Coax Connectors | Products

24. October 2014

The difference is in the details

Jumper Cables are a well-established product of the Telegaertner Group, having been manufactured in the UK and Slovakia using quality German connectors for the last 20 years.  Over this time, we have built up our expertise and knowledge of such products and although superficially simple in design, when you look more closely there is more to them than meets the eye. 

Cable Types

The most common cable for jumper cables is 1/2” flexible cable. From the table below, we can see the drivers for this and the drivers behind this selection when compared to the other most common cable sizes (1/2” feeder, 3/8” and 1/4”).

  1/2" Feeder 1/2" Superflex 3/8" Superflex 1/4" Superflex
Min. Bend radius 125 mm 32 mm 25 mm 25 mm
Attenutation at:
 900 MHz  6,8 dB/100 m 10,2 dB/100 m 13,3 dB/100 m 18,4 dB/100 m
1800 MHz  9,91 dB/100 m 14,9 dB/100 m 19,4 dB/100 m 26,9 dB/100 m
2200 MHz 11,1 dB/100 m 16,7 dB/100 m 21,7 dB/100 m 30,1 dB/100 m
2700 MHz 12,4 dB/100 m 18,8 dB/100 m 24,3 dB/100 m 33,7 dB/100 m
         
Diameter 16 mm 13,5 mm 10,1 mm 7,4 mm

As can be seen from the table, the 1/2" flexible cable fits the median of the specifications.  If low attenuation is the customer driver, the 1/2" standard cable would be the best choice.  As the cable diameter decreases, the minimum bend radius also decreases, meaning much greater flexibility.  At the same time, the attenuation increases, so it depends on the application as to the best-suited cable.  For internal use, such as within a Base Transceiver Station (BTS), where flexibility is of the greatest importance, the cables tend to be 1/4” and 3/8”.  For antenna line purposes,  1/2” cable is generally used, whether it be 1/2” standard cable for longer lengths where signal loss is more of an issue, or 1/2” flexible for shorter lengths.

Differences in Cable Construction

There are two main cable groups used within these products, with the main difference in the make-up of flexible and standard cable coming from the corrugation.  Flexible cables have helical corrugations, while standard cables have annular corrugations.  Helical corrugations improve the flexibility of the cable, however they have detrimental effects on the electrical performance.  Annular corrugations are designed to offer better electrical performance but with this, the cable loses its flexibility.

spiralförmig.jpg     ringförmig.jpg

Helically corrugated cable (Superflex)       Annularly corrugated cable

Used materials

The standard material used for the outer conductor of the cable is copper with the centre being copper-clad aluminium.  Although copper offers the best performance, its price can vary dramatically and in order to offer a cost-effective alternative, aluminium is now also offered by some manufacturers as an alternative to copper for the outer conductor.  Alongside a drop in electrical performance, the aluminium version is easier to damage and the risk of this must be weighed up against the cost-saving. Telegaertner has always used copper corrugated cable for their jumper cables.

Connector Types

There are now three different connector types available for jumper cables, namely 7-16, N and 4.3-10.  The differences between these connectors can clearly be seen below.

Technical data Series
   N 4.3-10 7-16
Nominal Impedance 50 Ω 50 Ω 50 Ω
Frequency (Standard) 11 GHz 6 GHz 7,5 GHz
Cut off frequency 19 GHz 13 GHz 8,3 GHz
Intermodulation (IM3) 2 x 20 W Typ. -155 dBc Typ. -166 dBc Typ. -165 dBc
Working voltage at sea level 1,4 kV 1,8 kV 2,7 kV
Power Rating

450 W at 1 GHz

300 W at 2 GHz

700 W at 1 GHz

500 W at 2 GHz

1.200 W at 1 GHz

850 W at 2 GHz

Outer conductor Contact

Face contact

Contact bushing

Face contact

Coupling Mechanism

Screw

Screw, Push-Pull, Hand Screw

Screw

Coupling Torque

3,0 Nm

5 Nm (Screw Type)

30 Nm

Flange Size

1 Inch (25,4 mm)

1 Inch (25,4 mm)

1,26  Inch (32 mm)

The 7-16 connector is most commonplace, especially in Europe, due to the good performance for both PIM and return loss.  N on the other hand, although popular in the US, is used more often where space constraints are to be considered.  This profile may change with the arrival of the 4.3-10, as this connector has both the same footprint as an N connector, and the same, if not better performance of the 7-16.

Applications

On a traditional feeder line, jumper cables are used at the top and bottom of the line due to their flexibility to connect the feeder cable to the antenna and the base station.  Over recent years, technology has evolved and Remote Radio Heads (RHH) have become more prevalent in the field, where a fibre cable can also be used up the mast to the RRH.  From there, a jumper cable is still used for the last stretch to deliver the RF signal to the antenna.