zondag 30 juni 2013

Bitx20 V3 "Dead Bug Style" Test stage.

May I present to you,my "Dead Bug Style" Bitx20 V3 in working order.The finished PA-Amplifier from the last blog is now connected via RG174 coaxial cable to the exciter board.I added a front and a back from copper board.In the front you see the volume and fine tune potentiometers.The main tune is from an old radio.The S-meter is not working yet,I have to build another circuit for that.The Amplifier does about 1,5Watt when my power supply deliveres 13,5Volts DC.On the back I mounted a PL259 socket for the antenna and a cinch plug for the speaker.Are we finished now,unfortunately, no.There is a problem.I first discovered that when I was only listenging on the band.It seems that the further I went up in freqency,the more deaf my Bitx sounds.I had to adjust my bandfilter slightly.As I mentioned,my Bitx does 1,5Watts,but only in the range of the bandfilter where it`s not deaf.Under and above that "deaf" frequency,there`s now output on the Bitx.It seems that the bandfilter is only 80KHz wide.That`s not enough,it must cover the whole 350KHz.(14,000MHz-14,350MHz).So there`s work to be done.I think that when I solve the issue with the bandfilter,I automaticly have solved the problem with the output of the PA-Amplifier.

This is the bandfilter I`ve used for the Bitx20.The bandfilter was originaly posted on the PI4RAZ site.They build it years ago with a bunch of OM`s .Only they used a IF of 11MHz.I don`t think that the IF of 10MHz I used,can cause this problem.Maybe when all my aforts to correct this problem doesn`t solve anything,I can alway`s post a question on there site.OK,on the pictures bellow you see the Bitx20 V3 at this moment.Hope a can fix the bandfilter soon,because all the components for the Multiband Bitx are in the house.Can you imagine that,a homebrew tranceiver from 10 to 160 meter with a DDS VFO with the firmware of PA0KLT and 20Watts output.I cant`t wait to start with that project.You can take a look at the site of Andy,I think he don`t mind the link.Multiband Bitx

If you take a good look at the bandfilter,you see that I already did some experiments on the trimmers and the 82pf capacitors.They are not as nice alligned as the original parts on the bandfilter.

vrijdag 28 juni 2013

Bitx20 V3 "Dead Bug Style" The PA-Amplifier

Last week I started the build of the Linear Amplifier for the Bitx20 V3 project.I tried to stick close to the original circuit board design.As you can see on the picture,I only use one diode (1N4001) in stead of four,because the power supply is a 13,8V DC.If you decide to increase the power output on the IRF510,you should use the 4 diodes and the LM317 voltage stabilizer.After that you can connect an AC-power supply to the board.On my other Bitx20,I used a transformer with a secundairy output of 16Volts/2Amps.OK,next problem.How do I put the two relais on a "dead bug"style secure on the board.Two pieces of copper board where used,and with a sharp knife I made "islands" to isolate the pins of the relais.Then I soldered the the relais on the little board.After that ,the board with the attached relais was placed on the circuit board with some solder.The two big capacitors are not the 2200uF 25V,but after a look in my used parts box,these fine capacitors where found.They are 3300uF 35V.I think they will do fine.So,what`s next.Testing,but I will do that at a later time.

zondag 16 juni 2013

Bitx20 V3 "Dead Bug Style" Building the Case

First I want to start my blog with a special thanks to my radio friend PA1SBM.Alex was so kind to put some nice comments on his blog.Just like me,Alex is also building a Bitx20 and has some other interresting things to tell on his blog.Pay him a visit on PA1SBM. Since I`ve been out of the country for two weeks,it was time to do some work on my Bitx20 V3 project.The plan is to put all the modules onto a larger piece of double side copper circuit board.I put the modules on a rail,so they are 5mm above the main board.I can now later do some wiring under the modules,so you won`t see.On the pictures you see the projekt until now.An S-meter and the knobs from an old CB-radio.
Here some pictures how the modules are positioned on the 5mm rail.
After I de-soldered all the modules I`ve put the first module (Audio module) on the big board.Here you have a good look on the two 5mm rails.
Two modules on the rail,BFO/Mixer module.
Detail of the rail.

And another detail of the rail,this time you can see the bandpass filter in close up.

View from the top.The two potentiometers for the volume and for the VFO fine adjust.The empty hole is for the tuning capacitor.Maybe later I will replace the tuning capacitor with a varactor with a 10 turn 10K potentiometer.Also the S-meter from an old Danita CB radio is in the front.