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.


zaterdag 7 september 2013

Multiband Bitx: The MK1 Exciter

After not posting for two months now,it`s time to post a new blog about my Multiband Bitx.A few months ago I purchased the Multiband Bitx kit by Sunil and a ordered the G6LBQ linear PCB by DXKits.In the meantime I spent some time to build the bitx20 V3 in dead bug style,waiting for my parts for the multiband.Now the exciter is finished and tested.The manual which you can download from the G6LBQ Yahoo group is quite good,so I`m not gonna bore you with pictures where the different stages of the build are displayed.I choose to build the MK1 version of the multiband in stead of the MK2 version which is now availible,because I had all the parts already in stock.

On the picture overhead you see the exciter with the little ad-on crystal filter.Just like my Bitx20,I paired 6 crystals with the use of my BFO and a frequency counter.(Picture bellow)You need four crystals for the filter and one for the BFO.I paired six,because I want to put the USB/LSB mod on in the future and that requiers another crystal.For the IF I used the 10MHz crystals.Remember always to put the crystal with the lowest frequency in the BFO section.For T1 in the BFO I used a coil from Sunils Bitx20 bandfilter with a 82pf padding capacitor.Special attention when you solder Q4 (2N3904) on the PCB.Earlier versions of the PCB had an error in the pad positions for the transistor.On my PCB,this error was corrected.

During the build,you have to test the individual completed stages.I constructed two toggle switches on a PCB so I could switch from TX to RX and 12V on/off.

After putting all the parts on the PCB it was time to test the circuit.I connected a speaker,antenna and a volume pot.Because I didn`t build the bandfilter yet,I bridged the bandfilter connection with a piece of wire.After switching on the power,I could hear two Dutch radio stations.Not bad.Time to connect the VFO.For the VFO I used the IK3OIL.The difference between a VFO or without a VFO was big.An increase of audio output and several stations and CW all togheter.Next week I will start with the bandpass filter.

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.

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.

vrijdag 26 april 2013

Bitx20 V3 "Dead Bug Style" Post IF-Amplifier and 1th Mixer section

After a few hours of soldering ,I almost completed the 7th and 8th stage of my Bitx20 V3 "dead bug" style 20 meters QRP Transceiver project.Transformers T1 and T1a are the same as in the BFO.13 trifilaire windings thrue the ferrite core.For the diode bridge I used a piece of double side PCB.Just one more transformer has to be wound,but I will do that the next time.After that I have to test the whole circuit.

donderdag 18 april 2013

Bitx20 V3 "Dead Bug Style" 2nd IF Amplifier + Crystal filter.

Just completed the 2nd IF stage amplifier and the 10MHz crystal filter.The "beeps"on 10MHz are now hearable with a piece of wire as antenna and I had to turn the volume as low as can be,what a gain.When I touched the 10MHz IF crystal with my finger,I could hear a foreign radiostation.Yes,the first signals are received.

On the picture bellow,the six stages of the Bitx20 V3 are shown.Next stage is the build of the post IF-amplifier and the first mixer section.

Bitx 20 V3 "Dead Bug Style" BFO section.

I build the Bitx20 V3 Audio Section in about 3 hours.So it was time for the next chapter,the BFO/Modulation section.I took another 5 by 5cm double sided board.On the picture bellow you see the transformer made of a binocular core.Put 13 trifilaire windings thru the core and beep the wires for right connection.Stick it to the PCB with a hot glue gun.In this stage ,I put it together with the audio section.Apply 12Vdc to the receive line and now you can receive the "beeps" on 10MHz when you use a 10MHz crystal as IF.This is also the part where you can determine if your crystals for the filter match.I used a IC-connector,so I can easily change the crystals in and out the socket for measuring the right frequency.So you can pair the crystals for the crystal filter.Just connect your frequency counter and search for 5 chrystals where the frequency`s are closed together.

Bitx20 V3 "Dead Bug Style" Audio section.

While I was still waiting for my Multiband Bitx printed circuit boards and all the parts,I wanted to build another Bitx20 V3,just too kill time.So I took a large piece of double sided copper PCB and made a few little boards ,just 5 by 5cm.The plan is to build one or two sections of this popular homebrew QRP transceiver on this 5 by 5 board.Then place it all togheter on a larger board to make it a complete and working 20meter QRP transceiver.On the picture bellow you see the audio section with the LM386 for the speaker and the two 2N3904 transistors.When you apply 12Vdc to the receive line,you can hear some noise comming out of the speaker while turning the volume up.When you also put a + on the transmit line,you hear a very loud tone coming out of the speaker.So now I know the circuit is working.

Multiband Bitx (2)

This week all the remaining parts of my Multiband Bitx project were delivered at my door.Tuesday I got my PCB`s from Sunil Lakhani.Wednesday the ADE-1 mixers from Boris LZ2JR arrived.(Thank you so much Boris!),and today the Linear Board from DXkits.com arrived as well.
On the picture you see the complete PCB kit from Sunil Lakhani VU3SUA.On the right corner you see the Linear PCB from DXkits.com.

ADE-1 mixers from Boris (LZ2JR) as a gift.

donderdag 11 april 2013

Multiband Bitx (1)

After the succsesfull build of three Bitx20 20 meter QRP transceivers,it was time for another project.My first idea was building the Lima SDR,but I`m an old fashion guy,and as the computer is a very important component of the SDR kit,my choice fell on the Multiband Bitx.
Today all of my parts I ordered are arrived.Only the ADE-1 mixer is missing on the picture.LZ2JR was so kind to send me two of those missing parts.Hopefully Mr.postman delivere`s them this week.Another very important part of the build are the PCB`s from Sunil.I`m still waiting for the exciter,LPF,BPF-pcb`s.Last week I made a reservation for the linear PCB on the dxkits.com site.

On the picture you see the complete bandpass filter set by G4CFY (Spectrum Communications) and the rest of the parts for making the exciter and the complete bandpass filter from 10M to 160M.

dinsdag 26 maart 2013

Bitx20 V3 20 meter QRP transceiver

Yes! You`ve seen it right.PA1ED`s first blog item.First let me introduce myself.My name is Edwin Groot and a live in the North West of the Netherlands in a place called Zaandijk,5km above the capital city of Amsterdam.I,m 44 years old and a very enthusiastic radio amateur.Last year I`ve build tree Bitx20 V3 20meters QRP transceivers.On the picture you see the latest version in the shack.

Here are some pictures of my first Bitx20 "dead bug" style and my latest projekt,the Bitx 20 V3 building stage.Since this is my first blog,other pictures will follow.