Thursday, August 3, 2017

A New Line of Transceivers ~ DifX

So What Do You Want To Build?

 
 
 
8/7/2017 Mikele, 9A3XZ has provided this video of two rigs he built and enables you to listen to a  Bitx40 and a DifX side by side.
 
 
 
 
 
73's
Pete N6QW


 

8/5/2017 I mentioned a new project in the text of this posting. Shown below  is a before and after photo of V.1 of the 20 Meter Shirt Pocket Transceiver.
 
Updates include:
  1. Full 20 Meter Band Coverage versus only 100 kHz in the original VXO version
  2. USB/LSB front panel selectable
  3. Si5351 and Arduino Nano versus the Crystal Switched Heterodyne VXO
  4. 1/2 inch high OLED versus crude Analog circular dial
  5. Tune Function using a 988 Hz Pulsed Tone (you Bitx guys need one of these)
  6. MOX switch
  7. Homebrew 4.9152 MHs four pole filter --this really beats the Dishal or QER filters. Nice flat response with superb opposite sideband rejection
  8. Smaller than the rig shown on the masthead.
  9. Pout about 2 watts.
73's
Pete N6QW
2017 Updated Version of the 20 Meter Shirt Pocket Transceiver
 
Original Version I of the Shirt Pocket Transceiver

 


Compare the size of the new rig to the D-104 Microphone
 
 
Typically a week doesn't go by where  I receive emails inquiring about projects that I built several (or many) years ago. Much of this traffic is a  result of having posted about 125 You Tube videos and the subject matter of these video will spark a bit of interest which is followed by an email.
 
There was even a video I made on how to keep your feet dry while driving your Jeep Wrangler which suffers from a water intrusion problem. That one video had many hits (like 31,000) and even a few inquiries if I would manufacture the device that fixed the problem.
 
But fundamentally I think there is a desire today to return to our early ham radio roots where if you wanted to get on the air --you were faced with two problems: 1) there were no credit cards (or paypal) and 2) ICOM/Yaseu/Kenwood were yet to be in business. Thus to get on the air --you had to entirely build your own station -- everything was "homebrew". There is just something about the buzz you get when you can say " the rig on this end is homebrew". Which is often followed by "gee it sounds good for a homebrew radio!" Arrgh##$$$$!!!
 
Just yesterday (8/2)  I received an inquiry about the Let's Build Something (LBS) project that appeared in QRP Quarterly several years ago. Basically I was asked to create a special sub-channel on You Tube that collected all of the videos involving the LBS (to make easier for this person to look at all of the videos) and to provide a detailed parts list of all the parts need to build the project. I will do neither of these. If you want to build this project then you have to do some of the work! In fact the one major design criteria for the project was the use of all common parts that were readily available in most junk boxes. One fundamental axiom -- if you want to homebrew then you need a junk box!
 
The best piece of advice I can give if you want to homebrew a rig is to spend $59 and buy the Bitx40 kit from VU2ESE. The $59 gets you a nearly complete rig including being tested and the shipping to your QTH. Your homebrew contribution involves slapping it in a case and making any mods that are available on the Bitx reflector. For $59, you get all the parts, you get a tested board and you even get a digital VFO with LCD readout. Search on hfsigs.com for a link to his site. If you spend another $10 for expedited shipping you can have the kit in less than 3 days. My website has a tutorial on how to actually implement the Bitx40 project.
 
There is a bit of sound advice in this approach as taking on one of my projects for most hams new to home brewing, you simply do not have enough solder burns on your hands. You'll get there in time but there are many fundamental pitfalls to homebrewing a rig such as appears on the masthead. I didn't learn how to do that last week. My very first solid state transceiver was built in the early 1970's.
 
There was a lot of luck in getting that 1970's rig to work. Now today there is less luck involved as evidenced by the second version built just a few months ago. I also spend a lot of time learning about the techniques, processes and technology. That in itself is not a guarantee that everything will work the first time; but at least it gives a leg up on having no grounding in what it takes to build a rig. The very first thing I don't do is heat up the iron and start tack soldering  parts together. I also have learned to be skeptical about claimed results. My recent experience with the Dishal Filter bears testimony to that view.
 
I have a new transceiver on the work bench and this one is not so much new technology but more in the line of repackaging circuits to make a small rig even smaller. For those who have followed some of those 125 You Tube Videos, several years ago I built a 20 Meter Shirt Pocket SSB Transceiver. This new project takes aim at that former project; but with added capabilities in about the same size --yes the 1/2 size OLED display and the Si5351 are part of the mix.
 
Going back to yesterday's LBS email -- that project featured a building block approach where you started first with a direct conversion receiver (DCR) where almost all that was built initially was reused in the upgraded SSB transceiver. The simple idea --get the direct conversion receiver working and then advance to the more difficult sideband transceiver. By the way if you go to http://www.n6qw.com there is a link to the LBS project with all of the detail on how to build one.
 
Many new homebrewer's who undertook the LBS were unsuccessful, I might add, as they simply jumped right into the transceiver part thus bypassing the DCR. When things didn't work they emailed me with "your project sucks" or your design doesn't work. Ultimately those persons finally discovered that they had a wiring error, bad solder joints or failed to apply power to all parts of the circuit. These are rookie mistakes that are only overcome with practice, experience and starting small! It was important to build the DCR first!
 
 
Bill, N2CQR and I in our monthly podcasts (Bill, especially) have advocated building the Michigan Mighty Mite CW transmitter --about 8 parts total -- as a good place to start the home brew Odyssey. Yes even with 8 parts there were many learning failures as evidenced by emails that Bill and I received. But that project is a much better place to start than having limited experience or knowledge and undertaking a 500 part project and then trying to figure out the problem/issue why the board is inoperative.
 
 
But it all comes around to having a solid grounding in the basics before you undertake the complex. At the risk of being politically incorrect, those at the seat of our government should well understand this concept and tenet as applied to governance --and that is not Fake News! This comes back to the Bitx40 -- start there and learn all you can. Then and only then should you undertake an entirely scratch built rig.
 
 
73's
Pete N6QW