HiQSDR Preselector Assembly
Preselector PCB Components
HiQSDR Filter assembly
Filter Module PCB Components
All filters are relative simple to adjust, most of them do not need to be adjusted.
But:best Performance is always coupled with a good and clean work!
Use only good RF capacitors with <= 5% tolerance and wind the toroids cleanly as instructed!
You can use your HiQSDR as Vector Network Analyser (thanks to Jim, N2ADR!) to see and adjust your filter passbands!
If you use the HiQSDR as Analyser use an Attentuator to save the HiQSDR input. (-30dB Attentuator)
We used our HP Networkanalyser HP8752A to verify the filter designs and adjust our prototype filter modules.
This task is relative easy if you wind the cores exactly to the turns given and measure/correct the inductance with an good LCR-Meter.
We used for this task a new calibrated AGILENT U-1733C LCR-Meter with 0.25% tolerance, but any other good LCR meter (like the AAA-LCR Meter...) will do.
To test our filter modules we built a small test fixture to connect the modules to our network analyser.
Toroid core winding
The winding of the toroid cores are realy easy see our example of a tapped Toroid Amidon T30-6.
Wind as first the "cold" (lower) part of the turns up to the tap, spreading all turns over the toroid.
The circuit diagram shows as example "T30-6, 7+21=28T 0.3mm" that means:
Use Toroid Amidon T30-6, wind 28 turns with 0.3mm wire, tap at 7th turn.
Make the tapping about some centimeters long and drill the two tapping wires.
Then wind the remainder of the needed turns onto the core evenly over the first windings.
Spread all remaining turns over the core so that you end again on the lower part of the toroid.
It may be helpful to use a little hint to mark the wire order:
Let the first wire about 2cm long, the tapping wires 3cm long and the last wire 4cm long.
With this different length of wires you can easily recognize the wire order!
To correct the inductance, only remove or add turns of the the second winding!
You NEVER (!) will make the absolute correct inductance because a toroid can have only full turns, not half ones.
Try to be as narrow at the needed inductance as possible. (allow less than 5% tolerance!)
Sort the turns varfully with a small needle-nose-plier or tweezers to be evenly spread over the toroid.
Position tapped cores
The begining of the tapped core must be at pcb ground. (Short end)
HiQSDR Preselector connection
Image of the preselector connection to the HiQSDR board.
The preselector board contains some plugged filter boards and the 1 Watt amplifier from german magazine "Funkamateur".