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Showing posts with label resonance calculations. Show all posts
Showing posts with label resonance calculations. Show all posts

Wednesday, October 7, 2026

About the Guy Who Brought Us the AADE L/C Meter -- Neil W. Heckt

 

There it is.  The AADE L/C meter.  Many of us have been using these things for years.  I have two of them -- the one that I bought is here in my shack in Virginia.  The other was given to be by Todd VE7BPO and it is in my shack in the Dominican Republic. I sometimes wondered who was behind Almost All Digital Electonics.   Today I got the answer. 

Rishav is from Nepal,  He has been studying in Germany.   He is working on homebrewing the test meter (the company shut down when Neil passed away).  In the course of his research, Rishav gathered some very nice info about Neil W. Heckt, the fellow who created AADE and the meters that so many of us used.  Thanks Rishav! 

Memories of Neil W. Heckt

My work with Tobias (KK7BCO/2M0TFF) on a LC meter as the fifth build in Red Summit RF's Homebrew Workbench series for beginners introduced me to the clever LC meter design of Neil Heckt. As we celebrate his work by building one ourselves, in this post I hope to celebrate his life through the memories of those who knew him.

Neils's AADE L/C Meter IIB was a great hit, with thousands of units sold both as kits and as fully assembled instruments. It is not difficult to find praise for the meter. Many owners have written about its accuracy, usefullness, limitations, and clever design. Scattered among those reviews, however, are also small glimpses of Neil himself—stories from people who corresponded with him, asked him for help, or sent their meters back to him for repair. The reviews of the AADE L/C Meter IIB on eHam.net are particularly valuable in this respect. Many are written by people who dealt with Neil directly, and aongside their praise for the meter they remembered his kindness, honesty, and unusually generous customer service.

Memories

There is surprisingly little written about the man behind the instrument. While trying to learn more about him, I found most of the biographical information in his obituary. While searching further, I came across a moving remembrance titled Celebrate the Sun, written by Jill L. Ferguson, Neil's daughter-in-law. It offered something quite different from the technical accounts and product reviews: a glimpse of Neil as a husband, father, and person. One story in particular reveals a wonderfully personal side of him:

She (Kay) said her favorite book and life philosophy came from Celebrate the Sun. Back before she and Neil dated she had told him about this book. Not only did he borrow her copy and read it, but he photocopied the whole thing and pasted page by page into a photo album and intermixed the pages with his own photographs of the sun, of himself on hikes, and of the two of them walking in the woods. He decorated the front of the book with black electrical tape and two die-cut pelicans as they are key characters in the book. After Neil and Kay moved in together and married, she found this book he had created but had never told her about. She intimated that part of the way she knew he was the man for her was because he had taken her interest in this book so seriously. On his last night, she had the book Neil had created with them in hospice center and was reading the end of it to him shortly before his passed.

I was deeply moved by the story and wrote to Jill to ask whether she might be willing to share a few more memories of Neil, and perhaps a photograph. She kindly replied that she would speak with Kay, Neil's wife, and with Neil's son, her husband.

Two days later, I received a message containing a wonderful remembrance written by Kay herself, together with a photograph of Neil as a younger man. I have reproduced both here.

Young Neil
Photograph of Young Neil, thanks to Jill, sent to me by Kay.

Neil Heckt worked for the Boeing Company for more than 30 years. He was a member of their early air and space team. In his earliest years he worked on getting satellites into orbit and later getting men onto the moon. He developed his first inventions during those years which, of course, were owned by Boeing.

When we met he was a few short years from retirement. He was anxious to start his own business and create new products unrelated to his work at Boeing. He named his company Almost All Digital Electronics.

The inventions that followed seemed focused on developing ways to measure very, small units of...? He invented an atomic clock. It is my understanding that the Bureau of Weights and Standards in Colorado used it and that it was displayed there. Here I must state that I am woefully unknowledgable about any aspects of his work. I am neither a business woman or an inventor so, though I found him brilliant I rarely understood what his inventions really did. We were very different in many ways but genuinely admired each other's talents.

The last invention was an L/C Meter kit for hobbyists. He did very well with that product. The arrival of the internet and eBay made it a commercial success.

I thought his philosophy about not patenting his products was unusual. He told me that he developed a product, sold as many as he could and when someone copied his work he would stop production and leaveit to someone else to deal with it while he invented something else.

He had talents and ideas brewing in his brain that craved to be made real. He told me that whenever he needed money he would invent something that people would buy and then he paid his bills.

He wasn't like me and the people in my world who took on a second or third job when we needed money. I found his confidence and creativity to be amazing!

Neil was scrupulously honest in his business . Once he purchased two antique vacuum tubes for less than $100 from an eBay customer. When they arrived he discovered that they were quite valuable. He wrapped one tube up and sent it back to the customer with a note telling him what it was worth. Instead of selling it and making a good deal of money he sent it back. I asked him why. He said it wouldn't be fair to the seller for him to keep all of it for himself because the guy just didn't know what he had.

If anyone had a problem assembling one of his kits they sent them to him and he would fix their problems without charge.

Neil was sick for many years before his death. His brilliant mind was with him to the end.

I hope these memories help preserve not only Neil Heckt’s work, but also something of the thoughtful, generous, and inventive man remembered by those who knew him.

***

Thursday, August 11, 2022

What Coil for the Polyakov Input Circuit? How to calculate a coil value for resonance.


So,  what is the value for L1 and L2?   What coil should I use?  
Michael AG5VG had that question.  And so did I when I built this receiver.  See below for the process I used in answering this question. 

On Tuesday, August 9, 2022 at 10:53:32 PM EDT, Michael S  wrote:

Good Evening Bill,

My name is Michael and I really enjoy your podcast with Pete. I have also spoken with him in regards to the design of a 20M bandpass filter I made for a homebrew rig.  I am currently in the process of making a 20 meter DSB - SC type. Thank you for all the information that you speak and teach about during your podcast. I also enjoy the humor. It's great.

The Polyakov is a simple DC receiver and it amazes me and how the sound quality is. My question is, what is the turns on the toroid for the antenna primary side and the radio secondary and how did you figure out the turns because looking at the schematic it doesn't give that information that I can see. Also how you resonated it with the variable capacitor that looks like a 365pf air variable. 

Thank you for your time and keep up the great work on the podcast and the content on YouTube.

73s,
Michael
AG5VG

My response: 

Good questions Michael.   When I saw the SPRAT article I too was struck by the fact that it didn't give a value for the coil.  But DK2RS did have a large value variable capacitor... And he was billing this as a dual-band (80-40) rig.  So I figured he wanted that LC circuit to resonate as low as 3.5 MHZ and as high as 7.3 MHZ.  So, with a variable cap that goes up to 350 pf, what value L should I use?   I started by calculating the resonant frequency of the frequency mid-way point: 5.1 MHz.   I figured the variable cap should be around 162 pf at the mid-way point.  At this point I went to the on-line resonant frequency calculator: https://www.1728.org/resfreq.htm (a REALLY useful site!).   This site revealed I needed a coil of about 6 uH.  This put me in the ballpark.   But then -- with the site -- I tested it with the values of the variable cap I had on hand.  Mine was 23pf to 372 pf.  (you really need an LC meter to do this kind of thing). 

Again at the resonant freq calculation site:  23 pf and 6uH = 13.5 MHz           372 pf and 6 uH = 3.3688 MHz

This would have been OK, but I wanted to move the frequency range down a bit, so I tried. 6.5 uH 

23 pf and 6.5 uH = 13 MHz                 372 and 6.5uH = 3.23 MHz

Now, how many turns?  First look at the overall coil -- don't worry about taps at this point.    I use the Toroid Turns Calculator: http://toroids.info/

 Start by asking yourself "What core do I have on-hand?    Let's say you have a T-50-2 (red/clear).   The calculator shows you need about 36 turns.  Do-able, but physically kind of tight.  

I found a big core in my junk box.  A T-106-2.  The calculator showed I'd need about 22 turns on this core. It was much easier to get these turns on the larger core.  

You have to measure the core after you wind it to make sure you are at the desired inductance.   One side of the main coil went to ground, the other side to the top of the variable cap. 

 Now for the taps and secondaries:  The schematic shows a tap.  This is usually about 1/4 of the number of turns up from ground.   I picked about 5 turns, and wound a little tap in there at that point -- that tap went to the antenna.  You also have a secondary coil --no value is given, but based on experience I guessed around 5 turns -- I wound these turns on top of the primary one lead went to ground, the other went to the diodes and the switch. 

 The last thing to do is to see if the circuit resonates on both bands that you want to receive.  You can do this with a signal generator, or with the band noise:  Hook up an 80 meter antenna.  Put the cap closer to its max value and tune the cap -- can you hear band noise?  Or can you hear (or see on a 'scope) a signal at 3.5 MHz?   You should be able to peak it with the main cap.  Try to do the same thing on 40 meters -- here the variable cap should be closer to minimum capacity. 

 That's it.  That's how I did it.   You can do it too!   Good luck with the Polyakov.  

 One hint:  Building the VFO is the hard part.  You can get started by using a signal generator in place of the VFO.  Just make sure you have the level right -- around 620 mV input.  

 Good luck -- Let us know if you have trouble. And please let us know how the project goes.   

 73    Bill    N2CQR  

20 meter rig built by AG5VG