Thursday, 25 December 2014


Best to you in 2015!

I got 2 new books this holiday season. I read them lying down — for low back and hip pain kept me off a chair for several weeks until I regained the needed core muscle strength plus re-established hip flexion and extension. I now appreciate that quality of life and back health lie directly related. Perhaps you might relate? I better go stretch; back in a moment...

Small Signal Audio Design: 2nd edition by Douglas Self.

Above — Small Signal Audio Design: 2nd edition by Douglas Self. With its content boosted by about 50%, Self took his great first edition into the stratosphere with this follow-on. I wish someone with his writing skills (epic clarity, practical insight and warmth) would write about RF topics. This book could serve as your the AF design bible for a long time.

Handbook of Microwave Component Measures by Joel Dunsmore.

Above — Handbook of Microwave Component Measures by Joel Dunsmore. Dr. Joel (a staffer who comments on the Agilent (now Keysite) Network Analyzer forums) wrote this book as a follow-on to his original and it's not a book for people who dislike math, theory and equations. I love this book for opening my eyes into the ways modern engineers measure Scattering parameters, consider the DUT, + calibration and also how an exciting "VNA design evolution" is exploding big-time.

My dad told me "if you hang out with and/or read stuff  by smart people you just might get smarter; so choose friends and authors wisely".  This book serves as a case in point. Although, I don't understand every chapter, equation or concept, I've got a new appreciation for and direction to go in home lab measurement know-how.

In short, modern microwave measures get done on VNAs, not 'scopes nor spectrum analyzers. New VNAs, although very expensive, may feature multiple signal sources and receivers with advanced calibration techniques to deliver amazing accuracy.

Each month, I hope to read that someone has released a fast but relatively cheap 3 GHz network analyzer with a dynamic range of  >= 120 dB (with at least 10 Hz minimum resolution) across its bandwidth. I'm not alone (see this thread for example), I've read many opinions and only 1 thing is certain, I want small gear and not bloated boat anchors from the past. At this point, getting a VNA for my desired minimum 3 GHz bench BW is not affordable.

No question homebrew or commercial hobbyist VNAs are a real option for some — just not me. The aforementioned book, an EE friend, and my experiences show a big source of bench error in network analysis is mismatch between the source and the DUT. All manner of mismatch may occur because of DUT reflections, crosstalk, receiver to source leakage etc.. It can take serious VNA design, added hardware and bench effort to isolate the source and receiver plus establish the proper 50 Ω test environment — even down at VHF - UHF.

Further, the calibration sets may cost ++ ; especially as you go into microwave. Consider this link by Kirkby Microwave Ltd. Modern commercial network analyzers allow you to input your particular calibration test set (or perhaps calibration connector parameters) to boost accuracy. Up-to-date, 2-port, professional grade network measurement costs $1500-2500 per GHz it seems.

All things considered, as amateur radiophiles, we live in exciting times and I'm sure you have your own thoughts and opinions on VNAs for 2015 and on.

Photography with cats proves difficult.

Photography with cats proves difficult.

Photography with cats proves difficult.

Above — Photography with cats in the house proves difficult. It never fails — depress the shutter and 1 cat or the other comes from nowhere and jumps in front of my intended subject. So here they are (hamming it up) with the lights set up for a dark colored book  — fairly strong + directional lighting at 5500 degrees Kelvin color temperature. I love experimenting with lighting and strive for different looks: some good, some harsh.

Blogger further processes photos so they look about 1/2 stop brighter than actual and this bothers me.

I run a calibrated monitor so the color and brightness of my local commercial lab color prints look like just my onscreen jpegs.


I get much less email with the blog. Some people are still quite upset I shut down the old website, even though I had no alternative. The traffic trouble continues and at least for me, vindicates my decision. That's fine — I respect your opinion to a point. 1 guy called me a f***head for stopping the site in October and then later in December bluntly asked for substantial design help. Sorry, I'm a f***head and can't help you.


An emailer shared respectful concern about my use of #43 material for broadband transformers at VHF ( ~100 MHz ). He strongly felt that #61 material was better suited at VHF.

So glad I made these experiments, here's an excerpt of my email reply:

10 turns on a FT37-43 ferrite toroid were placed in-series between 2 SMA connectors.

Above —10 turns on a FT37-43 ferrite toroid were placed in-series between 2 SMA connectors, padded at input and output and then swept from 0 to 500 MHz in a TG-SA.

10 turns on a FT37-61 ferrite toroid

Above —10 turns on a FT37-61 ferrite toroid swept as above. You see little clinical difference and if anything, the 43 mix ferrite looks a tad better down lower. Somewhere above ~20 MHz, the ferrite "disappears" and the results of both mixes look similar. Both are lossy and work about the same. More windings on the #61 toroid does not boost the attenuation and actually may drop the SRF due to extra interwinding capacitance. I normally use a small 43 mix binocular or FT23-43 bifilar wound ferrite at lower VHF in my feedback amps.

Again, all the very best in 2015!

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