HiQSDR Preselector Filter Module
Band Filter Module
The filter modules are built on a precutted PCB panel, which can be broken out and plugged into the HiQSDR-Module after assembling.
The module connectors holds also control signals and supply voltages to allow active filters and active parts like transverters a.s.o. to built on the filter modules.
The filter modules contains three or five pole filter structures designed for minimal loss in passband and maximal damping outside the band. The filter structures are designed in the lower bands as 3-pole Chebyshev with a tapped middle coil that allows to spare one core per filter.
The bandwith of each filter is selected that minimum loss and minimum ripple are reached together with maximum attenuation of out-of-band signals. The critical low bands are specially designed: the 160m-module is a 5-pole chebyshev filter in tubular construction with ripple less than 1dB and a bandwidth of only 250kHz.
The attenuation of signals outside the passband is more than 60dB at a offset of 300kHz.
The other two critical bands 40m and 80m has two different modules available at the filter panel:
One is designed as 3-pole Chebyshev-filter for minimal loss within the passband (< 0.3dB) and as 3-pole Cauer-filter with controlled stop-bands at the lower and higher neighbor bands (< -60dB) to be contest proof but has slightly higher passband damping.
All filter calculations are done with the professional Filter design program "Filter Solutions 2012" from NUSOFT and verified and simulated with the AAA-Filter designer and practically tested with a HP 8752A Network analyser.
The match between theory and pratical filter behaviour was nearly 99% (!)
In the following pictures you see the typical filter curve of the 30m-Bandpass filter of the 3-pole Chebyshev filter module.
Picture of 40m BP you see the typical filter curve of the 40m-Bandpass filter module.
Filter Module Board
The Filter modules are on a pre-cutted PCB-panel.
The prebuilt filter panel has all SMD parts (0805) and connectors ready built.
The core coils must currently be made by the user.
(this may later be changed if we find a competitive manufacturer for toroid coils....)
The capacitors are designed twice (0805) for each value to allow unusual values to be realized with two parallelled caps.
The TOP pcb contains also a LED which signals a activated filter and the solder bridge selections for RF connection routing and external power supply selection for remote supplied preamps.
Last but not least a nice view over the "sea of toroids"...