Hopmi Tulp spoel

Radiotechniek album
The tulip coil receiver. Was a special coil set that was developed by Hommi's manager, Mr. Tulp. Hopmi was a manufacturer of bicycle locks and other bicycle parts. At the end of the 1920s, the company manufactured coil sets for radio devices for a short time, an example of which is shown here.
The coil set consists of two sections primary and secondary.
The structure of the device. Of course there was no connection data from the coil.
So first we build the primary section.
And then we're going to test the primary section.
Here is the image on the scope. unfortunately wrong camera.
Then the construction of the secondary part with feedback.
It is experimentation because there is no data
It starts with the secondary tuning capacitor.
And then a simple test.
You need a power tube to hear something.
And then connecting the feedback.
Then we slowly replace the Chinese for fixed wiring.
Then test again and see what we can improve.
And then it will really become something.
The front panel of this radio.
And the total device ready, working. It turns out that the tulip coil works insanely well. Which is quite remarkable for a bicycle parts factory.