Microwave Antenna Alignment

May 2, 2016

An industry test equipment manufacturer recently estimated up to 40% of all wireless microwave paths are not aligned optimally. We believe it’s more, perhaps as high as 60%, or higher. Of course, it’s a difficult assessment to make. However, we frequently troubleshoot installation issues and have observed thousands of deployments.

Optimal antenna alignment ensures the following:

1. Regulatory and frequency coordination compliance
2. Maximized system performance
3. Predictable system availability

There are several factors that impact proper antenna alignment. First, one must consider the appropriate antenna construction and installation. Secondly, the proper mounting hardware and installation. Next, the installer and weather are taken into account. Finally, the procedures and the equipment employed to perform alignment.

Antenna Construction and Installation

In our experience, the fewer parts required to perform field installation, the better. Occasionally, we have to install antennas we don’t like. In those circumstances, it is best to build the dish in a controlled environment before transporting it to the site. This is particularly helpful when a dish comes with a lot of small parts. Following this strategy minimizes potentially costly issues while on site.

Mounting Hardware

The source of the alignment problem often stems from the mounting hardware. In many cases, it’s not appropriately sized for the dish or the pipe mast is not perfectly plumb. We have found that adjusting a dish through anything other than a single plane will result in completely unpredictable results. Installers forego perfect leveling of the pipe for a lot of reasons, but here are the most likely:

* Not properly educated on the importance of a perfectly level pipe
* Improper mechanical hardware to compensate for a tapered tower or uneven mounting surface
* The wrong tools and no level
* Fatigue
* Laziness

It should be obvious that mating the correct sized pipe clamps to the correct sized pipe is necessary. Unfortunately, we often see corners being cut as a way to save time and money.

The best way to ensure the dish mounting mechanism is installed properly is to require plenty of pictures. Doing so will remove any doubt that it was done incorrectly. Most importantly, pictures of a level placed on both axes of the pipe mast proves it is indeed perfectly level. This will help rule out any issues with the mounting hardware. In addition, you should include a photo with level on the back of the dish. This will show that the dish is level.

Installer Fatigue and Frustration

When proper alignment becomes difficult to achieve, and all other possibilities have been eliminated, it’s time to consider the installer. It can be physically and mentally grueling to spend hours on a tower performing the same procedure over and over, and not improving the situation. Nine times out of ten, the installer and their support people on the ground resign to the frustration and lack of discipline of proper alignment and just settle for low RSL.

I have witnessed proper alignment take multiple attempts by inexperienced people, until the “right person” arrives. Of course, the more experience someone has, the better they get at it. In fact, some installers can pre-align a dish with a high degree of success using simple navigation tools like a compass and nearby landmarks.

A favorite saying I’ve heard is that, “Plan B is not Plan A, with enthusiasm”. Sometimes it’s necessary to give the project a rest and come back to it, or put a new set of eyes and hands on it.


It’s very difficult to install relatively large dishes in the wind. Likewise, dishes that sustain exposure to high winds can move over time. It’s critical that appropriate tie-back hardware is used on larger antennas. Some customers require that 3′ dishes and larger have tie-back hardware. Often 6′ dishes have two tie-backs and 8′ dishes and larger have three tie-backs. The use of tie-back hardware (sometimes called “struts”) requires forethought and planning, to ensure that all of the correct hardware is purchased in advance.

In areas where propagation is more susceptible to inversions and weather-related phenomena (varying k-factor), it is very important to perform alignment during periods of stable weather. Generally speaking, ‘good’ propagation is accompanied by wind and sun, cold fronts can be good – once they pass, warm & stationary fronts are ‘bad’. I credit my friend and colleague, Tom Hendricks for this information.

Anticipate challenges in antenna alignment when shooting over or through reflective surfaces (ie large bodies of water or between many tall buildings or a narrow canyon). With a good design the results are predictable.

Alignment Equipment

We often use the microwave radio to provide fine alignment of the system. Most radios provide an indication of Received Signal Level (RSL), sometimes called RSSI. One should always be aligning to a planned RSL (dBm) value, which is derived from path planning tools or software. In addition to providing an RSL value, some radios also give audible feedback with a buzz or beep, or visual feedback with LEDs. Regardless, we generally only use these aids for course alignment and rely on an RSL measurement for fine alignment.

On occasion, the antennas are being installed before the radios are available, so the radios cannot be used for fine antenna alignment. There are some popular products available for antenna alignment under these circumstances, like the Spectracom Path alignR.

Similarly, we recently witnessed a demonstration from a company called Sunsight Instruments and their alignment tool called the AAT-08. We found it to be a highly innovative tool and seemingly valuable in terms of expediting alignment, versatility and reporting capabilities. We’re anxious to get feedback from the field about how they work.

Alignment Procedures

To reiterate, the right tools need to be used. This is typically ratcheting-style wrenches and socket sets of the correct size. In addition, a small torpedo level to ensure everything is perfectly plumb prior to alignment. We often see people using digital levels. These seem to work well. Your installer should also use a marker to put an indicator on the threaded rod. This will remind them how to get back to a certain signal level.

Prior to getting on the tower or building, a course alignment can be achieved using a simple magnetic compass, adjusted for proper angle of declination. Of course, this assumes that the path azimuth is known. Google Earth can help identify nearby and distant landmarks that the installer can use to aim the dish.

We always align the antennas with no up-tilt or down-tilt, unless the path is extremely short. This is the easiest way to begin alignment if the expected tilt adjustment is less than a couple of degrees.

Only one side of the path should be adjusted at a time. In addition, everything below assumes that both dishes are on the same polarization.

Once everything is level, the azimuth should be swept. You’ll often see one or more side lobes of the antenna before you see the main lobe. This is indicated by the RSL measurement. The main lobe is often distinguishable as having approximately 20dB more signal than the nearest side lobe. Likewise, it tends to rise and fall off very sharply, where side lobes can persist longer through a sweep cycle. Also, the main lobe is accompanied by the presence of at least two side lobes on either side of it.

If you were to start a sweep on the far left side of the radiation pattern of a dish, sweeping the dish to the left (pulling the left side of the dish towards them), you should see some amount of signal gradually increase and then decrease (one side lobe). Next, you will see the signal increase more than it did with the prior lobe and then decrease (another side lobe). Finally, the signal should increase significantly (~20dB) and quickly fall off. This is the main lobe. After this, the reverse of what was just described should be witnessed as the dish continues to be swept in the same direction, until the signal completely goes away.

Commonly, installers will only see a single lobe in the entire sweep. This is seldom the main lobe and evidenced by a signal level well below (10 – 20dB) the planned RSL. A lot of time is often spent aligning both sides of the link to keep landing on the lower-than-expected RSL. This is often due to one of the issues described above. Either mounting isn’t level, there’s tilt in the dish, or adjustments are being made on both side simultaneously, etc.

Another common symptom of poor alignment is that two rises and falls of signal will be seen, but well below the expected amount. This is just more evidence of either being above or below the main lobe, or not sweeping far enough through the entire radiation pattern.

Once the main lobes of both dishes are found, the elevation should be adjusted to optimize the link. Once both azimuth and elevation are fine tuned, the RSL should meet the planned signal level dictated by the path design.

There are definitely other things that can go wrong with microwave radio links. More often than not, the problems stem from a system that isn’t optimized. The most neglected step in optimization is proper alignment.


We’d love to hear your thoughts on the matter. Please take a moment and let us know how you deal with an installer or tower crew that swears the path is “on the main lobe”, when all of the evidence points to it being on a side lobe.

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12 Comments. Leave new

Mike Veselka
May 2, 2016 7:53 pm

If your using waveguide or coaxial cable, I want full system and feedlines sweeps before starting alignment. For 6 Ghz paths level the pipe mount, level the antenna feedhorn, coarse align with compass. I use the radio transmitter for alignment and a power meter at the bottom of the receiver filter stack. Of course lock the transmitter on high power. On ACM radios you will probably have to lock the radio in its lowest modulation mode but the power levels should be plainly stated in the equipment specs. After the expected receiver signal is found disconnect the power meter and check against the radio software readings. I really like using a power meter because I get instant feedback. Some radio software RSL readings are delayed or a laptop can be sluggish and slow you down.

May 2, 2016 8:16 pm

Great points Mike, thanks! The power meter idea is a great one. It would be important to ensure that it’s measuring all of the power in the channel and not just the peak power. We’ve even seen where the signal level indicated in the radio isn’t very accurate due to poor calibration at the factory. That’s a difficult problem to troubleshoot without taking the radios down and doing a back to back test, which we’ve had to do. Thanks for the excellent feedback!

Bob Moldashel
May 3, 2016 12:52 am

A few comments…

Level mast pipe is very important. It is extremely critical for E band systems. I have seen and repaired my fair share of 60, 70 and 80 Ghz systems that were installed on 1 1/2″ fence pipe or cheap non-pen mounts and these links were never installed correctly and subsequently cannot be aligned to target RSL.

Initial alignment should always be done at the lowest possible modulation rate.

ATPC should be off. :-). Stop laughing….

I 100% agree on sweeping waveguide prior to turn-up and alignment. The big issue is installers without the proper equipment to perform sweeps and installation people that have little to no experience with waveguide. Waveguide is not heliax….we know that. Unfortunately many tower dogs are not “gentle” when it comes to installation practice.

May 3, 2016 1:58 am

Thanks Bob! Great points regarding ATCP and ACM. That’s the second time it’s come up today.

One issue we’ve run into recently with people doing sweeps is that they can do the sweep, but aren’t qualified to interpret the results. That obviously makes for frustrating situations.

I wasn’t sure if I’d ever need the ability to sweep up to 18GHz, but was glad to be able to last week while we did some back to back testing. It’s really handy for characterizing your test cables and attenuators.

Palmer L. Greene
May 3, 2016 10:55 am

Two comments, Patience is a virtue when aligning MW dishes, go slow you will find that RSL.
Secondly pause at each adjustment, some radio displays take a moment to react to a change in received level, you can pass it up and not know it.
Your first point under Mounting Hardware about educating the crew (all of them) is far and away the quickest route to successful alignment. Understanding the systems you are dealing with helps!

Jim Johnston
May 4, 2016 2:32 am

Great post, Brett, and good comments from others.

Squaring the mount and squaring the dish are step one, everyone mentions it, but crews get confident and skip this step and when they do, it can take hours instead of minutes to align a dish. If someone tells you they eye-balled the mount, you’ve go the wrong guy, particularly on lattice towers where there’s no such thing as a straight angle.

Having someone drive a truck or put a cone or marker on the azimuth out in front of the tower helps the dish installer quickly get close to the azimuth. This helps when it’s one crew and they put of the first dish without any signal to use for alignment. There’s usually enough signal at the far end that the second dish can come up and be aligned on one trip.

I’ve found if the installer understands the antenna pattern and how much the signal drops on side lobes can save time. After a couple weeks of throwing up 3′ and 4′ dishes, I’ve seen crews struggle when trying to align an 8′ dish with a .5 degree main lobe. I encourage sweeping side to side slowly just to watch the RSL rise and fall before beginning fine align.

Taking time to make sure the dish is mounted so that it can be swung to left and right without hitting the tower can save time having to drop the dish and change legs or flip the mount.

Please explain to crews to not mount on the climbing leg if at all possible. What good is a safe climb if you have to unhook and climb around an obstruction. Also, consider other crews that come after you when mounting hardware or attaching cables. That clamp or cable you installed becomes a lever or a foot brace for the next guy.

Making sure the installers know the calculated RSL before beginning alignment helps them get off the tower sooner. They know when to quit.

Tall guyed towers without torque arms and with big dishes, the weight and wind on the installer on the tower can affect alignment. I’ve seen paths come out of alignment when the installer climbs down the tower.

Correct tools can save time also. Make sure the climber has the correct size wrenches. How many times have we gone to align a link installed by someone else with nuts and bolt heads rounded off by someone using a crescent wrench. Or, when we went to cast mounting brackets from steel clamps and had contract installers tighten the bolts until the casting breaks, letting you find out weeks later when the dish goes out of alignment and they are long gone.

Make sure the power settings at both ends is the same. I’ve seen crews spend hours looking for a discrepancy in RSL when the issue was the power setting at one end.

Another time suck is trying to align a dish in a multi-path null. We’ve all seen cases were some engineer thought the “higher the better” and the link never came in. I would rather deal with losing a few dB dragging the Fresnel on the ground than deal with multi-path. The crew needs to know when to step back and review what they are doing and be prepared to move the dish up or down.

May 4, 2016 12:29 pm

All great points Jim! Thanks for taking the time. I almost mentioned that there should really never be a crescent wrench on the tower.



This is a great blog post and just the tip of the iceberg. Other antenna alignment topics for the future:
– Diversity antenna alignment
– Cross-polarization alignment (especially with XPIC)
– Sector antenna alignment-understanding downtilt
– nLOS/NLOS antenna alignment tips
– E-Band/V-Band antenna alignment considerations
– Passive repeater antenna alignment tips

It amazes me how the importance of antenna alignment is overlooked. Transmission engineering is an exact science. A good Transmission Engineer designs a link to deliver an expected capacity/throughput with predicted up-time only to have it all compromised by a misaligned antenna system.

If only I weren’t afraid of heights…


May 4, 2016 1:56 pm

Great stuff Mike! Perhaps you’re offering to be our guest blogger??

Ted Langmack
May 4, 2016 4:25 pm

All good procedures from many very experienced technicians. But, I haven’t seen any comments addressing two items that I teach to my students. I provide Consulting Services and Training for Microwave radio equipment and antenna systems. I have always used the same method for path alignment as recommended by a major antenna system manufacturer. This is the best procedure I have found. I’ve been in the business for over 45 years and have aligned a lot of paths. I’ve corrected more paths that others aligned Back when I was a young technician we struggled with finding that “peak” and soon found out about the character of electromagnetic waves. As the electromagnetic wave transmits through the atmosphere many things happen to it. One being the buffeting to the main lobe can leave the alignment technician endlessly looking for the peak value. When buffeted by transmission we might see a flat area where the peak should be and a rippling effect that varies over time. This lets the technician peak on something and when coming back to it; it is gone. Thus, endless amounts of time are used trying to find that elusive peak. The manufacturer of one particular line of antennas created his alignment procedure way back in 1973 or so and it is still their standard. The procedure teaches you how to find the center of the beam…..not the instantaneous peak value at any specific time. This procedure is simple to understand and is best administered by an experienced microwave technician. So the second point of this comment is to advise that the equipment technician who is skilled at path alignment does in fact direct the efforts of the tower crew. When a tower crew makes peak alignments with a path alignment box then his peak may be happening out near the edge of the beam width instead of at its center. Today, may tower crews are over confident and are unwilling to work with the equipment personnel. The two parts must be able to work together and the equipment team must be experienced enough to properly guide the tower team. This procedure will provide very accurate alignment and save money for both teams. If that alignment team misses the center of the beam and aligns the signal near the edge of the beam width then the path can suffer catastrophic “wind fades” when the tower twists past that point. Note: On short paths the beam may exhibit a nice sharp peak since the path is short enough not to have a lot of flattening or buffeting but even with nice peaks the procedure of the manufacturer is true. And one last note; I train personnel from both technologies and there are about 25 equipment technicians to 1 tower technician in my classes. I would thing that ratio would be reversed.

May 4, 2016 4:49 pm

Thank you Ted. I respect and appreciate feedback from someone with the experience that you have.

I have often associated this “buffetting” with the depolarizing effects of reflections. In fact, I almost shared a story in the post about a 14mi path I had over corn fields of Iowa, but felt the post was already too long. On this path, the RSL was down 15 to 20dB and varied over time. I wasn’t involved in the initial alignment, but came out to help fix it. My first thought was polarization, so I rotated the feed horn 90deg expecting something to happen and the RSL practically stayed the same. This lead me to believe that propagation anomalies and reflections likely impact polarization. At that time I hadn’t had any training yet to indicate that.

I’m glad you mentioned communications between the tower tech and the radio tech on the ground. There’s no question of the importance of cohesiveness, but to your point this is often more of a social and political issue than say a technical one. It’s definitely something to be considered.


I would agree with you with all the factors that causes a microwave problem as you have mentioned above, thank you for sharing you interesting information. It enlightens me. Thanks


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