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SDR - Software Defined Radio

Spurtikus
SDR - Software Defined Radio Vor einigen Jahren hatte ich einen USB-Stick erworben, der Software Defined Radio (SDR) ermöglicht. (click to view larger version) Dieser Stick mit dem schönen Namen Nooelec NESDR SMArt v4 ist ein winziges technisches Wunderwerk. Er erlaubt den Empfang von Radio-/Funksignalen im Bereich 25-1700Mhz. Das ist schon eine ganz beachtliche Hausnummer. Der Preis von rund 45 Euro ist da fast lächerlich. Man bedenke, der komplette Bereich normaler Radiogeräte (LW, MW, KW, UKW) ist damit abgedeckt, darüber hinaus praktisch alle wichtigen Amateurfunkbänder und zahlreiche andere Bänder, die genutzt werden von Flugfunk, DECT-Telefonen, terrestrischen Fernsehen und vieles mehr.

spurtikus.de Relaunch Juli 2021

Spurtikus
spurtikus.de läuft jetzt auf Hugo! spurtikus.de läuft seit Juli 2021 auf dem Static Site Generator Hugo . Alle Seiten sind in Markdown erstellt. Dadurch dass nun alle Inhalte statisch generiert werden, ist der Seitenaufbau extrem schnell und auch noch ressourcenschonend. Die Umstellung von WordPress auf Hugo hat etwa 1 Tag Aufwand erfordert, gefolgt von ca. 3x2 Stunden Nachkontrolle in allen Dokumenten. Also in Summe ca. 2 Tage Arbeit. Das finde ich einen extrem guten Wert.

Experimenting with an old FM tuner

Spurtikus
I tried to buy a variable capacitor via ebay. What I got was the variable capacitor together with a small metal box. The box contains a FM tuner. It contains two germanium transistors AF121/AF125 and it seems it is from the 1960ies. (click to view larger version) This picture shows the variable capacitor, forming the base for the FM tuner. Metal box has been removed. I was not able to move the shaft/axis of the capacitor.

Modulation and Demodulation - HF-Probe

Spurtikus
When searching for a scheme for a HF probe, I found a good working solution at https://elektronikbasteln.pl7.de/signalverfolger-fuer-nf-und-hf-selbst-gebaut . The scheme uses two germanium rectifiers and looks like this: (click to view larger version) My hand drawing, a better image can be found on https://elektronikbasteln.pl7.de/signalverfolger-fuer-nf-und-hf-selbst-gebaut I tried that HP probe schema with good results. The original uses 2 diodes AA118, I have used AA143. In the next images, we can see a 25 MHz signal, AM-modulated with a 1 KHz signal.

Speed of SD cards

Spurtikus
This text simply compares several SDCards I own regarding speed. I use the cool tool “gnome-disks” to do the testing. In following image, a defect (?) SD card, that was used in a Raspberry as (only) disk. ON that Raspberry, a (seldom used) Kubernetes cluster was running. Card is a Sandisk Ultra 32GB , class 10, A1. Upper card: the broken Sandisk card, lower card, the Samsung, low write speed, but still considered ok

Tube Meter Heathkit IM-18D

Spurtikus
Since the 1950ies, Heathkit produced tube voltmeters. The Heathkit IM-18D is one of these, more from the 60ies, but I do not know the exact production year of my device. Heathkit sold these devices as kits. So you got all parts and soldered it all together. Also calibration was left to the buyer. You can compare this tube meter with my Heathkit V-7A, which is about 10 years older but very close…

Tube Meter Heathkit V-7A

Spurtikus
When buying my Heathkit IM18D (see here), I got this meter for a few more bucks. It was very dirty and was sold as not working. Also, someone has poured some silver paint over the poor device… Heathkit V-7A after some cleaning (knobs were in dishwasher when I took that photo) Some strange kind of line connector was found (this is a DIN connector, and I suppose someone had a cable that was used to put 230 volts in here…)

Grundig SV41 Signalverfolger (signal tracer)

Spurtikus
When entering the area of old tube receiver repairment, I found that a signal tracer device is crucial. With this device, you can trace a signal in the stages of the radio device and identify the stage that is not working anymore, so it is a great tool to troubleshoot radio receivers. Grundig SV41 signal tracer Signal tracers are not produced anymore, I think they passed when receivers and amplifiers were designed with ICs, where you have multiple or all stages of an electronic circuit in a single chip.

Hickok 539A tube tester

Spurtikus
Having 3 tube radios from 1950 .. 1960ies, I though it’s time to also have a tube tester. You can have the simple ones, but also a lab level device. All these tube testers come from 1950 .. 1960 years. You can have one for european tubes only or more general ones with american and european tubes. So I decided to get an american version. All modern amplifier tubes are american brand, so this is a good approach.

NEVA Netzgleichrichter for experimenting with Tubes

Spurtikus
To experiment with tubes, a power supply that creates higher voltages is required. Most lab power supplies supply up to 30, maybe 50 volts, some older ones may even go up to 100 volts. While tubes operate already somehow at these values, for testing etc., I looked for a real tube power suppy. I found one from an older german company, called NEVA. As far as I can see, they mostly produced for universities and school labs.