As a family heritage, we ever had an old radio from my great-uncle (brother of my grandfather) named Modestus, and ever since I can remember is had been standing in the bedroom of my parents. Eventually, it was no longer used there and moved into my mechanical workshop where it still serves to play background music while I am operating machines.

It was build some time in the early 70s, and is based on germanium transistors – to be precise, 11 germanium transistors. The sound is not bad given the relatively simple circuit. However, in the last year it must have suffered some degradation of the FM tuner, because this tends to drift, and the reception is not clear always. Especially in winter, switching it on after a “cold” start, it needs some re-tuning after about 30 minutes of operation. A little inconvenient. Rather than spending a long time trying to fix an old FM tuner, I decided to take another approach – adding a new digital (PLL) tuner.

In my stock of old parts I had a no longer used PCI TV card, which incorporates a Philips FM1216MK tuner, a combination TV and FM tuner use a TSA5523 PLL, and can operate from a single +5 V supply (because of an internal DC-DC converter).

The card is a combined ISDN-TV-FM card. The tuner can be easily desoldered. Control is by i2c bus, two wire interface. Some libraries exist, but I didn’t use those. Rather straightforward to send the bytes needed to set the frequency and to do some more configuration needed. The tuner has a stereo decoder, but I operate in mono mode – there is only one speaker in the OSTIA radio.

A quick setup with a i2c LCD added for debugging. Using a Arduino Nano3 board clone with an ATMega168p microcontroller. But any microcontroller will do.

Now, integrating the new tuner to the OSTIA – my objective was to not destroy the old beauty, integrate minimally invasive. A first attempt to use the build-in transformer failed, because it could not provide the roughly 200 mA current needed for the Philips tuner.

To feed the audio signal, I cut a bridge on the board (which carries the FM audio from the old tuner), and injected the audio from the new tuner via a 100 nF foil capacitor.
For control of frequency, there is no an incremental encoder on the back of the radio (I rarely change the station if at all), and when you push on that encoder, the last frequency set is stored in EEPROM. The LCD has been disconnected, not needed during operation.

Finally, the OSTIA back at its accustomed place in the workshop. Reception is good and stable now, all frequency locked to a small quartz crystal.

Certainly this radio now has no longer just 11 transistors – maybe 500 transistors now!