Clifton Laboratories 7236 Clifton Road  Clifton VA 20124 tel: (703) 830 0368 fax: (703) 830 0711

E-mail: Jack.Smith@cliftonlaboratories.com
 

I've added a photo of my HP3568B and an interesting ARGO spectrum plot of CHU's 14670 KHz signal from Ron, K8AQC, to my Off-the-air Frequency Measurement page.

I've added a new page discussing part of what I've learned in the last week or so trying to make accurate off-the-air frequency measurements. The page is Off-the-air Frequency Measurement

I hope to update the page more over the next few days.
 

Thanks to Dave, AB9CA, for catching an error on my Non-Linear Transformer Behavior page - I had used the Triad SP-70 THD plot twice. The error is now fixed and the correct THD plot for the Bourns LM-NP-1001-B1 transformer is in place.

I've revised the Non-Linear Transformer Behavior page to add frequency response curves for the three small signal transformers with 50 and 600 ohm driving impedance.

I've also added measured data to the page showing ringing in the transformers when fed with a 1000 Hz square wave. I'm not convinced that ringing, in the context of a bandwidth limited communications receiver, is important, but it seems to be considered important in certain audio circles.

I've finished a new page on non-linear audio transformer distortion, representing about 80 hours of measurement, analysis and writing.

It's available for your  reading pleasure at Non-Linear Transformer Behavior.

Although started with the thought of understanding why the Tamura TTC-108 transformer used in Elecraft's K3 works as it does, the scope of work significantly expanded and became more general.

The Dell SX260 desktop computer in my basement shop does not have Microsoft Office installed and a couple months ago, I downloaded and install the current (version 2.4) free Open Office suite. http://www.openoffice.org/.

I've used Microsoft Word, Excel and other members of Microsoft Office since Windows 3.1 and have found them to be solid products, almost never resulting in data loss. I don't care at all for the needless changes in look and feel Microsoft made in Office 2007, but it's still a solid product.

Using Open Office has been an interesting experience. Until today, my view has been that OO is a useful alternative to Microsoft Office. Although OO has fewer features, it seemed to be in general a stable product.

As I mentioned, I've been working on a detailed study of harmonic distortion of several audio transformers and rather than write the new web page directly into the web composer I use (Microsoft Front Page), I decided to write the document in OO and then transfer it to Front Page after completion. I used OO instead of Microsoft Word as I worked at the computer in the shop, next to the test gear and with ready access to my notebooks.

This is the first long document with integrated images that I've tried with OO. I did a few OO experiments with the Z100 manual, importing the Word file into OO and seeing how it handled the text---reasonably well, as a matter of fact. My transformer composition went moderately well with OO yesterday. Today, I decided to work from a different PC, installed OO on it, and loaded my draft web page text and imbedded graphics. At this point, the draft was about 25 pages, with perhaps 50 graphics. After a couple of hours more work, OO lost all the embedded images in the first half of the document. Closing and reopening the file didn't restore the missing images, and re-launching OO didn't either.

It's not a total disaster, as it shouldn't take more than a couple hours  to restore the missing images, but it is irksome. Needless to say, I've exported the document to Word and will finish the task in Word. I no longer trust OO for long documents, or work that I can't afford to have mangled.

I'll mention another serious shortcoming of OO for the type of writing I do. Word comes with a reasonably serviceable equation editing program add-in, Microsoft Equation 3.0 is the version in Word 2003. OO comes with a program SMath  that is said to perform a similar function to Equation 3.0. However, SMath is a pale shadow of Equation 3.0 and is essentially useless for my purposes. It's possible that my unfamiliarity with SMath is causing me to unfairly rate it as unusable, but I've not found a way to prepare a simple equation.

For example:

Microsoft Equation version:

I have been working on a detailed study of several audio transformers including the TTC-108 used in Elecraft's K3 transceiver. This has turned out to be a larger effort than I thought. I've finished almost all the data collection and have written 14 pages of the report, and have at least as much more to do. When finished, the work will appear as a new page.

The oscilloscope image at the right shows the B-H curve for one transformer I studied.

I received the new run of Z10000 buffer amplifier printed circuit boards today. All pending orders will ship tomorrow, and future orders will be back to my normal schedule, generally next day shipping.

I've added frequency response data for the TTC-108 transformer at my Elecraft K3 Receive Audio page.

I've also added a section to the Elecraft K3 Receive Audio page showing a single tone in SSB mode, spaced so that harmonics will fall within the DSP passband.

I've completed a study of why the Elecraft K3's LIN OUT audio exhibits significantly inferior performance in terms of harmonic content and intermodulation, compared with the K3's headphone or speaker output.

My conclusion, verified with detailed measurements, is that the choice of 604 ohm series resistors between the LIN OUT amplifier and the TTC-108 isolation amplifiers is the single largest reason for the distortion.

I've provided extensive details and a theoretical parts change fix at Elecraft K3 Receive Audio. However, I have not made this change in my K3 and anyone implementing it does so at their own risk.

At the suggestion of Geoff, GM4ESD, I've added measurements of two headphones taken in stereo mode, i.e., one transducer, not both in parallel, in free space (headphone cups aimed outward) and on a simulated head (two thick paper catalogs). I've added the data at the Headphone Impedance page.

I've added a new page Headphone Impedance with measured impedance data over the range 20 Hz - 6000 Hz for several headphones and loudspeakers.
 

I've added LIN OUT plots for LIN OUT gain settings of 2 and 5 to the Elecraft K3 Receive Audio page. I also added (at 4 PM EDT) two spectrum analyzer plots showing how the LIN OUT picks up much different 60 Hz hum levels depending on the K3's orientation.

I've made additional measurements of audio distortion in my K3, with single and dual tones within the SSB passband. The new data is at the end of my Elecraft K3 Receive Audio page.

As is my practice, I've moved the August 2008 updates to an archive page, readable by clicking here or via the links at the top of this page.