[Premium-Rx] RACAL 9442 OCXO

[Adam Farson]

Hi Andrew,

I recall designing an OCXO with a PWM heater for a VHF manpack project at
Racal in South Africa, in 1964. It is possible that this design found its
way into the 9442 OCXO.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----Original Message-----
From: premium-rx-bounces at mailman.qth.net
[mailto:premium-rx-bounces at mailman.qth.net] On Behalf Of Andrew Holme
Sent: 27-Aug-09 12:32
To: Premium-Rx at mailman.qth.net
Subject: [Premium-Rx] RACAL 9442 OCXO

I have one of these in my RACAL 9916 UHF counter and a spare on a 1792
mounting base.

The 1 MHz STD OUT from the rear of the 9916 counter has -70 dBc sidebands at
~ 1 KHz offsets.

The spare 9442 sometimes has them (at around -40 dBc) and sometimes not!!! 
I can make them go away (or come back) by momentarily interrupting the
supply.  It's had plenty of time to warm up and I'm only interrupting it for
a fraction of a second.

Does the heater work by PWM at around 1 KHz?

Any theories?

TIA