Freddy - What a ham.

Site last updated on April 27, 2012.

What's Happening:

Recent Stuff:

I've been working on a URM-25D signal generator that I've had since 1973. It worked very well for a number of years, as it was taken out of Navy service that year. Several years ago, it failed. The numerous paper/oil capacitors used in the rig were leaky...VERY leaky. These capacitors, which look very similar to the vintage flat silver mica capacitors, had split along their seams and the oily goo was forced out. I replaced eight of the caps on the AF modulator board, which is the only *relatively* easy board to remove. The instructions for repair in the manual are not very detailed. I removed the cast aluminum cover from the oscillator, crystal oscillator and buffer amplifier, but I had no idea how to go any further. By my count, three more capacitors needed replacing. The generator sat in a closet for almost 10 years. Recently, I found additional information online with step-by-step instructions on doing the rest of the repairs. The generator is working fine again.

I recently did some relative measurements of electrolytic capacitor ESR (equivalen series resistance) using the URM-25D as a 100kHz generator, a 2-resistor voltage divider and an oscilloscope to indicate high ESR. The setup is sensitive enough to see small differences between some new Cornell Dublier 100uF, 450VDC snap-in electrolytics that I purchased from Mouser for a power supply upgrade for one of my old rigs and several several caps of a similar range. I was particularly interested in the HV electrolytics removed from the Tempo 2020s I've renovated and eight 125uF, 450VDC caps removed from Heathkit power supplies. The way the ESR test setup works is that when the generator and scope are set for about full scale peak-to-peak on the scope, placing the discharged capacitor across the low resistance of the resistive divider (10 ohms) will show the parallel resistance of the cap and the resistor. A good cap will display a very small amplitude trace (the 10 ohm resistor in parallel with a resistance of much less than 1 ohm), and a high ESR cap will show a higher amplitude (ESR high enough so as to not change the parallel resistance combination much). So far, I've found a few bad ones, including an aluminum can electrolytic and several axial paper electrolytics. There are a few ERS measurement kits on the market for $100 or less, some with digital readouts of ESR. There are also some construction projects that use fairly simple IC and transistor ones with analog meters on the web as well. The total parts cost of my tester consists of 2 resistors, 2 female bulkhead BNCs, 2 banana jacks and plugs, 3 or 4 inches of wire, 2 alligator clips and a small aluminum box. I'm working on a standalone 50kHz oscillator that will produce about 1V peak for use in ESR testing; the URM-25D signal is lower.

I've added some projects to the Completed Projects section of the site, and I've added some content to the individual projects. If you haven't visited the site in awhile, you may want to have a look.

The Tempo 2020 transceiver is my main rig, a mid-late '70s generation hybrid (all solid state except for the driver and 6146B PA tubes.) I've gone through the rig, replacing electrolyic caps in the power supply along with some repairs and a general realignment. I kept a detailed log of every step in the work, my usual practice with restorations. Some highlights of the Tempo 2020: built in AC and DC power supplies; two 6146Bs in the final, with Zener regulation of the screen voltage; individual LSB, USB and CW crystal filters; 100 kHz-range VFO, with switched heterodyned and PLLed band segment ranges; a combination of analog and digital readout; conservative plate voltage at 600V; and a separate CW carrier oscillator that operates on the displayed frequency in transmit and receive. I've developed some repair instructions for a couple of common issues with these rigs as they age - replacing the sprockets for the preselector and bandswitch drive trains, and replacement of the PA compartment bandswitch shaft coupler. Both of these are something of a challenge. In doing the final checkout of the rigs, I used my homebrew Log Power Meter and -20dBm test source to check out the receiver and calibrate the S-meter readings. Click on the Tempo 2020 restoration item on the menu item for Technical Solutions for more details.

I've added a link to Todd, VE7VPO's QRP/SWL Homebuilder site. I've watched Todd's site develop over the years, and it is a great site for tutorial articles and experimentation. Todd has some new experiments for 2012, and he is detailing the use of S-parameters to develop new circuits from scratch, and then optimize them. You can access Todd's web site from the Links section (quick jump from the menu to the left).

Finished Projects:

Here are some 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. 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 AD8307 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 extends the measurement level to +50 dBm, which is 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 with 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.

A 40 Meter Superhet with Digital Readout I built this receiver for my grandson, who has an interest in all things electronic. Here's the link to the project.

The ELSIE L-C Meter. The ELSIE LC meter is an accurate, simple device for measuring inductance and capacitance. 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 made a board in EAGLE Cad. Instead of the possibly more familiar PIC microcontrollers, the ELSIE uses Steve's favorite, the Atmel family of microcontrollers. So, along with the ELSIE, I had to build a device programmer and locate software to "flash" the chip, an AT90S2313. My ELSIE is finished and working fine. I recently replaced the key capacitor that ELSIE uses for internal calibration with a 1% one (was 2%), and it's even more accurate. I use it a LOT. Here's the finished ELSIE.

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

A 30 meter transceiver for Straight Key Night.I built this rig for operation on Straight Key Night a few years ago. Click on the link and see the work as it progressed through the building period. This rig uses a modified Vectronics VXO transmitter unit, and the receiver section from the SW-40+ designed by K1SWL and described in the Elmer 101 web project.

An enhanced Guppy-WaTTa-PiG Multifunction QRP Accessory.This project is a culmination of a lot of work between Russ, AE4NY and some other members of the NoGa QRP Club and me over a couple of years. It combines several NoGa QRP club kits, commercial board units and some homebrew units. The result is a very useful box that simplifies QRP operation of various transceivers, transceivers and receivers. Click here for details.

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. This is my primary reference source of RF for adjustment and calibration work in a 50-ohm environment. It does indeed read -20dBm on my log power meter. Check it out on the k8iqy.com web site. UPDATE - To extend the range for MDS determination and S-meter calibration, I built a stand-alone 40 dB attenuator to use with the test source and step attenuator.

"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".

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. Unlike simpler chargers, AA4PB's design does not maintain a fixed-voltage, trickle current float on the batteries. It applies charging cycles only when the voltage is below a level set by a voltage comparator. LEDs indicate when the charging cycle is on (green) or off (red). Even in a fully discharged state, the battery is brought up to full voltage by cycling the charge current. It works very well, and it's a nice project. I keep my stock of 7 AH gel cells charged with it. Check out my finished build photos.

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 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 one of these test sets, or one of the other designs out there, for obtaining crystal parameters. Jim's design provides very comprehensive testing.

Ongoing Projects:

Here are some projects that I have in progress:

I'm working on an HF CW/SSB transceiver based on Experimental Methods on RF Design elements. First off the drawing board was a cascode-JFET IF strip, with IF-derived AGC. I originally did the board (see the board layout above) using Eagle CAD Lite, but I put that aside when Wes, W7ZOI made some changes. I ordered a new board designed by Roger Hayward, KA7EXM, the Hybride Cascode IF system. It is not only an improved design, it is quite a bit smaller than my homebrew board. The receiver front end, the VFO and the transmitter and PA all come from examples and projects in EMRFD.

A 20 meter SSB transceiver based on Ron Taylor, G4GXO's Belthorn SSB IF Module, with input from Pete Juliano, N6QW (formerly W6JFR) and Zack Lau, W1VT. With this particular SSB-only rig I plan to shoot for about 40 watts PEP output. I have mobile and portable operation in mind for this unit. I also intend to use this rig as a 20m IF rig to use with my Ten-Tec 6m transverter. One of the nice things about the Belthorn SSB IF module is that allows for lots of possibilities, while maintaining a solid basic transceiver design at the heart of the rig. The SSB IF module uses SBL-1 diode ring mixers and an LM1350 IF stage. Pete has built a Belthorn-based transceiver for 20 meters, along with several other rigs of various designs.

I'm working on a multiband push-pull power amplifier to give a boost to low power transmitters. 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 the eight SPDT relays allows for convenient placement of the bandswitch anywhere on the front panel of the amplifier enclosure. Since these are not latching relays, the relay coils selected (2 at a time) will draw DC current of about 16 mA. That may be a disadvantage for battery-powered opeating. I'll be using some planned rigs with various low outlet levels, so attenuators will be used with the amp. I've got the relays and silver mica caps mounted on the filter board. Output power will be limited to the capability of the relays.

In addition I've got many (too many?) projects that receive attention from time to time. These are just a few: I started on the 2N2/40 in 2005 or 2006, I think, and as of August 2009, I have added the switching section and RX RF amp to the board layout. Now the VFO doesn't feel so lonely sitting there in the middle of the board by itself. Also, I have a single band amplifier board etched, based on a W1FB design from the January '96 CQ magazine. I built it mainly to experiment with various drivers and PA transistors. I have some some inexpensive 2SC5739 transistors (Ft=180), some IRF510 MOSFETs and some Mitsubishi RF MOSFETs to see what I can get out of them on 40 meters at 13.6 volts. I'm also revitalizing my formerly-old standby HW-101. I've got a Zener diode string and shunt transistor screen regulator designed by Allison, KB1GMX, going in that rig as soon as I get it otherwise fully functional again. I checked out the design using SIMetrix SPICE, and it looks like it's a go. (Thanks to my friend Harold, KE6TI for introducing me to this very fine free SPICE modeling program.)

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.

Making Printed Circuit Boards

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

Restoration work on the Tempo 2020 transceiver.

I've been working on restoring a couple of Tempo 2020 '70s vintage transceivers. Here are some procedures (in downloadable PDF format) that I've developed for a couple of particulary difficult issues.

The DOS under Windows XP problem:

If you are having problem running legacy DOS programs in Windows XP or Vista, 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. So far, I have not had to do this. 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 was corrected in Version 0.70. Update: I downloaded Version 0.78 in March 2010, and it works with Vista. New info: I'm upgrading one of my PCs to Windows 7 (64 bit), so I'll have to see if DOSBox works with it.

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.

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. Visit Wes' web site for updated info on his projects.

Markus Hansen, VE7CA documents his outstanding homebrew creation, the HBR2000 160 to 10 meter transceiver on his pages. 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.

One of the most interesting sites I've followed for several years is Todd Gale, VE7BPO's QRP/SWL Homebuilder site. Todd has a lot of tutorial and construction articles with a focus on experimentation. Click on this link for some great info and ideas.

For some top-notch information on portable HF antenna design and many other homebrew topics visit the web site of Phil Salas, AD5X.

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!

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, WB9LPU's work, and recalibrate your thinking! Here he provides some insight into his process and thinking, as well as many examples.

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.

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.

Ken, K4EAA's web site is dedicated to repair of Japanese hybrid rigs, particularly the popular Kenwood TS-520/820 and TS/530/830 series. Ken has done some amazing stuff, machining custom parts to improve these rigs. His dedication in producing color highlighted high-resolution, 36" wide schematics for the rigs is admirable. Ken has a lot of technical info on repairing (and tuning) these rigs, complete with great photos. Also check out his design for a 1 quart-sized 100+ Watt capable dummy load with built in RF sampling taps. I think I'll building one to supplement my old homebrew "cantenna" filled with 1 gallon of genuine Heathkit oil soon.

Lloyd Butler, VK5BR's web 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!.

Stefan Vorkoetter hosts a great site devoted to electronics and RC aircraft. There is a lot of common ground between ham radio and the RC community in battery performance, charging and maintenance. Stefan has a couple of very interesting projects that he has developed, including a really full-featured battery charging/conditioning system (BattMan II) that is controlled from a PC. The schematic, PC board artwork and Windows software is available for download from his site. The types of batteries that have customized charging profiles in the software include Nickel-Cadmium (NiCd), Nickel-Metal-Hydride (NiMH), Lithium-Ion (Li-Ion), Lithium-Polymer (LiPo), Lithium-Nano-Phosphate (LiNP), and Lead-Acid (Pb-Acid) batteries of 1.2 to 14.7 Volts. The hardware connects to the parallel port of a PC, and it works with all Windows versions from Windows 95 to Vista. Plots of charge and discharge cycles are generated during the process which mave be saved as image files. Sample screen captures are shown on the web site.