I've added a new page "User Views," documenting comments of users working with the prototype units, from an on-the-air prospective. (The N5QVF Build page covers construction of a prototype Z91.) I've posted some photographs and written comments from Greg, W8WWV, concerning his experience with the prototype Z90 I showed at the Dayton Hamvention. Greg also used an early version of the buffer adapter board with success.
I've added pricing and ordering information to the Pricing and Ordering page. If you are seriously interested in a Z90 or Z91, please read the page and let me have the following information, not later than Friday, 18 August 2006:
I'm not asking for a deposit or "earnest money," so please don't tell me you will purchase a kit if you don't intend to follow through, as I will be writing checks for over $10,000 to purchase parts over the next couple months. I'll do this based upon your word, but please don't abuse my trust in my fellow hams.
If you miss the cut-off date, there may be an extra unit or two available, but don't count on it. Delivery looks to be in late October, as the enclosure parts are long lead time items.
I've also updated the K2 Interface page, based upon Stan Rife's most recent work. If you have a K2, take a look at how the buffer amplifier will be attached.
I've also tinkered a bit with a waterfall display for the Z90-Control program. The waterfall display is far from being completed, but the concept seems to work well. The horizontal span represents about 15 minutes with the signal strength indicated on a white to black scale. The sample image shows 200 KHz of the 7.4 MHz shortwave broadcast band, with a very strong signal about 50 KHz below center. The "fuzz" on the signals represent modulation sidebands. Vertical lines from top to bottom are static crashes.
Dario connected the Z91 assembly prototype to his Elecraft K2 transceiver yesterday, with good results. I've posted a couple of screen images at the N5QVF Build page. As a temporary measure, Dario connected to Q22, the K2's 2N5109 post-mixer amplifier, with a series 330 ohm resistor. That adds about 17 dB excess loss to the panadapter. I should have a lossless high impedance buffer amplifier designed to fit into the K2 out for testing in the next two weeks. If your K2 has extra holes on the rear panel for BNC connectors, one version of the buffer amplifier will mount on a BNC connector. If your K2 is "full up" it may be necessary to drill a small hole on the rear panel for an RCA-type connector. The amplifier PCB will mount on a standoff to an existing chassis point. As I work through the details, I'll add details to the new K2 Interface page.
I've added a new page discussing the K2 Interface board. The buffer board can be used with other receivers, of course.
I've also received the enclosure quotations today and hope to have Z90 and Z91 pricing prepared by the first of next week. I'll post the pricing as well as send an E-mail notice to the mailing list. I've added a Pricing and Ordering page, but it's blank at the moment.
If you've been following Dario's build at N5QVF Build, you may recall that his DDS Daughter board did not work after assembly. I've received the board and found that the 30 MHz clock oscillator (a surface mount Citizen unit) had failed. It's now replaced and Dario's DDS Daughter board is on its way back to him.
Updated the N5QVF Build page with Stage 6 and 7. Dario, N5QVF, has completed building a prototype kit. All that remains for checkout is for him to receive the replacement Gali-74 amplifier chip and the working DDS Daughter module. The Post Office says Dario should receive my parts package Monday, the 24th, as "Express Mail" to his QTH is two days from Northern Virginia, not "next day" as I originally thought.
I've also updated the Assembly Instructions to reflect all the comments I've received from Dario in the course of his test build.
Swordfish, the programming language I used for the Z90 micrcontroller firmware (also used by N8LP for his LP100 vector wattmeter), is now officially in "beta status" with a scheduled November 2006 release date. I highly recommend Swordfish for programming 18F-series PICs. For 16F-series PICs, MBasic remains my language of choice.
Speaking of N8LP's LP100 vector wattmeter, I read the August 2006 CQ Magazine yesterday and found a photo of the LP100 and a paragraph of text concerning it in the article Hot Stuff at Hamvention (& Ham-Com). It's at Page 25, and Larry tells me that he will have a copy posted at http://www.Telepostinc.com in the next day or two.
I've added measurement data to my Loads page for my venerable Heathkit HN-31 Cantenna and for a 500 watt Bird-style termination. Surprisingly, the HN-31 is a decent performing load up to 300 MHz, although with a strange jump in return loss around 200 MHz.
I've also added photos and discussion of the newest test fixture to my Prototyping page. The page also has photographs of the first panadapter I built, all analog circuitry with a rectangular CRT.
Most recently -- Dario called to say that the Post Office delivered the parts today (Sunday) which I certainly didn't expect. He installed the Gali-74 chip, plugged in the substitute DDS Daughter card and his Z91 is working. He found a small software bug (the purpose of testing, of course) that I was able to fix. The image capture he sent me is posted at the N5QVF Build page.
Updated the N5QVF Build page with Stage 2 results.
Dario, N5QVF has received the prototype kit and started assembly. I've added a page with his photos and comments.
I E-mailed Update No. 2 to those on the mailing list yesterday evening. Because its topics are covered on this Updates page, I won't repeat the message here. If you wish to receive a copy of Update No. 2, drop me an E-mail message and I'll sent it to you.
I've added a new page, IMD Measurements, showing intermodulation measurements I made with the Z91 on my Kenwood TS-940 and TS-870 transceivers. It was quite the eye-opener, as something strange seems to be happening with my TS-870. I seldom operate SSB (I'm mostly a digital mode guy) so I have not had off-the-air reports of bad audio with my TS-870.
The image at the right is my TS-940, operating at 100 watts output PEP, USB mode, with two tone modulation at 600 Hz and 2100 Hz.
I've also tinkered a bit with the Z90 Display program to add an on-window display of the current operational parameters. The status line is also copied with the COPY function and printed and saved.
I've added a new document, Updating the Z90 Firmware, describing the MicroLoader and procedure for flashing new firmware into the Z90's PIC18F4620 microcontroller.
I've also completed assembling the parts for a prototype kit build and will ship the parts off tomorrow morning. I hope to post some feedback on the prototype build in the next 10 days or so.
I've also been promised quotations on the cabinet punching and silk screening next week which will let me put a definitive price on the Z90 and Z91. The mechanical parts associated with this project will almost certainly be more expensive than the electronic components, particularly as the relatively small production run will be burdened with setup costs associated with programming the CNC punch press and preparing the silk screens.
I've had questions about using a Z90/Z91 with a receiver with a rather low IF output frequency, 12 KHz. such as TenTec's RX320D. (12 KHz is the preferred IF frequency for add-on Digital Radio Mondiale decoders.) The answer is yes, the Z90 and Z91 will work with a 12 KHz IF input, but four components must be changed as reflected in the schematic fragment.
Making the recommended component changes should reduce the -3 dB low frequency point to approximately 2 KHz and permit flat frequency response for a 12 KHz IF, 20 KHz span. I have not tested these component values, but the changes are quite straightforward. However, there may be some loss of sensitivity at higher input frequencies as these larger value capacitors will exhibit increased internal inductance compared with the standard component values. Hence, I recommend these changes be made only if the user has a specific need to operate with an IF input frequency below 50 KHz.
It goes without saying, of course, that with a 12 KHz IF, the maximum span should be limited to 24 KHz. Both a 12 KHz IF and 24 KHz span can be easily be added to the Z90's firmware as user-defined "custom" IFs and spans.
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.
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 184.108.40.206 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/.
Update No. 1
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.