In the world of wireless trail cameras, megapixels and trigger times always seem to get top billing. No one thinks about the lowly antenna until the camera is deployed in the field and the signal strength leaves something to be desired. Then all eyes turn to that little rubber-coated protrusion attached to the top of the camera. Fortunately, there are several options available for anyone experiencing signal-strength problems with their wireless camera. The solutions range from very inexpensive and easy to install to those requiring a little more money and time to install. This article is a guide to all things antenna, at least as it relates to trail cameras.
Before we talk about antenna options, let’s get some of the technical details in order. We just need to understand the basic terminology so that we can understand the reference numbers. The only real term we need to understand is dBm, which stands for decibel of radio power per one milliwatt. The power range we are interested in is from approximately -60 dBm to around -113 dBm. These figures are approximate values, not absolute thresholds. In the real world, most cell phone or wireless trail cameras will show full signal strength at -87 dBm. Since -60 dBm is a near-perfect signal, full signal on a 5-bar signal indicator indicates signal strength from -60dBM to -87 dBm. Obviously, we'd like the signal strength to fall within this range. On the other end of the spectrum is -113 dBm, which is the approximate value where a cellular connection can’t be maintained, or the bottom of the 1-bar limit. It's impossible to determine the dBm ranges that the various numbers of bars represent because they vary from device to device, as set by the manufacturer. In other words, the dBm range represented by 3 bars on one device may differ from the dBm range represented by 3 bars on another device. The most important thing to understand from all this is that the measurements are on an exponential (logarithmic) scale. This means that relatively small numeric gains in dBm represent large actual signal improvements. In the real world, most wireless trail cameras need at least 3 bars of steady signal to function reliably with a decent transmission time.
The Enhanced Antenna: a step in the right direction
Let’s start with the simplest solution. The enhanced antenna provides a slight boost in reception for little cost or installation effort. This antenna is a simple screw-on replacement for the original antenna and newer GoCams ship with it. It can provide perhaps 3 dBm, at most, of signal improvement. More importantly, it has an adjustable joint near the base that allows the antenna to be adjusted into different positions, which allows the antenna to be positioned away from objects such as trees that could be blocking signal strength. This antenna is best used in situations where the signal strength is already sufficient a stronger signal would improve transmission times. This antenna is a poor choice when signal strength is low because it most likely will not produce the gains necessary to make the camera function properly. Real world improvement: .5-1 bar of signal, signal improvement: 1-3 dBm
The Magnetic Mount Antenna: now we're getting somewhere
The next solution is the magnetic mount antenna. This antenna has several significant improvements over the stock or enhanced antennas. First, the antenna itself is significantly longer and bigger around. Where antennae are concerned, bigger is better. Second, and in some ways more important, is the fact that this antenna is a remote mount with a cable attachment. This allows for significant flexibility in antenna placement. The antenna is no longer directly on top of the camera. It can be placed away from potential signal interference or signal blocking objects. ***ground plane?*** Cable is both friend and foe because it causes signal loss over its length. In this case, the cabling type is RG174 cable which has approximately .27 dBm signal loss per foot. Since there is almost 5 ft of cable, the approximate signal loss due to cabling is 1.35 dBm. The antenna generates over 6 dBm of signal improvement, which takes the total improvement to over 4.5 dBm. Remember that gains are exponential. Real world improvement: 1-1.5 bars, actual signal gain: 4.65 dBm ***trucker antennae that don't require a ground plane*** ***connector required for connecting to camera***
The Directional Antenna: when I really want my wireless camera to work
Finally, there is the high gain directional antenna. The antenna options discussed so far are non-directional, meaning that it doesn't matter what direction the signal comes from. For the best gains, an antenna needs to be unidirectional, meaning it must be aimed directly at the transmission source (tower). When tuning this antenna, it is held straight out and moved in 10 degree increments until a signal peak is detected. This peak represents the direction of a cellular transmitter. For best results, a complete 360 degree circle should be made because there may be multiple towers to receive from and there can also be a peak when the antenna is facing directly away from the antenna as it is perfectly lined up but facing away. This "back course" peak will be much weaker because the antenna is designed to be point at the tower not away from it. As with the magnetic mount antenna, the directional antenna is a remote-mounted design. This antenna comes with 15 feet of RG58 cable. RG58 cable is visibly larger and is superior to the RG174 cable used on the magnetic mount in every way. This is necessary when using longer lengths as RG58 looses only .18 dBm per foot. Using 15 ft of included cable results in about 2.7 dBm of signal loss. However, the directional antenna produces a whopping 11 dBm of signal improvement, for a net gain of 8.3 dBm. This is a lot of signal improvement. This amount of signal improvement means that if any signal is present where the camera is deployed, this antenna can be used to make the camera transmit successfully. Finally there is an intangible factor to be considered with any remote mounted antenna, altitude. Altitude does wonderful things for cellular reception. Since cellular transmissions are a high-frequency, short-wavelength type of signal, they do not follow the curvature of the earth. That means that, for all practical purposes, cellular transmissions are line-of-sight signals. Being able to mount the antenna almost 15 ft. higher than the camera can provide a huge boost to usable signal simply because it has a better "view" of the cellular tower that it is pointed at. This altitude gain can also compensate for some amount of terrain blocking due to hills or valleys. However, it won’t compensate for placing the camera in a deep ravine. There has to be some signal present for any antenna to work since antennae don't create signal, they just receive the existing signal more efficiently. The directional antenna comes standard it what is affectionately referred to as "snow camo". It can easily be customized with spray paint but metallic paint or items adhered to the cover for camouflage should be avoided. Real world improvement 1.5-2 bars, actual signal gain: 8.3 dBm
The information provided in this article is informational or educational. Signal reception is inherently variable.The information presented in this article is based upon the rated specifications of the products. This in no way guarantees that any antenna solution will fix a signal reception problem. The end user is responsible for accessing the reception in their deployment area, considering the antenna specifications, and determining the correct solution. In other words, "Your mileage may vary." About the author: Jason Helmka is an avid outdoorsman with a passion for all things technical. His engineering experience comes by way of a BS in Aerospace from Middle Tennessee State University. Years of working as a professional pilot in both corporate and major airline service, along with the building of experimental aircraft radio and communication systems, have provided a deep understanding of the workings of RF theory.