How to Prevent the Microwave Path Survey from Being Your Weakest Link
When it comes to establishing a reliable and critical microwave path, should you do it yourself or hire a professional ? You’re thinking “why spend the extra money” or “how hard could it be to do it myself” ? Let me offer an analogy that I think everyone can relate to in an effort to demonstrate that money saved up front can cost you big time in the long run.
You’ve just purchased your dream acre and want to build a house to make it your home. You’ve decided that you’ll need a fence - so you look at your options and expenses. You can try to save a few dollars and build your nice new expensive fence based on where you think your property line is located. Or you can hire a land surveyor and spend a reasonable fee to definitively mark your property lines.
You decide to save a few dollars and do it yourself. The fence goes up, and then your neighbor shows you his survey plat that indicates your nice new expensive fence is actually encroaching onto his property. Your next option might be to come to some agreement with him about the encroachment. But alas, he’s planning to build a nice new expensive guest house exactly where your fence now encroaches. Guess what - the money that you thought you’d save by not hiring a surveyor to mark your property line is now going to look like spare change compared to the expense of having to tear down the fence and start all over – not to mention the cost of having to hire the surveyor anyway.
Accurate determination and avoidance of microwave path obstructions is critical to the design process
It’s interesting that companies willing to spend hundreds of thousands or even millions of dollars to design and install a microwave system will adopt the same mentality when it comes to budgeting expenses for a microwave path survey. They’ll spend copious amounts of office time performing feasibility design “paper surveys” utilizing all sorts of vegetation, building and terrain databases, throw in a fudge factor for clearance, throw in another fudge factor as a sleeping aide, and before you know it, have a multi-million dollar system designed to six nines (99.9999% reliability) without ever having set foot in the field to verify any data.
Another scenario might be that a company does decide that they need a path survey, but want to minimize the budget and have Joe, the Engineer-in-Training in charge of feasibility studies - who had a surveying course in college - go out with a GPS, camera and some maps to take a look at the path. Joe takes GPS readings at the terminal sites, drives to what he thinks are the critical terrestrial points on the path centerline, estimates average tree heights, goes back to the office, turns the crank on his computer grinder and comes up with antenna centerlines that he thinks will work. Is Joe a qualified microwave path surveyor? Is that a comprehensive path survey he performed? Is it any different from you building your fence where you think the property line is? These questions can become very relevant depending on the system requirements and how well you like to sleep at night.
The above scenario might be sufficient for minimal project requirements for less than critical systems. However, if a company wants to take a chance with a critical system carrying data for any number of alphabet agencies, it could turn into a financial and logistical nightmare. The old poster that says, “The good news is the project is finished. The bad news is, you used the wrong plans”, has come back to haunt many a project manager when they thought they could save a few budget dollars by shaving off services that they deemed “non-essential”, or by using someone less qualified with less experience to provide the data instead of hiring a professional. It is essential to utilize the right personnel to get the right data. Wrong, inaccurate or incomplete field data will sink a project no matter how well it’s designed. And as we say in aviation, “the accident chain begins at the weakest link”.
In reality, all systems are critical to the clients who are paying you to design them because their reputations are on the line as well. Would you be willing to bet the design and reliability of your nice new expensive super critical microwave system – not to mention the professional reputation and financial stability of your company - on the assumptions of someone other than a seasoned, trained path surveyor with years of experience and expertise ? You more likely would be betting on the possibility – nay probability - that an undocumented building, tree, or blown digitized terrain contour elevation in the databases that you rely on would turn your engineering design of six nines into a blocked path. Thoughts like this can make you waste a lot of useful time rehashing project details and wondering if you designed everything right.
The alternative to our original analogy is that you determine that you want the “insurance” of a path survey to back up your engineering design, and you want someone reliable with that particular experience and expertise to provide the data. This is where I come in. As a dedicated microwave path surveyor with an engineering surveying degree and over 25 years of experience surveying thousands of paths around the world, I have an upper echelon level of expertise. My experience and expertise goes well beyond that of typical line of sight (LOS) surveyors, "path flashers" & those who minimally grasp electromagnetic & wave propagation theory. Experience in transmission engineering design combined with my field expertise equips me to obtain the highly and dependable detailed path data necessary to properly design a reliable microwave path. I provide precision field work, accurate data, complete documentation with a combination of intellect and a complete command of the process.
Verifying dish locations with a surveying laser
Part of the path surveying routine includes climbing the existing towers at the terminal endpoints to observe the path from above ground level over nearby obstructions and to visualize how close significant vegetation or man-made objects might be to the centerline.
I never dreamed at the beginning of my career that I would be climbing microwave towers, but it is part of what I do and I love every minute of it. Utilizing my engineering expertise and climbing skills to provide a greater understanding of field conditions for my clients is a blessing that I thank the Lord for every day.
There aren’t many women out there who climb towers and it catches some people off guard when they find out what I do. I’m looking forward to writing more about life as a female tower climber in the near future. In the meantime, if you have any questions about finding the right professional to properly execute a microwave path survey, I’d be happy to discuss in more detail the important aspects of this critically essential task.
Finally, it takes a unique combination of skills and experience to perform a reliable and complete microwave path survey that you can stake your entire engineering design on. Personally, I believe that many companies in this lucrative field offer bare minimum path survey services utilizing personnel with minimal engineering surveying experience and an even lesser understanding of electromagnetic and wave propagation theory and how terrain, physical factors and climate affect the transmission of energy. Microwave systems - especially mission critical microwave projects - require a higher level of expertise and experience, and I recommend that as a microwave project manager or transmission design engineer, you should look for someone who has strong surveying expertise and experience, combined with transmission engineering design experience. I’ve been doing this for more than 25 years and would be happy to discuss with you how the right combination of training and years of experience can make a big difference in the reliability of your microwave system.
For more about Sandy’s amazing career, read “View from the Top – Adventures of a Female Tower Climber”.
Sandy: I read both your published articles, which I found refreshingly excellent, in educating our telecommuni-
cation industry in the important task of field surveying. For over 46 years I work-
ed as a communication project engineer for three long lines telephone companies and Washington St. DOT ITS Comm. & Wireless Tech, engineering new radio sites and new MW links. I also upgraded old sites & old MW links. I was a BSEE radio engineer and certified Master I NARTE engineer. In addition, I was certified as an instructor in tower climbing safety and rescue training, certifying our radio techs annually to maintain our radio towers and install our MW & LMR antenna-feeder systems on radio towers. I loved being in the field while many of my counterparts preferred the safety and comfort of the office. I did it all, designing the MW paths, straight single links and beam bender, single or dual passive reflector, links, installing the new MW antenna-systems on the towers, aligning the MW dishes over the link, and finally perform the sweep and fault location testing on both end antenna-feeder systems.
When I worked for the long lines telco in Alaska I was learning my radio engineer- ing craft, mostly in the field. My engineering friend, Dick Laine with then GTE Lenkurt, taught me that an engineer can only become an expert in his or her profession, if they got out into the field. The APUC gave our long lines telco the challenge of installing new MW backbone & spur link systems all over the state ASAP. The engineering dept handed out the new link projects to the new hires, who had no path designing experience. After some of links were Implemented and were later found to be in various degrees of degraded performance, I was hand chosen by the bosses to field investigate these poorly operating paths to come up with solutions. I discovered my co-engineers only performed paper map surveys and never once visited the radio sites. The no. 1 problem were near end or mid-path obstructions: solid ground, trees, and manmade structures. Some of these obstructed paths could have met the required clearance requirements, if they had implemented a new taller radio tower with the MW dish tower mounted at the required higher tower elevation. It was not cost-effective to replace the shorter towers with more expensive taller towers. Our telco had to live with providing some of their customers with degraded service.
The only MW radio engineer for one State agency would determine his MW link clearances by stretching a rubber band between two points in question over a raised contour map of the State. His Chief Engineer told me that half of his radio engineer’s “rubber band” designed MW links were either blocked or grazing. This State Agency spent millions trying to fix these obstructed paths or having to live with the degraded MW links.
With many of these inexperienced radio engineers out there designing MW paths without the necessary field surveys, your field service company should be kept busy for a long time. The word about companies such as yours needs to get out there to the uneducated public. Some time ago I had recommended you with your company to an engineer, Diallo Bobacar, with a Canadian power utility who was tasked with upgrading their existing MW network. This existing network needed a person of your talents to document this large telephone system. I told him that you had successfully done contract field work for Alcatel. I do not know if he ever contacted you.
Keep doing the good work; and, keep looking up. Regards,
Richard S Gunn, Retired Believer