Preamplifier for Kalundborg frequency reference

In all cases where reception of kalundborg is marginal using the ferrite at the input of S042P, the two-stage preamplifier shown here can help you ensure longer ‘lock’ periods of frequency standard.

The antenna indicator, L1, consists of 150 turns of 0.33mm  dia plastic, thin cardboard or paper former, positioned centrally on a ferrite rod with a length of 238mm and a diameter of 9.6mm. The indicator is resonated at 243 kHz by a fixed a capacitor, C9 and a timmer, C10. 

To keep the load on the antenna inductor, as small as possible the first stage of a preamplifier is formed by a FET Type BF245.

The amplified 243 kHz signal is fed to one of the inputs of S042P at the input of frequency standard (see the previous article). Using the preamplifier, the ( who lives in Denmark ) measured a signal level of 1.4 Vpp on pin 6 of  IC2  in the frequency reference.

The noise level normally measured after kalundborg switches off 0.30h CET is about 100 mVpp.

Preamplifier for Kalundborg frequency reference Schematic diagram

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