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Software Updates
Softrock Lite 6.2
Adventures in Electronics and Radio
Elecraft K2 and K3 Transceivers


31 July 2006

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.


30 July 2006

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:

  • Your name and callsign (if any)
  • Location (city, state if in the US, or province if in Canada or country otherwise)
  • Which unit you wish to purchase (Z90 or Z91)
  • Any accessories you wish?
  • Kit or assembled?

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.


26 July 2009

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.


23 July 2009

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 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.


21 July 2009

Updated the N5QVF Build page with Stage 3, 4 and 5 results. Also added a new page discussing prototyping techniques including photographs of the breadboard early version of the Z90.


19 July 2006

Updated the N5QVF Build page with Stage 2 results.


18 July 2006

Dario, N5QVF has received the prototype kit and started assembly. I've added a page with his photos and comments.


17 July 2006 - Update No. 2

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.


16 July 2006

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.






15 July 2006

I've added a new page Loads, presenting recent measurements  I made on several 50 ohm terminations I purchased from Ridge Equipment.

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.









14 July 2006

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.


13 July 2006

I've added a "troubleshooting" section to the draft Assembly Instructions, and uploaded the revised document to this site. I've also prepared an accompanying 7-page version of the venerable "Sam's Photofax" annotated schematics, showing DC voltages and typical waveforms as an additional aid to troubleshooting. I've added it to this site as well.  The new Assembly Instructions PDF has higher resolution photographs, but the consequence of the improved resolution is that the file is now 5 MB. 

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.

The image above show a 12 KHz carrier, modulated 100% AM with a 1 KHz sine wave to simulate the a 12 KHz IF output. The display is 10 KHz span, 10 dB/division. The current component values result in a 25 KHz -3 dB lower corner frequency, with a corresponding significant "tilt" in the frequency response below that frequency, to the point where the upper and lower sidebands in the test signal have visibly different amplitudes.  At 12 KHz, the frequency response is about -8 dB.  (The reduced image size shown may not fully reproduce the 8x10 graticule lines. Click on either of the two images for larger views.)

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.


12 July 2006

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 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

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 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