Analog Computing

I recently had the pleasure to visit Prof. Dr. Bernd Ulmann, leading Guru of Analog computing, an avid collector of aged computing devices and electronics paraphernalia. I had an older HP Spectrum analyser which  I wanted to donate and I was invited to see the beautiful collection of analog computers.

Unlike the recent devices that all of us use, an analog computer does not execute algorithms in a step-by step fashion but uses precise analog circuits that are wired to solve the problem in question. Interestingly, for many kinds of problems this approach is more suitable than digital, sequential processing. Calculations happen in real time by definition and parameters can be varied by the turn of a potentiometer, lending a tactile element to IT. One area of interest is the simulation of dynamic processes such as the control of a self propelled projectile or the suspension of a car. In fact, the A4 rocket was controlled by an analog computer called the “Mischgerät”.

Pictured below is a RA770 computer by Telefunken

There are some youtube videos detailing the systems operation:

Bernd also owns plenty of more recent digital computers, such as the lovely HP9820 (aka Model 20) on which I learned programming.

In case you are interested in these areas, check out his websites at: (more on the digital side of things)

and (the analog systems)

I can definitely confirm, the man has the knack! It’s time to get him into ham radio.

RF Field Strength Indicator

Here is the latest toy that I finished. It is an active RF field strength meter. So far, I had a passive one (a detector which feeds into a microamperemeter). This one here has an op-amp stage plus a nifty VCO that outputs a sound that varies in pitch with the strength of the signal that was received.

The circuit follows the one published in Funkamateur 10/2010 by DK6UU. The circuit contains a bug as that is is published with the wrong type of chip (74HC4046 should be: CD4046).



It is September soon.  I remember that in the early days of the last decade I had celebrated the 11th of September as a second birthday. Nowadays I tend to forget the date.

I still have a lot of scary pictures in my archive from that time.

It was a beautiful, warm and clear September day.

Only 24h earlier, I used to look at the people walking that street from my office window.

We must not forget those who died on that day.


We are going to Singapore later this year. Can not wait!

The last time I was there was in 2012, before I accepted my current role. I can not say how much I still love the country. Having lived there for many years has given me deep respect and love. I badly miss my old home, huge pools, ocean views, sim lim tower, funan center, my old motor bike and all the lovely folks that I had the honour to work with. I have never worked with people as efficient as the Singaporeans.

Happy birthday Singapore by the way. Singapore, same as myself were born in August of 1965, just 11 days apart. Maybe that is why we are close at heart.

Food channels

I have two food channels to recommend.

Number one is the holy grail of Asian food, Mark Wiens channel on Youtube. Mark is an American with Chinese heritage living in Thailand with his wife and son. He has produced some of the most delightful restaurant reviews.

Here is a sample:

The second channel is Munchies “Chefs night out” series. The idea is to have one chef take the team around to his favourite 3 or 4 culinary hotspots in his city, then returning to his own restaurant. This is an awesome travel guide.

Going to TEDx!

We are going to TEDx this fall! I am sooo excited!  Always wanted to go there. This is phantastic, intellectual entertainment.

If you want to know what it is about, check out as a sample this beautiful talk by the brilliant late Swedish researcher and professor of global health studies Hans Rosling


Storms in the tropics

I am just browsing through my old videos and ran into this interesting one. While living in Singapore in 2007, I had recently purchased my first Macbook and was experimenting with its builtin camera. I pointed it outside of one of the windows and let it run in time lapse mode as I wanted to see the patterns of ship movement in the Singapore straits.

When I returned home from dinner, I saw this on the recorded movie!

Endfed halfwaves (EFHW)

Some years ago I began to experiment with endfed halfwave antennas. My friend Eric WL7CMT suggested many years ago that I experiment with those. As this is an antenna which is a bit off the beaten track, I did not trust it. Then I built one for 20m and was surprised!

The one shown in the video is matched with a low pass, now I built one using a broadband ferrite transformer using two stacked Würth Ferrite cores (2 primary windings, 15 secondary windings, primary compensated with 110pF). The core material is a bit like Material 43

The results are not in yet but I am under the faint impression that the low pass is more efficient than the transformer. Certainly, using a single core drives the same into saturation.  FT140-43 would be the traditional building material.

Another insight was that two primary windings are more suitable for high frequencies than one. It is difficult anyway to get the cap to compensate for the primary inductance. I might add some screenshots of the VNA plots.


Every year, during the last week of school vacation, there is a fabulous model aircraft show in Kirberg. If you stay in the area, It’s well worth dropping by.

Which reminds me, I got to get out to fly the drone 😉