Frequency Stabilizer
Putting the Varicaps on the Main Tuning Capacitor

Step by Step Instructions

Step 1

On some of the capacitors, there are trimmers mounted on the side the varicaps are installed. The trimmers can be a source of drift, so removing them can help stability.

Unscrew the screws, lift the copper piece over the soldering tab and bend back and forth to break off. The arrow shows where the pieces are broken off. Remove the mica insulator.

The picture shows the sequence of the removal of the trimmers. The one on the left end, which is not on all the caps, is unsoldered.

Step 2

Two sections at each end of the main tuning cap are tied together for more capacitance. A jumper wire is used to tie the sections together. They are only tied together on this side. The connections to the stator on the other side of the capacitor are used to connect to the VFO.

Step 3

Two varicaps are mounted on the main tuning capacitor. The mounting is done on the tab side with round holes.

The arrow points to the symbol on the MV2104 that indicates the cathode side.

Note in the picture above that the cathode of the varicaps is attached to the stator of the capacitor.

Step 4

Finally, two 100K resistors are connected to the cathodes of the varicaps and tied together on the other end to connect to the frequency stabilizer output. Be careful, the resistors are in parallel, not in series.

The output of the stabilizer (labeled relay on the stabilizer board) is connected to the two 100K resistors.

Stabilizer Parts List

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Last Update: 8/13/06
Web Author: David White, WN5Y