Sansei Showa Co., Ltd.
Variable Load Capacitances for Transat PI Networks Data Sheet 
Transat offers Variable Load Capacitance Inserts which can be plugged into the load socket of various Transat PI Networks. Shown at the right, it consists of a fixed chip capacitor connected in parallel with a variable ceramic capacitor, mounted on a HC45 base. It is adjusted from the top by means of an adjustment tool. Transat PI Networks which contain load insert sockets have an inherent capacitance of about 4pF. This capacitance needs to be considered (ie added) when selecting a Variable Capacitor Insert.
Variable CL Insert 


5.0 7.0pF 
P/N 010127586 
7.0 9.0pF 
P/N 010127588 
8.710.7pF 
P/N 0101275810 
10.512.5pF 
P/N 0101275811.5 
12.514.5pF 
P/N 0101275813.5 
13.017.0pF 
P/N 0101275815 
16.020.0pF 
P/N 0101275818 
19.023.0pF 
P/N 0101275821 
23.027.0pF 
P/N 01012758 
27.032.0pF 
P/N 0101275830 
The capacitive temperature dependence is about 20ppm per °C for the fixed ceramic capacitor and 200ppm per °C for the variable portion of the insert. In the worst case this results in a composite temperature dependence of about 60ppm per °C. The corresponding load frequency dependence can be determined from the equation:
DF_{L} = DC_{L} ( C_{1}/^{2} (C_{O}+C_{L})^{2})
For example, for CO=5pF, C1=13pF, CL=20pF, and a 60ppm per °C change in CL, one obtains a DFl of about 0.01 ppm °C. This is negligible for most plating purposes.