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#1
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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, |
#2
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#3
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"Eamon Skelton" wrote in message
news 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 |
#4
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In article , "nn" wrote:
"Eamon Skelton" wrote in message news 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 |
#5
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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 |
#6
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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 |
#7
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On Sat, 03 Sep 2005 15:06:22 +0300, nn wrote:
"Eamon Skelton" wrote in message news 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 -- linux-2.6.13 Remove 'X' to reply by e-mail. |
#8
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"Eamon Skelton" wrote in message
news 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 |
#9
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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 news 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 |
#10
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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. -- linux-2.6.13 Remove 'X' to reply by e-mail. |
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