Softrock Lite 6.2
Adventures in Electronics and Radio
Elecraft K2 and K3 Transceivers
November 2009 Archive
29 November 2009
I've spent the last several days drafting the assembly and
operations manual for one of my new kits, the Z1203A DC power coupler. The
Z1203A couples DC power to a coaxial feeder to power a remote amplifier such as
the Z10040B, or a remote active antenna such as the forthcoming Z1501C active
The manual is about 85% completed, to be finished
when the enclosures arrive in the next couple days.
To write a manual, I follow a "build, photograph and
write" process. I built the first Z1203A printed circuit board several months
ago when the PCBs arrived. During the first build, I made a couple pages of
handwritten notes with a rough construction order and notes and took a dozen
The purpose of the first build was to verify the PCB
layout and compare performance against the prototype, not to develop the manual.
The second build this week used my earlier notes but I found several places
where a slightly different order made more sense. And, this time I completed all
the connecting cables in their finished format, or at least finished up to the
point where the enclosure work is required.
After installing each group of components, I
photograph the board and write the associated instructions. I repeat this
process until finished. This step-by-step process works well for me as it breaks
up the writing and building into small chunks.
By the time the manual is finished and this Z1203A is
completed and installed in the enclosure, I'll have spent about 40 hours in the
process. (This 40 hours is just the assembly and manual writing time, and does
not include the original design, prototyping, schematic capture, PCB layout,
etc.) The 40 hours breaks down to about two to three hours in actual soldering
iron work and the remainder in photographs and writing.
The Z1203A is a 100% through-hole part kit and I believe
an average builder will be able to assemble it in two to three hours.
About half that time to stuff the printed circuit board and half to build the
connecting cables and install the cables and PCB into the enclosure.
The photo below is of the Z1203A printed circuit board I
built this week.
23 November 2009
My sheet metal supplier is planning on shipping one batch
of my enclosures Wednesday, with the remainder a few days later. With some luck,
therefore, I will be ready to start shipping three new kits in the next couple
weeks. I will have to write the manuals, build one unit and photograph it, etc.
I've also revised the
Z10040B manual adding Appendix
F to provide measured performance information on the "high gain" option, where
the standard 1:11:4 transformer winding (11 dB gain nominal, 10.4 dB typical
measured gain) is replaced with a 1:29:6 winding (15.6 dB gain nominal). The
bottom line is a realizable gain of 14.6 dB, but a reduction in 3rd and 2nd
order intermodulation performance and a reduction in the upper -3 dB bandwidth.
These trade offs for increased gain may be acceptable to some users.
23 November 2009
I've made a small change to the Z10000B-U manual to
reflect corrected resistance reading at the DC input pad. The corrected reading
is 100K ohms to infinity, depending on your multi-meter voltage output when in
ohms mode. The main thing to look for is the absence of a short circuit to
ground, as the most common assembly error will be a solder bridge to ground.
20 November 2009
I've had a promise from my sheet metal supplier that he
would work at finishing my enclosures tomorrow, Saturday. I hope that nothing
interferes with his plans.
I recently had a customer request a Z10040B Norton
Amplifier to be built with higher gain than the normal 11 dB design. It's
possible to increase the gain, within reason, by altering the transformer turns
ratio. For the details on how this works, see the circuit theory section of the
Z10040B manual, along with the
underlying Norton amplifier patent reproduced in the manual. With a 1:29:6 turns
ratio, approximately 15 dB gain can be achieved. The down side to the increased
gain include lower upper 3dB frequency limit and degraded intermodulation
performance. I'll add details to the Z10040 page
over the next few days.
I've also prototyped a new filter, the Z10100 AM
Broadcast notch filter. The Z10100 is intended to be used where a single AM
medium wave broadcast station must be reduced in level by 50 dB or so without
affecting reception of other AM stations. In the amateur radio context, the
Z10100's advantage over the
Z10020 band reject filter
is much better 160 meter band performance. As the Z10100 becomes closer to
production, I'll add a page. The table below summarizes the differences.
Z10040 Band Reject Filter
Z10100 AM Notch Filter
Rejects 450 KHz - 1750 KHz
||3 dB bandwidth is
typically 150 KHz, between 500 and 1700 KHz, center frequency set at
time of filter construction.
dB minimum at deepest part of stop band, typically > 90 dB.
ohms; 75 ohms on special order
||50 ohms; 75 ohms
on special order
Where multiple strong signals in the medium wave broadcast band must be
suppressed, or one very strong station requires high reduction.
||To reduce a
single medium wave AM signal. Other AM signals experience minimal
reduction in signal strength. For amateur radio use, very low loss at
1.8 MHz is a major plus.
Typical insertion loss at 1.8 MHz (160 meter amateur band)
Standard Z10040B approx. 3 dB; 160 meter optimized version approx. 1.5
Insertion loss significantly
improves by 1825 KHz.
frequency < 1600 KHz, approx. 0.5 dB.
$77.50 plus options (if ordered) and shipping
$97.50 plus options (if ordered) and shipping.
Receive Only - 100mw max
||Receive Only -
The Z10100 prototype rejection, center frequency 1340 KHz. 50
dB rejection bandwidth is approximately 30 KHz.
08 November 2009
A report recently was posted on the Elecraft reflector noting anomalous
SWR values displayed on a K3 transceiver when a
Telepostinc LP-100 vector
wattmeter sensor was installed on the K3's output connector.
In order to independently assess this report, I ran a series of tests with my
K3 and LP-100 wattmeter, with the results at SWR
04 November 2009
One bit of amateur radio lore is "a toroid inductor is self-shielding"
and hence does not have an external field to interact with other inductors
or with nearby conducting objects such as the enclosures.
Like many fables, there's some truth in this statement, but it's far from
being 100% correct. In building a prototype notch filter recently, I ran across
a case where there was not enough room to space toroid inductors to minimize
unwanted coupling and hence found shields between adjacent inductor necessary.
This lead me to make some simple measurements to demonstrate the difference
between the external fields of a toroid and solenoid inductor. I've added a new
page Toroid and Solenoid
External Field with more information.
02 November 2009
I've added an update to my Softrock page with temperature
stability data on my 7 MHz Softrock Lite I receiver. The page is available by
clicking here and the new data is near
the bottom of the page.
I've also shortened the kit construction poll questions at
the top of this page to avoid odd text wraparound. If you haven't voted yet,
please do so. If you have voted, thank you.
02 November 2009
My sheet metal supplier reports some progress, with the
Z1203A DC power coupler enclosure in production. There's a reasonable chance all
the metal work will be finished during November, but no promises as it's not
within my control.
01 November 2009
As usual, I've moved last month's entries to an archive page, reachable by
clicking here or by the archive links at the top of this page.
Late last month, I asked a question of my readers and potential customers on
their construction preferences for new kits and to respond by E-mail. I've
received five responses, three for surface mount and two for through hole. To
make responses easier, I've constructed a "push button" poll using a service
from www.blogpolls.com asking the
question. I'll leave it at the top of the updates page at least this month and