With the insights from part 1 it is clear that we need a circuit which can produce the modulated signal: s(t)=Accos(2πfct)⋅(1+km(t)) After some searching and consideration I found the AD633 from Analog Devices which is an analogue multiplier with differential inputs which does the following: From the figure one can see that it basically performs…
Author: Geek
Bringing back the early days of radio, part 1: Background and thinking
I posses a number of very old radio receivers from the beginning of the last century – truly beautiful artefacts from the dawn of wireless communication and I have restored them all to working condition, see below. These old receivers were mainly built to receive radio broadcasts on very low frequencies, i.e. Long Wave or…
Reviving ancient computer equipment and software – genesis
As a young engineering mind I read and dreamt about computers during my childhood in the 70’s. I had my first hands-on computer experience with a Sinclair ZX81 which I borrowed from a friend during the fall of 1981. The computer only had 1kB of RAM which I soon found to be a bit limiting….
Repairing a gun metal spectacle frame
The frame of my glasses is made by Ray Ban, RB6333 to be specific. Some time ago the little pad on the left side broke and it simply fell off. I checked with my optician and they said they could fix it but since they claimed that the frame is made of titanium and therefore…
Braun MX2050 – Part 2: Replacing the engine clutch
Problem: A household blender, Braun MX2050, is not able to mix anything. Symptom: The motor works and the the blades in the jug are rotating when the jug is empty but no thick liquid or any solid substances are possible to mix. The cause: I can tell you already at this stage that the cause…
Braun MX2050 – Part 1: Replacing the clutch wheel
Problem: The clutch wheel at the bottom on the jug for a household mixer, Braun MX2050, is broken. Symptom: One or more teeth (of six) on the plastic clutch wheel are broken. Procedure:1. Remove the plastic clutch wheel. This is very simple. Just hold the blades with one hand while twisting the clutch wheel with your…
Fixing a bricked Sophos AP15
Problem, background: My Sophos AP15 became ’bricked’ after an update. Symptom: The LED is solid orange (yellow) and there is no response using ethernet. In addition, no maintenance port exists, at least not on my AP. Initial actions: A chat with Sophos support did not result in anything useful. Googling the problem resulted in quite…