's garage. These radios could link to Pinal Peak using a simple controller built by N7CK. This controller was later enhanced by Burgstahler audio cards and logic from the pre-Burgstahler controller. The GE Progress Line radios were replaced with solid state equipment and the whole package was moved into a new building on Mt. Lemmon built for hams by Ken Simpson, WB7DRD. The radio was linked and on the air at about the same time the Jacks Peak site became active. Coverage was now almost solid on I-10 from Phoenix to beyond Las Cruces.

Shortly thereafter, Rich, W7DTL, came up with a scheme for using the then new Motorola solid state power modules with GE Mastr Exec II exciter boards to make solid state transmitters. John, AK7Z, figured out a manufacturing process and many of these transmitters were built, greatly aiding the rapid growth of the system.

Within 2 years, the link was connected to a site on Mt. Franklin at El Paso, Texas. The link system was now connecting four states, all linked on 420 Mhz.

At this time, late 1976, the system had grown to be in excess of 1,000 miles of 420 Mhz duplexed links stretching from Sacramento to El Paso.

In the early seventies, Mike Roden, N5FL (now K7JR), was visiting Los Angeles from the Dallas, Texas, area. Mike had a 440 Mhz radio in his car and had built a GLB synthesizer to have frequency agility. Remember, this was long before synthesized VHF and UHF radios were available on the ham frequencies. All radios at that time were strictly crystal controlled. Mike stumbled across the actively operating Cactus System radio and spoke up with his distinctive Texas voice and call. He was fascinated with what he heard and found out about the system. After talking with Robin and Alan on the phone, he went back to Texas with a seed planted in his mind. Not too long afterwards Joe Jarrett, K5FOG, made a business trip to the Los Angeles area and spent an afternoon with Alan talking about control systems and audio interfacing. It was agreed that the Dallas, Texas group would use some unique control codes that were not used by the Los Angeles group so that if, someday in the far distant future, the two systems ever were able to connect, the control codes would be compatible with each other. That someday finally arrived, and the Armadillo and Cactus systems were finally connected.

One helper in spreading the system across the miles were system members from the Los Angeles area moving to other locations. Tom Robinson, K6TAZ, moved to the San Francisco Bay area and was successful in constructing a linked system back to the Santa Ynez Peak site near Santa Barbara. Lee Hendrickson, K6LQT, moved to the Sacramento, California, area and put up a system. At first he connected back to the main system through Tom's San Francisco area system, and later connected through central California to Frazier Peak, between Bakersfield and Los Angeles, and from there back into the main system. One member moved to the Salt Lake City, Utah, area and people became interested in linking back to the system. From their main site near Salt Lake City, and through two more sites further south in Utah, they finally became fully linked when the Mt. Potosi station site became active near Las Vegas, Nevada. Check the Cactus Map to see just how extensively the system has spread. More links to farther locations are sure to come.

Control Systems that started as transistor-resistor-capacitor-relay systems and progressed to TTL logic with no relays, have now given way to microprocessor controlled systems. This now allows an almost infinite amount of design change capabilities without having to hand-rewire the control systems to change operating characteristics, as had to be done earlier. The link system was installed as a full-duplex link, being active in both directions at the same time. This allows for a maximum amount of control over all the sites down the link. Since the person controlling the system might be controlling and operating a transmitter hundreds of miles away, he had to be able to control and override any potential system problems. A simplex link wouldn't allow that type of control.

Cactus Intertie, Inc. was officially established in 1973 to financially support the Los Angeles-based nucleus of the Cactus Intertie System. The club began having annual meetings and, as the Intertie system grew, members of the other linked systems were invited to the meetings to create and form a comradery and to pass along engineering innovations that would be of benefit to the entire system. The building trend for the Cactus Intertie System has continued over the years. The Cactus Intertie System is the largest amateur radio linked system in the nation with more than 120 linked remote base stations. These remote base stations are owned by 26 different amateur radio groups with over 1,500 total members, with each group having their own financial and administrative structure. The early development of and adherence to high technical standards in both the RF equipment, audio processing technique, as well as the system controller design and interfacing, has made the Cactus Intertie System the most reliable and best sounding linked system in the nation.

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Revised: May 7, 2011 by WA6PYJ
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