KX4OMLicensed since 1960 Here at KX4OM the main interests are restoring and operating vintage equipment, building stuff, QRP and straight key CW. You can contact me by email via this spam-free link: Contact me
Site last updated on October 20, 2017.
Updated March 17, 2017
Here are some projects that I have completed in 2016 and 2017.
A lot of new test equipment.
Updated March 17, 2017
Just the one photo for now, but each will be getting their own description on my page. In that group are the main components of the Poor Ham's Scalar Network Analyzer, including the new Log Power Meter I built for the project, the SNA unit which contains the Arduino controller and the DDS synthesizer, and the measurement receiver. Also in the stack are the CMOS 10 MHz square wave generator, which establishes the calibration at -10dBm, and the sine wave 10 MHz oscillator which is used along with a step attenuator to obtain the calibration data for -20dBm through -80dBm. The crystal measurement unit, along with the 4dB attenuator as part of the PHSNA to determine the characteristics needed to design crystal filters. The return loss bridge can perform many functions with the SNA, including sweeping filters and antennas. You may notice that the new LPM is larger than my original LPM (described on this page), and it is heavier as well. The new one uses a 0-50uA Weston all-metal meter. The entirety of the LPM circuitry is contained in a sealed and soldered PC board box, with all penetrations shielded and/or used feed through capacitors. Adding to the weight is a 9VDC battery pack made with 6 AA cells, and the case is a former PC power supply unit that happened to have a vertical form factor.
The 8640jr is a signal source designed by Wes, W7ZOI. Mine covers 3.3 to 32 MHz in 3 ranges. Like its namesake, the HP-8640, it uses a high frequency oscillator range and divides it down for lower ranges. In my case, the 13 - 33 range is digitally divided by 2 to get the middle frequency range, and then divided by 2 again for the low range. When I put up the web page on it, I will include photos from my Rigol 1102E DSO.The final unit is a Two Tone Generator designed and used by the ARRL. I built it based on the ARRL Lab Manual. It includes a built-in step attenuator for performing SSB transmitter testing beyond the usual waveform check for linearity. I finished it in March 2017, and I used it yesterday (March 16) to set the ALC on my Tempo 2020 transceiver per the alignment instructions using a measured 10mV input to the microphone jack and using the attenuator to set the ALC in the green band on the 2020's meter. I am going to put up a page on it as well. The design is also in the 2017 ARRL Handbook.
Here are some projects that I have completed earlier.
My original Log Power Meter
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 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.
I have recently updated
this LPM with a different
meter, that, like
the RadioShack meter, has a
0-1mA full scale deflection. I
replaced the scale with a -80
to +10 dBm scale that I
created with Jim Tonne's Meter
Basic freeware. I also
upgraded the circuit of the
LPM, squeezing 2 trim pots
onto the old homebrew board,
to include the calibration
functionality of the PHSNA
version of the LPM. This means
the graph of dBm vs. DC
voltage is no longer needed to
use the instrument. The 1 mA
meter is from All Electronics,
their Catalog Number PM-376.
The cost is still $3.50 as of
10-20-2017. The scale on
this meter can be removed
by very careful use of a razor
blade so as to not disturb the
D'Arsonval movement. Rather
than glue over the entire back
like on the RadioShack meter,
the glue is only on a couple
of spots on the PM-376. The
meter is such a bargain I
bought 3 of them.
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. After initial tests, I replaced the key capacitor that ELSIE uses for internal calibration with a 1% one (was 2%), and it's even more accurate. Although I now have an LCD-reaout tester from eBay, the ELSIE is very handy when checking out capacitors, especially variable caps at hamfests. 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.
Updated April 2, 2016I 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+ (with components for 30m) designed by K1SWL and described in the Elmer 101 web project. The rig is currently disassembled for a major upgrade. The "temporary" VXO based transmitter has been removed,and a companion to the receiver is to be installed, a transmit board based on the K1SWL SW-30+. The rig will then function as a true transceiver. I am also installing an RIT circuit for the rig.
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.
"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. 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 functionality of the NoGa PiG in a small package. I decided to build it because the PiG is an accessory I literally use every day I'm at the workbench or operating in the field. The PiG features reverse power protection, a "polyswitch", also called a resettable fuse for overload protection, and a voltage comparator IC and LED to indicate undervoltage conditions. Then I had the idea that I could sure use one in the car, when I'm connecting low current draw (1 amp or less) 12 volt gadgets to the cigarette lighter socket. I took apart one of those odd-shaped cell phone charger-adapters, and determined that I could re-engineer a PiG to fit. I added an LED to the circuit to indicate that voltage is available at the socket.
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.
Making Twelfth-wave Matching Sections for Coaxial Feed LinesUpdated October 11, 2016
Making Printed Circuit Boards
Restoration work on the Tempo 2020 transceiver - Updated - New source for sprockets!
The DOS under Windows 32-bit problem:
Here are some must-visit links to very fine technical information, used with permission:
web site was
Light on Windows
XP and is now
gedit on a couple
of Linux Mint 17