SUGGESTED EDITOR’S NOTE: Jim Andress is a WSMR retiree who worked in the communications area for decades. He has written several articles for the Hands Across History newsletter published by the WSMR Pioneer Group and WSMR Historical Foundation. This appeared in the February 2014 issue.
By Jim Andress
This is another one of my articles on WSMR’s commo history. In this piece I answer questions about the big billboard structure that was once up on the mountainside in back of the golf course – what was it? – why was it there? – what did it do?
Yes, it did look like a big billboard, but in reality it was a reflector for radio communication signals. Back in the 1960s there was a lot of innovation being done in instrumentation hardware and techniques. The same can be said for long-haul microwave radio communications.
We typically think of microwave radio as a point-to-point facility using a radio beam directed and focused between two parabolic, or dish shaped, antennas. Just like a beam of light transmitted from a flashlight, the parabolic reflector in back of and around the small light bulb, reflects the light energy into a beam and directs it to wherever you point it. Also, if the beam of light from your flashlight strikes a hard flat surface, particularly shiny metal, it is reflected, or redirected in another direction. Its Geometry 101.
In the case of the billboard, we were doing just that, reflecting a broadband high-data-rate telemetry radio relay signal between Bldg. 1512 on the WSMR main post and old Bldg. 841 at Holloman.
It was early in 1962 when the late Ben Billups, Director of National Range Data Reduction, contacted WSMR communications. He needed a broadband communications link for real-time, post-mission and related telemetry data transfer between the Land-Air data center in Bldg. 841 and Bldg. 1512. We had three options:
1) Put a radio repeater in the Sacramento Mountains. Establishing another off-range operation, security issues, and other logistic problems ruled against this idea.
2) Erect a 200-plus-foot tower in the tech area close to Bldg. 1512. With very little study, this was quickly determined to be administratively and appearance-wise unacceptable.
3) Place a reflective passive repeater in the mountains in back of the golf course.
All things considered, the passive repeater, or billboard, was the best option. In those days, the broadband fiber optic cable media that we take for granted today, had not yet been developed.
Since this was a specialized system for a special customer, we contracted with Rockwell/Collins. They had been in the microwave business for many years, were familiar with military telemetry system formats and techniques, as well as billboard technology.
So, a team was made up of WSMR commo engineers as project managers and Rockwell as the system engineering and integration contractor. Another vital member of the team was the WSMR Post Engineers.
Having the engineers on board was a good move. Their construction people already had security clearances, they had the construction equipment, and they had the skilled people with experience in building roads and precision structures. Plus, they were local, on post, and available with flexible schedules, all of which contributed to significant cost savings.
Initially, the construction effort required us to open an old mining site trail so material trucks and the erection crane could get to the site. One interesting individual on the job was the crane operator. He was an elderly gentleman who, as it soon became obvious, had many years of experience with cranes. He gently maneuvered his large crane up the difficult road, got it into place, and very carefully hoisted the precision components into place. This was especially important when it came to the big 4×10-foot reflector panels. If the construction personnel wanted a structural member or panel moved half an inch, he moved it exactly half an inch, any direction, up or down, very smooth with no swinging. It was a pleasure watching a real pro work.
As you can see on the page 3 photo, the mechanical construction of the billboard’s reflecting surface consisted of twelve 4×10-foot panels. It was 30×32 feet when assembled, for an area of 960 square feet. This largish area was necessary in order to achieve the required approximate 115 db of reflective radio frequency gain for the propagation path. We were able to achieve this minimal size due to the very small reflection angle of the radio path, less than 10 degrees as I recall.
One other interesting engineering number – since we were using radio frequencies in the 7000 mhz frequency band, this required that the face flatness across the 960-square-foot area be no more than plus or minus an eighth of an inch. This figure is one of the reasons that the construction effort had to be very precise.
Being a technical issue for the Range instrumentation support, it was relatively easy to get master planning board approval for the project. However, after the board was installed, there was occasional criticism from the garden club and others who liked to look at the mountain scenery. It was understandable. Without question, the board certainly was not visually or environmentally attractive. I had to address this issue occasionally over the years. The most common requests were to move it and/or paint it. Moving it would have just made it useless and painting would have caused a constant maintenance issue, plus potential distortion to the flatness requirement.
Interestingly, under certain weather conditions, the board was essentially invisible from the main post. But under other conditions, it was highly visible and reflective. It stayed put until the mid 1980s, when communications requirements changed, and it was removed.