Measuring Coax Length and Loss

Sunday 2015-11-01

100-1015 BNC T ConnectorEver 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:

Measuring TDR
Read the rest of this entry »

How to get your users to install JCE

Friday 2015-09-04

220px-Lorenz-SZ42-2In 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.

Read the rest of this entry »

Ashley Madison in perspective

Monday 2015-08-24

lady justiceHowever 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.

Read the rest of this entry »

Solving the JAXB “unexpected element” problem

Monday 2015-06-08

-1If 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):

Read the rest of this entry »

Better modulation for the Baofeng UV-5RA

Sunday 2015-05-10

baofeng-uv-5ra-plusUndoubtedly 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.

Read the rest of this entry »

Import/export an Oracle Schema using JDBC

Friday 2015-01-02

Everybody gets a database!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.

Read the rest of this entry »

Arduino and the QVGA 2.2″ TFT SPI screen

Monday 2014-11-17

QVGA SPI 2.2" 320x240 screenI 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.

Read the rest of this entry »


Get every new post delivered to your Inbox.

Join 33 other followers