Friday, 13 April 2018

SNA Completed and Many other Projects to Fill the Gap.


Been a while since my last entry, but at least that’s due to being so busy at the bench.  Finished all the testing for the SNA, completed the documentation all in time for last week’s buildathon.
The buildathon went great and there were about 18 builders present with a few more to start the build this weekend. 

We had a solder oven present, and I was surprised that there were I think at least 4 or 5 completing the build by hand. The boards I saw that used the oven turned out very well.  This is the second time we have used the oven for a project and it’s proving that the oven method is indeed a good approach.  I have had some parts on hand for a while to build an oven, but never got around to it.  I think I may just bump it up on the shack to do list.  Then there is the issue of solder paste. I get that the shelf life often mentioned is likely for industry standards, but I think for use in the shack the life can be extended.  By how much who knows?  I wonder if you can freeze the stuff and thaw it out when you want to use it. 

At the moment I’m trying to figure out how to communicate to an ESP8266 module.  This endeavor is looking more and more like it’s going to get the better of me. Between trying to just simply use it or flash it, nothing is going smoothly.  This project is one of those things that you build or do and figure out a use for it later.  I thought it might have been a good exercise in clearing my mind from the sna project.  Well it’s certainly has done that.

Another project in mind is using Python to communicate to the sna command line interface. It means learning something about Python and I haven’t even got a good handle on the Arduino environment yet.  

The Chat With the Designers have a good series this year with projects involving Arduino. So I’m thinking I might pick off a project or two there. 

The sna project started several conversations around all kinds of different concepts which offer good learning opportunities. However one in particular revolved around complex impedances and how to measure them.  The AD8302 chip seems to be the answer and I do have an 8302 board on hand. So there’s another project on the list.

During the sna project the use of an rf bridge was required for some of the measurements.  I have a homebrew one on hand and I’ve never really questions its use.  When making comparisons with others in the group with the results they were getting, questions on the accuracy of the different bridges came into play.  So I ended up building 3 more versions. One of which was made as small as possible and with SMT components. I also purchased another bridge that is of a different design. So another item on the to do list is a through testing comparing these bridges.

Time for re doing my crystal test fixture. I think I’ll change components to smd and re package it so I don’t need wires going to the crystal socket and bnc connectors. Try and eliminate as much as possible any stray influences. 

Problems attributed to patch cables came to light during the sna project. I guess the sensitivity of the sna highlighted possible issues with cheap cables and connectors. Haven’t decided how I’m going to approach this as top quality cables has a price tag that I don’t want to deal with.  I had one cable in the mix that seemed to be intermittent and eventually I noticed that the centre pin in one end was the issue. So maybe my eBay cables will do fine as long as I keep an eye on the connectors.

Another project I’m contemplating is an automatic switching attenuator.  There are some interesting attenuator chips out there that seem to be right up what I’m thinking so we shall see what happens there.  Maybe I’ll find something at Dayton this year this will fit the bill.

The list never stops growing and still on the list is finishing up my Bitx.  Won’t take much to get it completed.  Far more time will take place doing all the hacks for it.

Here's a picture of the finished sna in its case:

Well time to get back to the bench and see what happens.  True to fashion is one project leads to a couple of more and the sna project certainly lived up to that statement.

Saturday, 2 December 2017

Alpha Build PARC SNA Update 3



Got a lot accomplished over the last few days on the SNA project.  All the parts are now installed including the LCD screen. In order to expedite the build I went on a “field trip” to Ottawa to pick up extenders for the LCD.   And then off to Toronto to pick up the LCD… Ok I did pick up the xyl at the airport so it was a multi-purpose trip.

The shield for the AD8307 circuit I managed to get done without any real fuss. I thought for sure it would be a little problematic to do, but in the end it went ok.  Sure it’s a little ugly and not as good as I would have liked, but it will do. 

The final smoke test was completed and software routines for testing the individual circuits were completed. Dave VE3OOI, had written routines to test the functionality of the 8307, 9850, encoder and buttons, memory chip, as well as the LCD.  What a terrific idea that was. Well done Dave.

The main SNA program was loaded and went smoothly.  I am having a problem with the calibration routine, but I’m sure Dave will set me straight before too long.  The only other issue at the moment is the display is not oriented correctly with the controls. I’ll have to lean on my hardware department to be on the same page as the software department. Can’t be making mistakes like this again. Not sure yet how I’m going to remount the controls, but I don’t think it’s going to be as clean as it is now.  Well, that’s what Alpha builds are for, work out the details.

Up next is putting the SNA through its paces. I need to think up some protocols that will include not only the real world and most likely scenarios, but some with extreme specifications as well so I can see how the SNA behaves.  You never know.  





Wednesday, 29 November 2017

Alpha Build PARC SNA Update

Finally after spending considerable amount of time tracking down and removing solder bridges and a couple of shorts in the traces, checking the board over several times to ensure no shorts remain, I had to admit it was time for the smoke test.  But first a beer to think about it.  Never have I've been so apprehensive to power up a board.

I'm pleased to say all went well with the smoke test. The 8v and 5v voltage regulators remained cool as was the 8307 and memory chip.  Now it was time to plug in the Mega and following that the AD9850 board.

Almost perfect. I have a bit of a loose connection on the ground for the 12v power supply but that's no big deal.

Current draw for the board alone was .03A.
Current draw for the board and Mega was .11A
Current draw for the board, Mega, and the AD9850 board came in at .21A.

Not sure what the draw should be but there's the baseline for the 2 other Alpha builds underway now.

9850 board in the upper right corner, 8307 behind the left bnc connector and the memory chip to the left of the 8307. The MAR6 amplifier is located just to the left of the right side bnc.  The blue wire passes just beside it.  The rather big looking blob of solder is due to the several ground pins coming through the board to ensure good ground for the MAR6.  Hidden under the blue and purple wire is the ground connections on the other side of the MAR.

Up next is to nibble away the pcb area containing the holes for the LCD.  They are not needed and are in the way for the pin extenders needed to raise the LCD to the proper height.  I'll be picking up the screen tomorrow and once that is working ok it will be time to load up the software and put this puppy through its paces.

So far I have about 9 hours into the build. Lesson for me here is hand soldering with such narrow clearances is not the best methodology to be putting a board together.  Good experience though.



Sunday, 26 November 2017

Alpha Build PARC SNA

Started to build the PARC SNA.  The challenge I figured was going to be, and still likely will be, putting it through its paces and hopefully cover off on all the possibilities. But I'm sure our software designer, Dave VE3OOI, has thought of everything and it will be perfect.

However, as with most projects on my bench, there are challenges with each project.  No different with this project either.

This board was etched by a laser machine and it is a very nice looking board. The trace clearances are somewhat tight and the through holes are not plated.  The clearances did present some challenges with a few solder bridges that proved to difficult to remove in a couple of cases. After using a solder sucker and solder wick, the shorts had still remained.  Even under a well lit magnifying glass the short could not be seen. Scrapping with a dental tool in one case did not help but a rub with a small fine wire brush did work.

The other self inflected problem, one that I can never seem to avoid, was, well, stupidity. I knew the via's were not through plated and I was given some fine wire to use where necessary. Yet I still managed to forget this and went ahead and soldered in headers tight to the board when I needed to allow a space in order to apply solder. Gave the solder sucker a really good workout and I'll bet I used up more solder wick on this project than all the others I've done combined. HiHi.  But thanks to the quality of the board, it survived the abuse.

About 6 hours into the build so far and today I shall carry on with installing headers and connecting up the via's


Wednesday, 25 October 2017

BITX 40



Spent a pleasant afternoon yesterday working on the Bitx 40 with two other hams. Sort of a mini buildathon I suppose. Dave, VE3EAC, offered up his terrific shack/workshop for our get together. 

Dave not only has all the usual electronic test equipment you would ever need, but has all the tools needed to work on your cases as well. This makes things go so much smoother.  No need to mess around with inappropriate tools to accomplish what would be a simple task.  I need to re-think that end of my shack.  Another thing that came to light is the use of a 3d printer.  Dave printed up bezels for the lcd screens. Makes for a nice finished front panel that would not have been possible in my hands. 

I got no further than mounting the lcd, circuit board and the various controls and jacks. I did manage 2 connections as well but I decided that the layouts and mounting the hardware was time better spent first. Paul, VA3LX however, went with wire up the whole thing first and put it into a case later. It wasn’t too long before while filing out the square hole for my lcd, that we heard the hiss of 40 meters. Connecting up an antenna we were able to hear some strong ssb signals and we were pleased with the initial tests.  It was very encouraging to hear this. 

Since I’ve built transceivers before, kits and from scratch, I'm looking forward to putting most of my energies into other aspects of building transceivers with the Bitx. Software improvements and other hardware modifications. Possibly the move to 60 meters comes to mind but maybe a multiband would be a better proposition. Playing around with enhancements and not just getting the rig to work does have some appeal. Maybe not all the time but this time anyway.

Incomplete projects on the bench is growing again and I really need to start finishing some of them. The shack is in a little bit of disarray as I work on repairing my spectrum analyzer and SNA. The SA is so big that the other equipment that lived on top of it are now on the floor. The SNA is in pieces and the SA covers and various brackets spread out. In the middle of all that mess is the current project. It’s getting a little hard to move around.