Frequentite Coil Former 1090

The Eddystone Cat. No. 1090 coil former is intended for use in the tank circuits of transmitters at frequencies of 3 MHz upwards, or in other high frequency apparatus. The spiral grooves take up to 26 turns of wire of size up to 12 swg, and 14 holes are provided for leads and coil taps. Eddystone provided a chart indicating the number of turns of 14 swg wire required for resonance in the 3.5, 7, 14, 28 and 56 MHz amateur bands for different values of tuning capacity.

The coil former is made of Frequentite, a low-loss version (C221) of magnesium silicate Steatite (C220) that also has improved mechanical and dielectric strength.

For plug-in use, the coil former can be attached to a Frequentite Sub-base, Cat. No. 1091, which has 5 plugs with tinned phosphor-bronze self-locking solder tags. Bolts, lead washers, and mounting pillars are included with the sub-base.

The sub-base can be plugged into a Frequentite Base, Cat. No. 1092, which has heavy-duty sockets in place of the male contacts of the sub-base. The pillars, bolts, and lead washers provided are suitable for chassis mounting.

The Eddystone 1090 coil former carries the 'Eddystone' name cast in relief. Similar coil formers were produced by other manufacturers. Although its mounting base has differences of detail, the XR-10A coil former that was sold by National Co is almost identical. It is identified by an adhesive label with the NC logo. Unlabelled coil formers were also made that are very similar in design but of much poorer quality.

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