vrijdag 20 september 2013

Multiband Bitx:The MK1 Bandpass Filter

This week I finished the build of the Multiband Bitx Bandpass filter.In the beginning of March 2013,I purchased the complete G4CFY bandfilter kitt by Spectrum Communications.In the meantime there was a re-development of the choice in components ,used in this bandfilter.So I needed to do another investment to buy those components used in the revised 29May kit.Spectrum Communications can supply you a kit with the changed capacitors and the 3 coils for the 30M band.I also purchased the switching parts.(BA243,33uH chockes and 100ohm resistors).So now I have the latest version of the bandpass filter.Just follow the manual in the building process.It`s no rocket science.Be carefull do when you install the ceramic capacitors.Several NPO capacitors have a 2,5mm pitch while the PCB has a pitch of 5mm.Don`t stick the capacitors to the bottom of the PCB.The risk of destroying your priceless NPO capacitors is very high.Just leave them a couple of mm`s above the PCB.After the build was done,I connected the bandfilter to the Multiband Exciter.I didn`t hear anything,only a little noise out of the speaker.Silly me,I forgot to give the bandfilter a supply power.Now I heard several stations immediately,but they seemed to be some KHz of frequency.That problem was soon discovered.As you can see on the picture on the MK1 Exciter blog,you see that I measure the BFO frequency.The reading say`s 9,999,26MHz.That`s way to high.I had to adjust the BFO frequency by means of the trim capacitor to 9,997,50MHz or so.With the 4,7uH chocke I used,I couldn`t come nowhere near this frequency.The range was to small.So i changed the chocke coil for a 10uH from an earlier Bitx 20 V3 build.Now I could adjust the frequency to 9,997,50 MHz.With the IK3OIL VFO connected to the Exciter,it was time to listen for any activity on the band.The first QSO I heard was a Italian station having a QSO with a station located in Florida USA.Not bad for a homebrew rig which hasn`t been alligned yet.Now what`s next.I will order a VFO.I think I go for the PA0KLT VFO.First I`m gonna build the PCB`s in a case.I still have a simular case in which my Bitx20 V3 is situated and that looks nice,so why not use it then for the Multiband Bitx.


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