QRP Labs QRSS/WSPR Kit (Part 5 – mitigation)

Continued from Part 4

I looked at the design of the transmitter again, thinking about where all the VHF energy could be coming from. The transmit signal is generated by the Si5351A synthesizer module, and then goes directly to the FET Power Amplifier (PA). Low pass filters for each band are then switched into the output to remove harmonics.

The synthesizer generates a square wave, which by its nature contains all the odd-integer harmonics of the fundamental frequency. This is the source of the VHF.

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QRP Labs QRSS/WSPR Kit (Part 4 – chasing the problem)

Continued from Part 3

I replaced the 25mm standoffs between the main and filter boards with aluminum ones, and retested.

Things got better . . . and worse.

It was now passing on half the bands but still failing on 10m due to VHF emissions, and on 40 and 80m due to second harmonic emissions. The 10m VHF emissions were worse than with the nylon spacers!

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QRP Labs QRSS/WSPR Kit (Part 3 – Testing)

Continued from Part Two.

When I put the kit on the test bench, I found that it didn’t meet FCC Part 97 requirements on any of the six bands: 10, 15, 20, 30, 40, or 80 meters.

Part 97.307 requires that “. . . the mean power of any spurious emission from a station transmitter or external RF power amplifier transmitting on a frequency below 30 MHz must be at least 43 dB below the mean power of the fundamental emission.”

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QRP Labs QRSS/WSPR Kit (Part 2 – the User Interface)

Continued from Part 1

The user interface for the unit is a two-line LCD display, and two pushbuttons. The LCD is a good looking White on Blue backlit display. There are construction options to set autodimming of the backlight, and I may go back and set that up. As I built it, the display never dims.

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QRP Labs QRSS/WSPR Kit (Part 1 – the Build)

I recently built and tested the QRP Labs “Ultimate3S” kit, and I wanted to share the experience, including an issue I had.

At $USD 135 the Deluxe 6-band U3S set looked like a fun if slightly challenging kit to build, and I’ve been wanting to get a WSPR transmitter on the air, because it’s a kick to see what sort of propagation you can get with very low power (less than a watt). The price includes the case, parts for 6 HF bands, and a GPS receiver, so it’s a lot for the buck.

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Ubuntu File System Benchmarking

UPDATE: The URLs below are dead. I no longer work at Canonical, and don’t know if file system benchmarking is still part of their kernel testing process.



I’ve been working to implement file system benchmarking as part of the test process that the kernel team applies to every kernel update. These are intended to help us spot performance issues. The following announcement I just sent to the Ubuntu kernel mailing list covers the specifics:

[EDIT] Fixed tags to enable the copied email text to flow.


The Ubuntu kernel team has implemented the first of what we hope will be
a growing set of benchmarks which are run against Ubuntu kernel
releases. The first two benchmarks to be included are iozone file system
tests, with and without fsync enabled. These are being run as part of
the testing applied to all kernel releases.

== Disclaimers ==


1. These benchmarks are not intended to indicate any performance metrics
in any real world or end user situations. They are intended to expose
possible performance differences between releases, and not to reflect
any particular use case.

2. Fixes for file system bugs reduce performance in some cases.
Performance decreases between releases may be a side effect of fixing
bugs, and not a bug in themselves.

3. While assessments of performance are valuable, they are not the only
criteria that should be used to select a file system. In addition to
benchmarks, file systems must be tested for a variety of use cases and
verified for correctness under a variety of conditions.

== General Information ==

1. The top level benchmarking results page is located here:
This page is linked from the top level index at kernel.ubuntu.com

2. The tests are run on the same bare-metal hardware for each release,
on spinning magnetic media.

3. Test partitions are sized at twice system memory size to prevent the
entire test data set from being cached.

4. File systems tested are ext2, ext3, ext4, xfs, and btrfs

5. For each release, each test is run on each file system five times,
and then the results are averaged.

== Types of results ==

There are three types of results. To find performance regressions, we
(the Ubuntu kernel team) are primarily interested in the second and
third types.

1. The Iozone test generates charts of the data for each individual file
system type. To navigate to these, select the links under the “Ran” or
“Passed” columns in the list of results for each benchmark, then select
the test name (“iozone”, for example) from that page. The graphs for
each run for each file system type will be available from that page in
the “Graphs” column.

The second and third result sets are generated by the
iozone-results-comparator tool, located here:


2. Charts comparing performance among all tested file systems for each
individual release. To navigate to these, select the links under the
“Ran” or “Passed” columns in the list of results, then select the
“charts” link at the top of that page.

3. Charts comparing different releases to each other. These comparisons
are generated for each file system type, and are linked at the bottom of
the index page for each benchmark. These comparisons include:

3A. Comparison between the latest kernel for each Ubuntu series (i.e.
raring, saucy, etc).

3B. Comparison between the latest kernel for each LTS release.

3C. comparison of successive versions within each series.

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