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31 August 2010
I've made some changes to the
Z10046A manual to reflect comments
of the first independent build. The manual now includes an optional extended low
frequency range extension version of T1 and T2.
The custom enclosures for the Z10046A and Z10042A
amplifiers are schedule to ship to me today and should be available for sale
early next week.
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29 August 2010
The second new kit is now officially available. It's a
surface mount Norton amplifier, the Z10042A. The Z10042A is not a replacement
for the Z10040B, as some builders will prefer to work with through-hole
components and I plan to make the Z10040B available as long as I can obtain
through hole parts.
I've added at web
page for the Z10042A, and kits are in stock, ready to ship. The Z10042A
manual (in near final draft form) can be read by clicking
here.
The main advantages of the Z10042A over the Z10040B are:
- Lower noise figure, made possible by improved surface
mount transistors. If noise figure is the sole objective, by sacrificing
OIP2/OIP3 performance to some degree, the noise figure can be reduced to
1.25 dB or so.
- Better low frequency response, without the 15 KHz
notch in the Z10040B's response.
- Low power option, with total Z10042A current
consumption 25 mA. This optional configuration is suitable for battery
power. OIP2 and OIP3 are reduced when operated in low current configuration.
- Smaller PCB size, 3.5 inches x 2.5 inches.
- Custom powder coated, punched enclosure available in
the near future.
Pricing is identical with the Z10040B for PCB kit and
assembled PCB. Prices on the custom enclosure are not yet available.
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28 August 2010
I've updated the Z10046A
manual to add additional
performance data and clarify a few instructions.
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28 August 2010
I've mentioned my fondness for wooden spring clothespins
as a handy tool for holding parts in place during soldering as illustrated
below. It takes but a few moments with a sharp knife to trim the end of the
clothespin to a more suitable blunt triangular point.
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However, there are places where the spring clothespin won't open enough to fit
the part, or the part is too far from the board edge. I recently ran across a
good solution for those jobs where a spring clothespin won't work. It's a Bessey
CLIPPIX Needle Nose Spring Clamp with a 2 inch (51mm) long jaw.
The spring force is strong enough to hold parts in place, but
not so strong as to damage typical components. The main drawback of the CLIPPIX
is that it is made from a polymer plastic and can be damaged if it comes in
contact with the soldering iron.
The CLIPPIX is an inexpensive tool; I paid about $6 for a
package of two clamps. The CLIPPIX is available in several sizes; the 2 inch
needle nose is the one I bought.
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27 August 2010
Although it seems as if it has taken forever, I now have a
new kit/assembled preamplifier available, the Z10046A. For details on the
Z10046A, click here.
The Z10046A is not a replacement for the Z10040B Norton
amplifier, but rather is aimed at applications requiring more gain (23.5 dB with
the Z10046A) while retaining good intermodulation performance. (2nd order
intercept > +90 dBm; 3rd order intercept > +42 dBm to +45 dBm depending upon
bias current setting) and reasonable noise figure (2.7 dB up to 30 MHz.)
The Z10046A has a new PCB size (3.5 inches x 2.5 inches)
that I hope to use as a standard for several new kits. This standardization has
allowed me to have a custom (powder coated, punched with threaded standoff
inserts) enclosure manufactured for the Z10046A and other kits. I've been
promised enclosure delivery by the end of the next week.
I have another amplifier kit awaiting time to finish
writing the assembly and operating manual.
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10 August 2010
I recently tried an experiment with my Z1501D active
antenna to determine how much signal pickup occurred in the coaxial cable.
The Z1501D is located about 125 feet from the house and is fed with RG-6
quad-shielded CATV type cable. There's a common mode choke near the active
antenna and the feed line is buried a few inches into the Northern Virginia
red clay.
With the DC power removed from the feed line, it has
some similarities with the 'snake' antenna, which is a length of coaxial
cable laying on the ground, short circuited at the far end. A snake antenna
works by coupling the signal induced on the cable shield's outer surface to
the center conductor via the remote end short. In my case, the center
conductor is not shorted to the shield and, moreover, the common mode choke
further reduces any leakage that might occur between the shield and center
conductor inside the active antenna amplifier. So, this configuration is not
the classic snake antenna arrangement.
Simply connecting the unpowered cable to the spectrum
analyzer showed only a few indications of signals, all in the AM broadcast
band. So, I connected a preamplifier between the unpowered cable and the
spectrum analyzer. The preamplifier consisted of an experimental Norton
Amplifier (11 dB gain) followed by the Z10046A amplifier I mentioned in the
04 August 2010 post, for a composite gain of 35 dB and a composite noise
figure around 2.5 dB.
With the preamplifier connected, I first looked at one
of the Washington DC area AM stations, WMAL at 630 KHz. The spectrum
analyzer plot below shows that the Z1501D in normal powered operation
(magenta plot) yields about 3 dB more signal than can be obtained with 35 dB
of preamplification applied to the unpowered coaxial cable.
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