In message , Uncle Peter
writes

"Anthony Fremont" wrote in message
...
Hello all,

I was playing around and saw that my junk box had all the parts so I
started

Get rid of the series choke and just use the small value variable
capacitor to go higher in frequency. I believe the inductance will
lower the frequency--the combination works to give an increased
VXCO range if I am not mistaken.

Pete k1zjh



If the series capacitor is very small, the oscillation will stop. In
these circumstances, I have successfully pulled VHF crystals (3rd, 5th
and 7th overtone, between 70 and 200MHz) HF by adding an inductor IN
PARALLEL with the crystal. The value will be somewhat less than that
required to neutralise (ie parallel resonate with) the parallel
capacitance of the crystal. The lower the inductance, the higher the
frequency.
Ian.

--

Ian Jackson wrote:
In message , Uncle Peter

Get rid of the series choke and just use the small value variable
capacitor to go higher in frequency. I believe the inductance will
lower the frequency--the combination works to give an increased
VXCO range if I am not mistaken.

If the series capacitor is very small, the oscillation will stop. In
these circumstances, I have successfully pulled VHF crystals (3rd, 5th

It hasn't stopped, but it has gotten weak or unstable (I can't be sure right
now) with capacitance below 10pF.

and 7th overtone, between 70 and 200MHz) HF by adding an inductor IN
PARALLEL with the crystal. The value will be somewhat less than that
required to neutralise (ie parallel resonate with) the parallel
capacitance of the crystal. The lower the inductance, the higher the
frequency.

Are you referring to the capacitance inside the crystal, or the 100pF
external cap? Do you have a ballpark number on the inductance value I
should try?