Softrock Lite 6.2
Adventures in Electronics and Radio
Elecraft K2 and K3 Transceivers
30 January 2007
I've sent a set of corrections back to the ARRL for my Z90
QEX article. To provide for a uniform appearance, all schematics and figures are
redrawn by the League's graphic artists and that opens the door to errors, of
course. And, I found a few places where things changed between submitting the
article and the current Z90.
I've shipped the Z90's for all new orders for which I have
29 January 2007
I spent all weekend working on Z90 documentation,
preparing 18 document sets. That might seem as if it would not take all weekend,
but it does. To maintain the best reproduction quality and to keep the price
down, I've printed all documents on my printers, an HP4000 laser for black and
white with color documents and 11'x17" schematics on an HP1120C inkjet. A set of
documents runs about 250 pages. In addition to printing, the print run pages
have to be collated (in order to speed up printing, it is necessary to print 18
copies of Page 1, then 18 copies of Page 3, etc. Then flip them over and print
the backside, as my HP4000 does not have automatic duplex printing. The output
is thus 18 copies of page 1, etc. and has to be hand collated into 18 sets of
page 1, page 2, etc.) Fold the oversize schematics, insert tabs, etc.
I dropped off the collated and tabbed sets this morning at
Kinkos and will pick up the bound copies tomorrow.
I have sent out an E-mail notice to all non-waitlisted Z90
customers, but I have only received a few responses. If you intend to carry
through with your commitment to purchase a Z90, please respond to my message.
I plan to ship several Z90 kits tomorrow.
The pages after printing, but before collating and
assembly. Only a part of the 11x17 schematics and trouble shooting pages are
Here are the 18 sets of documents, collated, with tabs
inserted, ready to go to Kinkos for coil binding.
25 January 2007
Brent Crosby, the technician at Crystalfontz with whom
I've been working, has solved the mystery of why a few Z90s have experienced
stray characters appearing on the screen and also some display freezes. I've had
two customers experience this problem, and I've duplicated it with some
unshipped displays as well.
The problem is related to tying Pins 18,19 and 20 of the
display to the Z90 ground plane. In particular, the display's Frame Ground (pin
18) is the problem. (Pins 19 and 20 are identified as "no connection" in the
display data sheet.) Whether it was a ground loop, or stray coupling or some
other problem may never been determined, but clipping these three pins on the
display header solves the problem. And, since the problem manifested itself
differently with different displays (and there is no problem with most displays)
it was a difficult glitch to troubleshoot.
I've verified the fix with two displays that experienced
the problem at intervals from a few minutes to a couple of hours. After cutting
these three pins, both displays operated error-free for 24 hours each when I
terminated the test. The Z90 and buggy display Crystalfontz was using also
operates error-free after with the modification.
Instructions on how to make the modification are posted at
the Construction Update page. If your
display is not showing these errors, you do not need to make the modification.
Solving the display glitch also means that the remaining
Z90 kits are ready to ship. I will send payment notices out over the next few
days. I will probably continue to test the displays before shipping, including
attaching the 20-pin header and making the pin 18/19/20 modification.
Crystalfontz has been extremely helpful in solving this
problem. I'm not a particularly large customer of display screens, but I have
been given great assistance by Brent Crosby and Brian Lilly at Crystalfontz. If
you find yourself in need of LCD products, keep Crystalfontz in mind.
23 January 2007
I received a pair of Z91 test panels from
Emachineshop today. Mechanically, both are fine, and the rear panel has good
paint and silk screening. The front panel, as I was told, is in fact silk
screened upside down.
The upside-down status of the front panel may not be clear
in the top photo, but it is obvious in the bottom photo. The last information
from Emachineshop was that the front panels will be stripped via sandblasting or
chemical bath and then re-powder coated and re-silk screened.
I've also had a note from Crystalfontz suggesting a fix
for the stray character problem. I've implemented it on a display that showed
problems. In the "before" part of the test today, I confirmed that the display
still had character glitches. I've just implemented the fix, and will report
tomorrow on the results of an overnight run. I'm cautiously hopeful that the
problem has been identified.
21 January 2007
Mike, W2PY, has provided detailed instructions on how he
modified the Z90's back panel to mount the Z10010 bandpass filter. I've added
Mike's description and photograph to the
Constructions Update page. If you plan to make this modification, originally
developed by Doug, N6TQS, you will find Mike's information useful.
20 January 2007
What frequency do you use for your K2 BFO in CW mode? I'm
working on a tuning indicator and would like to understand the range of
frequencies commonly used.
My BFO is set to 600 Hz, which is a bit higher than I
like, but any lower and the K2's built in speaker response is down too much to
Drop me a note with your BFO setting, whether or not you
use a K2.
19 January 2007
I've added an AGC sweep for my Cubic R3030 receiver. The AGC
study page can be seen by clicking here or
via the navigation links at the top left of the page.
17 January 2007
I've received an update from Crystalfontz concerning the
odd behavior of some of the "C0" graphic display boards. It's possible that they
have found the reason some displays sporadically show extra characters. I'll
expand on this when more definitive tests have been concluded. [The
latest, as of the afternoon of the 17th is that this was a false alert - the
problem remains unresolved.]
I also have copied and expanded the K2 frequency stability
test data of 11 January 2007 to a new page, and added cold (20°F) start to room
temperature data. You can view the page by clicking
here, or via the navigation links at the top
left of this page.
I've also added a page presenting the results of AGC
operation measurements made on three receivers:
- Elecraft K2
- Drake R7
- Racal RA6790/GM
The data shows audio output versus RF input over the range
-130 dBm to 0 dBm. The curves show where the respective designers have placed
the AGC threshold and also show how effective the AGC is at holding the audio
output constant for variations in signal level. You can view the page by
clicking here, or via the navigation links
at the top left of this page.
16 January 2007
I shipped the remaining new Z90 panels today, via Priority Mail to domestic
customers and International Priority Mail to international customers. I have
also notified all customers of the date of replacement panel shipping, so if you
are a Z90 builder and have not received an E-mail from me about shipping your
replacement panel, please let me know.
There's no need, by the way, to return the old panels to me. And, if you have
modified your Z90 to mount the Z10010 4915 KHz filter on the back panel, you may
wish to just replace the front panel.
Going through the second box of panels, I found two more defective paint jobs
-- in both cases the Clifton Laboratories logo at the upper left had paint
smudges from where the silk screen had been dragged across the fresh paint. I've
set those aside, of course.
A few days ago, I added a page showing how to
use your Z90/91 to measure FM deviation using the Bessel null technique.
I've added a new page showing how to measure AM modulation percentages using the
Z90. (The page also includes a quick check you can make to see if your signal
generator has simultaneous AM and unwanted FM.) You can visit this page by
clicking here or via the navigation links at the
top left of this page.
12 January 2007
I shipped 12 replacement Z90 panel sets today via Priority Mail, so they
should arrive Tuesday or so. All customers for this shipment have received an
E-mail note. I plan to package the rest of the replacement Z90 panels over the
weekend and will mail them Tuesday, as the Post Office is closed for the Monday
I also opened the second box that I thought contained Z91 panels and found
that it had the remainder of the Z90 shipment. Not too much later, I received
the following E-mail from E-machineshop about the Z91 panels:
Your job [Z90] has been completed and will ship today. [actually it
shipped yesterday and it arrived today.]
Your job [Z91] has also been completed, but final inspection has
revealed a problem. The silkscreen printing on the front panel has been
transposed 180°, so the Status label is not oriented near the
I am writing to ask if you can accept the parts as-is to avoid further
I sincerely apologize that this job has been problematic before. We
have restructured our finishing processes and feel we have reduced the
possibility of such errors in the future. If you need us to remake the
job, please note that though we aim to complete remakes as quickly as
possible, the job must go thru many phases and you would experience a
We apologize for this inconvenience and thank you for your
My response has been to ask for a photo of the inverted panel, and to
suggest that the most expedient solution would be for eMachineShop to have
the Z91 front panels chemically stripped and repainted and re-silk screened.
I cannot accept panels with that sort of error. I don't think you--my
customers--want a Z91 with a mis-printed front panel.
Here is how the Z90 looks with the charcoal panels installed. The smudges are
my fingerprints. I'm finding out that black shows smudges and dirt like all
getout. I used latex gloves when inspecting the panels I shipped today to avoid
leaving smudges behind. When you install the replacement panels, I recommend
cleaning with a damp paper towel or lintless rag. Please be careful not to get
moisture into the LCD display--that is to say, don't spray the front panel with
mild cleaner, such as water plus a tiny amount of detergent or an alcohol-based
screen cleaner. Rather, apply a small amount onto a towel or rag and gently
clean the panel and screen, or use one of the pre-applied screen cleaner wipes.
Both the front and back are the same color, but lighting
causes the back panel to look more blue/gray than the front.
Also, this particular panel shows three white horizontal
ghost lines. I've inspected all the panels that I shipped out today and found
one more with similar ghost lines. I've kept those for my own use and sent out
panels without this problem.
12 January 2007
I received the replacement Z90 and Z91 panels this
morning. I've only unpacked the Z90 panels and looked at four or five, but so
far all look good.
These panels are the original color I requested, matte
charcoal with white and yellow lettering. It should match the black cabinet
covers and your K2 better than the current light paint / black silk screen color
I plan to package up the panels and ship them out to
customers who have built their Z90's and Z91's first. I should be able to get
that done early next week. I will also notify customers waiting for the re-done
panels to arrive that their kits are ready. I plan to ship the Z91 kits first,
as I am still working with Crystalfontz on the random character issue and they
have almost all of the display modules I was reserving for the Z90 deliveries.
Here are the Z90 panels. The finish is a matte
charcoal/dark gray. The back panel lettering is OK, but the flash reflections
make it look odd in the photograph. This afternoon, I'll add a photo of a
completed Z90 with the panels.
11 January 2007
I bought a used Racal Dana model 1992 counter, with
IEEE-488 and high stability oven options and it arrived a couple days ago. To
the best of my ability to check its calibration against WWV, it's as close to
right on as I can determine. I used an indirect method, using the internal
counter function in the R3463 spectrum analyzer, to measure WWV at 20 MHz. In
the 1 Hz resolution mode, the R3463 reads 20.000000 MHz, which says that the
R3463's 10 MHz time base must be quite close to correct; certainly with an error
of less than 0.5 Hz at 10 MHz. Measuring the R346's 10MHz time base output with
the 1992 counter shows 10 MHz within 0.05 Hz. Unless I can snag some time with a
Rubidium or GPS-disciplined standard, I'll consider both devices close enough to
right for my purposes.
I've used the 1992 counter to run two stability tests on
my K2. I set the K2 to USB mode and locked the dial at 9999 KHz, and connected
it to the 1992's 10 MHz output port through a 30 dB 100 watt attenuator. The
counter input is connected to the K2's audio output. If my K2 were perfectly
calibrated, the result would be a 1000 Hz output; in fact it's pretty good
in that regard, but that was not the primary purpose of the test. Rather, it is
to see how stable the K2 is, both from a cold start and as it changes
temperature cooling down from a transmit cycle and during a transmit cycle. I
collected data from the 1992 via the IEEE-488 interface bus and a Prologix
http://prologix.googlepages.com/. This card looks like a serial COM port to
the computer and as a full bi-directional IEEE-488 port to the device it is
attached to. If you need an inexpensive ($120 or so) IEEE-488 adapter, I highly
recommend it. It is not fully compatible with LabView and most other software
written for a National Instruments card, so if that's your need, take a look at
Prologix's FAQ page for more detail. I use it with
PrintCapture to grab plotter and
print images from several instruments. It can be used with your favorite
language to write control programs via mimicking of a standard serial COM port.
In this case, I used Terminal
to capture the 1992's output data, which I then reformatted in Excel and plotted
with Origin 7.5.
My K2 resides in my basement workshop, and the temperature
stays in the range 70-75 degrees this time of year, so this is not a test over a
wide range of temperature. It is, however, representative of typical ham shack
environments, at least for those of us who do not take the K2 along on winter
camping trips, or operate mobile.
The data below represents 14 hours of measurement,
starting around 5 PM and concluding this morning around 7 AM. There's about a 60
Hz excursion from cold start to stabilized, with around a two hour stabilization
period, although the worst of the drift is over in less than one hour.
At the end of the test period, I disconnected the counter
and did a key-down transmit sufficient to warm the hottest spot on the heat sink
to 145F, as measured with a Fluke 62 Infra-red thermometer. The K2's internal
fan was running at maximum speed at this point. Upon return to receive, the
frequency had dropped about 30 Hz, and it started to recover when I terminated
the data set and started a second data set. The downward spike at the transmit
interval represents a partial counter reading and should be disregarded. Note
that the K2 continues to drift downward after returning to receive mode, as the
heat sink's energy is conducted to the rest of the chassis.
To see how long it takes the K2 to recover from the transmit
heat, I continued taking data with three additional transmit cycles. In each
case, I stopped transmitting when at 145F. The maximum excursion is around 30
Hz, and it takes the better part of two hours for the K2 to return to thermal
equilibrium, as measured by the frequency shift.
Elecraft's drift specification is "less than 100 Hz from cold
start at 25C," and my K2 more than meets that in these tests.
10 January 2007
I am still waiting on an answer from Crystalfontz on why
some displays have stray characters pop up whilst most work without a problem.
The results so far are negative -- they believe the data timing I built into the
Z90 firmware is OK. I'm not surprised by this, as my timing values are extremely
conservative, and well within the data sheet values.
I've added a new page to the site presenting some quick
phase noise measurements I made at 13.5 MHz on a variety of signal generators
available to me, including the Z90 in signal generation mode. It comes as no
surprise to find that the venerable HP8640B is the hands down winner of the five
signal sources I tested. Click here
to see the data or go to the oscillator noise page via the navigation links.
I've also been experimenting with low frequency antenna
systems a bit, and took advantage of the abnormally warm weather over the
weekend to refurbish my old home brew active (voltage probe) antenna. I
believe there's significant room for improvement in power-line related noise
reduction through better isolation and grounding, but it's still possible to
receive WWVB at 60 KHz with a standard receiver (Drake R7) connected to the
active antenna during the day with decent signal-to-noise.
Here's WWVB as seen on my Advantest R3463 spectrum
analyzer, in a zero-span amplitude versus time plot, with 200 Hz RBW and 10 Hz
VBW. WWVB uses an amplitude-level digital modulation system, with one level at
full power (around 50 KW ERP) and the other level a -17 dB reduction. It looks
as if the 17 dB drop puts the signal right at my current noise level.
The plot below uses a vertical scale of 5 dB/div to better
show the difference.
05 January 2007
According to Emachineshop, the replacement panels are now
scheduled for 15 January 2007. I've revised the status report accordingly.
I exchanged a flurry of E-mail messages yesterday with the
ARRL's editor working on my Z90 article. I should receive a proof copy in the
next few days. It's not clear if the second article, describing the Z90's
Gaussian crystal filters, will appear in the Mar/Apr issue or if it will be held
for a later edition.
04 January 2007
I've added a new page showing how you can use the Z90 to
check the calibration of your signal generator's FM modulation using Bessel
nulls. You may view the page by clicking here, or
from the navigation menu.
03 January 2007
QEX's "In the next Issue" paragraph says that my Z90
article will appear in the Mar/Apr issue. I have not yet received proofs and
hope they arrive soon.
02 January 2007
I received a report that a Z90 printed circuit board had
poorly etched pads associated with the 1 watt, 100 ohm surface-mount resistors
(the bias resistors for the Gali-74 amplifiers). The pads were not fully
separated from the ground plane. Although this problem will normally be detected
by the stage resistance and voltage checks, it's always better to find a problem
before parts are installed than discover them afterward. Hence, if you have yet
to assemble your Z90, it may be worth checking these pads for an etching
problem. A magnifying glass may be useful, or you may make ohmmeter checks to
verify that isolated pads are not tied to ground by poor etching.
This is the first PCB production problem report I've
received, so I believe it is an isolated incidence. But, boards are normally
etched in large panels and the sheared into their final size. This means that
there may be another board or two with etching problems. I'll add this
information to the builder's update page.
01 January 2007
As customary, last month's postings have been moved to archives, so the
December 2006 page is accessible by clicking here
or via the link at the top of this page.
I recently purchased a new (to me, at least) Advantest
R3463 spectrum analyzer. I've been trying to understand how it works and have a
basic understanding of which buttons to push. I expect to receive an operation
manual in a few days, which will help, I'm sure.
Here's an image from the R3463 showing the entire two
meter band, 144-148 MHz, in "peak hold" mode, whereby the trace shows the
strongest signal received during the time peak hold has been engaged. This
screen capture shows about three hours of activity. The strongest signal is the
146.79 MHz repeater in the City of Fairfax, perhaps six or seven miles airline
from here. The spectrum analyzer is connected to a 25-1300 MHz discone antenna
about 75 feet above ground.
The R3463 has a color LCD display but I've selected
black-and-white mode for data save as the traces are easier to interpret without
the color distraction.