Wednesday, September 18, 2019

Back to some Techie Stuff!

Upgrade that IRF510 Final Amp!


[Once you have done this upgrade you should consider putting your homebrew SSB Transceiver on FT-8 and here is a great digital adapter kit from: 

The price point is about $15 and there is an assembled version for an additional fee of $5. The digital adapter I built cost more than $15 --so I think this is a bargain. However I did not look at the specific interface to a computer aspect, so be sure you check to see if you can trigger this from a USB port on a computer. Most new computers including the RPi do not have a plug in serial port. (You might be able to jury rig a serial port on the Pi with the GPIO pins. I just don't know.)  

My adapter took a small kit board that required a serial interface --I had to purchase another board (Adafruit) so you could have a USB to serial hand shake. I think the assembled version should be appealing to many wannabe homebrewers who still ponder which is the hot end of the soldering iron. For those who don't have a homebrew SSB Transceiver it most likely WILL work with that uBitx or an Icom 7300.]

Many of us homebrewers have one or several IRF510 Linear Power Amps as a final in our rigs. Typically below 15 MHz you get a lot of bang for less than a buck ($1). But at times I like to foray out above 20 meters and see somewhat of a drop off in RF output.

I do not believe I am misquoting; but even the uBitx documentation notes that on 10 meters the Pout is somewhat reduced. 

So what does it take to take to change out the IRF510 so that there is a better gain distribution at the higher frequencies. Secondly what is the device that would replace the IRF510. The chosen device is the Mitsubishi RD06HHF1 which is good for 6 watts out across the HF Bands.

BTW before those with itchy trigger fingers start emailing me I am not disparaging the IRF510 other than to note is that it was never intended to be an RF device --we just used it that way.

Now what I am about to share has worked for me -- YMMV and there were no Tayloe Detectors or elaborate simulation programs used for my evaluation. Just some simple changes.


  • First the bias can be higher and since I always use three terminal devices (78L05) to supply the bias a small modification will let you run a bias level close to 6 VDC. The middle pin on the 78L05 is ground. Simply lift the middle pin from ground and install a RED LED with the Anode to the middle pin and the Cathode to ground. Thus when voltage is applied to the bias circuit during transmit --the LED is ON. A bonus you will definitely know that you have bias as the LED shines a bright RED when the bias trigger voltage is applied
  • The RF FET has a very high idling current with bias applied so you will need something more than a TO-220 clip on heat sink! You will definitely need a robust heat sink!
  • The Pin Out for the IRF510 (face up) left to right is Gate, Drain and Source. KB1GMX (Allison) has recommended cutting off the center pin on the IRF510 and make all Drain connection to the Tab. In the case of the Mitsubishi RF FET the Pin Out is Gate, Source and Drain. There is good Karma here as the tab is the Source so you can directly screw that puppy down on the heat sink face. But do use the thermal grease.
  • All other circuit elements remain the same and you should carefully advance the bias so it does not exceed the recommended level. Yes you will be forced to look up the data sheet to discover that level.
Here is my reworked Linear RF Amp Board with the Mitsubishi RD06HHF1 installed. You can see the LED near the 78L05 and the RD06HHF1 is screwed down to the heatsink directly and the center tab soldered to the circuit board. The heatsink is two by four inches and multi-ribbed on the bottom side


73's
Pete N6QW

Monday, September 16, 2019

Giuseppe Biagi ~ QRP -- Ham Radio -- and a Rescue


Giuseppe Biagi



At times we might forget the import of ham radio but to a group of Italian polar explorers in 1928, our hobby was a true lifesaver. Do an internet search on Giuseppe Biagi the explorer (not the painter).

Ham radio to the rescue and I believe it was QRP.

73's
Pete N6QW

Friday, September 13, 2019

More CRAP --- Cool Rigs And Projects!

Yet another SSB Transceiver --More CRAP!



You have heard of single board computers --well here is a single board rig!

Custom LCD Characters and S Meters
See https://maxpromer.github.io/LCD-Character-Creator/

If you are not wiring direct but using I2C select I2C and binary





Pete, N6QW

Tuesday, September 3, 2019

Dipping the Toe into the World of CW

A New Found Opportunity--Arduino + CW!

The Left Coast Loafer CW Transceiver






Hey John Bolton now that you have some free time, have you considered getting a ham ticket?

A New Definition for MAGA

More And Greater Avarice. 

Maybe the wrong guy just got fired yesterday!


*****************************************
9/7/2019 ~ CW Output Across 50 Ohms




*****************************************
9/6/2019
More Tidbits for your amusement and amazement!

So here are a couple of "tricks" I would like to share with you.


  1. First is how to have sidetone. Well with my super duper DPDT TR switch I added a 470 Ohm 1 watt resistor and a 1N4007 diode. The 470 Ohm connects on one end to the voltage contact that supplies the Transmit voltage. The other end is connected to the Anode end of the diode. The Cathode end is then connected to the contact that receives juice on Receive. Thus on receive no voltage is fed back to the transmit side; but when in transmit voltage is fed to the receiver. The 470 Ohm dropping resistor is a 2 watt unit which essentially operates the receiver  at about half voltage and the audio is not very loud. With the scheme I am actually listening to the transmitted signal -- thus sidetone.
  2. Next is the method of turning CLK2 ON/OFF for transmit. I am not actually keying the clock; but during the transmit sequence CLK2 is continuously on and the transmit RF chain is keyed through a 2N2905 PNP "keying" transistor. You do hear a bit of backwave in the headphones but that is not transmitted. So back again to my DPDT TR switch and voltage is taken off the transmit contact and fed to the Base of a 2N3904 through a 1K 1/4 watt resistor. The 2N3904 Collector is connected to Pin 4 on the Arduino Nano which has been set HIGH in software. The Emitter is grounded. So when voltage is applied to the base via the 1K resistor the transistor switches and essentially Pin 4 is made LOW which turns ON CLK2. Throwing the DPDT back to receive stops the CLK2 (OFF) and all is normal.
  3. A further refinement as found in SSDRA (not seen in EMRFD) is an electronic TR switch using a NE555 and a few diodes. This would automate the sending so all you do is hit the key and the rest is automatic.

What started out as a bunch of scrap/surplus circuit modules is now a full functioning CW transceiver. You just got to love all of this technology.



73's
Pete N6QW

*****************************************
9/5/2019

Something new learned today!!!!!!!!


This is the very 1st time I am using all three clocks on the Si5351. and it has been an excellent learning experience for me that I want to share with you.

So CLK(0) is supplying the LO signal at around 5 MHz and CLK(1) is supplying the BFO signals ( 12.096 MHz +/-) for CWU and CWL. Should mention I used an AD9850 stock oscillator to find the proper BFO frequencies and then modified the code with those frequencies. So the grand plan was how to use CLK(2) in such a way that it spit out the proper frequency for the transmitter including a plus/minus 600 Hz offset. 

Setting the third clock to give that frequency output so that it automatically tracked the received frequency was not too difficult. The nut to crack was to only have that third frequency output only while transmitting. 

My code senses a LOW condition on Pin 4 and when that happens and depending on whether you have CWL or CWU engaged the transmitted frequency is +/- 600 Hz from the received frequency, the third clock is turned on and the display shows that frequency. The problem I initially had was that once turned on -- it stayed on! There were some references to how to do it and they were not clear nor was the data sheet helpful. That is when I spotted something in the si5351.h file --the ah ha moment.

With a simple line of code and a change in one coefficient it is possible to turn ON and turn OFF a clock --in software/

Turn ON:     si5351.clock_enable(SI5351_CLK2, 1);
Turn OFF:   si5351.clock_enable(SI5351_CLK2, 0);

(OK you missed it -- the "1" turns it on and the "0" turns it off.)

So my code senses if Pin 4 is LOW and if so then turn ON the CLK2. If it is not LOW then turn it OFF. This is the standard If Else regime. You also have to blank out the frequency in the else part of the code. Here is the code

 void CheckCW() {
         
                 digitalRead(4);
                 if(digitalRead(4) == LOW){
                 si5351.clock_enable(SI5351_CLK2, 1);
                
                 si5351.set_freq( bfo+O-rx2, 0, SI5351_CLK2);
                 ucg.setFont(ucg_font_ncenR14_tr);
                 ucg.setColor(255, 255, 0);
                 ucg.setPrintPos(15,80); 
                 ucg.print(bfo+O-rx2);
           
            
                 
             
         }
            else{
              
                si5351.clock_enable(SI5351_CLK2, 0);
        
               
                 ucg.setColor(0, 0, 0);
                 ucg.setPrintPos(15,80); 
                 ucg.println(bfo+O-rx2);
            }
                
       

 }


Note: O is the offset variable and is set by a selection in the code. If you select CWU then O = +600 and if you select CWL then O = -600. 


Now the Code for CWU CWL Selection:

There still may need to be some tweaking to get CWU CWL in the right relationship which only requires changing the signs on the O = 600 or O = -600. But the display does change from having the transmitted signal above or below the received signal by 600 Hertz. If you don't like 600 Hertz the change the 600 to what ever you like such as 800 or maybe 500. The code below is based on my filter frequency which is above the signal frequency. If you use a different filter frequency below the incoming (homebrew, heathkit or early Yaesu)  then you will have to diddle with the U or L and the offset. The photos below are to merely show that the transmitted frequency is either above or below the received frequency --my scheme works! The code now makes CWL = -600 and CWU + 600. On the Air tests will help me affirm that is the correct sequence. If not just changes the two signs of the 600 and you would be there. Gets a bit confusing. 

 void CheckSB(){
     

     if(digitalRead(SW)){  //If SW is true do the following.
       bfo = 12098500L; 
       si5351.set_freq( bfo, 0, SI5351_CLK1);
       {
          O = +600; // + Offset Value
     
        ucg.setFont(ucg_font_ncenR12_tr); 
        ucg.setColor(0, 0, 0);
        ucg.setPrintPos(42,98);
        ucg.println("CWU");
      
        ucg.setFont(ucg_font_ncenR12_tr);
        ucg.setColor(255,10, 200);
        ucg.setPrintPos(3,98); 
        ucg.println("CWL");}
    
     }
      else{                //if not, do this.
         
         
         
        
          bfo = 12096500L;
          O =  -600; // - Offset value
       
          si5351.set_freq( bfo, 0, SI5351_CLK1);
          ucg.setFont(ucg_font_ncenR12_tr); 
          ucg.setColor(0, 0, 0);
          ucg.setPrintPos(3,98);
          ucg.println("CWL");
      
          ucg.setFont(ucg_font_ncenR12_tr);
          ucg.setColor(255, 10, 200);
          ucg.setPrintPos(42,98); 
          ucg.println("CWU");
          }
         
      }


    
      




I still have some wiring to accomplish. When I use my exotic DPDT switch for TR it will also close a relay to provide a LOW condition at Pin #4. When you go to Receive then the clock is turned OFF and the screen is blank where the transmit frequency was showing. 

I bypassed the crystal oscillator transistor and straight into the EMRFD board. I get over 500 MW and my SS amp now registers 50 watts out. Shades of my Johnson Adventurer (on steroids). A few more checks and we may actually have to make a contact.

After I get things cleaned up I will post the code on my website www.n6qw.com.

If I had thought how to do this before --it might even be possible to build CW into most of my homebrew SSB transceivers  using a method I used in my KWM-4. There the generated CW signal bypasses the mechanical filter and dumps the CW signal right into the transmit mixer chain. In the KWM-4 it is fixed so that it receives only on USB (the two schematics below show the KWM-4). 

Now much of the work would be done with the Arduino/Si5351  and a simple keyed buffer amp. Look at the dates on these schematics -- almost 7 years ago I had a scheme for SSB and CW in a homebrew double conversion multiband transceiver. OK I will say it -- ahead of its time!




Pete, N6QW
******************************************
9/4/2019


I have received some inquiries about the "innards" of the Left Coast Loafer CW Transceiver and will over time will supply some technical data about the rig. The rest is up to you.



Firstly this rig just sort of happened like spontaneous construction. I had some spare and/or obsolete circuit board modules in the junk box and the next thing you know -- we have a transceiver. 

Note this is essentially a Trans / Receiver and the common element is the Digital VFO which generates the LO and BFO signals for the receiver as well as a secondary VFO that offsets the received frequency by + or - 600 hertz for the transmitter. It is not a true transceiver (sharing many common elements) like I usually build





  • The Audio amplifier board was originally in the LBS transceiver project. I never liked the discrete components amplifiers -- too many parts and I really have no need or desire to know what every components does in an audio amp circuit. But I did have the board. One premise of the LBS was to only use discrete components.
  • The main receiver board is comprised of a homebrew  DBM, a healthy (2N5109) post mixer amplifier and a three pole 12.096 MHz crystal filter thence followed by a BF991 product detector. That board also had a J310 Crystal Oscillator for the BFO. The board size was maybe 3 x 4 inches. It was initially built again as a part of the development effort for the LBS project. [The LBS project was a two part article in QRP Quarterly authored by myself and Ben KK6FUT (now AI6YR)  -- LBS = Let's Build Something.] Needless to say --it works pretty well.
  • The Rx RF amp stage is just a single "hot biased" 2N2219 and is untuned. In fact there are no Band Pass Filters in the Rx section -- probably one would help with out of band signals --but this is a "loafer" build.
  • The transmitter, initially crystal controlled on one frequency (7.030) in its original form was an oscillator stage in a 30M CW transceiver which also was published in QRP Quarterly. That transceiver has been cannibalized and the parts and boards have found their way into many of my current SSB transceivers. This board has a 2N3904 crystal oscillator essentially followed by the EMRFD stage (2N3904/2N3866) and develops about 1/2 watt. An afterburner delivers about 15 to 20 watts to the antenna. The transmitter will now be driven by one of the outputs from the Si5351 and is offset by +/- 600 Hertz from the received frequency.
  • My initial construction had a 5 MHz VFO operating the receiver and the single crystal for the Transmitter. Now with the Arduino/Si5351/Display we have the Rx LO and BFO and the Tx VFO all in one neat package.
  • For now we will use manual switch over from Rx to Tx but the Arduino will be reprogrammed so that you hit the key and it is automatic --you are on the air. 
  • Other possibilities drawing upon the collaborative efforts with AI6YR and use the articles we penned for QRP Quarterly for the CW Sender and incorporate a keyboard for sending CW. It may require the use of a Mega 2560 --but that is just more space on the breadboard.
  • The Box has been opened...



*****************************************

9/3/2019

This post is a result of too much Temperature (90F), too much Tequila and too much Time on my hands.



In the process of creating a new rig, I actually ended up with a spare Arduino Nano and Si5351. This was a fatal error for now I had a driving desire to couple these two with my new found color OLED Displays --an worse yet to integrate these three items into a simple CW transceiver.



An earlier foray in August with again the terrible three's (Temperature, Tequila and Time) I built an analog VFO controlled VFO receiver with a 3 pole 12.096 MHz crystal filter and then mated that with a QRP 7.030 MHz Crystal Controlled transmitter. So now how to make the lash up work with the Arduino & Si5351.



The Easy Part 1st!

That is the beauty of having lots of code snippets as it now becomes possible to port over code to new projects without having to start with a clean sheet of paper.

My initial configuration is to have the following:


  1.  The LO will run around 5 MHz and mated with a 12.096 MHz IF results in signals in the 40 Meter band. So the code was changed so that CLK(0) would spit out the LO signals and the display would read the 40 Meter Band
  2. The crystal BFO would be initially kept for the testing purposes so a BFO frequency as such (typically CLK(2)) would not be generated. However CLK(2) would only be activated on transmit would take the BFO (IF) frequency and subtract the LO but would add 600 Hz as the offset. I call that CWU so that the transmitted signals would always be 600 Hz higher than the received frequency. With additional code, a simple switch would give you CWL which then would cause the transmitted signal to be 600 Hz lower in frequency. Again initial testing will be at the +600 Hz offset.
  3. The first photo below shows the display in the receive condition with a default boot up of 7.030. The second photo shows the transmitter engaged (a Pin goes low on the Arduino) and the transmit frequency is generated via CLK(2) at 600 Hz higher in frequency. Unkey the pin and CLK(2) stops and only the recei9ved frequency is displayed. Initial tuning tests with the encoder indeed shows that the transmitted frequency tracks the received frequency by +600 Hz. Pretty cool.







So the next steps are as follows:



  1. Mate the Arduino/Si5351/Display with just the receiver section and run the various test such as birdies, noise, sensitivity etc.
  2. The output of the CLK(2) is not a sinewave and so some cleanup might be (very likely will be) needed. I also need to determine how to replace the crystal with the signal from CLK(2) and also address the signal level which might require a booster amp.
  3. The current configuration has a DPDT switch that changes the voltage to the Rx and TX as well as switch the antenna from Rx to Tx. This may need to be a bit more refined. so that you hit the key and all is automatic.
  4. Finally this may be an opportunity to try CLK(1) which would supply the BFO signal thereby eliminating the Crystal BFO.

Note this is a measured approach so that changes are made in such a way as to test, evaluate and refine any modifications being made.



I just hope it gets cool so I can get back to some serious other SSB SDR work. Stay Tuned!





73's

Pete N6Qw

Sunday, August 25, 2019

The Thrill of Making Contacts with a Homebrew Radio Station

The Station Here is Homebrew!

Yesterday I had the good fortune to have a bit of time to actually get on the air on 40 Meters. I was running a new homebrew transceiver (non-SDR) and it was such a buzz to be able to say that the station on this end was 'homebrew". In this case because of the specific topology of this new rig I even had to homebrew an electret microphone.

Now as to the other station -- he was running a FLEX6700 and a brand new FLEX KW Amplifier that he evidently had to wait months to receive. His antenna was not unlike mine ( a wire) but he also had a three element 40M beam. The other station was in Nebraska and I of course not too far from Los Angeles. It was early evening and the signals were quite strong. The general comment from the other station (not even acknowledging that I was ruuning homebrew or that he was looking at my signal on his large display) was that I was a solid 5X8 into his QTH. That I considered as positive. 

Don't get too excited -- I was not running QRP but my new homebrew rig was driving the SB200 to about 600 + watts into my dipole. So I am able to run with the big dogs using a homebrew station. 

Should mention that the new homebrew rig runs 5 watts with the IRF510 in the final and the intermediate amp is a "brick" (literally the size of a common red brick) came out of a defunct Atlas 210X. This amp runs 100 watts + and has been fitted to a small chassis and includes a fan for cooling the heatsink --so there is much homebrew into this piece of the station. The former Atlas 210X amp easily drives the SB200 to 600 watts +.

But back to the other station and a discussion about his new FLEX Amp. He described that there is circuitry in the amp much like a diplexer (my words) that takes out of band signals that are generated in the transmit chain and dumps them into a dummy load built into the amp. He is able to monitor the level of the dump and was telling me that it was close to 200 watts and he could even look at his output spectrum and all he could see was the primary signal power output.

This was not the first time I had heard of this. I believe over 10 years ago I saw  such a process in an article where this was done. It might have even come from someone with or formerly associated with Collins Radio (Bruene ?? or Sabin??). 

But something I have personally noted and watch for at my station when running QRO. I will briefly tune up a rig (at QRO) into my antenna to assure the SWR is 1:1. If I get on the air and I see the SWR pop up on voice peaks --I know there is something slipping through outside of the desired operating frequency and I immediately stop! If there is nothing coming through other than the desired signal then the SWR will not change. 

As described to me with the FLEX KW amp -- they are automatically terminating that out of band signal into an internal dummy load. Given that the other station mentioned it was 200 watts -- that is sizeable.

Now a few comparison comments on the new conventional filter rig. This new rig (notice I didn't say HDR since that is trademarked by N2CQR) is in a different class from my RADIG. I miss being able to see the energy in the incoming signals. I also miss tinkering with the filters and having a built in accurate S Meter. 

Don't get me wrong -- the new conventional rig does a yeoman's job (have had 6 contacts so far) but it is just that it is not an SDR transceiver. True it is small, does not require a computer and of course no computer screen so it is ideal for portable operation. It does however make serious contacts and most importantly runs with the big dogs. Isn't that really the overall determinant?

There is another important consideration and that is the ability to replicate this conventional filter rig. Few feel comfortable homebrewing any rig. An even smaller percentage feel at ease in fabricating an SDR transceiver. So this project would appeal to a larger set of potential homebrew constructors and is worth more than a look see as a potential winter project.

I must stress again if you are not a member of the GQRP Club -- you best get that done. Enough said.

I relish when I can say to a station running over $10K worth of hardware not including any antennas -- the rig on this end is homebrew and cost about $100.

73's
Pete N6QW

Friday, August 23, 2019

Experience with the OLED Displays -- Careful what you buy!

More Expensive and More Flash -- Not always the best course.


I have been evaluating two types of the 65K Color OLED Displays. One uses the SSD1331 application contained in the Ucglib Library and is a bit larger in size than the one using the ST7735 application. Frankly the colors and background on the SSD1331 is like uptown versus the colors and display size on the ST7735. The there is a 3:1 price difference too.

But you don't always get what you pay for! The SSD1331 display was so noisy when installed in a rig that it was useless without some major additional noise reduction techniques. The buzzing noise completely obliterated the signals. In looking at the backside of the SSD1331 there appears to be some sort of switching power supply right on the substrate! The high end color and sharp features has to come from somewhere!

Whereas the ST7735 just popped in the circuit and no noise issues. So what you have my friends is the high end call girl and the street walker --- the ST7735 which I paid $2.58 works perfect.

There is another advantage to the ST7735 and that is size --it is about 2/3 the size of the SSD1331 and should make for retrofitting into existing rigs a much easier task. 

Stay tuned as there is a N6QW application for the ST7735 OLED Display that will be forthcoming. But it comes with a price! If you are not a member of the GQRP Club --then you best get a subscription today. Enough said.

73's
Pete 

Saturday, August 17, 2019

Dress Up your Homebrew Rigs with these new Displays

Once again from the N6QW Leading Edge!



No Tayloe Detectors or ADE-1's were involved in this  project and there are no LT Spice Simulations to pick apart. Just plain old hard work to get the displays to work.

I have seen many videos of the new Color OLED's but I have not seen any where they are actually used in a Homebrew Rig. So this may be a first. Most of the demo's involved taking the stock sample programs and just loading them on to an Arduino. This video was built from scratch!

Pete N6QW

Back to some Techie Stuff!

Upgrade that IRF510 Final Amp! [ O nce you have done this upgrade you should consider putting your homebrew SSB Transceiver on FT-8 and...