<< pa0nhc 45dB 50 Ohm step attenuator 20180707

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Preliminary development information.
The designed PCBs below are yet not available.

This design consist of seven professional quality PCBs. One contains the attenuator circuits. With the other six panels (Top, Bottom, 2x long side, Input, Output), a cheap, exact fit, neath screening housing can be constructed. Top and bottom panels are screwed for easy maintanance. The other panels are soldered together, with solder mask cutouts and silkscreens as guidance. All panels are paintet (the solder mask), and contain clear texts for construction and use.

Attenuation : (1 + 2 + 4 + 8 + 3x10) dB = Max. 45dB in 1dB steps.
In- and output impedances : 50 Ohms. Connections made by BNC busses.
Max power and voltage : 0.25W / 3Vrms.
All stages are of the "PI" type and connected in series.
The attenuation is set by cheap but rely able and sturdy slide switches. These will keep good contact over time.
A wide frequency range is obtained, by applying a full mass plane. It introduces small capacitances to resistors, reducing the influence of their self inductance.
Easy soldering is ensured by using axial wired, 2.5x6.5mm 0.25W metal film resistors, RM8.6 / 1mm PCB holes, and exact fitting switch holes.
Accurate resistor values and attenuation are obtianed by connecting two standard value 1% resistors in parallel. 
Housing dimensions : L x W x H : 13.3 x 4.6 x 2.9 cm3.


2x side.

Bottom

Main

Top

INput

OUTput


Principle

Parts list
Parts locations

Construction