Friday, August 24, 2018

2018 ~ The Year of SSB Transceivers

FT8 & WSPR on your Homebrew Rig!

For several months now I have been working on a new SSB rig that will be the subject of a couple of articles in  future issues of the GQRP Club publication SPRAT Magazine.


Run don't walk if you are not already a member of the GQRP Club so by joining you can gain access to the articles. Most of my operation is on SSB but I have come to recognize that many in our ham community have moved over to the digital communications dark side and therefore challenged myself to enable my SSB rig design to "do digital". I am happy to report that I have been successful in running both WSPR and FT8 from the new rig.

All that was needed was the software WSJT-X, a $10 (delivered) sound card interface board, some cables and an old computer with a serial port DB9 connector. That is it. 

With technology advancement comes change. Most new computers do not come with a serial port and thus that presents some difficulties in using the sound card interface device. A tour of Adafruit Industries webpage revealed a product that provides a USB to Serial interface device that has as outputs the DTR or RTS signals (either one) that will key the transmitter. It is a modest price ($15); but opens the door for possible uses with a Raspberry Pi3B or an Asus Tinker Board. WSJT-X  comes in Windows and Linux distributions so there may be a possibility for a very small (and portable) FT8 station. I have ordered one of the units and you can read about it here https://www.adafruit.com/product/284

Here is the interface board kit.






But the real proof is how it works on the air. Below are some screen shots that document the contacts I had. In the WSPR log you will see an entry from VK2ALR when I was spotted 7500 miles away running 5 watts on 40 Meters.



But the most Buzz today is about FT8. So I had to try my hand at that mode and so far have made two contacts. Here is a log of the 2nd contact made this afternoon.


Now I must confess that the FT8 is almost like remote sex. Push a button and the computer takes over and makes the contact. So no long rag chews here. But FT8 levels the playing field using low power and modest antennas.

I am in the process of reworking the sketch for the VFO (it has two). One VFO will boot up normal at 7.2 MHz and the second one I will program to boot up on 7.074 MHz. Thus, flip the VFO select switch and flip the rig to USB and you are on digital!

This is exciting.

73's
Pete N6QW

Thursday, August 9, 2018

2018 ~ The Year of SSB Transceivers

Something for the SDR Crowd!


You too can build your own SDR Transceiver!

Second Generation Main Board


The board above is a second generation board and contains the two ADE-1 Detectors and the Modem coupling transformers, the divide by four 74AC74 and to be installed is the band pass filter. If you look close you can see the ferrite core balun used to split the signals going into the two detectors. This is a deliberate attempt at isolating signals and keeping things neat and tidy. I am thinking about a separate enclosure just for this board. Later today I will install the bandpass filter with the intent that it may be used at 9 MHz with a possibility of a different front end. You will have to stay tuned for this.

How about using the SDR on WSPR?





While I can claim I built this rig and added several modifications, by and large the credit goes to Charlie Morris ZL2CTM for his design and software development. You can follow ZL2CTM on YouTube and he has many videos and tutorials!

The bottom line is how your signal sounds AND LOOKS  at the other end. I am really surprised at the number of hams that use either an SDR rig in the shack or use an SDR receiver on the Web for the receiving end of things. Not too many are using a homebrew SDR! Thus it is not unusual to hear that my signal looks really good. To date I have made close to three dozen contacts including a 8000 mile DX QSO with a station in Australia --on 40 Meters. My usual set up is the rig followed by a 100+ watt Solid State Amp kit from CCI and then the Heathkit SB200. Based on my upgrade of the SB200 I typically see in excess of 600 Watts to the antenna. That is a smoking signal!

My 40M antenna is a droopy dipole and that means if I spent a bit more time on the antenna I would hear and work more stations. The center pole is up about 25 feet and the length is 98 feet 3/2 wavelengths on 20 Meters. It is in the shape of an L as it runs along the back end and one of the sides of the lot. The fiberglass support pole is strapped to the tree.



But let us start with the Block Diagram of the basic hardware. Beyond this I have a transmit Driver Stage with a 2N3904 and 2N3866 and the Final amplifier is a IRF510. The relay Switched J310's and the audio amplifier (2N3904 + LM386) are located on the main receiver board. One other item needed to make this play is another bit of hardware from PJRC and that is the sound isolator which I think is nothing more than a modem transformer sealed in a box. The Codec board needs to keep the DC and AC grounds isolated and this is what this device does. In line you hear the amazing SDR signals -- out of the circuit and straight through coupling --garbage!!!!!! It cost $6. One of my modifications was to add modem coupling transformers following the ADE-1's --again the same issue as with the sound isolator. You simply cannot ugly construct this rig and have expectations for success! You will note the date on the block diagram and you will realize this has been a year in the works.





 (R1 is for Simulation Purposes in LT Spice and not used in the final circuit)


The above circuit forms the basis of the driver stage and has been used on many transceiver projects. Ignore the notes and focus on just the 2N3904 and 2N3866 parts of the circuit.


This circuit is used for the Final RF amplifier stage on the SDR. Now a modification to this circuit to accept the Mitsubishi RDHF RF FET would include the replacing the Zener with the 78L05 three terminal regulator and inserting a LED in between the Ground pin of the 78L05 and Ground. which raises the output voltage > 6 VDC. A higher bias level  is needed for the RF FET. Typical output is 6 Watts but higher levels close to 10 watts may be experienced. All other circuit constants remain the same. this is an easy conversion. What is so cool about the LED -- when the circuit is biased "ON" the LED glows --more lights, bells and whistles.

Below are a couple of additional schematic circuits for the SDR Rig with the first being the steerable Dual J310 Amp stage. R3 is for simulation purposes and not used in the final build. R7 is as noted is a 10K trimpot connected as a variable resistor. Note the schematic shows the amp stage amplifying from left to right but the actual install has the amp stage direction going from right to left. I just know someone will install it backwards and then email that it doesn't work. RTM!








The Below sketch shows the modem transformer install.




Now you ask why would you do this when you can buy the IRF510 for about 80 cents and the RDHF is about $5. Well it all depends if you want to operate above 20 Meters. The power output drops off at higher frequencies with the IRF510. So it is all about choice of operating frequency.
Why even the microphone was homebrewed (a first for me). I bought this electret Lavalier style microphone from All Electronics. It is a superb microphone but somewhat costly -- about $1.15 with 15 foot cord. It does not have a PTT switch so I built the PTT using a microswitch I had in the junk box. Starting with a piece of scrap 2X4 about 6 inches long I milled out a cavity so I could mount the microphone and PTT. The remainder of the 2X4 was simply sawed off and ths is what was left. It is palm sized. See below. Aside from some splinters all went well. Not bad for some junk parts a piece of scrap wood and a $1.15 microphone. If you look closely you can see the PTT button sticking out of the case. Not very elegant but it works.
As of 8/11 I have had about 3 dozen contacts including one this morning with a VK station on 40M.

My homebrew Electret  Microphone: (This is one heck of a buy!)




Started like This...




This rig was built based on the design/software from Charlie Morris, ZL2CTM. This is a truly amazing rig as no external computer is required to make it play. While something more than an Arduino Uno R3 is required to make it work,  the Teensy 3.5 and the Audio Codec Board from PJRC will make it stand up tall. This is a $150 class rig but offers many possibilities for use on multiple bands or as I have on the drawing boards a hybrid Crystal Filter/SDR rig.





73's
Pete N6QW

Friday, August 3, 2018

2018 ~ The year of SSB Transceivers

Boat Anchor to Silk Purse.




Start looking for some old boat anchors as they offer possibilities for upgrading to modern radios. 

Right now I am personally trying to locate a reasonable condition, reasonably priced Heathkit Hot Water HW-32 or HW-32A. The plan --Color TFT/Arduino/Si5351 upgrade so it will have full band coverage and offer switchable sidebands. Possibly even CW with the 3rd Clock.

Email me at n6qwham@gmail.com  if you have one of these rigs hiding in your garage and are looking for a new home for this jewel of the 1960's. Remember reasonable condition and low cost.

If I can do this to a HW-101 just think what a HW-32 or 32A would look like.



73's

Pete N6QW

2018 ~ The Year of SSB Transceivers

What it takes to build a SSB Transceiver? I could flippantly answer the question by saying a lot of luck, lots of parts (and/or lots of...