2304 MHz mods: Local Oscillator, Harris SD-96405 (Farinon division)

Le cristal doit être remplacé et l'oscillateur doit ensuite être synthonisé sur sa nouvelle fréquence d'opération.

The crystal must be replaced and the LO tuned to its new operating frequency.

Photos

Précautions, électricité statique

 ESD rules in effect !

Electrostatic Sensitive Devices (ESD)

Field Effect Transistors (FET) in this module can be destroyed by static discharges.

  • Take applicable precautions:
    • Always touch chassis first, before touching anything inside the module.
    • Ensure your soldering station is "ESD safe".
Notes about soldering at Elecraft.

Noter la position du fourneau
Photo #1
See "plus" signs on oven and board.

Note the positionning of the crystal oven

  • This oven is a polarized device.
  • Note the markings on the oven and on the board.

Retirer le fourneau
Photo #2
Oven cap may come apart!

Pull-out the oven

  • Look under the board to ascertain the oven and crystal are merely plugged-in (rather than soldered).
  • Pull the oven up so as to expose the crystal.
  • It is very likely that the cap will come off the oven base because the glue has totally cooked over time.

Remplacer le cristal
Photo #3

Replace the crystal

  • Trim the crystal leads and "sandwich" a Mylar® insulator between the crystal and the board.
  • The insulator prevents the crystal metal casing from touching traces on the board.
  • The insulator must withstand the 80 °C temperature of the oven.

Remettre le fourneau en place
Photo #4
Red dot identifies positive terminal.

Position the oven over the new crystal

  • Again, note the red dot on the side of the oven.
  • Ensure it is on the side of the "positive" marking on the board.
  • Use Contact Cement to glue the oven cap if it came unglued.

Syntonisation
Photo #5
Component designations on LO.

Tune-up

  • See written instructions for details: capacitors can be preset to documented positions.
  • The ability to measure level and frequency at 90 MHz and 180 MHz is a plus.
  • Output frequency is 2160 MHz ( 90 × 2 × 2 × 6 ).
  • Final frequency tuning will only be done after a 3 to 4-day burn-in period.

Syntonisation du doubleur
Photo #6
Peaking the doubler at 180 MHz.
Photo #7
A parallel tuned circuit serves as a preselector.

Sniffing the second harmonic

  • A preselector on the input of the frequency counter may be useful.
  • The one shown tunes from about 135 to 235 MHz.

Si vous n'avez pas de splitter...
Photo #8
Hole for 2nd coaxial in the ouput slug.
Photo #9
Second coupling loop.

Alternative to splitter, provide second LO output

  • If you did not obtain a splitter, this is "Plan B":
    • Note the position of the brass output slug and pull it out.
    • Drill a hole through it for a new (teflon core) coaxial cable.
    • Shape a coupling loop next to the original one.
    • Use the original output for TX and the added output for RX.

Thanks to Bertrand VE2ZAZ for sharing his expertise, experiment and pictures.


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