Hi,
I am building a 455KHz to 12KHz converter for DRM reception. I need the
local oscillator to operate around 467KHz, if I use an old IF coil as the
resonant element, what values of capacitors would you suggest for the
base/emitter/ground capacitor divider in the Colpitts oscillator
configuration?

Regards
Phil G0ELM

Phil Green wrote:

Hi,
I am building a 455KHz to 12KHz converter for DRM reception. I need the
local oscillator to operate around 467KHz, if I use an old IF coil as the
resonant element, what values of capacitors would you suggest for the
base/emitter/ground capacitor divider in the Colpitts oscillator
configuration?

Regards
Phil G0ELM



You're probably safe doing anything that works. I'd start by scaling
the caps from an app note, or choose 100 ohms at the target frequency.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Phil Green wrote:

Hi,
I am building a 455KHz to 12KHz converter for DRM reception. I need the
local oscillator to operate around 467KHz, if I use an old IF coil as the
resonant element, what values of capacitors would you suggest for the
base/emitter/ground capacitor divider in the Colpitts oscillator
configuration?

Regards
Phil G0ELM



You're probably safe doing anything that works. I'd start by scaling
the caps from an app note, or choose 100 ohms at the target frequency.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Tim Wescott wrote:
Phil Green wrote:

Hi,
I am building a 455KHz to 12KHz converter for DRM reception. I need the
local oscillator to operate around 467KHz, if I use an old IF coil as the
resonant element, what values of capacitors would you suggest for the
base/emitter/ground capacitor divider in the Colpitts oscillator
configuration?

Regards
Phil G0ELM



You're probably safe doing anything that works. I'd start by scaling
the caps from an app note, or choose 100 ohms at the target frequency.

Actually you can use an old transistor radio if can. Connect the
primary of the coil up as the tuned circuit and hook the collect tap
of the coil up instead of using a capacitive divider. IE: use a Hartley
oscillator circuit. You can connect the tap using a .001 cap to avoid a
dc connection.

Tim Wescott wrote:
Phil Green wrote:

Hi,
I am building a 455KHz to 12KHz converter for DRM reception. I need the
local oscillator to operate around 467KHz, if I use an old IF coil as the
resonant element, what values of capacitors would you suggest for the
base/emitter/ground capacitor divider in the Colpitts oscillator
configuration?

Regards
Phil G0ELM



You're probably safe doing anything that works. I'd start by scaling
the caps from an app note, or choose 100 ohms at the target frequency.

Actually you can use an old transistor radio if can. Connect the
primary of the coil up as the tuned circuit and hook the collect tap
of the coil up instead of using a capacitive divider. IE: use a Hartley
oscillator circuit. You can connect the tap using a .001 cap to avoid a
dc connection.