QRP Labs 20m Bandpass Filter

Some days ago I received a parcel from my friend Silvio, DM9KS. There was a 20m QRP band-pass filter from QRP Labs inside. I then built the kit as it was there anyway. I did not wind the torroids very accurate, but I have an insertion loss of 2.1 db only on 20m and I have -53db attenuation on 40m and -32db on 15m. I would say great piece of kit! Silvio also told me, that some guys use their Raspberry Pis as a 10mW WSPR beacon. So I connected the filter to my Pi to see what happens.

Ascom SE540 BOS-Funkgerät

In diesem Beitrag geht es um den Umbau von Ascom SE540 BOS-Funkgeräten. Es war Michael, DB7MM der mich auf die Idee gebracht hat, 2m BOS Funkgeräte von Ascom so zu umzubauen, dass sich diese für den Amateurfunk einsetzen lassen. Er selbst hat das schon einige Male gemacht und gab mir daher eine „vorsichtige“ Empfehlung. Ich habe dann bei eBay ein Angebot gefunden. Ein Händler wollte inkl. Versand nur 30 Euro pro Gerät haben. Ich bestellte also gleich 2 und baute sie dieses Wochenende um. Das Ascom SE540 ist ein Behördenfunkgerät und dementsprechend massiv ausgelegt. Die Verarbeitung und Haptik ist ausgezeichnet. Man bekommt mit dem SE540 ein sehr wartungsfreundliches Gerät, das eine gute Dämpfung von Außerbandsignalen hat.

Nagoya NA-24 antenna repair

Some weeks ago I bought a new -ultra flexible- Nagoya NA-24 antenna for my Baofeng UV-82L. When I used the Nagoya antenna for the very first time I received almost nothing. I first thought that I (again) bought a counterfeit Nagoya antenna and put this one in the drawer. Just yesterday I found it again and became a bit annoyed as I wasted another 20 bucks here. I decided to open the NA-24 with a pair of two big pliers. The black cover had an internal thread and was fixed with some superglue. With some force I was able to disassemble the whole connector and could inspect all the antenna parts. I found out that the flexible radiator was not soldered on the socket of the antenna so it had no electrical connection to my Baofeng radio. I soldered the radiator to the antenna socket and put everything back together again. I tested the NA-24 antenna on the local repeater while I walked on the streets in the city. It worked flawless.

Tuning the front-end filters

Some days ago I decided to install an APRS RX-only iGate here in my apartment. The iGate simply takes the APRS signals from the air and forward them to the internet. I live almost in the center of the city and I have a free sight over the buildings. Good preconditions for a „fill-in“ iGate I thought. I had a Raspberry Pi and a cheap RTL-SDR dongle (DVB-T stick) for this purpose. Sounded like an easy job first but I received nothing within the next 12 hours. I knew that something must be wrong. In this project I learned more on designing HF-filter than on Linux and Raspbian, what actually was my aim at the beginning of this project. In this blog post I will show you, how I successfully dealt with massive QRM from two 100kw and 2 50kw radio transmitters.

FT-817 interface for digimodes

Some time ago I bought one of these small and light 2 in 1 tablets with Windows 10. The device was very small in size but the battery lasts very long. With only 1,7kg the weight was not too high for my portable ops. I did not take it into the field yet. The reason was simple: The tablet has one USB-port only. I need one port for the USB cat lead and another one for the USB-soundcard to connect my existing PC-interface made by Alan, M0AQC. After a long search on the internet I did not find a simple FT-817 interface with one USB lead, CAT-control and built-in soundcard. So what did I do? I built an interface that meets my requirements by myself.

Built FT-817 android interface

Some time ago I came across the Wolphilink Interface. It's a small box which connects an smartphone to a Yaesu FT-817/857/897 transceiver. I was about to buy one, but the interface was quite expensive, especially if you include the optional cables and the shipping to my QTH in Germany. I googled a bit and found an interface built by Christian Petersen, DD7LP. I made the decision to take a closer look on his schematic diagram and built my own interface to use APRSdroid and PSKdroid on my FT-817. Luckily Christian also provided a buying list besides the schematic diagram. As I don't have any knowledge and also no tools to etch a circuit board, I first planned to build the circuit on a simple stripboard.