Rubbish. Varactors are not used for freqency mulitplication.
Google"varactor multipliers", still used. Popular technique in
the 60's for getting 70 cm output from 2m TX.
As osc control keep RF across diode low, high levels produce harmonics
and reduce tuning range. Most tuning varieties have max V = 30.
At low freqs power diodes work ok and have high V rev.

If you aren't using the turnip truck you just fell from, could I borrow it for a
while? {;-)


Jim


Paul Burridge
shared these priceless pearls of wisdom:


-
-Rubbish. Varactors are not used for freqency mulitplication.
Jim Weir, VP Eng. RST Eng. WX6RST
A&P, CFI, and other good alphabet soup

On Mon, 05 Jan 2004 09:14:28 -0800, Jim Weir wrote:

If you aren't using the turnip truck you just fell from, could I borrow it for a
while? {;-)

Hehe! Fair comment. Thank God I don't have any reputation to lose on
this group. :-)
--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill

On Mon, 05 Jan 2004 09:14:28 -0800, Jim Weir wrote:

If you aren't using the turnip truck you just fell from, could I borrow it for a
while? {;-)

Hehe! Fair comment. Thank God I don't have any reputation to lose on
this group. :-)
--

"I expect history will be kind to me, since I intend to write it."
- Winston Churchill

Paul Burridge wrote...

Tim Wescott wrote:

The varactor capacitance change is instantaneous -- think of a capacitor
who's plate spacing is dependent on it's voltage. This is why varactors
are used for frequency multiplication -- that capacitance change
"squeezes" the pulse to generate lots of harmonics.

Rubbish. Varactors are not used for freqency mulitplication. They are
freequenty used in VXCOs for modulating (or otherwise varying) the
oscillator output frequency by means of applying a DC bias voltage
which alters the capacitance of the PN junction.

Your own rubbish, Paul. In truth of fact, varactors are nicely used
for frequency multiplication, just as Tim stated. They also work well
for VCO FM modulation, but users must keep in mind their instantaneous
capacitance-change property and be careful to bias them in appropriate
higher-voltage bias regions, or risk unintended distortion. When used
as multipliers, low-voltage bias with large signals enhances the effect.

Thanks,
- Win

whill_at_picovolt-dot-com

On Mon, 05 Jan 2004 02:40:07 +0000, Paul Burridge
wrote:


Rubbish. Varactors are not used for freqency mulitplication.

If you are determined to be arrogant, it helps to occasionally be
right. Varactors are still used for frequency multiplication. They
were also commonly used as parametric amplifiers and mixers before
other semiconductors got fast enough to work at microwave frequencies.
Varactors were even used as paramps in the front ends of opamps.

Google "varactor frequency multiplier" and "parametric amplifier" and
maybe learn something.

John

On Mon, 05 Jan 2004 02:40:07 +0000,
said...
On Sun, 4 Jan 2004 16:22:32 -0800, "Tim Wescott"
wrote:

The varactor capacitance change is instantaneous -- think of a capacitor
who's plate spacing is dependent on it's voltage. This is why varactors are
used for frequency multiplication -- that capacitance change "squeezes" the
pulse to generate lots of harmonics.

Rubbish. Varactors are not used for freqency mulitplication. They are
freequenty used in VXCOs for modulating (or otherwise varying) the
oscillator output frequency by means of applying a DC bias voltage
which alters the capacitance of the PN junction.

Dude, please.
--
Best Regards,
Mike

Rubbish. Varactors are not used for freqency mulitplication.
Google"varactor multipliers", still used. Popular technique in
the 60's for getting 70 cm output from 2m TX.
As osc control keep RF across diode low, high levels produce harmonics
and reduce tuning range. Most tuning varieties have max V = 30.
At low freqs power diodes work ok and have high V rev.

If you aren't using the turnip truck you just fell from, could I borrow it for a
while? {;-)


Jim


Paul Burridge
shared these priceless pearls of wisdom:


-
-Rubbish. Varactors are not used for freqency mulitplication.
Jim Weir, VP Eng. RST Eng. WX6RST
A&P, CFI, and other good alphabet soup

Motorola's first solid state 450 car phone, the MK, used a 50 W 150 MHz PA
followed by a varactor tripler for 10W at 450. Varactor triplers are tricky
however.

Steve K;9;d/c/i

"Paul Burridge" wrote in message
...
On Sun, 4 Jan 2004 16:22:32 -0800, "Tim Wescott"
wrote:

The varactor capacitance change is instantaneous -- think of a capacitor
who's plate spacing is dependent on it's voltage. This is why varactors
are
used for frequency multiplication -- that capacitance change "squeezes"
the
pulse to generate lots of harmonics.

Rubbish. Varactors are not used for freqency mulitplication. They are
freequenty used in VXCOs for modulating (or otherwise varying) the
oscillator output frequency by means of applying a DC bias voltage
which alters the capacitance of the PN junction.
--

"I expect history will be kind to me, since I intend to write it."
-
Winston Churchill