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. Read the rest of this entry »
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:
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.
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.
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):
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.
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.