oscillator problem: pulling crystal abt 500 Hz in LT2S SSB Electronics -transverter
 

I have SSB Electronics transverter LT2S. Its 116 MHz crystal oscillator
is about 500 Hz off the frequency eg. running somewhere 116 000, 500 kHz.
How could this be tuned to pulled 116 MHz? Or is even impossible/too hard to
do?

See picture http://www.g1ogy.com/projects/LT2S/page13.jpg

The oscillator is T1/Q1 I am talking about. Any ideas, any help?

73 Pasi, oh2pt,

On Sat, 03 Sep 2005 11:02:02 +0300, Pasi wrote:


The oscillator is T1/Q1 I am talking about. Any ideas, any help?

73 Pasi, oh2pt,

What happens if you adjust L7?

73, Ed. EI9GQ.

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"Eamon Skelton" wrote in message
. ..
What happens if you adjust L7?

73, Ed. EI9GQ.

I haven't touched it. But as far as I understand its there to avoid
oscillation
to disturb regulation process insuide L09. So it should have nothing
to do with the crystal "pushing". (Let me know if I am totally wrong... :)

Pasi, oh2pt

In article , "nn" wrote:

"Eamon Skelton" wrote in message
. ..
What happens if you adjust L7?

73, Ed. EI9GQ.

I haven't touched it. But as far as I understand its there to avoid
oscillation
to disturb regulation process insuide L09. So it should have nothing
to do with the crystal "pushing". (Let me know if I am totally wrong... :)

Pasi-

The 1 microfarad capacitor prevents the regulator from oscillating.

L7 would normally be adjusted for maximum output from the oscillator
stage, but may also have an effect on frequency. Since it is all you have
to adjust, I suggest you adjust it.

I believe the crystal is connected in a series-resonant configuration,
which is less affected by circuit values. The only recourse may be to
purchase a new crystal.

73, Fred, K4DII

I believe the crystal is connected in a series-resonant configuration,
which is less affected by circuit values. The only recourse may be to
purchase a new crystal.
=======================
If crystal is indeed in series-resonant config. , by putting a trimmer of a
few pF in series with the crystal, it will highly likely be possible to pull
the freq 500 Hz.
After all this is only just over 4ppm of the nominal frequency.

Frank GM0CSZ / KN6WH

Frank and Fred,

Thank you for your help. I will try L7 first (and then trimmer of pair of
twisted wires).
Let's see what happens. I need counter to borrow first.. I will be back.

73 Pasi, oh2pt

On Sat, 03 Sep 2005 15:06:22 +0300, nn wrote:

"Eamon Skelton" wrote in message
. ..
What happens if you adjust L7?

73, Ed. EI9GQ.

I haven't touched it. But as far as I understand its there to avoid
oscillation
to disturb regulation process insuide L09. So it should have nothing to do
with the crystal "pushing". (Let me know if I am totally wrong... :)

Pasi, oh2pt

It looks like a fairly low inductance which resonates with
the 12pf, 68pf and other capacitances in the oscillator to form
a 116MHz tuned circuit. Try adjusting it to see if it will
pull the oscillator to the correct frequency. If you turn
it too far, it will reduce the L.O. output or stop it
from running. If you are not happy with the result, you
can always put it back where it was.

If all else fails, you could try putting a variable capacitor
or inductor in series with the crystal.

73, Ed. EI9GQ




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"Eamon Skelton" wrote in message
. ..
a 116MHz tuned circuit. Try adjusting it to see if it will
pull the oscillator to the correct frequency. If you turn
it too far, it will reduce the L.O. output or stop it
from running. If you are not happy with the result, you
can always put it back where it was.

If all else fails, you could try putting a variable capacitor
or inductor in series with the crystal.

73, Ed. EI9GQ

Ed,

What is the best way to know the value before i touch it?
Should I measure the voltage after this coil - or how?
And most probably there is RF-voltmeter needed?

Pasi

Count the number of turns as you adjust. If it has little or no effect
on frequency, return the slug to its original position by turning in the
opposite direction for the same number of turns you counted while
adjusting it.

Scott
N0EDV

Pasi wrote:
"Eamon Skelton" wrote in message
. ..

a 116MHz tuned circuit. Try adjusting it to see if it will
pull the oscillator to the correct frequency. If you turn
it too far, it will reduce the L.O. output or stop it
from running. If you are not happy with the result, you
can always put it back where it was.

If all else fails, you could try putting a variable capacitor
or inductor in series with the crystal.

73, Ed. EI9GQ


Ed,

What is the best way to know the value before i touch it?
Should I measure the voltage after this coil - or how?
And most probably there is RF-voltmeter needed?

Pasi

On Sun, 04 Sep 2005 14:09:14 +0300, Pasi wrote:


What is the best way to know the value before i touch it? Should I measure
the voltage after this coil - or how? And most probably there is
RF-voltmeter needed?

Pasi

It would be very difficult if not impossible to find the
exact inductance of L7 while it is in circuit.

Just count the number of degrees of rotation you make
to the tuning slug. You could mark the slug and former
with white paint or tipex before you start. If you don't have a
VHF frequency counter, you could use a 2M beacon as a frequency reference.
Most of the 2M beacons audible from here are correct to within +/- 200Hz.
GB3MCB is usually within 100Hz.

Even a very good crystal oscillator is unlikely to
be stable to less than 1 ppm, so there is little
point in trying to get an error of less than 100Hz.

73, Ed. EI9GQ.


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