Gerard's Gerard Jampot

18
Item nr.

Gerard Jampot Crystal set

An easy-to-build crystal set to a classical design of the nineteen forties.

**Data for Gerard Jampot**
Production	The Netherlands, 1995.
Bands	MW.
Cabinet	Glass jar. Size 14 cm. Weight 0,4 kg.
Power	none.
Documents	Building instructions (Dutch): Part1, Part 2.

The Design

A crystal set contains no tubes or transistors, and no signal amplification is used in any form. This means that it requires a strong antenna signal (20m longwire) to receive just the strongest local stations.

Obtained	4/1995 from Homebrew.
Condition	8.
Disposed	Scrapped 4/2020.
Sound sample	PLAY SOUND ABBA sings Chiquitita.

This Object

This Jampot Ontvanger uses scrap material and a home brew coil, was built in an evening (April 5th, 1995) and it works! At first I thought the performance (it receives three to four stations) was meager but it is not. I hear from other people that their crystal sets never work in the first place, and I later tried a high quality crystal receiver using better parts, but it did not work either. Gollum reports his design receives ten stations, but he uses an additional battery.

To build this crystal receiver yourself you need some parts easily saved from a scrap radio: a tuning condensator, a diode, a condensator (1-10 nF), connectors. The coil is made by winding isolated wire on a toilet roll or similar object. The handwork is easy, but to determine the number of winds some formulas must be used: I found 105 winds (length 8.6 cm) to be appropriate (with antenna tap halfway). This gives you the desired inductance to tune the Medium Wave band (550-1500 kHz roughly). Enclosing it in a glass jar is easy (though I did not find any way to fix the coil, it just dangles) and cheap, and you can always see what is inside.

The headset: I could hear stations using a cheap modern device, a walkman earphone set. The performance can be improved slightly by rewiring it to have the two parts in series. However, this still does not compare to these old-fashioned headsets with high impedance. I get the best results with a 5000 Ohm headset I once bought in Prague. Surprisingly, the output is strong enough to drive a speaker as well. With a 600 Ohm speaker connected, the set delivers about 5uW (5 microWatt) and the sounds come out clearly understandable. It will not make your neighbors complain about the noise, but in a peaceful place it can be heard over several meters.

Part of Gerard's Radio Corner.
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