QH 40 A - Installation of a crystal heater into a Icom IC-746

Reference - QH 40 A - Installation of a QH 40 A crystal heater into a Icom IC-746

Hello,

Here are the photos I made for installing properly the QH40A in my Icom
IC-746, using an internal 8V line given by a 7808 regulator in the
tranceiver as supply for the QH40A.

For better thermal stability I used silicon compound between the
reference XTAL and the heater, and I placed cotton arround the
oscillator as showned on the photos..

The mesure I did with my Marconni 2955 (OCXO) Radiocom test set and
Racal Danal 1991 (TCXO) frequency meter give 50Hz drift on 145.000 MHz
when transmitting continuously 5 minutes after 4 hours standing on
receiving (to get the tranceiver warm up).

This give frequency stability better than +/- 0.2 ppm ... and better
than the Icom CR-282 TCXO solution wich is +/- 0.5 ppm.

Best reguards, Gerald - F4AVW.