Many years ago, I used to do some radio fox hunting with cars. Usually these hunts are at night to make it more exciting, and can be great fun. As I got older I lost interest and moved on to other things. But last year, I decided to have a go at a popular balloon fox hunt on 144MHz. This is quite a large scale and professionally organized fox hunt by Dutch Radio Amateurs.
Measuring Coax Length and Loss
Ever wondered how well your 50Ω coaxial cable is working? If you have a reasonably fast oscilloscope, preferably up to 100MHz and a signal generator which can generate short bursts, you can measure not only the length of your cable, but also the return loss at a certain frequency. From that, we can learn the attenuation of the cable.
This blog post describes the classic time domain reflection measurement using the following setup:
How to get your users to install JCE
In every Java project where I need to do strong cryptography, I run into these dreaded unreadable stacktraces which send you into the woods. After a long search I usually discover that the Unlimited Strength Java Cryptography Extensions are not installed. To prevent frustration of users of your software, you can simply add a bit of informative logging to help him/her solve it when the solution is known.
Ashley Madison in perspective
However I disagree with sites like Ashley Madison and the way its owners scam people, last week I have noticed something far more disturbing. As I understand, Ashley Madison was charging people for their profiles to be deleted, and then did not (promptly) delete them. I guess some of it’s “hackers” got caught up in this and decided to attack Ashley Madison for that. Up to this point, merely a quarrel between two parties which may have better been solved by legal procedure.
Solving the JAXB “unexpected element” problem
If you are using JAXB in a maven/java project to unmarshal an XML document and you get:
javax.xml.bind.UnmarshalException: unexpected element (uri:”urn:iso:std:somestuff:xsd:somestuff”, local:”Document”). Expected elements are (none)
Or if you are using JAXB to marshal an XML document and you get:
com.sun.istack.internal.SAXException2: unable to marshal type “generated.somestuff.Document” as an element because it is missing an @XmlRootElement annotation
You have probably fallen victim of the fact that JAXB does not do “Simple Binding” by default. If your project is a maven project and you generated classes based on an xsd file, this is how you fix it (without changing the xsd file):
Better modulation for the Baofeng UV-5RA
Undoubtedly the Baofeng UV-5Rx delivers a lot of radio for your buck. However some models in the range have a bad reputation for the transmitted audio sounding soft and muffled.
In 2013, Remco PA3FYM obtained the schematics of the radio and devised a modification where transistor Q17 of the VOX is re-purposed as preamplifier in the microphone audio circuit. It works wonders for your radio. For people needing a bit more visual guidance, below is a walktrough of how I did this to my Baofeng UV-5RA.
Import/export an Oracle Schema using JDBC
When doing integration testing or fixing a bug in a piece of Java code that uses Oracle as a database, being able to do quick exports and imports of your schema can be a big help. Sometimes just calling Oracle’s imp/exp commandline tools from your code can be of help, but I was looking for something a bit more portable and less demanding on my local development machine. I found that Oracle’s datapump functionality can be called from stored procedures, which in turn can be called from a normal JDBC statement.
Arduino and the QVGA 2.2″ TFT SPI screen
I went through all the struggles everybody else seems to be going through to get this screen connected to my Arduino Nano. I had the 5V to 3.3V voltage conversion problem, and the “only works with software interrupts” problem which makes the display run slow. The solutions are not complicated but not very wel documented. Until now.
IARU Region 1 Bandplan up to 500MHz
For some reason I have trouble finding a document which lists the complete IARU Region 1 Band Plans. To end my “can I transmit here” quests, I’ve combined the information from several resources into a usable graphical representation of all Amateur Radio bands and modes up to 500MHz. I’ve not listed bands above 500MHz, please post links to those in the comments if you have them.
Exact use of a frequency may differ in your local region, so always listen first.
Hand me a napkin
It’s not until you or someone very close to you becomes dependant on a wheelchair until you notice that the world is not as wheelchair friendly as you might think. Hotel rooms are wheelchair accessable, but the lobby can only be reached by stairs. People with kids can take strollers all the way up to the airplane seat, but people in wheelchairs need to magically heal themselves and leave the wheelchair at the gate.
But this is not a rant about inconsiderate travel company employees. This is about helping people with “a challenge”, as our funny American neighbours tend to call it. And no, this is also not a rant about helping in a big way, raising a million for a cause, getting all the local supermarkets to give away groceries to people in wheelchairs, or TV shows selling tear-jerking advertisement minutes while building a house for a familiy who really needs it.
No, this is about the little things. Things that make you and me different. Things that require only a little twitch of a muscle for healthy people. Quirky things like aligning the napkin to the edge of the table, or petting a cat, or getting a different color straw because it doesn’t match the color of your shirt.
Imagine you had to ask somebody to align your napkin to the edge of the table. That person would find you demanding, and because he doesn’t see what’s solved by doing that, it’s very likely that the napkin will never move. Soon, you will stop asking people to do the little things that used to make you who you were.
It’s a tough choice. Loose friends because they think you’re too much of a demanding prinsess, or loose friends because you stop being you.
When you see or know somebody in a wheelchair, remember that their mind still wants to do those quirky things that make them who they are. It’s okay to say no, but please consider this little blogpost when somebody asks you to straighten their bracelet or clean their glasses.
The world does not need one-time big-mouthed Facebook-selfie heroes. The world needs polite people who can discretely hand over a napkin without asking what’s it for.