Softrock Lite 6.2
Adventures in Electronics and Radio
Elecraft K2 and K3 Transceivers
25 May 2008
I've spent the last week working with a color LCD display.
I have a few projects in mind that may benefit from a color display,
possibly with touch screen input.
The image on the right shows 12 nested boxes overlaying a
line sequence from a test program I wrote.
The display has a 5.7 inch diagonal and is near quarter
VGA resolution, in this case 320 x 234 pixels versus the 320 x 240 pixels
of a true QVGA display.
Getting the data transfer hardware protocol working was
difficult, and I was close to packing the display away for another day. I'm
driving the display with an 18F4620 PIC, running Swordfish BASIC. The data
transfer requires 8 data lines and four control lines, plus a few other control
and power lines.
18 May 2008
I've downloaded Mozilla's Firefox 3, Release Candidate 1
earlier today and see that the two "pointing finger" symbols in the Sticky
Updates page are not rendering correctly, although shown correctly with Internet
For a test, you should see a pointing finger on the line
below. A capital "F" is incorrect.
I believe Wingdings is a standard Windows installation
font. Regardless, it's on my computer and if it's available to Internet
Explorer, it's available to Firefox.
I've turned this anomaly into Mozilla's reporting system.
It's entirely possible, of course, that it's a problem with my HTML coding. I
use Microsoft FrontPage for this site and don't try to tweak or modify the code
by hand. I'm not an HTML expert and have no desire to become one, so I rely upon
FrontPage to translate my layout into acceptable HTML code.
I've used Firefox as my primary browser for a couple
years, along with Thunderbird for E-mail, and I like both programs over their
Microsoft counterparts, Internet Explorer and Outlook.
16 May 2008
I've taken another look at signal generator phase noise,
improving the dynamic range of my test setup with a notch filter. The results
can be seen at my
signal generator phase noise page.
15 May 2008
The last few days have found me working on computer
networking. I decided to add a Raid-1 redundant network attached storage (NAS)
box to my home computer network. After researching the available options, I
purchased a Netgear ReadyNAS Duo. As the name "Duo" suggests, it has a maximum
capacity of two drives. It's available with 500, 750 and 1000 GB drives, and I
went with a 500 GB, the model RND-2150. It ships with one drive, with the
purchaser responsible for buying and adding the second drive, which I did. With
the second drive and shipping, the NAS price was about $450.
I configured it as "Raid-X," Netgear's name for
Raid-expandable. With only two drives possible in the box, it's the
functional equivalent of Raid-1, where the data is mirrored in both drives. The
result is 500 GB disk drive space, but redundant so that if one drive fails, no
data is lost. In fact, the drives are hot swappable, so that it's possible to
unplug one drive and remove it or to install a new drive without turning the
power off. Installing the second drive took all of five minutes. It's a
matter of opening the hinged door on the NAS, unlatching the empty disk caddy
and using four screws to mount the second 500 GB drive in the caddy. Then, slide
the caddy back into the enclosure and close the door. The NAS's firmware
recognized that a new drive had been added and it proceeded to format and set up
the new drive for mirroring. When this process was completed, a corresponding
message popped up on my computer screen. (I did install the NAS control
software, of course, without which the message would not have been displayed,
although the automatic disk recognition and formatting would have occurred
whether or not a PC was attached.)
This addition has caused me to rethink and revise how I
load and save data. With relatively few exceptions, I have been using one
computer mostly as a file server, so all my documents, spread sheets, etc. were
on that computer's hard drive, backed up to a second hard drive in the same PC.
(I currently have six computers in my home network, which even I admit is a bit
excessive. The network uses a 4-port Netgear 10/100 MB wired router, a LinkSys
802.11.g wireless transceiver and a Buffalo Wireless Bridge in the basement
shop. Two computers have 802.11.g wireless cards. It's grown up like Topsy, over
time and could be simplified with a combination wired/wireless 8-port router.)
Where this process failed is that I habitually
stored programs I wrote in a sub-directory of the compiler. Hence, all my
Swordfish 18-F series PIC programs were stored on the Gateway laptop in the
c:\program files\Swordfish directory. Likewise for Delphi programs. While this
speeds up disk access, my shortsightedness became apparent when the Gateway
laptop was stolen in our house burglary this spring. I had made some backup of
Swordfish files, but almost none of my Delphi programs. Although I kept the
Swordfish and Delphi installation disks, I lost all my Delphi work and
substantial parts of my Swordfish code.
A related issue is backup software. Netgear supplies
backup software with the NAS, but it's not suitable to back up Windows operating
files and program files. It's fine for backing up working files, such as
documents, spreadsheets, etc. This lead me to explore the world of backup
software. Backup software divides into two categories; one aimed at making disk
images with a snapshot of all the bits on a disk including Windows and
program files, and the other for backing up user files, such as the documents
and spreadsheets. There's clearly overlap between these two categories, and a
copy of the complete disk obviously grabs all the user files as well as the
system and program files. And programs aimed at backing up user files often
include a "disaster recovery" module to save and restore the system and program
files. After reading PC Magazine's reviews of backup software and after reading
on-line manuals and downloading and using trial copies of the best ranked
programs, I've decided that
Manager Pro 8.0 is the best suited for my use.
Image is a good alternative. Genie is more a user file backup program with
disk image option whilst Acronis is more a disk image program. I think either
would work well for me, but I found Genie a bit easier to use during my
experiments. But, the difference between the two was slight.
In order to make the backup software and NAS work, I've
created a directory (share in NAS terminology) on the NAS disk to hold nothing
but my user files, programs, documents, spread sheets, graphs, raw data, the
source files for this web site and the like. It's 20 GB in size, although
there's probably some duplication in the files, as they have also grown
like Topsy. I need to rearrange my Delphi and Swordfish files to move their
code-related files to the NAS box as well.
I should add that although Raid-X means that a single hard
drive failure causes no loss of data, it's still possible for both drives to
fail (lightning strike, for example) or for the NAS to be stolen or damaged in a
fire. Hence, there's still need for a true backup. At the moment, that is to be
via a separate USB-attached hard drive plugged into the NAS. Once I have my
files sorted out and properly arranged on the NAS, I can then back them up to
the USB drive. The USB drive can be disconnected except when the backup occur
and kept locked in the fireproof safe I added after the break in. It's a matter
of discipline to keep the backups going, and that's something I'm not all that
I should also mention that the NAS has
three USB ports, one of which I'm using for a USB-connected hard drive. The
other two USB ports are usable as printer connections, with the printers
appearing as attached to the NAS. This means that it's no longer necessary to
keep one PC running as a print server. Both the printers I use pre-date the era
of direct USB-printer connectivity, so I attach them to the NAS with Belkin
USB-to-parallel adapters. My HP Laser Jet 4000 appears to the network as a LJ
4000, but my Desk Jet 1120C color inkjet printer comes up as "unknown printer."
It was simple enough, however, to match it with Window's stock 1120C driver.
Both printers work nicely through the NAS box.
12 May 2008
I've collected more analog phase detector data comparing
the Thunderbolt with the H5065A Rubidium standard. The plot below shows 28 hours
of data. It should be obvious that the two frequency standards grew
significantly closer between hours 7 and 10. The beat frequency dropped, with
the period increasing to about 1.25 hours.
An FFT analysis shows the most common offset period
corresponds to 3.54x10-11 Hz, but as the spectrum plot shows, there's
quite a bit of jitter around this offset.
It's considerably easier, of course, to see this jitter in
the FFT analysis.
11 May 2008
I've given further thought to measuring the frequency
offset between the 10 MHz outputs of the Trimble Thunderbolt GPS receiver and
the HP 5065A Rubidium standard.
At the minute difference in frequency between these two
standards (the difference is around 0.0005 Hz), it's easier to measure phase
difference. I've used a Racal 1992 frequency counter in phase measurement mode,
with the results presented on 07 May. I understand the preferred methodology is
to look at the 1 pulse-per-second GPS output, but for my purposes the frequency
offset between the two 10 MHz outputs is the most useful.
Analog phase detectors come in a variety of forms, such as
an XOR logic gate. Another phase detector is the
common frequency mixer, provided that the mixer has an output that extends to
the essentially DC frequency we expect to see here. I decided to use a
mixer operating as a phase detector and an Agilent 34401A digital multimeter
to look at the mixer output. I've set the 34401A to automatically output a DC
voltage reading once every 10 seconds, with the data being captured over
the GPIB interface and saved to a disk file.
The 34401A is the center instrument in the photo at the
right. The ZP-1MH output has a range of about 625 mV plus and minus when driven
by the 10 MHz signals. Since the phase detector output varies so slowly, we
measure the output with a voltmeter operating in DC mode, not AC.
The output shows a lumpy and jagged appearance. Some of this, particularly
around the zero crossings, is due to the mixer diodes not being perfect
switches. Other parts of the output, such as the reversals are real and result
from minute changes in the Thunderbolt's 10 MHz output as the GPS corrections
nudge the oscillator one way or the other to stay in synchronization with the
GPS signals. These changes are truly small by the standards we normally care
about in amateur radio, but are more than large enough to be seen in this plot.
The frequency difference, or beat note, in the plot below is around 1 Hz change
about every 38 minutes.
One way to determine the offset is to use the data plotted
above and measure the time between peaks or between zero crossings. If we look
at the time between the last peak and the first peak (a total of 9 cycles), we
can calculate that the average time per cycle is around 2305.6 seconds. This
corresponds to a frequency offset between the two 10 MHz signals of 4.34x10-11.
This is a bit worse than the 3x10-11 determined from the regression
analysis performed on phase measurements taken with the Racal 1992 counter.
Another way of extracting the frequency error from this phase
data is to perform a fast Fourier transform and look at the spectral lines.
The figure below shows an FFT analysis of the analog phase
data. We see a spectral peak at 4.394x10-4 Hz, quite close to the
average figure we came up with by just looking at the time difference between 9
cycles of the phase data. The FFT data, however, also shows by the peak width
how stable the frequency offset it. We note the width is rather broad and other
peaks can be seen, although of significantly lesser magnitude. We can also see
the change in offset by carefully looking at the raw phase voltage data plotted
above. The time between the 2nd and 3rd peaks, for example, looks to be very
close to 0.5 hours, or 1800 seconds. In contrast, the last two peaks are closer
to 0.75 hours or 2400 seconds apart. Thus, the estimated frequency offset of
4.4x10-11 is not constant and varies considerably over time. This
variation can be a function of many things, including changing quality of the
satellite signals as more or fewer satellites are visible to the Thunderbolt.
In theory, we should be able to see the frequency with
which the Thunderbolt applies individual "nudges" to the disciplined 10 MHz
oscillator. This should be around 1 Hz, but the data has far too much noise to
show this level of detail.
11 May 2008
I've made changes to the Z10000 buffer amplifier
construction and operation manual. The changes were suggested by Jerry, W4UK, to
clarify the differences between the -K2 and -U versions by adding photographs
and to provide a photograph of the board keyed to the post-construction
resistance checkout test points. The revised manual may be downloaded by
here or from the documents page.
09 May 2009
I've written about lamps and their use as feedback
elements at my Bill
Hewlett and his Magic Lamp page. The classic HP audio oscillators, such as
the 200CD, use small (10 watt or less) tungsten filament lamps as amplitude
The standard incandescent lamps used for illumination use
tungsten as a filament material for several reasons. One of the more important
ones is tungsten's self-stabilization effect. As the filament temperature
increases, the resistance increases. Thus, there's a negative feedback mechanism
here as well; if the line voltage increases, the power drawn by the lamp is less
than it would be should the filament be made from a material with a relatively
constant resistance material.
Edison (and his contemporary, Joseph Swan in Great
Britain) used carbon filaments. Carbon was relatively easy to make into
filaments, although a great deal of practical engineering work was necessary to
develop a usable carbon element.
It took twenty years until a practical tungsten filament
became available around 1900.
Carbon, unlike tungsten, has a negative resistance
temperature coefficient, i.e., as the temperature increases, the
resistance decreases. Ron, K8AQC, recently sent me two old Western Electric
model 2W switchboard lamps, with carbon filaments. These are slide-base lamps,
about 1.75" long, with a nominal operating voltage of 24 volts. The identifier
is "2W" which does not mean the lamp is a "2 watt" device.
Western Electric 2W Carbon Filament Lamps
To characterize these lamps I measured their resistance over the range 0.2 volts
to 24.75 volts. I used a GPIB-controlled power supply, an Agilent E3631, running
software I wrote to collect the data. I computed the resistance in an Excel
spreadsheet, based on the voltage and current, and plotted the data with Origin.
As the plot shows, the lamps start with a rather high
resistance, between 2 and 3 Kohm, and rapidly drop as the applied voltage
increases and the filaments warm up, at which point the resistance becomes
The difference between the 2W carbon filament and a small tungsten filament lamp
can be seen in the plot below, showing the resistance versus applied voltage of
a standard no. 47 pilot lamp. At room temperature and very low power (ohmmeter)
the filament measures 5 ohms. At the lamp's standard operation condition, 6.3V,
the filament resistance is about nine times greater, at 45 ohms.
07 May 2008
I purchased a used Trimble Thunderbolt GPS-disciplined 10
MHz oscillator unit a couple weeks ago. It arrived Monday and I completed an
enclosure and power supply for it this afternoon.
Inside the Thunderbolt. The large silver module is the
precision 10.000000 MHz oven crystal oscillator. The rest of the electronics
are the GPS receiver and controller.
Thunderbolt mounted in enclosure with power supply. The
Thunderbolt is the gold anodized box.
Front View - Green LED indicates +12V power is applied
Rear View. Connectors are (L-to-R):
- Antenna In
- 10 MHz Out
- 1 PPS Out
- RS-232 Control
- AC Input
I had a couple of TenTec enclosures purchased for Z91 digital panadapters, so I
used one for the GPS. I also had a
12V@4A 90-250V switching power supply that fit nicely into the
The Thunderbolt version I bought is
an OEM special, with an enclosures but without the +24V input power option
commonly found. Instead, the board requires +12V, +5V and -8 to -12V. The
switching power supply takes care of the +12V, and I installed a 7805
three-terminal fixed regulator to reduce the +12 to +5 for the +5 requirements.
The -8V is, fortunately, only required for the oscillator steering DAC
controller, with a current requirement of only a few mA.
This suggested a flying capacitor voltage inverter which I
built on the small piece of perf board visible in the second photograph near the
IEC AC input socket. The voltage inverter starts with a 78L09 regulator to knock
the +12V supply down to +9V. The actual voltage inversion is accomplished
through a Microchip TC1044S charge pump voltage inverter. The TC1044S works by
charging a large value capacitor (I used a 33 uF Tantalum) across the +9V supply
during one half of the 10 KHz switching waveform. During the second half of the
10 KHz period, the capacitor is inverted, which yields -9V. The negative output
voltage is stored by a second large value capacitor (another 33uF in this case)
to smooth the output voltage.
If much current is drawn, the ripple increases, but at the
2 or 3 mA required by the Thunderbolt, the ripple easily meets Trimble's
After four hours of operation, I've made a quick comparison
between the Thunderbolt and my HP 5065A Rubidium standard. The comparison isn't
all that meaningful yet, as the GPS should run for some days to accumulate data
and refine its Kalman filter coefficients.
below shows the phase between the Trimble's 10 MHz output and that of the 5065A,
measured with a Racal 1992 counter, operated in phase measurement mode. The data
is taken once every 10 seconds and the measurement range is 0-360 degrees, so as
the phase difference exceeds these bounds, it "wraps" around 360 degrees. Hence,
the sharp jumps represent phase wrapping.
The phase error is not constant, indicating that the two
oscillators differ in frequency.
To compute the difference in frequency, we can fit a linear
regression line to the unwrapped phase. This shows an offset of 3.17x10-11
between the two oscillators. The offset is computed from the slope of line,
-0.11402 degrees/second. Considering there are 360 degrees in one second, the
proportional difference between the two oscillators is (ignoring the algebraic
sign) 0.11402/360 cycle, or 3.17x10-4 per second. Since the
comparison is between two 10 MHz oscillators, the absolute error is 3.17x10-4/10x106,
If we remove the 3.17x10-11 frequency offset by
subtracting the regression line phase estimate from the raw unwrapped phase data
we wind up with the "residuals" or the error that would result if the long
term average frequency of the two oscillators were identical. The residuals show
periods of an hour or more where the error movement is consistently in one
direction or another.
The data presented will be
more meaningful after the Thunderbolt has operated a few days without
04 May 2008
As usual, the preceding month's Updates are now archived
and may be read by clicking here or via the archive
link table at the top of this page.
I've been busy getting a few orders for assembled
Z10000 amplifiers and Z10010 filters out in the last couple days so this page
has not been updated.
I've also taken a more detailed look at a few audio
transformers, including harmonic distortion and transformer modeling in LTSpice.
I've added a page with the details, viewable by clicking
here, or by clicking on
the Audio Transformer Data and Modeling link in this site's navigation menu.