Replacing an LTE Antenna

Our customer installed a Poynting LPDA-92 antenna in the same location and orientation as her previous antenna, but she wasn’t getting better reception. We turned to Poynting in South Africa for an answer. Their engineer’s response is worth sharing. The original is filled with technical language and delightful but confusing British phrasing. We’ve translated it into American and condensed it.

When a new Poynting antenna is installed to replace another brand, it will have different characteristics than the previous one. We recommend treating the installation of an upgraded antenna as a new installation. There are several reasons. The most obvious is that two antennas from different manufacturers, even with similar specifications, will have different radiation patterns.

A Poynting antenna will deliver an even gain over its entire frequency range with a smooth radiation pattern. In contrast, a different antenna may have gain spikes in one segment of the frequency band, or at one point in the radiation pattern. If the old antenna is placed SSE 167° and receiving a good signal, it does not assure that the tower is at SSE 167°. One off-axis spike in the antenna’s pattern could be picking up a stray signal from the side. To quote the Poynting engineer, “with the previous installation they may have just been lucky to receive some spurious signal from an adjacent angle.” Installing a new antenna in the same location, without the flaws of the old antenna could result in no reception improvement, or even lower reception. The answer is to re-orientate the new Poynting antenna as part of its installation.

Locate the network cell towers before you install the antenna.

It is not always clear where cell signals originate. Locate nearby cellular sites by trying a combination of the following:

  • Check your cell provider’s web site. Sadly, this is a long shot because carriers don’t want to disclose this information, to either customers or competitors.
  • Ask your cell provider’s help desk or tech support. You are probably not going to get this information from the level 1 support people, but with persistence, you may find someone who can give you the locations of your nearest towers.
  • Use your eyes. Look for towers or rooftop sites (not all cellular sites are on towers). In Frontier’s home location, there is a cell tower disguised as very tall, oddly symmetrical pine tree.
  • Check antennasearch.com, which will show existing towers and antennas. Unfortunately, it will not always tell you which carriers are using which towers, but it is one of the best indicators of tower locations. Cellmapper.net will allow a search by carrier. With its interesting coverage and broadcast diagrams, Cell Mapper will sometimes show that the site closest is not the one broadcasting in your direction. Antenna Search, Cell Mapper, and a little deduction can help you figure it out. Sources on the Internet change often, so a Google search is probably worth a try.

Finding your carrier’s nearest broadcast sites best achieved by using several of these resources.

Setting up the Antenna

Once the nearest cellular sites are determined, begin installation by pointing the antenna toward them and testing to refine the orientation. The nearest site or site with best Line of Sight (LOS) is usually preferred. A nearby site completely blocked by tall buildings, dense trees, or terrain features may offer less signal than one farther away with a clear path. The only way to identify the ideal location is to test more than one antenna orientation toward different cellular sites (see below).

When Cellular site locations are unknown

In situations where the locations of the cellular mobile network sites are unknown, and where the known locations do not provide sufficient results, we recommend the more methodical and involved process of testing in all the directions.

Point the antenna towards a direction where coverage is expected, or you can start in a known direction. Test your reception in this starting orientation. After your first test, redirect the antenna clockwise and test again. Keep repeating this until you have tested a full 360 degrees. The angle you move for each test depends on the horizontal beam width of your antenna. Test at an angle slightly less than the horizontal pattern width of your antenna.

For example, the Poynting LPDA-92 antenna has a beam width of approximately 50 degrees, so a 45-degree angle will be sufficient. For the LPDA-92, you would take measurements in eight different directions, 0, 45, 90, 135, 180, 225, 270 and 315 degrees. For any antenna, the beam width is different for each specific frequency band. Using the published data for your antenna, choose a test interval slightly less than the antenna’s narrowest horizontal angle.

How to measure the antenna performance in each direction.

You can measure the values with most LTE enabled routers, which are capable of reporting the cellular network signal strength and quality as RSRP, RSRQ, or SINR. Nearly every cell phone has a signal meter built-in, although it is mostly hidden from the consumer. It’s pretty easy to find on Android, under ABOUT DEVICE: STATUS. You can find it on iPhones too, but it’s not so easy (search Field Test Mode). The meter will show the value in –dBm. There are apps on the market that will show this as well.

LTE Signal Strength

It is best to reboot the device before each measurement to ensure that it is not holding on to the previous cellular site. A cellular router or cell phone can ‘lock’ onto the previous cellular site even when the new cellular site is available with a much better signal level and quality.

Take note of the signal strengths measured in each direction. Finally, use the best performing direction as the baseline and install the antenna in that direction. Even with a known antenna location, fine tune and further optimize the placement by re-testing at +20 degrees and -20 degrees from the determined position. It is a slower process, but the only way to assure you are finding the best performing antenna orientation.

General Tips
  • Although installing an antenna as high as possible is generally recommended, it is possible that the highest position is a weak coverage spot. In other words, vertical placement can make a difference. Poynting has found that a lower installation height achieves better results in few cases.
  • Cellular network signals and quality can fluctuate as much as 6 to 12 dB. A measurement taken now and a few moments later can differ substantially even if nothing apparent has changed. Reflections, interference, and load capacity cause signal variations. Network throughput can also change significantly for the same reasons.
  • Network topology and usage change over time, even from one minute to the next. If a previously tested antenna position begins to yield poor performance over time, you may have to re-test, and reorient the antenna. It is possible for a cellular site to become over used, or taken out of service. As the network design and topology changes, so will the experience change.
  • Poynting has many informative webinars on YouTube. This video gives a detailed overview of the factors involved in cellular reception.
  • An antenna can only pick-up an existing signal. If the ambient cellular signal has an RSRP -110dBi or less, it is unlikely even the best antenna can improve reception.

Frontier Computer stocks Poynting and Axxess Marine Antennas, WilsonPro and weBoost cellular amplifiers, and the entire Peplink and Pepwave lines of SD-WAN communications.

Contact Frontier at 866.226.6344.