It's An Addiction - Product Development
The week before last I was triggered by a YouTube video that led to an internet rabbit-hole experience.
On YouTube the simple 49:1 UnUn rules supreme and ‘works great’ for everyone with its lovely 1:1 SWR range across a bunch of bands. With that SWR it just must be good is the rationale.
So where’s my simple 49:1? The answer was ‘I don’t actually have one’ – so I built one. And it is a little beauty!
Part of the end result is the 3D print design above. This is for a “conventional” 49:1 UnUn, or a small form factor 1:1 balun depending on the build I do – I just need to change the winding to suit.
The real goal was to make a simple 49:1 UnUn, no balun included, and to test the common mode current that produces
Also, well, I really wanted to make a nice one, capable of more power and with better efficiency.
For those interested in the pic above; the top left hand part is a banana binding post fitted end to go into 33mm OD plastic pipe. The bottom left piece is for the SO239 coax connector, and the right hand side items hold the toroid.
The above is the end result. This needs a label – the bane of my life – and it is “done”.
I measured the S21 through loss for a 1:1 build and it was 0.1db from 3.5mHz to around 15mHz, then rose to about 0.2db at 28mHz. SWR was excellent at around 1.1:1 rising slightly at the top end. As a 1:1 balun, this is quite a good option.
Then I built it as a 49:1 and measured its loss. It was pretty much the same as the 1:1 when I used the resistive terminator method – at around 0.1dB from 3.5mHz up to around 14mHz. It rises at the top end to maybe 0.3db which while comparatively high, is still excellent.
Then All Change!
On its first outing in public, this little UnUn was a firm favorite with a good friend. He loved the size. Then when I explained it was a “classic 49:1” he was disappointed. He wanted a hybrid that has a 1:1 inside. Of course he did!
Why? Less to worry about with common mode current and it is super easy to use. He does not mind having to use the short radials and has had a lot of success with other hybrid UnUn’s I’ve built for him.
So that was the next thing I made. It took an evening to do the re-deisgn then a few pints later the next version was born.
Going Back to My Roots
I grew up on a farm in country Victoria. With my brother and sister away at boarding school and no television, I found that listening to AM radio, reading and a rapidly growing interest in electronics and hobbies became my enjoyment. It was the dawn of the silicon chip era, micro processors were in their infancy and solid state devices were the coming thing.
I played with model boats, kites and a home-chemistry lab, but they were short term mild interests.
It was the electronics and radio hobbies that captivated me and stuck. I built a TRF radio using an LM372 chip, since gone the ways of the dinosaur, and gained immense pleasure from it listening to international short wave stations and the local CFA raio nets on something like 2.6mHz am – so many years ago!
I enjoyed building crystal sets, then valve radios, and the little TRF I.C. based radio was a revelation. But it was the pleasure of making things that pulled me in. I enjoyed and still enjoy building something. For some reason those hobbies stuck with me to this day, now and some far too many decades later it is just as strong.
Oh. And the test equipment I have today would have been science fiction when I started. The nanoVNA, the digital storage oscilloscope, the multimeter and SpecAn take test and measurement to a level I would not have believed.
Now I still find great pleasure in building something useful. I like to play with it, see where it will be good or bad, evaluate it from every possible angle. If practical, I’ll have something new I’ve built in my pocket for days. I’ll touch it, look at it, think about it. My subconscious ‘lizard brain’ will mull it over and may well raise alarms or ideas for improvement.
Back To Front Development
One thing I’ve learned over the years is that the packaging, the box, the enclosure – is the most difficult part of the process.
That is something I see first when I buy something and it sets my expectation levels. It really does. You see a shabby crappy box on anything and your expectation is not great. Conversely, if it’s shiny and looks well made on the outside, that is a very different story.
From a product point of view, if that magic design of something I really like can’t be fit into an enclosure, then it can’t be finished or made use of.
I’ve also got a mantra, “You wouldn’t want an ugly one” which for me means the end product must have at least some basic visual appeal.