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February 2010 Archive


26 February 2010

I'm making progress in reducing the backlog of Z1501D orders. Three kits and one assembled unit shipped today and I'll be busy over the weekend assembling more Z1501D active antennas and Z1203 couplers. I believe all pending orders should ship by Tuesday.


24 February 2010

I'm working on getting Z1501D orders out. So far one assembled antenna and coupler has shipped and I expect to ship five or six (mix of kits and assembled units) by Monday.


20 February 2010

The Z1501D Active Antenna is now available for purchase. Details are at the Z1501D page.

The Z1501D has been a challenging project, in that every time I thought it was ready, a way to make it better surfaced. Some I discovered on my own and in others I was assisted by test evaluators who wish to remain nameless.

The result is an active antenna with 2nd and 3rd order intermodulation performance as good as almost any other active antenna currently available, particularly considering it operates from 13.8V power. My January Updates page has a performance comparison table (it will be added to the Z1501D page in the next day or two) with the published 2nd and 3rd order performance specifications of wide selection of active antennas presently available. In addition, you may wish to read the Z1501D Intermodulation Performance paper.


11 February 2010

A recent controversy flared up on the Softrock mailing list over the bad effects of isolating audio transformers. Claims were made that transformers have too much phase shift and amplitude shift to be used with a Softrock receiver.

Among the best transformers for the purpose of breaking  ground loops, i.e., isolation, of the Softrock are Triad's SP-70 parts.

I have added phase and magnitude  comparisons of four SP-70 transformers to my Softrock Lite page. You can jump to the measurements via the navigation links at the top of the page.

I have previously provided distortion and frequency response measurements for the SP-70 at Non-Linear Transformer Behavior.

11 February 2010

I have a revised and expanded  version of the Z1501D intermodulation paper. Click the foregoing link to read.

The new version contains independent intermodulation measurements made by Dr. Dallas Lankford, a well known author and developer of active antennas, amplifiers and other things of interest to the amateur community and short wave / medium wave DX'ers.


10 February 2010

It's still snowing - after the 24 inches of three days ago, we now have a second storm. Perhaps 6 inches of new snow have arrived as of 11 AM´┐Żand it's still snowing.

I'm still working on the Z1501D active antenna documentation, and have completed the 2nd/3rd order intermodulation paper. It's available by clicking here - a 400 kB PDF file. The Z1501D is quite a decent performer in terms of 2nd and 3rd order intermodulation performance. I've tried to cover a variety of intermodulation related topics in the paper and it will be of broader interest than the Z1501D, I trust.


07 February 2010

As reported in the national news, the Washington DC area received a record snowfall over the weekend.

The photos below show the snow depth in a sheltered spot in the front yard - 24 inches or 61 cm on the metric side of the measuring stick. The official figures from Dulles International Airport, perhaps 10 miles from here, was 32.4 inches.

In addition to facing 24 inches of snow, the electricity failed on the 6th, shortly after noon. We ran on our backup generator system for 25 hours. Internet service was also lost when the electrical power was out.

I have several kit and assembled unit orders to ship, but it will be several days until I can reach the post office. I should also mention that the most recent forecast calls for up to 5 more inches of snow to arrive Tuesday, the 9th. I sure hope not, as I will still be digging out then and don't need more snow.

The bird feeder has been busy in the snowstorm. This year has seen an unusual number of cardinals. Although the Cardinal is the state bird of Virginia, we usually see one or two pairs at most. In the last couple months, I've seen as many as six pairs of cardinals hanging around the feeder. The two males below are typical.

Another look at Mr. Cardinal.


04 February 2010

The most recent set of active antenna printed circuit boards arrived and I've built a couple. No problems with the boards that I can see.

The photo below shows a completed board. Because the circuit has changed a fair bit from the "C" version, I've given this the Z1501D designation.

I would prefer to sell the first few Z1501D's as assembled and adjusted units until I'm satisfied with the 2nd order intermodulation bias adjustment procedure for kit assembly. Kit builders can return the assembled board to me for bias adjustment as well.

I should have the Z1501D web page up in the next few days with ordering and pricing information.

Performance is in line with the prototypes.


01 February 2010

As usual, the preceding month's Updates have been moved to an archive page, reachable by clicking here or via the table at the top of this page.


01 February 2010

I promised an update on the Z1501 Active Antenna. The release version will be the "D" model, i.e., Z1501D.

Based on the optimization work of a couple weeks ago, I decided one more PCB revision was necessary, the Z1501D-rev 02. Those boards arrive Tuesday, 02 February. Since the changes from the last PCB were relatively small, I am not anticipating a problem with the new boards (famous last words).

Assuming so, by the end of this week, I should have several boards built to update the ones used by beta testers and to make some changes to the Assembly and Operation Manual reflecting changes to the board from the "C" version the manual is now based upon. If all goes well, the Z1501D will be available for sale about a week to 10 days from now.

I'll add a Z1501 page towards the end of the week, with pricing, manual link, performance specifications, photographs and the like.

It seems as if the Z1501 has taken forever to complete, but I wanted to get it right. The photo below shows some of the boards I've designed and built as part of the Z1501 development. The photo is not complete as some earlier prototypes were disassembled for parts and it does not show prototypes and development antennas that are still outside pulling in signals.