An FPV drone antenna connector is the linkage between the antenna, video transmitter (VTX) or video receiver (VRX). The purpose of these is to provide a solid connection whilst shielding the signal wire of the antenna from external electrical noise. Currently, there are three competing FPV drone antenna connector standards; SMA, MMCX and U.FL. This article will discuss each of these FPV drone antenna connectors and provide some recommendations regarding which one is best for your application.
SMA FPV Drone Antenna Connector
SMA connectors are the most common FPV drone antenna connector. They have been in the hobby since it first began. SMA FPV drone antenna connectors are the standard for use on VRX’s. Many VTX’s also use SMA connectors however their use is reducing due to the introduction of MMCX and U.FL FPV drone antenna connectors. SMA connectors are attached by screwing the male and female components together.
The main disadvantage of an SMA FPV drone antenna connector is its weight. Weighing over 5 grams per connector (in regard to racing quad copters) makes them quite heavy. Their size also takes up quite a lot of space in a build.
These FPV drone antenna connectors are available in two variants: SMA and reverse pole SMA (RP-SMA). This can be confusing as whilst both types look similar, they are not compatible with one another. I’m sure that most of us have has the annoyance of purchasing a product the wrong SMA FPV drone antenna connector variant. Out of the two variants, SMA is the most common however it is always important to check before purchasing a product with an FPV drone antenna connector.
The main advantage of an SMA connector is its durability. If securely mounted (using cable ties or mounting brackets), it is quite rare to break one. The average SMA connector is also rated to last a minimum of 500 mating cycles. This exceeds the cycle rating of MMCX and U.FL connectors.
SMA connectors also have the widest range of available antennas and also allow pilots to use the same antennas on both their VRX and VTX. I have not yet come across an analogue VRX using anything other than SMA connectors. SMA connectors are also ideal for VRX antennas as their screw connection allows the antenna angle to be set and locked into place.
U.FL FPV Drone Antenna Connector
The U.FL FPV drone antenna connector is the smallest of the three. The connector’s components are attached by ‘popping’ them together. Currently, this FPV drone antenna connector is almost exclusively used on VTX’s. Most U.FL video transmitters (including the ImmersionRC Tramp & TBS Unify) usually come with a removable U.FL to SMA adapter. This allows you to use SMA and U.FL antennas on the same VTX.
Due to the size and sub 1g weight of the connector, it is quite weak and is easily prone to damage. U.FL connectors can also be easily ripped from their circuit board in a crash. They also have the lowest mating cycle rating with an average rating of 30 attachment cycles. The connector can also pop apart quite easily under slight forces.
Personally, this is the antenna connector I choose to use on my racing drone builds due to its low weight. To prevent the U.FL connector from popping or ripping off, I like to put heat shrink over the connection on the VTX to secure it in place and leave some slack in the antenna pigtail. Although it is rated for few cycles, I rarely need to replace or remove the antennae on my racing quad copters as I fully shield them inside a plastic canopy. For this reason, I have never needed to replace a U.FL antenna on my 2018 race frame.
I would recommend this FPV drone antenna connector for pilots determined to shave of every gram of weight from their craft. This connector is also excellent for micro FPV applications due to its miniscule size.
MMCX FPV Drone Antenna Connector
SMA is too big. U.FL one is too small. MMCX is just right! MMCX FPV drone antenna connectors are gaining popularity due to their balance between weight, durability and cycle rating. An MMCX connector pair attaches by clicking the two ends together. This makes it very simple to swap antennas.
The connector is rated to last up to an average of 500 mating cycles compared to SMA connectors rated for at least 500 mating cycles. 500 Mating cycles is easily enough for an FPV drone as the craft is more likely to encounter a tree before the VTX connector reaches that quantity of cycles.
I would recommend this antenna connector to most pilots. It can withstand more then enough mating cycles, has significant durability and moderately low weight. Many manufacturers including Lumenier and Team Black-Sheep are picking up on this and adapting their product ranges accordingly. A review of the Lumenier TX5GS MMCX video transmitter can be found here.
Fortunately, due to the increasing popularity of MMCX and U.FL connectors, there is a growing range of VTX’s using these connectors. Personally, I think that MMCX connectors are ideal however I be sticking with U.FL connectors for my race craft. For most pilots, I would recommend using MMCX connectors on their VTX’s and SMA on VRX’s.