The Best Antenna Coupling Presentation by W0QE

Excerpt from Palstar BT1500A balanced antenna coupler.

I did a few Google searches for “LC Antenna Tuner” and found the best presentation on the topic yet:

It is just packed with so much useful information – and it covers the topic at a level that reminds me that I still have a lot to learn. In fact, it pulls everything that I have been thinking about into one presentation and offers the reader a way to go back to the books and study each area one at a time (which I will do).

The ARRL publications and the W8JI web site does cover some of this but not all in one place, and not in the same scope and scale as this presentation.

In just the first pass, I have learned that just having one variable capacitor and one roller inductor is fine if you are coupling / matching a limited frequency range, but that you will usually need at least three components if you want a wider range tuner. It also confirmed that there are high pass and low pass designs and that the Palstar BT1500A is a very unique coupler, and that me having it at the base is a very good decision and that for all of the low bands it does in fact seem like the right decision.

So, when someone asks “What is the best antenna tuner?” the answer is “It depends”. I also like how Larry describes what most hams call an antenna Tuner a Coupler instead.

One very important thing that I learned is that the SPE Expert 1.3K FA amplifier will be fine if I use its internal ATU in conjunction with the Palstar BT1500A at the antenna. The SPE manual says to never use the ATU with another antenna tuner – but what they don’t say is that they mean another ATU. What you don’t want at high power are two ATU’s trying to find a match and getting confused. Since I go out back and set the BT1500A manually right now – if I needed to cover more of a band using the SPE ATU I can. On 80 and 75M this would be very useful, but its a moot point on 160 and 30M since I never go more than say 20 khz across either of those bands. And since 80 and 75M are my least favorite bands, all of this is pretty much moot. Of course, if 3Y0Z miraculously bangs in on 80M, well, I will learn to love that band.

I will be reading and re-reading this presentation for some time. Its awesome. He also has a series of videos:

U.RAT Ready for World Domination!

The final part of this u.RAT “science fair project” is wiring the variable capacitor and roller inductor with a 50 ohm dummy load resistor and then attaching the Rig Experts AA-30 so we can see how tuning the components affects SWR and what the L, C and X values are.

I have been playing with different “equivalent circuits” and using a 56 ohm as a dummy load for an antenna, but the control that seems to affect the SWR the most is the variable capacitor.


Which shows the components that would be in an “L Tuner” and the other components / values for the equivalent circuit. I will re-read my theory books to figure out why the capacitor is the component that is doing all the work. The inductor almost seems to look like a short because of the resistor – I’m not sure.


Superb W6 – ZL Path on Top Band

I’m hearing several ZL stations very well on Top Band this morning, and they are on SSB no less.

I hear some lightning strikes that seem to be mostly in Kansas and Nebraska, but not enough to quell the ZL’s.

Its really starting to feel like the “Lowband Season” is near – we lose a full hour of daylight this month, and the first 5 days of August we have already lost 7 minutes of daylight. While I love riding my bike to and from work in the daylight, I must admit – I like my cozy shack when “Lowband Season” is in full swing. This Fall and Winter I will be in mt best shape low band wise. The Mod Bob and BT1500A and the DX Engineering DV-40-P phased array antennas are all I need. The 20M 2 element home brewed yagi might get a work out – for 3Y, yesterday a CE station came booming in, and so that path to 3Y was looking great there.

Yes, I’m still a DXer, just one at the end of my “paper chasing” phase. One day soon I will only be on the low bands.

This Blog Featured on the “Geeky Gadgets” Blog

There is a very cool blog called “geeky gadgets” and they have featured the u.RAT. I’ll follow them for sure – and I continue to be amazed at the cooperation and collaboration between “Makers”

The IMSAI 8080, Ham Radio and Me

It was 1976, I was newly minted WA2QHN (after passing my General Class Ham Radio test on vacation in Seattle at their FCC Office), and I thought I wanted to be an Electronic Engineer. It all started in Ms. Goodin’s 4th grade class when she taught a series on “The Inventors”. I wanted to be an inventor at age 9 or 10. At age 11, I built my first Heathkit, the SW-717:

My Novice station in Newton, NJ was this receiver, a Hallicrafters HT-40, a Dow Key Relay and a handful of crystals.

Anyway, my father’s good friend and Electronic Engineer, Joe Secundo, visited and plopped an IMSAI 8080 on the kitchen table and after I tried to impress him with my proclamation “I am going to be an Electronic Engineer”. He said “No you are not!” and went on to convince me to instead become a computer programmer. Two years later, I was getting straight A’s in my COBOL, Fortran and Basic classes at the County College of Morris – and after a year transferred to Lock Haven State College in PA. I graduated with a Business Computer Science degree.

My first job was at Kodak in Rochester, NY coding Octal Assembler and Machine Code on PDP-11’s using the Kodak Park OS:

I hated it. It was too abstract – my job was “process control” – to try to track waste in the manufacturing of Instant Print Film. Ironically, I’d love this job now!

I have told this story in my old blog, but after designing and building the u.RAT, things have magically come full circle. Today, designing and building something electronic is the same as designing a system and drawing a block diagram. You assemble a set of boards that have functions, wire them together, and then download code from Github and mash them up to make the set of circuits to do what you want.

My parents bought one of these for me in my 9th birthday…

I am 100% sure that I thought that in the future this would happen. I had “Systems Analysis I” and “Systems Analysis II” classes, and we basically drew block diagrams at the systems level and drew flowcharts at the program level. We even used those plastic templates and drafting paper if I remember right. That’s when I thought “what if the system was a block diagram?”.

Well, that’s exactly how I approached the u.RAT, and 40 years later, my 1970’s era thoughts and predictions just happened  with my first “Maker” project.

u.RAT and This Blog Featured on the Adafruit Blog!

The Adafruit Blog, Copyright Adafruit featured this blog today, August 1.

Adafruit was founded by “Lady Ada”, AC2SN, and I am finding more and more that if you want a reliable component, you will never go wrong ordering from Adafruit. Their site is amazing wealth of resources – including CAD drawings for their designed components – such as the cute little Pi-OLED that really make the u.RAT rock! Some drawings are in Eagle and Fritzing format, and they always have tutorials and information to help you make your project a success. Their forum is very helpful – and in the case of the Pi-OLED, Mike, KJ4Z helped me find Larry Banks FB library, and I shared that with the Adafruit forum – so that others using C will be able to make the Pi-OLED work.

Adafruit products are available at their site and also sold at Amazon and other outlets on the web. I have been burned by some cheap knock off Chinese clone products, and so will be a lot more likely to look for the Adafruit, Arduino or Raspberry Pi official logos. And their prices are very good too.

Fantastic Electronics Book

This hands down the best electronics book that I have ever purchased. Yes, even better than the venerable ARRL Handbook. I say this because today’s electronics is more about integrating pre-assembled boards and processing power than soldering discreet components.

I still encourage all hams to purchase the ARRL Handbook, ARRL Antenna Book and (especially) the ARRL ON4UN Lowband DX-ing Book, because they cover the things that this book doesn’t – RF from DC to daylight.

In the 90’s I did try to get back into ham radio by building several QRP Kits with discreet components – the SST, K1, KX1 and a few others, but there is no way that I would do that again – now everything I build will have a processor at its core, and the Raspberry Pi Zero W is by far and away my favorite platform, and Python and C are my favorite languages.

So, for “modern” circuit building, and even the theory part of the book, this one is my new favorite.