vrijdag 16 mei 2014

Multiband Bitx: The VFO

After the succsesfull reception tests I did with the Multiband Bitx on 20 Meters using the IK3OIL VFO,it was time to decide what kind of VFO I would use for my project.There where several options.The first one that came on my antenna HI,was the N3ZI DDS VFO.Another option is the VFO by DXkits.This VFO was specialy build for use with the Multiband Bitx.It`s a great VFO with build in band switching outputs for the low pass and bandfilter PCB.So this was an excellent choise for me.After a quick study of the manual and components ,I saw that this VFO was actually the PA0KLT design with the band switching outputs edit.Because I`d like to keep my hobby cheap,I decided to buy the PA0KLT A-kit VFO from SDR Kits.On the picture below you see the finished VFO and the Rotary switch.I also purchased the aluminum dial for the VFO.It`s heavy and it looks also great.
For me it was the first time that I had to solder SMD components.If you follow the manual that you can download from SDR Kits,you will find no problem at all to build this VFO.Because this VFO is not equiped with the band switching outputs that the DXkits VFO offers,I first will use a rotary switch which switches the voltage to the correct filter of the low and bandpass filter..After that stage I will make a PCB for the automaticly VFO controlled band switching using the HEF4028 BCD to Decimal Cmos decoder.

Screenshot of the excellent G6LBQ VFO by Andy.

All the parts for the band switching outputs.
On the picture above you see the VFO by Andy G6LBQ.More than half of all the components on the PCB are needed for the band switching outputs.I allready purchased a HEF4028 and the transistors BC547,BC640 and a few diodes.When my project works fine with the Rotary switch,I will make the right side of the PCB,because the PA0KLT VFO already controls these ouputs in the firmware.
Rotary Switch.
You can find a lot of information about this Multiband Bitx project on the Yahoo G6LBQ Group.On the next blog I hope that I`ve started the build of all the PCB`s in the case.

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