Saturday, 30 June 2018

A 3d printed knob for sma connectors

Sourced a bunch of 3d printed knobs for sna fittings.  I found it a bit of a pain to turn the fitting and these knobs fit right onto the fitting via a friction fit.  There are other designs that have a catch in them to hold on to the backside of the fitting, but these seem to work just fine.

For another run I would reduce the outside diameter. Using sma cables to link up pcb boards, the smaller size would offer better clearance to the mounting board for the pcbs.

Monday, 25 June 2018

New Toys to Play With

Finally I’ve been able to get some shack time.  It’s been a little busy with the household chores but now that list is down to a reasonable level, time for some bench work.

The trip to Dayton and FDIM was very rewarding.  Picked up my Siglent Spectrum Analyzer, IOT kit from Kanga, attenuators, test cables, and a few books.

Putting the IOT kit together went smoothly, or so I thought. Everything went smoothly as far as establishing a WiFi connection and communicating to the board with my phone. Frequency changes appeared to be working well but, I was getting a very poor signal output.  As I checked things out, I thought I blew the output port somehow as the signal now was completely lost.  So I wired up the B output port to a header and in the process of that I was getting intermittent output on that port and then the 1st port began to work.  Closer examination of the dds chip revealed that the pins in the output area were slightly offset from the pads. So a little solder and heat with a touch up from solder wick seems to have cured the problem.  Take a look at the upper right corner of the chip in the picture.

Not sure exactly where I’m headed with this project, but at the moment it’s a learning exercise for something down the road. I find it interesting to be able to control something from a phone or computer via WiFi.

As well I’m working on getting ready for portable hf operating.  Rig is ready to go but antenna I’ve just started to work on.  I bought a no tune end fed half wave antenna kit from qrpguys that is almost ready to try out.  Just need to source some #22 or #24 wire and make a couple of insulators.

Between all that I’m trying to learn how to use the Spectrum Analyzer.  Great addition to the bench.  So far I've just been observing the signal output of dds chips and the IOT board output.  One other thing I tried out is connecting a 40meter BPF to the tracking generator and the SA input.  The ability to adjust the filter in real time is a really nice feature. I'm now thinking about using the SA on the LBS project I built a couple of years ago. Should prove to be interesting checking out that rig.

73, Peter

Saturday, 12 May 2018

Dayton and Four Days In May

Off to Dayton and FDIM next week.  Can’t wait as I’m planning to spend some of the kids inheritance and purchase the Siglent Spectrum Analyzer. Looking at the SSA3021X model.  Also on the list are some attenuators, patch cables, solder rework station and who knows what else.  But I’ll know when I see it.

Looking forward to this years FDIM.  Action packed with all kinds of time to mingle with fellow homebrewers and talk to the elite of the hobby. At club night I will be showing off the SNA project that we had worked on with my fellow Peel Amateur Radio Homebrew Group buddies over the past year. This should be fun talking to the homebrew community about our project.

I’ll be participating in the buildathon as well and the project is a 4 port return loss bridge.  I don’t really need another bridge, but the SNA project has shown that there can be different results between different bridges and so far I think the 4 port type might prove to be the most accurate. Now I also believe I’m splitting hairs here as the differences while small, are none the less different.

So hopefully back to the bench in a couple of weeks fully energized from Dayton and FDIM.

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.