The story of a "Schaaper" reciever.
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note of translator: Schaaper was a manufacture, that produced parts for amateur radio building. the reception coils they sold had quite a good reputation, and therefor, their name was quite known in the Netherlands.


Some years ago i visited a friend of mine, a farmer in the rural South-Limburg town of Elsloo. After chatting a bit, the subject went to radio. As usual, you would say...

Oh, now you mention it, i got a really old one standing somewhere in the attic, he told me. Old radios on attics, who of us doesn't get nice visions with that?
After having a cup of coffee, we climbed the small ladder to the attic.
Try to imagine how an old radio, which has been standing there for over forty years looks like! I turned around the cabinet to examine the interior of it.
I saw it was a home-made set, using "Schaaper" parts. Two nice copper coil tins flanked the double tuning capacitor. This ensemble was mounted on an small aluminium chassis.

The other parts were mounted on the floor of the radio. It was equipped with four pen valves. The RF valve had been positioned horizontally, that way the distance between the first and second tuned circuit could be kept the largest. 
The Erik Schaaper institute, at that point of time established in The Hague, provided courses on paper, and also sold schematics and parts. Especially the coils had a good reputation. 

In my imagination, I already saw the radio standing on my own workbench, here it was only wasting space. But alas, farmers never throw anything away...
He told me that it had been built by a boy from the village (who knew veeery much about radio and stuff) in the thirties, specially for the family.
When in 1943 all recievers were collected by the germans, this one was brought to the town hall too, using a horse-and carriage. There, a label with name and adress of the owner was attached. Then it was brought to the cellars by a clerk, extensively apologising for the inconvenience, to his partners in distress, waiting for the things to come. Some time after the war, there suddenly came a letter, calling for the owners of the radios that had been taken, to recollect their posessions.
This was totally unexpected, the place of the schaaper had been taken by a more modern radio. Farmers like to have something in reserve, and so it happened that the reciever was placed between the cattle's winter hay on the attic. 
"It doesn't work anymore but I am not putting it away, you can fix her up for me one time, then it gets a nice place in the living room" cheered too early, thought I.

About a year later, I was in Elsloo again, and visited the farm too. I couldn't resist and started again about the radio. "I would like to have one of those 27mc-rigs, if you can provide me one you can take it" I was told. Aha, things started to change for the good!
Having asked here and there, I managed to buy one for 25 guilders (about 11 US$). That way, unexpectedly the Schaaper got to me after all.

After a thorough round of "de-haying" the wiring and positioning of the parts were written down, and dismantled completely. The rotatable plates of the tuning capacitor were somewhat bent. This was corrected carefully. The tubes and other parts were measured.
So far so good; all in order, exept for the capacitor block and the so called "spaghetti-resistors" these were used in schaaper schematics often, they exist of a piece of asbestos wire around which a resistance wire is wound. This ensemble was covered by a protecting mantle. Cable connectors were attached to the end. At first sight they look like ordinary pieces of supple wire. All Caps in the smoothing block were as leaky as a sieve. That could be expected after all this time. The block was opened and the Caps were replaced. Close the box again and you see nothing of it. 


All other components were mounted back on there original place. The resistors were replaced by standard ones, later we could look on, first it had to play.
I turned up the vaciac slowly, while keeping an eye on a few currents and voltages on the measuring instruments I placed on crucial positions. All seemed to go well, but the sensitivity was far from what was hoped for, or otherwise said, only the strongest station in the air could be heard very weakly. The Coils became under suspicion.
Signal detector on the antenna circuit: working perfectly.
I went on with checking the second circuit.
Nil.
The Tektronix L-C meter was brought into position.
Measurement prooved it too light, something was seriously wrong here.
I had no choise, the tin had to be opened. Drilling out the hollow staples which kept it in place revealed the remains of what once should have been a coil. The trolitul coil holder was collapsed as a pile of jelly.... A sorry sight.
It was clear what happened here: The + HV was lead through the coil to the anode of the RF tube. One section of the tuning capactor was placed between this anode, and earth. I already wrote the plates were bent, causing them to short. In that case the current goes from coil directly to earth, turning the coil into a heater element, which at its turn caused the coil holder to melt. Had Erik used glass coil forms, just as philips at the time with their "Superinductance" coils, then the effect of the short might have been less terrible. Now, I faced a real difficulty.
Face it, making a fitting replacement would be sheer impossible to do; winding a coil on low-capacity holder material, with the same Q-factor and selfinductance as the original, let alone how to get 16-core litze wire for the windings.
As mostly, a half-way solution was archieved by using a coil I had in stock, with about the same selfinductance as the antenna coil was placed in the can. The results were, of course, saddening. Only a handful of stations could be recieved, not mentioning anything on the selectivity. It would be a pitiful end of this story if it wasn't for Frans Driessen.
He proved himself the saviouring angel half a year later, he managed to deliver me an original coil. It was mounted, and yes, the radio deserved the name radio-reciever again. 

What if old radios could talk...


Translation of an earlier published article, "Radio Historisch Tijdschrift", feb. 1997 by Herm Willems. Translation by Wouter Nieuwlaat, Okt. 2001