Simple tools for winding toroids.

One of the more intimidating challenges to fledgling homebrewers can be the dreaded toroid coil.  When I first started building I would often try to avoid  circuits that required me to wind coils. This didn't leave many options in the way of radio frequency circuits. I first got my feet wet with simple air wound coils used in projects like single transistor FM band transmitters & similar projects. The time came when I knew I had to start winding coils around toroids. In this post I am going to share a couple simple tools that I use to get the job done.

Most of the projects will tell you how many turns to make around the core. Certainly one can just make the specified number of turns around the coil and hope that it is the right inductance needed. Most projects recommend compressing or expanding the turns while monitoring the output on a scope or power meter. That works fine too. However, if you want to be able to actually measure and control the coil inductance than you need to have an accurate way of measuring it. There are a few options out there, including some DIY analog & microcontroller based L/C meters. I took the advice of my digital elmers and went for the Almost All Digital Electronics L/C Meter IIB . I had to save up for a bit to get it but it was a very smart investment and I recommend it to the RF curious. It's a powerful tool that I use nearly every time I build a radio frequency circuit. It allows one to measure the value of capacitors & inductors of the small values used in such designs. One use for it that I like is to see how a particular component's value reacts to temperature changes. A quick blast of freeze spray to test an NP0 versus an X7R capacitor or a coil wound on a type 6 or 7 mix versus one wound on ferrite core. It's fun and has given me a better understanding of how well different component types hold up to fluctuating temperatures.Even if you don't decide to obtain an AADE L/C you can absolutely still use the so called 'cut and try' methodology by compressing/expanding while monitoring the output of the stage. Whatever methods you may use, I hope the following is helpful .

Here are some of the tools that I use to make winding toroid coils a bit easier. Please know that I claim no originality or blame for the effeciency of these 'tools' . I offer my most sincere and humble respect to the many homebrewers that came before me and shared their experiences and wisdom by publishing it online or in zines like sprat, hotiron, AmQRP homebrewer, QRPQuarterly, etc. There are so many amazing builders that have inspired me with their articles, webpages & other contributions to homebrewing that I hope to dedicate a post in the future in celebration of their accomplishments. Now, let us learn of these simple techniques.

The tool that I find most helpful for winding coils is a simple "Chop Stick", the utensil commonly used to eat Asian cuisine. These are incredibly easy to acquire. They often come attached at one end and are then split apart into two separate chopsticks. Each stick being tapered at one end. Using a vise (You can get creative here if you don't own a vise) to hold the chopstick, the toroid core is slipped over it and allowed to rest. I added a ring of tape to stop the coil from sliding further than about 2/3rds the way down.

Slide the core up just enough to feed the magnet wire through, observing proper phase, and then pull straight down making sure it's taut. Note that care may be needed to make certain the magnet wire's enamel doesn't get scraped off in this process. Some have coatings that flake off easier than others. I then push the core back down, gently, just to sort of press the wire as firm & flat as possible against the core. Next, sliding the toroid core up again just barely, feed the wire back up through the center of the core and pull gentle but tight straight up. You now have two passes or turns through the toroid. I usually push the windings right next to each other and try to make it as flat, firm & tight as possible without scratching the enamel off or breaking the wire (especially the finer gauge stuff).  Do this repeatedly for the required number of turns.

Moving on now to the next tool, which is a really simple one I came up with that I gave the silly name of ''The Denameler' because it De-Enamels the magnet wire. It is simply a metal fingernail file, "borrowed" from my xyl, broken in half  and then affixed to itself to create a simple & quick way of scraping the enamel off the magnet wire. I think the picture will do more justice than my words will.

After "De-namalling" it (i know this is not a correct use of the "de-" prefix, it's just silly) we need to measure the inductance with our trusty AADE L/C Meter IIB. Compress/Expand the windings until the desired inductance is reached.

Next on the list is poor man's "Q-Dope". Some folks use real Q-Dope, I never have, and others make their own by dissolving packing peanuts in acetone. I just "borrowed" another item from the XYL. It is called "Hard-As-Nails" with Nylon & Retinol. I coat my coils with a thin layer of it and it holds the windings firmly in place. If you wish, you can leave a small portion of the windings uncoated so that you can make minor adjustments by expanding/compression them in the future. Let it sit until dry and you have yourself a very well made coil. I am curious if anyone else has used this or similar type items to seal their windings. Please share.

When first starting out, it helps to be able to order just one or two of each type. Earl, in Canada,  runs http://www.NettyElectronics.com/ and sells small quantities of toroids to homebrewers.

There are lots of great tools, wares & tips available to help make homebrewing easier and possible for everyone. It's important to try all that you can, find what works for you and develop your own system or routine for the process of designing, building & measuring rf circuits. Please be sure to share your helpful tips with others because it is the contributions of the community that keeps homebrewing alive.

 If you can't find the right tool for the job, you can always make one. It doesn't matter how simple or ugly it is, if it makes the job easier or better.

73

An RF Mandala

 

I thought I would add a beautiful shot of a naked SRF3864 so you would have something to meditate on while I proof read my coming posts.

The Hombre's Return - Handy Homebrew RF Resources, Permission to Fail & Errata

Greetings to all. Please excuse my hiatus from updating this blog. I assure you that it was not from a lack of productivity. I have been busy building, studying & experimenting with all aspects of my autodidactic pursuit of RF wisdom. I have SO many projects and builds that I am eager to share with you but there will be plenty of time to "show off" my projects in the future.

Many of my projects fail to work or meet my goals in some way. Sometimes it is an issue of poor planning, incorrect assumptions, wrong measurements or even over ambition. Many of the times it is the inability to create the circuit/system in the form factor that I envisioned.

One of my recent projects was Roy LeWallen's Optimized QRP Transceiver. I worked on this project over the course of three months. Most of that time was spent drafting the layout on graph paper. I will share this story, including photo's, design/layout tips and a humble true confession of why the project failed in the end, in a planned future blog post titled: "QRP My Problem Child". For now I am simply giving that experience as an example of a very frustrating failure to turn a homebrewed transceiver into a user friendly radio. The problem was the inability to create a proper enclosure for it. Steven, KC2SIZ, created a post on the QRZ > Homebrew forum called 'The Homebrewer's Lament' that I recommend you check it. He shares his thoughts and frustrations that I believe many of you will relate to.

The topic of failure is important. If we don't give ourselves permission to fail then we are denying ourselves the right to learn. Experimentation is all about failure! I wish to encourage everyone who is interested in building circuits of any kind, whether you have years of experience or none at all, to watch this incredible video by Jeri Ellsworth: Secret to Learning Electronics - Fail and Fail Often

In this informal post I also wanted to share a few tips for resources that I have found helpful. Whether you are recalculating the component values to change the band of a published transceiver design, designing your own circuit from the ground up or needing to do quick math on the bench to determine how much parallel capacitance you need to bandspread your VFO, a calculator is a wonderful tool. There are a number of great online calculators and free programs to help us solve design problems but sometimes it's nice to have one on hand, in pocket or on the bench.

 While in fact any dollar store calculator will work just fine, I wanted to find one that was a little more specific to my needs (I should mentioned that if it wasn't for my father offering to purchase it for me, I would most certainly have taken the route of the skint hombre & got the $1 shop calculator). I started my search by digging through posts on the EEVBlog Forum to see what the real engineers were recommending. What I discovered was dozens of pages of discource debating the merits & faults of various brands, models & systems. There seemed to be as many different types of calculators as there are branches of engineering! I started tallying up the recommendations for each particular model. I then narrowed it down to the ones that were in my price range & being sold as new online. Many of the suggested models where vintage and extremely expensive or unobtainable used. I decided on the Casio FX-991MS Plus.






The Casio FX-991MS Plus has the feature of being able to use the engineering notation for pico, micro, nano, Kilo, Mega, etc. so it makes solving circuit problems much easier than other calculators that require you to count the zero's or use other forms of notation. I highly recommend it. In a later update to this post I will cover some of the keystrokes & features of this calculator as well as give some examples of how to solve some of the equations we use when working with RF circuits. So please check back in the near future.

Thanks go out to Chris Gammell (of TheAmpHour, ContextualElectronics & parts.io) and to Pops aka Todd aka VE7BPO (http://qrp-popcorn.blogspot.com/) for their neighborliness and encouragement for me to continue developing this blog despite the lack of visitors. Thanks guys.

That is all for now.  This was just meant to be a quick informal post but I plan on creating many more in the coming weeks so please check back for more homebrewing tips, circuits, project photos, tutorials & ramblings of an RF Hombre.

73, -.-    .    -----    -...    ..-.    ..-.

Homebrew Layout Methods & Tips

Greetings.

I have been experimenting with different ways of designing the layout for my RF homebrew circuits over the past few weeks. We all know of the common methods like etching a board with ferric chloride, dead bug, ugly style, tag strips, veroboards, strip boards, & Manhattan style. I've even made a post on how I make my island pads. Innovative homebrewers have been developing and sharing these methods for decades.

Circuit Layout on Foam

One method I read about described using a sort of styrofoam as a base. A piece of paper is laid on top and the components are pressed into the foam just like they would be laid out on the circuit. Then the traces are drawn and this drawing is used as the template for the board. I decided to experiment with this method but with a twist.

Toy Projector used in layout experiment

 I used this old toy projector that I acquired at a thrift store many years ago, to project the layout directly onto the copper clad.

Projecting the layout onto the copper clad

I then traced the layout onto the board and finally used a dremel with a cutting disc to cut the design into the board.

Safety glasses & a respiratory are mandatory when cutting copper clad!

Although this method kind of worked, it was a bit of a hassle and didn't turn out as well as I would have liked.

Result of first layout method experiment.

Many homebrewers before my time extol the many uses of Blu-Tack, also known as Sticky Tack.

'Hombe' Putty Par Excellence

This is that putty like material that you use in place of thumbtacks to fix a poster to a wall. It can be purchased at just about any department or general store. It was when I was deciding how to build a 40-Meter version of W1FB's Universal VFO from his book, 'W1FB Design Notebook' that I stumbled upon two new uses for Sticky Tack. I am hesitant to say these uses are new, because everything I know about homebrew RF design comes from the grace of those who came before me and openly shared information. However, these two uses are new to me and I hope that they will be new and useful to you as well.

Some authors suggest boiling your toroids after winding them as a way to "anneal" them. Others suggest using Q-dope. I usually use Elmer's wood glue but now I will be using Sticky Tack.from now on. Simply wind your coil around the form. Using your AADE L/C meter (Absolutely essential to successful homebrewing), compress or expand the windings of your coil until the desired inductance is reached. Now place a layer of Sticky Tack on both sides of the coil and join them together around the outside & inside of the coil. Double check that the inductance is correct again and fix it to the desired place on your board. This seems to make the coil quite mechanically stable.

Now on to the second use of Sticky Tack.This was the second layout method experiment that I did. I was much more pleased with the ease of this method and the results in comparison with the projection method.

I start by placing the components on the board by sticking their leads into the putty (StickyTack). Note the coil wrapped in putty to the left side, below the off board variable capacitor.

 

Ignore the different coil used, not mechanically stabilized in putty, during these layout images. 

 Using a hand tool that allows me to bend component leads at an angle, I found the best way to place the components into the putty is to slant them down at an angle sharper than what is shown in the image above.

 Components leads that are to be connected to the ground plane are not placed in putty, Using this method of layout lets you try all sorts of arrangements with great ease.

 Once you have determined the best arrangement of the layout, remove all the components and straighten the edges of the putty, I used another small handtool for this but a flat head screw driver or something similar would work.

No that's not chewing gum and those aren't bite marks. Thats Sticky Tack, putty, and the edges are like that from the small tool I used to straighten out each isolated "putty pad".

 Once all of your "Putty Pads" are straightened out, use an indelible marker (Sharpie) with a fine tip to trace around each pad.

 Remove the putty, and you have your layout. It's still a little less than perfect, but all my circuits are ugly, so I'm fine with that.

 I went over the layout one more time with the marker, to make the lines darker and well defined for the next step.

I like to use a lower power rotary tool for cutting islands & pads. a dremel with only one speed is a bit overkill for this. i use a cutting disc. It only takes a few minutes and the results are great. Use safety glasses and a respiratory! Do it outside and make sure other people or animals will not be able to breath in the resulting dust. It is very dangerous.

 Once the cuts are made use your favorite abrasive to clean up the board. I prefer the wet/dry sandpaper sponge on the upper right.

She's a beaut!  Cleans up awfully nice doesn't she? Note that the solder already on the board is there because I am reusing this piece of copper clad from an earlier experiment. It is single sided, as it is being used for a VFO.

 

As always, check for continuity using a multimeter. Make sure all the pads are isolated from each other and ground. If any shorts exist, fix it with a utility knife. (safety glasses!)

 ----------------------------------------------------------------------------------------------------------

 I hope that the above information and images explained this layout method experiment well enough to comprehend.  Below are pictures of the build process for the VFO for your enjoyment. It turned out really nicely. :)

So there you have it. I sure would love to hear some feedback. Maybe you have been using this method of layout for a long time. If so, please speak up so we can share suggestions! What uses for Sticky Tack do you find helpful in the RF homebuilding lab?

Thank you for your time. As always, keep your iron hot and stay fluxy!

 72,
KE0BFF
FreestateQRP

Xtalfind - Calculate a future for those junk box crystals

Greetings.
Today I am excited to share with you are very handy resource for finding new uses for those crystals that have been sitting in your junk box all these years. I discovered this very useful utility about a year ago when I happened upon the website of Paolo Cravero, IK1ZYW, an Italian ham. Paolo had the great idea of creating this software, which he calls XtalFind, that would quickly calculate the possible uses for his collection of crystals. With his kind permission, I have edited the script to make those calculations for ITU region 2, as the original was allocated to his region, and I am making it available here on this blog.

XtalFind is capable of accepting single frequencies or an entire list, which makes it very useful to examine the possibilities of a large rock collection. It currently checks for the crystal's fundamental and harmonic frequencies for the following applications (for use in the ham bands):

• TX or Direct Conversion RX
• RX with 455kHz IF
• RX with 10.7MHz IF
• RX with 12kHz IF 
• RX with a custom IF frequency
• SDR use: Johnson counter - Center frequency
• and several DRM uses that can be enabled by editing the script.

Of course, any of the above parameters can be edited and customized in the script.

I want to thank Paolo for taking time to write this software many years ago, for graciously sharing it and for allowing me to edit it so that I may use & share it with my fellow ITU region 2 homebrewers.

Please share your thoughts below and if you have knowledge of perl and can find ways to add functionality to this script, please let Paolo &/or myself know as we would certainly be interested.

Xtalfind - modified for ITU region 2

IK1ZYW's original Xtalfind (for ITU region 1)

Thank you and best wishes.

Bypassing Capacitor Lore

As an eager new homebrewer still learning the fine details of how RF circuit stages are designed, I find the wealth of information online and at my finger tips to sometimes be overwhelming if not even contradictory. One topic that I have found to be of the latter category is that of decoupling capacitors.

Working with low speed digital logic circuits in the past taught me the importance of adequate decoupling. Stabilizing DC supply lines is one thing but decoupling high frequency RF stages is a whole new ball game.

Many different respectable sources have described that the trick to proper decoupling is to pair a low value capacitor with a higher value one. The idea behind this seems to be that a low impedance path to ground will be presented to a wider range of frequencies due to the the reactance of the pair. Oppose to a single value capacitance (and its reactance) decoupling a smaller bandwidth. Although I may have not described it all that elegantly, the idea seems perfectly logical to me.

Soon after learning such a juicy nugget of homebrew wisdom I found out that sometimes the logical may just be lore.
 
Looking for a better explanation of how to select the proper capacitance values to achieve a wide decoupling bandwidth I turned to my copy of EMRFD.* Page 2.28 if you're following along at home. For those without a copy I present the following excerpt below:

Traditional lore tells us that the bandwidth for bypassing can be extended by paralleling a capacitor that works well at one frequency with another to accommodate a different part of the spectrum. Hence, paralleling the 470pF with a .01-uF capacitor should extend the bypassing to lower frequencies. ...when tested... The Results were terrible! While low frequency bypassing is indeed improved, a high impedance response is created at 63MHz. This complicated behavior is .. the result of inductance (of the capacitor). Each capacitor was assumed to have a series inductance of 7 nH. A parallel resonance is approximately formed between the L of the larger capacitor and the C of the smaller. The Smith Chart plot showed us that the impedance is nearly 50-ohms at 63MHz. Impedance would be even higher with greater capacitor Q. This behavior is a dramatic example of lore that is generally wrong!   Bypassing can be improved by paralleling. However, the capacitors should be nearly identical. This was observed by using paralleling a 390pF with a 560pF capacitor. Only a hint of resonance was observed, not significant enough to cause any complications. These anomalies disappear as the C values become equal. The ideal solution is to place a chip cap on each side of a printed circuit run or wire at a point that is to be bypassed.

Continuing::

 Matched capacitor pairs form an effective bypass over a reasonable frequency range. Use two parallel chip (SMD) capacitors of nearly identical values (i.e. 390pF + 560pF) at the points to be bypassed on each side of a wire run or strip/track on the circuit board.  Two .01-uF disks had a reactance magnitude less than 5-ohms from 2 to 265MHz. A pair of 0.1uF chip SMD caps with wire leads attached were even better, producing the same bypassing impedance from 0.2 to 318 MHz. Even better results can be obtained with multi-layer ceramic chip capacitors.

I am beginning to better understand the importance of not just following the traditional design wisdom but to actually experiment, test and measure. The terminus of the homebrewing experience I seek is the ability to truly understand, witness and control the ethereal forces of nature within a system of my creation. I can take it on faith that the circuit I build is working as the designer intended it. I can take it on faith that when I follow the principles of good RF design, the stage that I've just built will perform as it should. Or I can measure, test, experiment and truly develop an intimate understanding of the nature & behavior of the circuits I build. As a homebrewer on a budget, I may not always have the test equipment necessary to make such observations, but I will always strive the greater understanding.



  If you would like to share your thoughts on decoupling RF circuits or can contribute to a better understanding of the above, please share your comments below. Do you have a spectrum analyzer to perform the same measurements? Give it a try and let us know your results, maybe they missed something critical when they performed the experiment and you will be the one to find it.



Thank you for taking time to read my post.

*'Experimental Methods in RF Design' by Wes Hayward W7ZOI, Rick Campbell KK7B & Bob Larkin W7PUA

NOTE: If you do not have a copy of EMRFD, I highly re

commend that you obtain one before it meets the fate of Wes (& Doug DeMaws) earlier work 'Solid State Design for the Radio Amateur' which has been unfortunately discontinued,

HOWTO: Create your own PCB Island Pad cutter tool

Greetings. After Bill Meara posted my Mighty Mite design on his SolderSmoke blog, a lot of folks found there way to my Transistor Islands post. I think it would be helpful for others if I shared a bit more about how I make my island cutters. First, I must state that in no way is this an original design. I owe great homage to all the homebrewers who have contributed there own techniques of making island pads on copper clad. It took me trying a lot of different ways of rapid prototyping to find that I enjoyed this method the most. I should mention that when I am building a final (non-experimental/prototype) version of a circuit, I make the layout different than the island pad method. I will make a post about that method at a later date.

Always wear safety glasses and a respirator mask when cutting into copper clad material. The resultant powder can be very dangerous.

Here is my "method":

 I make them from Wood Carving Set from a Hobby Store.

I use an off-brand "dremel" type rotary tool. It is much less powerful than my Dremel brand rotary tool which I find actually helps as it gives me more control when making the blades.

Here is a very crude template for the general shape I cut the wood carving blades into for use as an island pad cutter. If you are going to fit them in metal utility knife handles, the bottom / base of the blade must be shortened to fit the metal handle (at least in my case).

                                             I've made some by cutting the Wood Carving blade while it is still in its original wooden handle.

 I have also made them by removing the wood carving blade from the wooden handle and using a Panavise to hold the blade while I cut it to the desired shape.

 Remove the blade from an X-acto type utility knife. Reduce the size of the bottom/base of the island cutter blade that you make so that it will fit snuggly in the utility knife's metal handle. It makes for a sturdy and attractive island cutter

 I find that using one of these types of files, which I believe are used for sharpening chainsaw blades, makes it easy to keep your Island Cutter nice and sharp after regular use.

 Here we see three island cutters that I made from the wood carving set. One is in the original wooden handle while the other two are in metal utility knife handles. there is an example island to the left.

 Here I begin the process of creating an island by press firmly down on the copper clad. I put a bit more pressure on the side of the blade that will act as the pivot

 Rotate the tool around the pivot, dragging the other side of the blade across the surface of the copper, applying enough pressure to carve just enough of the surface off and expose the FR4 (or whatever your preferred board type) layer below.

 Rotate clockwise, rotate counter clockwise, dig into that clad and isolate your pad! This is fun!!

Within a few seconds, with a few twists of your mighty CW fist, you wil have a beautiful isolated island home for your precious RF components!






A scouring pad helps remove the copper debris from the carving process.

The most important part of the procedure, check continuity, make sure your island isn't a peninsula!







There you have it, folks. I hope that by illustrating it this way, anyone who didn't have a clear understanding of how to make islands on copper clad, will have such an understanding now. As I said in the beginning, I make no claims to originality. This is just my method. There are many others. I simply used what I had on hand to make this, purchasing nothing to build the island cutters, in the true spirit of homebrewing. Lets hear about how you make islands! Please share below. Maybe you are trying to make an island cutter similar to mine but having trouble, please feel free to ask questions or give feedback below or email me.

Thank you for your time, best wishes, keep your iron hot and stay fluxy!

-KE0BFF