23 April 2009
I've revised the
non-linear transformer page to
add three inexpensive Stancor transformers and the very high performance (and
likewise very expensive) Jensen transformer. Click on the link in the above
sentence to view the page.
22 April 2009
I've been remiss in not updating this page recently, but
I've been trying to get two new projects closer to completion.
By the end of the week, I should receive prototype/final
printed circuit boards for the Norton amplifier and a high performance,
expandable 4/8 output receiver multicoupler.
I've said prototype/final because I've been through
several iterations on these boards already and I've gone ahead and ordered a
small quantity of production quality boards, with solder mask and silk
screening. Absent some blunder on my part, these boards should be ready to make
into kits in the next few weeks. The major pacing item on the multi-coupler is
the sheet metal, which has a several week lead time and I can't complete the
layout drawings until I have the boards in hand and verify dimensions and
I've also received four audio transformers to analyze and
have completed performance measurements and started adding the new material to
my non-linear transformer page. I hope to wrap it up in next couple days. One
transformer I looked at in a Jensen DIN-2LI, and it's an amazingly good
performer, with THD below the ability of my HP 8903B audio analyzer to measure
over most of its frequency range. The individual transformers packaged
into the DIN-2LI run around $80-90 each so it's not suitable for every
application, but it's the best transformer I've measured. For a more
budget-acceptable combination of price and distortion, I have a couple of
recommendations on the non-linear transformer page.
14 April 2009
I recently acquired a couple of Kepco BOP bipolar power
supply / amplifiers and used them today to measure the forward drop of a 1N4007
silicon diode and a SR2010 Schottky diode at current levels up to 5 amperes
using a 300 μs pulse. This technique obviates the junction heating Vf reduction
found in my DC measurements. I've added the new data at the end of the
1N400x Diode Family Forward
13 April 2009
I've added a SPICE simulation plot to the RC snubber
discussion at Diode Turn-On Time.
11 April 2009
I've expanded the relay snubber discussion at
Diode Turn-On Time to include RC snubber
networks, designed using the Zobel network technique. It works well, but
requires a non-polarized capacitor.
08 April 2009
The myth that a 1N4007 power diode isn't fast enough to
work as a snubber and clamp the inductive kick from a relay has surfaced again.
I made an extensive series of diode turn on time measurements in December 2007
showing that the difference in turn-on time between a 1N4148 signal diode and a
1N4007 power diode is small at best. (Note that I said turn-on time, not
To address this myth in even more detail, I've revised the
diode turn on measurement page to include measurements of the inductive "kick"
of a typical relay when controlled by a 2N7000 MOSFET transistor with three
- No diode snubber
- 1N4148 snubber
- 1N4007 snubber
These tests confirm what the turn-on time measurements
showed; the 1N4007 works just as well as the 1N4148 as a relay snubber. And, the
1N4007 will handle much more current than the 1N4148, which may be a
consideration in some instances. The page also looks at how much the relay's
release time is lengthened by adding a snubbing diode.
For all the details, see
06 April 2009
I've revised the
DC Transformer Saturation page to show the effect of DC in the winding upon
intermodulation products for a Coilcraft PWB1010-L wideband RF transformer.
05 April 2009
At the request of G3TJP for a shorter Z10000 manual, I've
prepared an alternative version. It concentrates on using the Z10000 as an
adjunct to Elecraft's K3 transceiver IF output port. You may view the
alternative manual by clicking
here, or via links on the Documents page or the
I've also added a new option for Z10000 amplifiers—a die
cast enclosure. Details at the Z10000 page.
03 April 2009
I have a limited number of
Z100 kits remaining in inventory and ask that anyone planning on ordering
one contact me before sending money.
I've added a corresponding note on the Z100 page.
01 April 2009
As normal for the first of the month, I've moved the March
2009 updates to the archive, viewable by clicking here
or via the link table at the top of this page.
01 April 2009
I put together an active antenna kit with the "Revision B"
printed circuit board for a test builder over the weekend and the kit is now in
the hands of the builder.
I have parts for one more Rev. B prototype active antenna
and, depending on the results reported by the first prototype builder, I may ask
for a second volunteer builder. The next step will be to make a few changes in
the printed circuit board layout for Rev. C, which should be the
production version. I also have a very small change or two to the power coupler
as well. Assuming all goes well, the active antenna should be ready to go around
the end of April.
I've also worked on the
amplifier design this week. I plan to shrink the PCB to fit into the same
weatherproof enclosure used with the Active Antenna as a standardization
measure. The Norton amplifier needs one more test PCB as a safety measure before
ordering production boards, and I plan to finish the layout and order
another prototype round before the end of next week.
As I've said before, the Norton amplifier is quite a
remarkable device. I re-measured the one prototype I built late last year on the
first PCB and found IP3 above +40 dBm and IP2 above +80 dBm.
The Norton amplifier will be available as a kit or
assembled amplifier, with an optional enclosure, either a die-cast indoor
enclosure or a die-cast weatherproof enclosure. The amplifier will be provided
with an option for external DC power feed or duplexed DC feed over the coaxial
cable. This is particularly useful for outdoor use.