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August 2010 Archive

 

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.

 

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.

 

 
 
28 August 2010

I've updated the Z10046A manual to add additional performance data and clarify a few instructions.

 

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.

 


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.
 

 
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.

 

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.