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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.
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.
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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.
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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.
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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.
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Here's
a collection
of good ideas that I've come across in my travels through the
internet and the real world.
<Top>
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!.
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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
This web
site was sparsely created using NoteTab Light, and is
maintained using PSPad and FileZilla.
Web site links are with the expressed permission of the
owners.
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