vrijdag 24 mei 2013

Bitx20 V3 "Dead Bug Style" VFO

Yesterday I`ve finished the VFO.First QSO`s succsesfully heard on my Bitx20 V3 Dead Bug Style.After I connected the VFO to the rest of the Bitx20,the reception was not that great.I only heard some beeps and SSB far away.After some investigation I discovered that there was an error in the connection of the 2SC2570A.When I`ve corrected that error,I could hear several QSO`s in the 20M band.Also the CW gave booming signals.As I discribed earlier,I don`t seem to have an issue with the transformers.The manual say`s 8 windings through the cores.I used 13 trifiar through the cores.After I was very pleased about the reception of the Bitx20,the next step was the transmision.I soldered an electret microphone to the PCB and connected a switch in the + line to toggle between send and receive mode.Yes,I can now hear myself on my good old Kenwood TS820.Next step is to connect al the modules on a larger PCB and make the permanent connections.When the circuit is stable a can start with the build of the PA.See the video I shot of the test with the Bitx20 V3 so far.

Testing CW reception  http://youtu.be/VHJHHRuSIB8

Testing SSB reception  http://youtu.be/S4xfSOff7lY

Testing SSB transmission  http://youtu.be/W4_B1dKVgwU

zondag 19 mei 2013

Bitx20 V3 "Dead Bug Style" PA driver.

On the picture bellow you see one of the smallest circuits in the Bitx20 V3 build.It`s the PA driver,the last step in the transmision line before the transmit signal enters the PA Amplifier.As you can see,I used another binocullar core,only this time with bifilair windings.I also discovered that the circuit diagram I found on the internet is somewhere different as the one`s I`ve allready build.On my other Bitx20 V3 there are only 8 windings through the cores.So far in this build I took 13 turns through the cores.Hmmmm!Maybe I have to correct this.The transistor is the 2N3904.Next and final step on the exciter is the VFO.

vrijdag 10 mei 2013

Bitx20 V3 "Dead Bug Style" Bandpass filter.

Today I finished the bandpass filter.The bandpass filter is a very importand part of the build, because we only want the frequency between 14.000Mhz and 14.350Mhz through the bandpass filter.All the other frequency`s must be blocked.Because I use a IF of 10Mhz and a VFO that can generate between 4.000Mhz and 4.350Mhz,I can cover the whole 20 meter band as I add the VFO frequency to the IF.But it is not that simple.We also have to substract the VFO from the IF frequency.That means that 10.000Mhz - (4.000Mhz-4.350Mhz) = ~ 6Mhz.We don`t want that frequency and other frequency`s pass the bandfilter.I`ve add the filter to the already completed stages of my Bitx20.As I tuned this Bitx20 to the same frequency on one of my other Bitx,I could hear myself when I give a shout in the microphone.Not bad for now.Just two more stages to go,first the PA-driver and after that the VFO.The VFO on the last picture below is the one from my earlyer build Bitx20.

woensdag 1 mei 2013

Bitx20 V3 "Dead Bug Style" RF amplifier section

After a few hours of work I completed the RF Amplifier section.Be carefull that transistor Q1 is a 2SC2570A in stead of a 2N3904.If you cannot purchase a 2SC2570A,you can use the more common MPSH10.No special cores have to be wound in this stage of the build.Next is the bandpass filter.I`m thinking of using the same as the one discribed on the PI4RAZ forum.

Photo of the completed stage`s this far.