Guide to Antenna Cables & Connectors

Introduction

All cables lose some signal, the amount depends on the quality of both the cable and connector. As a general guide the thicker and less flexible the cable, the better the cable. This is because to reduce signal loss cables often have a number of layers designed to insulate and shield the inner core from external noise.

Cable Connectors

After you build your own antenna, you need proper cable with connectors to connect antenna with your modem/router.

First find out what type of external antenna connector your modem/router has.

Most common connector types (photos not to scale):

Connector Type	Standard		Reverse Polarity
	Male	Female	RP Male	RP Female
SMA
TNC
N			X	X
BNC			X	X
FME			X	X
MCX			X	X
MMCX			X	X
SMB			X	X
SSMB			X	X
U.FL / IPEX / MHF			X	X

Usually Router/Modem has RP-SMA(female) connector while USB dongle (3G/HSDPA Modem) has CRC9, TS-9, SSMB or U.FL (female) Connector. If you not sure what kind of connector your modem has try google it “your-modem-model external antenna connector or socket“.

Some USB dongles have hidden external antenna connector under a rubber cap or inside its plastic case.

If your USB dongle has CRC9(female) port and antenna has N(female) port, it best is to use short cable CRC9(male) to N(Male) or pigtail as CRC9, TS9, IP9 connectors use very slim cables with great signal loss at high frequencies through cable. If you are forced to use a long cable you should use an extension cable (wider in diameter Low Loss Cable) with adapter or short pigtail (High Loss Cable):
Adapter CRC9(male) to RP-SMA(female) + longer extension cable RP-SMA(male) to N(male). This will minimize signal loss in cable over long distances between modem and antenna. If the signal at your location is really poor and you must you use very long extension cable you could try some amplifier which will allow you amplify the signal negating the loss that cable creates.

Note: An extension cable (linking cables together) isn't always recommended because you induce more cable loss from the connectors. 

CRC9(male) to RP-SMA(female) Pigtail	CRC9(male) to RP-SMA(female) Adapter

It’s highly recommended to use short length cable between antenna and modem as common Low Loss coaxial cable, 5mm in diameter 50 ohm, through 4 meters losses ~2.5dB ! Or more if your cable poorly made.

Long Low Loss Cable RP-SMA(male) to N(male)

Cable Types

What cable you should use for long distances between antenna and modem/router?

The chart below outlines the typical loss/attenuation values of low loss coax cables commonly used in wireless network applications:

Nominal Attenuation - Signal loss from external antenna to modem in cable.  The longer the cable length, the more signal loss you'll have through the cable. If you have too long cable, you'll completely defeat the purpose of the antenna. That’s why you have to use a cable short as possible to preserve as much as possible the strength of signal.

Recommended cable lengths:

100 series cable ø 2.7 mm for distances under 3 meter: I.E. – 3 meter (10ft) cable creates attenuation loss of 2.3-3.9 dB
200 series cable ø 5 mm for distances under 5 meters: I.E. – 5 meters (16ft) cable creates attenuation loss of 1.7-4.5 dB
240 series cable ø 6.1 mm for distances under 7.5 meters: I.E. – 7.5 meters (25ft) cable creates attenuation loss of 1.9-5 dB
400 series cable ø 10.3 mm for distances under 15 meters: I.E. – 15 meters (50ft) cable creates attenuation loss of 2-5.4 dB
600 series cable ø 15 mm for distances under 30 meters: I.E. – 30 meters (100ft) cable creates attenuation loss of 2.5-7.2 dB
900 series cable ø 22.9 mm for distances over 30 meters: I.E. – 50 meters (164ft) cable creates attenuation loss of 3-8 dB
*ø –  the diameter of the cable.

Note: Attenuation loss depends on the frequency. The higher the frequency the greater the loss.

Where to buy a cable?

You can find different types of ready to use cables in Amazon, eBay or order specially made according to your preferences from most radio-tech shop online. I.E. – google “N-Type Male to RP-SMA cable”.

Last updated on 12 Jul 2014