I received an E-mail from the ARRL acknowledging receipt of my QEX manuscripts. They are being reviewed by the QEX technical staff for a decision on whether they will be published or not. Larry, N8LP, told me that his LP100 wattmeter article ran 18 months from submission to QEX publication, but he was notified it was accepted for publication within about 6 weeks of submission.

I've had questions about the Z90/91's compatibility with receivers with a first IF in the 70 MHz range, such as Icom's R70 & R71 (70.4515 MHz), and Yeasu's FT-1000D (73.62 MHz). Above 8 MHz, the panadapter's local oscillator operates below the receive frequency, so for these IF frequencies, the DDS local oscillator will be centered around 62.4515 MHz (Icom) or 65.62 MHz (FT-1000D), which is above the anti-alias low pass filter's 60 MHz cutoff frequency. Although the local oscillator's drive to the mixer is reduced, the net effect of panadapter performance is minimal. and I measured only a 2 dB drop in sensitivity with a 73.62 MHz IF input frequency, and essentially no reduction at 70.4515 MHz. I see no problem, therefore, using the panadapter with the R70 & R71 receivers or the FT-1000D transceiver. I've modified  the specifications accordingly. 

11 July 2006

I've completely re-worked the web site in Microsoft FrontPage, with an easier-to-read format. The effort reminds me why I will never be a successful graphics designer. I've tested the site with Internet Explorer v. 6.0, Firefox 1.5.0.4 and Netscape 7.02. Firefox is my normal browser, and  my site work of the last few days shows some subtle (and some not so subtle) differences in their respective rendering engines. Drop me an E-mail if you find anything strange or broken at the site.

I highly recommend Firefox, available as a free download at http://www.mozilla.com/firefox/.

10 July 2006

I’ve received and built one last prototype board. The board layout is stable and ready for production in the solder-masked and silk-screen version. The completed board, with the new design DDS Daughter board is shown here.

I’ve uploaded the crystal motional parameters notes (PDF format) to the web site. This is not a polished, ready-for-publishing article, but is more of a summary of my workshop notes, with photos and plots.

I’ve also uploaded several Z90 documents (all in PDF format):

· Quick Operating Instructions (the name is misleading; this is the Z90 draft User’s Manual)

· Schematic

· Assembly Instructions

These three documents are based upon the prototype boards. They are “works in progress” and I will review them for consistency and update to reflect changes before the first real kits are released.

I’ve found a volunteer to assemble and evaluate the second prototype board and hope to get it out by mid-July. I have all the parts on hand, except for a cabinet.

Also added are many sample spectrum display images of various modulation types from the Z91, running under Z90 Display software, shown at Samples.

25 June 2006

Update No. 1 

The following E-mail update went out on 25 June 2006 to those on the mailing list:

This message is sent to all those who have asked to be updated and reports my progress on the Z90/Z91 panadapter and asks you for some information.


1. I've finished two articles on the Z90 and will submit them to the ARRL for consideration to be published in QEX. Here's how I described them in the cover letter:

• The main article, The Z90 and Z91 Digital Panadapters, describes two micro-controller based panadapters that I’ve recently constructed—one with a liquid crystal graphic display and the other intended for computer control via a Windows display program that can also be used with the graphical display unit.

• The second article, Designing the Z90’s Gaussian Crystal Filter, is an in-depth examination of one part of the Z90’s design, the crystal filter. It covers measuring motional parameters as well as the filter’s design, matching and testing.

2. I've also written the first draft of a comparison of a variety of methodologies to measure the motional parameters of crystals. This is not a polished article, suitable for publication, but more of a collection of notes and formulas. Its title is Crystal Motional Parameters.

I have put together PDF copies of both draft articles and the crystal parameters notes. I'll send copies to anyone wishing them. The length ranges from 500 KB to 1MB.

Because these are submitted for publication, please do not further circulate copies without my consent.

I will likely put the Crystal Motional Parameters article on www.cliftonlaboratories.com later this week, but not the two articles that I've submitted for publication.

3. I've finished what I hope will be the final PCB revision. It's relatively minor, but, of course, those are famous last words. My plan is to order two "prototype" boards, i.e., double sided, plated, but no solder mask and no silk screen.

I will assemble one board, but I would like a volunteer to assemble the second board as a check of whether my instructions are clear and whether there are any pitfalls that I'm not aware of. To keep things simple, it will not include an LCD, so it will be a Z91 software-only version. I will make the cabinet panel cutouts in my basement shop, and the panels are unlikely to be labeled.

To obtain the maximum exposure to test operation, I would like the volunteer to try the unit out for a week or two, and then ship it to another user for evaluation. Ultimately, I would like four or five users to try it out and provide feedback.

I'll provide the board and parts without charge.

So, anyone interested in participating should drop me an E-mail and let me know whether you would like to be the assembler, or an evaluator. It would help if you would let me know the rig(s) you intend to use and whether it has an IF output.

I also have one Z90, with LCD screen that's currently being evaluated by Greg, W8WWV. When he is finished with it, I will consider sending it to a couple of evaluators as well. Let me know if you are interested. This is the prototype that I exhibited at Dayton and will not reflect the last PCB revisions, but the performance should be substantially the same as the new prototype.

4. I've also designed and had test boards built for a buffer amplifier that will provide modest gain, but an input impedance of > 1K ohm, and can provide one if needed for the evaluation. The buffer amplifier uses an AD8007 and is briefly described in the first article.

5. I would appreciate feedback on the rig(s) you would use the panadapter with, the IF frequency and whether the rig has an IF output port or whether you will need to add it and whether the IF buffer board would be of use in any modifications. It would also greatly help me to know if you prefer a Z90 with the LCD display, or a Z91 for computer use only.

6. I hope to have a price figure in the next week or so. The electronic parts are straightforward to compute, but the cabinet and other mechanical parts are highly dependent on volume. For example, the front panel of the Z90 has 8 countersunk screws that hold the soft key board and the LCD to the front panel. I can have an Lexan appliqué printed to cover the front screws and provide a more professional appearance than silk screening, but the cost is highly volume dependent.

Based on the level of interest, I am contemplating an initial build of about 50 units, but the exact mix of Z90/Z91 units is unclear.

Assuming the prototype build and evaluation circulation goes well, I foresee the initial build occurring in September or October.



73 de Jack K8ZOA