Northern Airborne Technology STX100 - Manual (Page 19)

SM67 Rev. 4.10 STX100-000 Globalstar ™ Satphone Transceiver Manual
Fabrication & installation of wiring harness should be in accordance with AC 43.13-1B,
chapter 11, sections 5-12.
Grounding and bonding should be in accordance with AC 43.13-1B, chapter 11, section 15.
2.3.4.1
Coaxial Cables
The RF budget for the STX100-000 is very specific for both the RX and TX paths. The
type and length of coaxial cable is critical in order to achieve proper performance of the
STX100-000 system. It is recommended that the coaxial cables be sourced from a
vendor that specializes in the fabrication of low loss cable sets. Refer to Tables 2-1 and
2-2 for examples.
Coaxial cable should be in accordance with MIL-C-17 unless otherwise specified. Do
not use coax with PVC insulation. Teflon dielectric cable is recommended at or above
UHF frequencies or where cable runs exceed 8 feet. Note that at these frequencies, cable
losses due to long cable runs and tight bends may cut the ERP (Equivalent Radiated
Power) to less than 50% of specification.
RF cables must be neatly terminated (solder or crimp), and tested for shorts prior to system
check-out (not while connected to the radio or antenna). Keep cable bends to a minimum
at the antenna. Avoid sharp bends in the coax cables to prevent severe reflections. If
sharp bends are required, use 90
° elbow adapters.
When routing the coaxial cables make sure they are properly identified as they use the
same connector for both the RX and TX connections at the STX100-000. This can also be
true of the antenna, depending on the model used for the installation.
2.3.4.2
Cable Lengths
The transmit and receive coaxial cables and TX Filter have a minimum and maximum
signal loss that must be taken into consideration. Exceeding the min/max signal
strength by having an improper coax length may cause poor system performance. For
reference, the calculations are based on a transmit frequency of 1.6 GHz, and a receive
frequency of 2.5 GHz.
Transmitter path loss (min): 1.35 dB * Receiver path loss (min): 1.50 dB
Transmitter path loss (max): 2.15 dB ** Receiver path loss (max): 8.50 dB
* Includes the transmitter filter insertion loss (nom) of 1.8 dB.
** Includes the transmitter filter insertion loss (max) of 2.0 dB.
The tables below identify examples of coax cable types that can be used and shows the
min/max cable lengths for that type. The calculations take into consideration the losses
associated with the transmitter filter (transmit cable only) but they do not take into
consideration the losses associated with the coaxial connectors. Any other quality coax
cable can be used provided it meets the requirements for min/max cable loss.
Sep 7, 2005 Page 2-3
ENG-FORM: 805-0106.DOT
CONFIDENTIAL AND PROPRIETARY TO NORTHERN AIRBORNE TECHNOLOGY LTD.