Table of Contents
Advertisement
lower than -70dB. Finally read the S parameter of mark1, which is the insertion loss of
the duplexer to the receiving signal.
Chart 4-2: Typical curve of duplexer's LOW side, uncompensated cable loss
Try to switch LO mode and choose which ever makes the curve's bottom the
lowest. When adjusting both sides of the duplexer, different OSL modes may need to
be used.
Some duplexers' parameters of both sides can influent each other. In this case,
user may need to do the steps above again till the attenuation parameter is up to
-70dB.
Do not make the notch curve of the duplexer too sharp pointed at the bottom.
user can reduce the SPAN to 1MHz. To observe curve's bottom, the width should be
more then 100KHz. If the curve is too sharp, its tip may drift out of the used frequen-
cy once temperature or the matching of antennas has changed.
When there is conflict between the insertion loss and the attenuation, consider
the attenuation at RX side first. Properly lower repeater's transmission power to lower
the demand of isolation. In this case, keep in mind that "adjust TX toward inside, ad-
just RX toward outside" to try to keep the balance between insertion loss and isola-
tion.
For coupling level, user can adjust the coupling bolt with the duplexer which is
adjusted by the screws. If other adjusting screws are not long enough, they can be
replaced by the long screws. If the screws need to get inside very deep, duplexer's Q
value will reduce. If needed, user can lengthen solenoid by taking apart the duplexer.
If the insertion loss can't be reduced to reasonable level, user might consider
using S11 (connect the dummy load to the untested port and it's not preferred to
connect it to instrument's port) to try different adjustments. Also balance it with oth-
er parameters and make SWR stay within 1.5.
- 24 -
Advertisement
Table of Contents
