Antenna interface in-depth selection guide (including scenario-based decision-making logic)

The core of antenna interface selection is "hardware matching + scene adaptation + performance optimization", which needs to be implemented accurately according to the steps to avoid signal loss or adaptation failure. The following is a detailed description by dimension:

Ⅰ. First clarify the core premise: matching of equipment and frequency band (basic threshold)

1. Check device interface parameters (to avoid physical mismatch)

Check the official manual: Confirm the interface model (such as SMA-J, IPX 1st generation), polarity (positive/reverse polarity), and installation mode (internal/external). For example, if the EBYTE module is marked "SMA-K", it needs to be equipped with an SMA-J antenna. The IPX 1st generation interface is only suitable for the corresponding adapter cable.
Distinguish easily confused interfaces: SMA and RP-SMA have similar appearances. The male connector of the former is "external thread + internal needle", while the latter is "external thread + internal hole". If they are mismatched, the connection will be completely impossible and the signal will be interrupted.

2. Match the working frequency band (to avoid frequency incompatibility)

High frequency scenario (GPS/Beidou 1575.42MHz, 4G/5G, WiFi 5/6, 1-6GHz): Priority is given to SMA, IPEX, N type, TNC can also be adapted (upper limit 11GHz);
Medium and low frequency scenarios (433/868/915MHz digital transmission): universal for SMA and N-type, IPEX is suitable for built-in low-power modules;
Low-frequency scenarios (<500MHz, such as shortwave): only UHF interface, rarely used in industrial communication scenarios.

Ⅱ. Accurately select interface types according to scenario dimensions (core decision-making layer)

1. Built-in integration scenario (no external connection requirements inside the device)

The first choice is IPEX (including IPX series): extremely small size (adapted to high-density PCB), frequency 0-6GHz, impedance 50Ω, low power capacity (only internal low-power transmission), plugging and unplugging life of 300-500 times, suitable for space-limited equipment such as vehicle-mounted station announcers, small sensors, portable terminals, etc. EBYTE built-in GPS antennas (such as TXGB-FPC-3615) are all adapted to the IPX 1st generation interface.
Alternative MMCX: Ultra-small buckle design, frequency 0-6GHz, suitable for micro portable devices (such as smart watch modules), only a small number of customized models are supported.

2. Indoor/general industrial scenarios (medium and low power, no harsh environment)

The preferred SMA: compact size (outer diameter 6.5mm), frequency 0-18GHz, power capacity 50W, threaded connection, plug-in life of 500 times, strong versatility, low cost, suitable for most industrial wireless modules, indoor APs, and GPS external glue stick antennas, making it the mainstream choice in communication scenarios.
Note: Frequent plugging and unplugging can easily cause the wire to slip. Frequent disassembly should be avoided. No additional waterproofing measures are required.

3. Outdoor harsh environment scenarios (high power, long distance, anti-interference)

N type is preferred: larger size (outer diameter 16mm), frequency 0-11GHz, power capacity 100W+, IP67 waterproof and dustproof, thread sealing design, strong vibration resistance, plugging and unplugging life of more than 1000 times, suitable for field operations, base station deployment, outdoor monitoring equipment, EBYTE fiberglass antenna (TXGB-BLG-20) comes standard with N-J interface, and can be used with RG213 feeder to reduce long-distance losses.
Supporting measures: N-type lightning arresters are required to protect against lightning strikes, and the length of the feeder is recommended not to exceed 20m.

4. Vehicle vibration scenario (need to take into account both earthquake resistance and flexible installation)

The first choice is TNC: size between SMA and N type, frequency 0-11GHz, impedance 50Ω, thread tightening (improved version of BNC), vibration resistance better than SMA, medium power capacity, basic waterproofing, suitable for truck positioning terminals and vehicle-mounted communication equipment, more resistant to bumps than SMA, and smaller than N type.
Optional SMA: It needs to be fixed with anti-vibration buckles to prevent the threads from loosening due to vehicle bumps.

5. Laboratory test scenario (low power, temporary connection)

BNC is preferred: snap-on connection, frequency 0-4GHz, low power, suitable for test instruments such as oscilloscopes and signal generators. It is rarely used in industrial deployment scenarios and is only suitable for temporary debugging.

Ⅲ. Performance optimization details: impedance, feeders and protection (reducing losses)

1. Impedance uniformity (key performance indicator)

Communication and industrial modules are all 50Ω impedance, and mixed connection of 75Ω (for video only) is strictly prohibited, otherwise the standing wave ratio will increase (>1.5) and the signal loss will exceed 20%, which will directly affect the transmission distance and stability.

2. Feeder matching (select specifications according to distance)

Short distance (<3m): Choose RG174 (adapted to SMA interface), which has low cost and high flexibility;
Medium distance (3-10m): Choose RG58 (adapted to SMA/N type) to balance loss and cost;
Long distance (>10m): Choose RG213 (only suitable for N type). The low loss feature is suitable for long-distance transmission.

3. Environmental protection (extended service life)

Outdoor scene: N-type native waterproofing, SMA needs to be equipped with a waterproof kit (such as a waterproof nut) to prevent rainwater from penetrating and causing a short circuit;
High vibration scenarios: TNC or SMA with anti-vibration buckles to reduce the risk of interface loosening;
High/low temperature environment: Give priority to metal interfaces (SMA/N type) to avoid aging and cracking of plastic interfaces.

Ⅳ. Pitfall Avoidance Guide: Common Mistakes and Solutions

1. Judging the interface only by its appearance: SMA and RP-SMA, and IPX 1st and 4th generations have similar appearances, so refer to the manual markings. Mismatching requires additional connections, which increases signal loss (0.3-0.5dB);
2. Ignore the power capacity: SMA interfaces for high-power equipment (>50W) are easily damaged by overheating, so you need to choose N type;
3. The feeder does not match the interface: If the RG213 feeder is connected to the SMA interface, the connection will become loose, so you need to choose a connector with corresponding specifications;
4. Outdoor lightning protection and waterproofing are not provided: the N-type interface needs to be equipped with a lightning arrester, and the SMA needs to be equipped with a waterproof cover, otherwise it is prone to failure due to lightning strikes or rain.