What's Happening:

KX4OM Event Log:

I maintain a serial log of significant events here at KX4OM. The most recent are here on the main page, and previous entries are on the Event Log page. Also, as I learn more about HTML coding, I am striving to improve the navigation of the site.

2/14/08

Ron, K5DUZ sent me an email that I had the order of the 12th-wave matching sections wrong in my description. That was a typo, as I had the order correct in the calculation spreadsheet. I've fixed that, and I've also added another link under the 12th Wave item of "Technical Solutions" directly to the download location for the spreadsheet. Previously, it was mentioned only at the end of the article, and I'll bet some folks didn't notice it.

2/13/08

I have added a kit that I built in the Fall of 2007 to the Finished Projects section, the Mcount Morse-readout frequency counter from Jackson Harbor Press.

9/18/07

My most recent homebrew project is a 40m superhet receiver that I built for my grandson, who is learning Morse code. I've also added a project page for my step attenuator, with internal photos.

8/3/07

I have added my completed ELSIE CW-readout LC meter to the Finished Projects section. Now I can measure those toroids that I wind and caps down to the sub-5 pF range.

7/30/07

I have added a discussion of Twelfth-wave matching sections for matching, for example a section of 75 ohm feed line to a 50 ohm feed line. Included is a method for making the coaxial cable connectors and a spreadsheet for calculating the lengths of the matching sections. It's the first item listed under Technical Solutions.

Finished Projects:

Here are projects that I have completed:

A Log Power Meter, designed by Wes Hayward, W7ZOI and Bob Larkin, W7PUA (June 2001 QST; article available as a Members Only download). See my step-by-step photos and description here. I'd like to thank Mike, KO4WX and the QRP Amateur Club International's editorial staff for publishing my work on building the Log Power Meter in the Fall 2006 issue of "QRP Quarterly". This device allows direct measurement of signals of over 20 mW (+13 dBm) to less than 0.1 nW (-70 dBm). It consists of an inexpensive Analog Devices logarithmic amplifier IC, a common 78L05 voltage regulator, an LM358 op amp, a few common resistors and capacitors, two RF connectors, a SPST switch, a $12.99 Radio Shack panel meter, and a die-cast or standard Radio Shack aluminum box as the enclosure. A DVM may be connected through a feed-through capacitor when greater resolution is required. Using this device, stage gains can be directly measured in homebrew transmitters and receivers in the development phase. Also, by attaching a signal generator and a return loss bridge (a simple homebrew passive device), RF filters can be measured for insertion loss and even filter adjustment can be done. An auxiliary 40-dB power tap attenuator described in the article will extend the measurement level to +50 dBm, 100 Watts. Wes suggested that this would be a very valuable instrument for me to use in homebrewing and experimentation prior to building his spectrum analyzer. Wes has updated information on his web site.

A Step Attenuator is one of the most useful test units you can have in the shack. Combined withe a signal generator and a Log Power Meter or oscilloscope, you can make very accurate readings of things like stage gain in a receiver or transmitter. I built mine just a bit different than some others that I've seen. Check it out.

40 Meter Superhet with Digital Readout I built this receiver for my grandson, who is learning Morse code. He picked up the startup sequence from my ELSIE LC meter, and was running around the house di-dah-ing the letters. He even does it through the snorkle at the swimming pool, and I can hear him at the other end of the pool. He was serious about learning CW, so I built the receiver for him, after loaning him my 30m transceiver for awhile.Here's the link to the project.

Protection when you need it: the Plug PiG. This handy little unit includes most of the basic funtionality of the NoGa PiG in a small package. Idecided to build it because the PiG is an accessory I literally use every day I'm at the workbench or operating in the field. Then I had the idea that I could sure use one in the car, when I'm connecting who-knows-what to the cigarette lighter socket. I took apart one of those odd-shaped cell phone charger-adapters, and determined that I could reengineer a PiG to fit.

A QRP dummy load, the prototype of which was built for Russ, AE4NY, as part of my work in upgrading his NoGa "Guppy-WaTTa-PiG" multifuntion unit. That project is described, here.

The ELSIE L-C Meter. I made a presentation to the North Fulton Amateur Radio League during February and April 2007, and I discussed the general topic of homebrewing, and specifically, the tools we need to do it effectively. While I'm also building an LCD-readout L-C meter from an "Everyday Practical Electronics" article, the Program Committee Chairman, Walt, KJ4HE had expressed interest in getting the club members more into Morse code. Well, the ELSIE LCF meter fits the bill for that...its method of output is Morse, through a built-in speaker. The ELSIE was designed by Joe Everhart, N2CX and Steve Weber, KD1JV. At one time it was kitted by the American QRP Club, but it's no longer in production. Although it can certainly be built using one of the free-form methods, including Ugly and Manhattan construction, I of course just had to make a board in EAGLE Cad. Instead of the possibly more familiar PIC microcontrollers, the ELSIE uses Steve's favorite, the Atmel AVR micros. So, along with the ELSIE, I had to build and AVR programmer and locate software to "flash" the chip, an AT90S2313. My ELSIE is finished and working fine. Here's the finished ELSIE.

A 30 meter transceiver for Straight Key Night. We NoGa guys like challenges, I guess. Mike, KO4WX sprung this one on us December 10th, at a get-together after our monthly meeting. Click on the link and see the work as it progressed through the building period. I'm currently building a transmitter board that uses an SA612 mixer fed from the existing VFO module, and this will convert the "trans-receiver", which was built with a modified Vectronics VXO transmitter unit, to a nominal 5-Watt output, full-transceive rig. Taking a cue from Chuck Adams, K7QO's web site, I'm Manhattan-breadboarding another VFO to use for testing. Eventually, I'll modify this test VFO for dual outputs at the 0 dBm level for SA612-based mixers and +7 dBm for diode ring mixers for other projects.

A -20dBm 20 meter test source, designed by Jim Kortge, K8IQY. I'm not providing any build photos, etc., on this one, because it did it just like Jim did, down to the 1/4" copper shielding tape. Check it out on the k8iqy.com web site.

"The Challenger 40", a homebrewed 40 meter transmitter based on the Wes Hayward, W7ZOI-designed transmitter in Chapter 1 of "Experimental Methods in RF Design". This rig was built for the NoGa building challenge in December 2005. I had some bugs to work out, so I actually didn't put it on the air until early in January.

"The NoGa Javelin", a homebrewed portable vertical HF antenna of my own design, extending the ideas of Phil Salas, AD5X and James Bennett, KA5DVS (see it in the Fall 2005 "QRP Quarterly", published by the QRP ARCI.

I recently modified the mast configuation from the prototype Javelin, now using four 18-inch mast sections for greater portability (fits in a gym bag). On a trip to Richmond, VA this summer, a strange occurrence was noted. After the flight, the Gorilla Glue used to secure the coupler nuts inside the mast sections was not holding very well. The joints could be twisted with some effort after they were supposed to be locked. Too many rads from the baggage xray machine? Freezing temperatures in the cargo hold? I don't know, but I fixed the problem for the long term, and enhanced the metal-to-metal junctions as a result. I drilled and tapped 6-32 holes near the bottom of the nuts as they were positioned in the mast, making sure that the hole was below the point where the 1/4 x 20 rod will seat, and screwed 6-32 stainless steel bolts through the mast section. I cut the extra length off with my Dremel tool. Now the drop-in anchors are forever locked solidly in place. As a result of this new metal-to-metal contact to the anchors, I'm now using 1/4-inch stainless steel split washers instead of the zinc-plated star washers. I also color coded the correct mast joinings using a 5-pack or colored electrical tape. This new version made its public debut at the October '06 NoGa Antenna Shootout in the park.

A Sealed Lead Acid Battery Charger of a rather unique design, by Bob, AA4PB. Hmmm...it just struck me that "Pb" is the periodic table abbreviation for Lead. The article appeared in the May 2001 issue of QST. Check out my finished build photos.

A home-brewed circuit board version of the Precision VXO and Crystal Test Fixture designed by Jim Kortge, K8IQY (if you homebrew superhets or SSB transmitters with crystal filters, you really need these two units to obtain crystal parameters).

A Manhattan-style 80 meter QRP CW transmitter, which I call the "H80", in honor of our host and mentor of NoGa "Building Days", Steve Hudson, AA4BW. Steve's Building Day articles appear regularly in QRP Quarterly.

The famous NoGaWaTT, a fractional-watt to 6 Watts, dual-meter QRP Wattmeter. I built mine in two stacked "Altoids" tins, although it will fit in one.

The NoGa PiG (Power Indicator and Guard)...don't hook up your DC supply to your rig without it. It's invaluable during testing of those new designs and kits...saves your circuit and $ worth of power supply fuses).

A Morse-readout frequency counter, the "Mcount" from Jackson Harbor Press. I don't have many kits in my "Projects" here on the site, the two NoGa QRP Club kits being the exceptions, but I included this one because it is an inexpensive way to add a frequency counter to your testing capabilities. I also wanted to show off the interesting packaging I used, which is the case of one of those ubiquitous imported $2.98 digital multimeters.

Current Projects:

Here are some projects that I have in progress:

A 20 and 15 meter CW/SSB transceiver has popped to the top of the stack of longer-term projects underway. This is another project based on Experimental Methods on RF Design elements. First off the drawing board is a cascode-JFET IF strip, with IF-derived AGC. I've done the board in EAGLE Lite, and it is etched and complete except for the component selection for matching the 9 MHz IF crystal filter. The receiver front end, the VFO and the transmitter and PA all come from examples and projects in EMRFD. The 9 MHz IF works out well with the local oscillator frequency of 30 MHz for 15 and 23 MHz for 20, achieved by mixing a 5 - 5.5 MHz VFO with HFO frequencies of 25 MHz for 15 and 18 MHz for 20, using on-hand, readily available inexpensive crystals. As a fallback position, given my limited supply of 9 MHz crystals, I've also bought a larger batch of 9.213 MHz crystals, which would be an alternative IF, if I need to go to crystal filters with more elements than cyrrently designed. The VFO range would shift up by 213 kHz accordingly. The circuit boards are for the most part single-sided, and some, like the IF board, are ground plane on the component side. Special care is being given to proper termination of all mixers. Each stage with a mixer will be checked using a spectrum analyzer for port isolation. Although the critical piece of test equipment will be a spectrum analyzer, I will also use my log power meter to check stage gains, and I will have to construct 2 well-filtered and terminated -20 dBm 21 MHz VXOs for the intermodulation tests. One special thing originally planned for this project is that, rather than use commercial doubly-balanced mixers, I intended to homebrew my own on 14-pin dual-in-line low profile, machined-pin sockets. I am using Agilent/Avago Technologies HSMS-2827 Schottky ring quads designed for RF mixer service. The transformers are being constructed using FT-23-43 toroid cores, and very small trifilar wire I obtained from a friend. My intent is to achieve near-commercial quality on the diode ring mixers. Things don't always go as planned, however. I recently had a lightning strike at the QTH, destroying my Hakko 936ESD soldering station, and my oscilloscope/spectrum analyzer, among several other things. It will take awhile to get set back up again. In order to try to get back close to my schedule for this rig, I'll use commercial DBMs, and do the homebrew mixers on a later project.

A two-band, 17 and 12 Meter QRP SSB transceiver based on Ron Taylor, G4GXO's Belthorn SSB IF Module (with input from Pete Juliano, W6JFR and Zack Lau, W1VT). I'm currently reviewing plans for this project, potentially adding the MS-DDS-60 VFO, which could eliminate the need for HFO oscillators for each band, and allow me to expand the number of bands covered. Otherwise, I'll use the same VFO and HFO design that I use for the 20 and 15 meter transceiver. Pete has built a Belthorn-based transceiver for 20 meters.

I've made the PC boards for an 80-40-30-20 meter push-pull higher-power capability (when needed) IRF510 amplifier. The basic design is the WA2EBY amplifier from QST and the Handbook, but I've decided on an alternative to the bandswitched filter board. I'm using a design based on the CDG2000 by G3OCQ, modified for Omron G5V-1 relays that I was able to get for $.99 each from the Electronic Goldmine, and I've added 30 meters. I worked out the values for the filter components for 30 meters following the standard CDG2000 topology using the excellent (and free) RFSim99 program. Rather than attaching the switch wafer to the filter board as in the basic WA2EBY design, using eight SPDT relays allows for convenient placement of the bandswitch anywhere on the front panel of the amplifier enclosure. I currently have a 1.7 watt output SW20+. I'm building additional rigs with the same output for 80 and 40; and the SKN Special 30 meter rig currently has and will have the same output level when the new transmitter board is installed. All of these rigs will be set at a conservative power level that will produce 5 watts out with one attenuator setting of the amplifier, and full power out at the other. The amp will give me full QRP-Gallon capability on all of the bands that I need in the near term, and the ability to put out 20 watts when needed during the current doldrums of the sunspot cycle. I've got the relays and silver mica caps mounted on the filter board. If I hadn't been so cheap and gotten "bargain" relays with only 1 amp contacts, I could run the amp at higher voltage and get about 40 watts out.

The KD1JV-designed MS-DDS-60 DDS VFO controller. Used in conjunction with my AD9850-based DDS Daughter Card, the combined unit will be capable of direct digital synthesis of frequencies up to 30 MHz (an AD9854 Daughter card goes up to 60 MHz). Steve, KD1JV's controller, a kit (which is no longer in production), adds several important control features, including logic output for band-switching of filters, etc., and stored frequencies, CW enhancements, and others. My most likely application for this may be as a high-resolution signal generator; I've done so much design, planning and parts-gathering on the 20/15 and 17/12 meter transceivers that I think it's better to go with HFO crystal-mixed LO's on those.

An 80 meter version of Wayne McFee, NB6M's 5 Watt QRP amplifier. I'm still in the testing phase on this one. Since lightning took down my 80m doublet, the priority has slipped on this. I'm building it to use with a planned 80 m CW transceiver, and to experiment with broadband matching for transmitter PA stages. The experience will be useful when I get to that point with the two major tranceiver projects. I've been testing the 5 Watt amp with the 80 meter "Hudson" transmitter described on these pages. So far, using Wayne's variable input attenuation circuit, I've been able to get only 3.5 Watts out with 1.7 Watts in; so, I've designed a 1.7 Watt to 1 Watt fixed Pi attenuator network for the board to perform subsequent testing. That should give me a clearly-defined input, and I can mess around with the toroid windings, etc., to figure this out. For some reason, the RF sensing circuit to switch the T/R relay isn't working.

Jim, K8IQY recently sent me some screen captures of his version of Tom Hammond, N0SS's Wideband Noise Source that he'd used to display the shape of a homebrew crystal filter. Jim has much more sophisticated equipment in his workshop, but I don't, only a 16 MHz PC-based spectrum analyzer/oscilloscope (update: not after an August '06 lightning strike destroyed it! The replacment has a 25 MHz bandwidth). The N0SS noise source actually can be used with Spectrogram and a PC sound card. Tom provides details on his site for setting up the filters on the Elecraft K1 and K2 using this method (Google N0SS). I'm going to build the noise source to check out the filters for the rigs I've already built as well as the ones under construction.

Technical Solutions:

Making Twelfth-wave Matching Sections for Coaxial Feed Lines

Coaxial feedlines can be easily matched to each other; for example you can use low-loss 75 ohm RG-6U to feed a dipole, and then bring 50 ohm RG-58U into the transmitter, matched at 1:1 SWR. Based on an article on Darrel Emerson, AA7FV’s website at http://ourworld.compuserve.com/homepages/demerson/twelfth.htm, I have developed a method for making connectors to join the coaxial matching sections for the two main feed lines, and I have created a spreadsheet for performing the calculations for the length of the two matching sections required. Here's the solution.

Download an Excel spreadsheet to calculate 12th-wave matching sections here on this website.

Tuning Linearity Improvement for the SW20+

Through some experimentation, I was able to improve the tuning linearity of the VFO in my SW20+, and also provide an expanded scale around the QRP calling frequency of 14.060 MHz. Here's how.

Making Printed Circuit Boards

Here's the process I use to make printed circuit boards.

The DOS under Windows XP problem:

If you are having problem running legacy DOS programs in Windows XP, here's a solution: DOSBox, a free and still under development virtual x86 environment that runs on top of Windows XP (DosBox.sourceforge.net). Many DOS programs that ran in a DOS window under previous versions of Windows run full screen in XP, and there is no way to do a screen capture or printscreen. DOSBox provides its own environment such that the programs run in the DOSBox window. The screen resolution is best if you set it at 800 x 600. Note that since DOSBox is a virtual environment, it runs with a defined memory space, so you may have to temporarily close down other running XP applications. Note: I used version 0.63 when I was evaluating DOSBox. The next version, Version 0.65 gave me problems in running the programs. This has been corrected in Version 0.70.

I was pleased to be able to provide WES Hayward, W7ZOI and Kirt Blattenberger of RF Cafe with this solution to their long-standing problem, that of getting certain of their older DOS software to run effectively under Windows XP.

See Wes's web site and RF Cafe (link below) below for a detailed explanation with examples on how DOSBox is used with legacy programs under XP.

Presentations:

At the February and April 2007 meetings of the North Fulton Amateur Radio Club, I gave a presentation on "Building Your Technical Arsenal - Hardware, Software and Brainware". The objectives of the presentation are to #1 Add testing and homebrewing capability to the amateur radio skill set, and #2 Learn as you use it, to be able to move up the license ladder and break out of the "Test Question Pool" sysndrome.

At the January 2007 Gwinnett Amateur Radio Society TechFest, I gave a live demo of EAGLE CAD, creating several schematics and PC board layouts. As the event was not strictly ham radio-oriented, one of the designs I made was for a two-way intercom, which will come in very handy, as I've moved my office to the basement, while my wife's office remains on the top floor of the house.

At the November 2006 monthly meeting of the Kennehoochee Amateur Radio Club, I gave Part 1 of a presentation on using CAD tools and making PC Boards. I presented information on several popular free CAD tools, and I focused on EAGLE CAD, as that's the program with which I'm most familiar. I was so impressed by the club and its activities, I also joined KARC at the meeting. At the February 2007 meeting of KARC, I followed up with Part 2, a live demo of the program, creating a schematic from a drawing and producing the PC board layout.

At the NoGa meeting on April 8, 2006, I gave a PowerPoint presentation on the Toner Transfer method of making printed circuit boards. This presentation was authored by Jim Larsen of the Alaska QRP Club, and used with his kind permission. I added a few slides at the end, also. The presentation is also viewable with OpenOffice. I have removed it from the site due to site bandwidth limitations, so please contact me if you would like a copy. Techniques for toner tranfer that I have used is described on this site under Technical Solutions, along with some photos of PC boards.

Miscellaneous Good Ideas:

Here's a collection of good ideas that I've come across in my travels through the internet and the real world.

Selected Web Site Links:

Here are some must-visit links to very fine technical information, used with permission:

Wes Hayward, W7ZOI is the author of many published articles and books on electrical engineering and amateur radio. His designs have inspired thousands of hams over the years to build their own equipment. His book, "Experimental Methods in RF Design", published by the ARRL, is truly one of the most influential works for amateur radio.

Markus Hansen, VE7CA's site documents his outstanding homebrew creation, the HBR2000 160 to 10 meter transceiver. Markus's remarkable design was published in the March 2006 issue of QST, and his further work continues with the rig, with details on his site. It is a beacon in the night to those of us who design and build our own equipment without the benefit of a degree in engineering.

Ian Purdie, VK2TIP's excellent tutorials on basic electronics and circuit design.

For some top-notch information on portable HF antenna design and other topics visit Phil Salas, AD5X's site.

If you haven't yet built a QRP rig for 30 meters, check out Jim Kortge, K8IQY's "Manhattan Madness" project page and the 2N2/30. It's evolutionary!

Learn how to build top-notch enclosures for your QRP rigs using ABS plastic at Bill Jones, KD7S's Site.

Morse keys and homebrewing...nice, if you have a shop full of power tools and are an accomplished machinist, right? Well, take a look at Richard Meiss, WB9BLU's work, and recalibrate your thinking! This site gives a detailed explanation, with photos, on building your own first-rate straight key. Here is a gallery of some of Richards finest work, and here he provides some insight into his process and thinking, as well as more examples. Richard's keys were on display at Four Days in May in 2007.

RF Cafe is a unique portal for RF and microwave engineering resources. There you will find a vast collection of original content with definitions, equations, references and conversions that cover electrical, mechanical, physical, chemical and mathematical fields. Many interactive calculators are available for everything from filters to voltage dividers. In addition, you will find extensive links to other websites for vendor parts, application notes, test notes, amateur radio information, technical magazines and books, patent and communications standards, and much more. Kirt Blattenberger does a fantastic job in maintaining this site. If you are designing a receiving system, check out his RF Cascade Workbook for Excel, and try out RF Workbench. Kirt has posted some updated (December, 2005) information regarding how to use the latter while running under Windows XP.

Rich Herzer, AF2CW's site. Rich recently contacted me regarding the new Straight Key Century Club details, and I got his permission to link to his site. Seems like everybody has a "Mega-Links" site on their page, but Rich has one that has my favorite topics...CW and Classic Radios, along with links to other popular Links sites, such as AC6V.

Lloyd Butler, VK5BR's site contains a wealth of articles on theory and technical practices that he has written for the Australian journal "Amateur Radio", as well as several interesting technical projects and experiments. Be sure to check out his heterodyne sweep generator and other homebrew test equipment...no microcontrollers required!.

Memberships and Affilitations:

QRP Amateur Radio Club International #10610

The North Georgia QRP Club (NoGa)

The North Fulton Amateur Radio League

The American Radio Relay League

FISTS #11818

SKCC, the Straight Key Century Club #40