Homebrew 40M Transceiver - Transmitter Section

Discussion in 'Homebrew and Kit Projects' started by K5UOS, Mar 20, 2010.

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  1. K5UOS

    K5UOS Ham Member QRZ Page

    I needed to update some of my old 40M CW gear and try some new stuff. I am finishing a 40 CW transceiver which began as a SSB rig last year. For the RX I use some of the ideas from the K2 for the front end and some of the KK7B direct conversion RX ideas for the product detector and audio section. The RX covers approx 7 to 7.100 MHz.

    I have completed the transmitter section. It is a 16W mixing type TX. The carrier is 9.216MHz and the LO runs 2.07 to 2.216MHZ.

    The 1st board is the carrier, mixer and triple tuned band pass filter. I used my HB LC Tester to build the filter and some other test gear from EMRFD to measure outputs as I was building each stage. It obviously built ugy style.

    [​IMG]




    This is a rough copy of the schematic for the above circuit board. Pretty classic circuit and something I have done several times.

    [​IMG]
     
  2. K5UOS

    K5UOS Ham Member QRZ Page

    Driver and Power Amplifier Boards

    This section is the driver and power amplifier. I considered using an IRF530, a cheap MosFET switching transistor. I even built the MosFET amplifier but it required approx 25VDC and that could be inconvenient at times since I operate portable.

    I used a 2SC1307 for the PA. It is similar to the relatively cheap 2SC1969 available from many sources. Either is a good workhorse transistor in this power range. The PA is narrow band and used L-C-C Networks for the input/output. I designed all the filters and matching networks on software(spreadsheets) I created.

    The drive chain Q1, Q2 and Q3 are all inexpensive transistors from Mouser. I filtered each stage more than I needed.

    [​IMG]


    This is a schematic of the driver and PA section. It is complete except for the the TR circuit. I haven't decided what method I will use for TR but I don't particularly like QSK. The 1N914 diodes provide a simple QSK method popularized by Roy, W7EL.

    [​IMG]

    This is how the boards will be mounted on the end wall of the chassis.

    [​IMG]

    Power amplifer board. Most of the board is the LCC networks for matching the low impedance of the base and collector. It would have been simpler to use broad band.

    [​IMG]


    Mechanical work and preparing the PA board:

    [​IMG]

    [​IMG]

    Testing the completed TX.

    [​IMG]

    Pretty soon I can get back to my tube receiver project.

    K5UOS
     
  3. KA0HCP

    KA0HCP XML Subscriber QRZ Page

    Looks great! All the arrows point to the right on the schematic so you must have done a good job designing it!! :)

    73, Bill
     
  4. K5UOS

    K5UOS Ham Member QRZ Page

    PUT side tone from old 1970's SSDRA circuit

    Hi Bill,

    Thanks for the comments. :)


    I enjoy building and I did design the transceiver. But I used a lot of ideas and stuff I learned from my favorite homebrewers like W7ZOI, KK7B, W1FB, W7EL and others. The arrows are the points where I tested output and between the arrow is essentially one board.

    One old circuit I worked on yesterday was a sidetone oscillator design from Solid State Design for the Radio Amateur using a PUT. I didn't have a PUT because they are about $2.10 from Mouser (who uses PUT's?). I simulated the circuit using common 2N3906 and 2N3904. I tried some other circuits but they were either hard starting or harsh sounding. This is a pretty good choice as it is easy to change audio frequency to one I like listening to.

    [​IMG]

    The schematic shows an additional PNP keyed switch and an LM386 for driving a separate 2" speaker. I tried several methods to inject the sidetone into the RX audio. The best try still had a very slight click/thud making the QSK distracting. So I will add the LM386 and speaker. Now the mute function appears to be totally smooth and almost unnoticable. Now I have to add the transmitter and TR function.

    This is the prototype board I built the circuits on. Dead bugly style. The circuit shown is the one I will use but needs rebuilding. The diode at the bottom goes to pin 5 of an MC1350P IF amp.

    [​IMG]
     
  5. KL7AJ

    KL7AJ Ham Member QRZ Page

    It's just just just.....byootiful. *sob*


    Nice job!!

    Eric
     
  6. AC0FP

    AC0FP Ham Member QRZ Page

    I looked at the schematic and appears you know what your doing. :) I like the choice of the SBL-1 mixer. I also noticed you have the TUF-1 as an alternate.

    I used a similar construction for my 6 meter rig as shown in my profile on QRZ.

    73,

    fp :)
     
  7. K5UOS

    K5UOS Ham Member QRZ Page

    Old class project

    Hey Eric,

    I thought about you when I was looking for a small speaker for the sidetone. I know you have been teaching some classes lately.

    I found an old project I used for Boy Scout and homeschool electronic/radio classes I used to teach. It is an audio oscillator controlled by a photocell. The more light the faster and higher pitched. Five parts, a battery and a speaker.

    I remember the thread about the Dripper so I hid it in the dark bathroom yesterday before my wife got up. I went in later when she had the light on and I didn't hear it. I told my wife I was playing a trick on her but it had not worked. She told me it had worked.....for while. I noticed she had one of the speaker wires pulled out. Oh, well....:(

    Some people have no sense of humor at 5:30AM.

    [​IMG]
     
  8. K5UOS

    K5UOS Ham Member QRZ Page

    SBL-1 and TUF's

    Hi Franklin,

    I used a TUF-1 and a TUF-3 in the RX as front end mixer and PD. They are amazing little devices! I bought about 40 ea SBL-1's for dirt cheap a while back. I gotta use them up somewhere.

    I have several other Mini Circuits DBM's including some special order mixers not listed on their site. It is hard to spend the time building DBM's anymore.

    I also like the SBL-1 because I can add a balance control when used as a modulator to maximize carrier balance.

    I didn't see the 6M rig in your profile? Take a picture of the rig and post it. I really like to see other projects.

    73....Don
     
  9. AC0FP

    AC0FP Ham Member QRZ Page

    I see you found out Mini Circuits mixers also make great modulators. I used a SRA-Hi for the balanced transmitter modulator in my 6 meter rig. They work great as modulators as long as the output port on the mixer is rated down to DC.

    On my profile page look on the right hand side in the Album section. Go down to the bottom where it says View all albums and click on that.

    I still have a few SRA-1, SBL-1 and TUF-3 mixers in my parts bins.

    73,

    fp
     
  10. K5UOS

    K5UOS Ham Member QRZ Page

    Great HB rig

    I didn't know QRZ had that function for file storage.

    Your 6M rig looks great, Franklin. It looks well thought out and easy to work on which is one reason I build my gear large. I used my 1st MCL mixer about 1980. I have HB'd a few more since but don't know why. It is just easier to use store bought ones.

    I have never operated 6M or many other bands for that matter. I know I may be missing something but I have a terrible habit of just building mostly 20 and 40M gear. It is more in the building than the operating and these two bands are convenient for building. I like 15M, too

    I love vacuum tubes and vintage solid state. If I could live another 30 years I might build myself into the new digital age. Unfortunately (or fortunately) I am an analog guy in a digital world.

    I see you traveled in Germany. I lived in Wiesbaden for about a year. My dad was a civilian at Lindsey, AFB working on the first up-link and downlink for one of the 1st communications satellites.

    Thanks for the pictures.

    73, K5UOS
     
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