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How to make a 15625 hz oscillator ?
- Thread starter Marmelado
- Start date
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E-design
Advanced Member level 5
varicap 4046
Hi
It sounds familiar, the horizontal line freq of countries in Europe.
I once made a 10MHz reference osc and locked it to line frequency of a TV set. I knew that the one TV station actually locked their subcarrier etc. against a Cesium standard.
Well I took a 10MHz crystal with a 4060 and took the /64 output and then another /10 chip to get to the 15625 Hz that I needed as a ref for the 4046 to compare the line freq from the TV with. I then also had a varicap acting on one of the crystal's capacitors that connects it to the 4060 which was fed from the 4046 o/p.
This way I could vary the crystals freq slightly to get it to lock to the 15625
So you should be able to get enough swing on the 15625 side from changing the 10MHz
Hi
It sounds familiar, the horizontal line freq of countries in Europe.
I once made a 10MHz reference osc and locked it to line frequency of a TV set. I knew that the one TV station actually locked their subcarrier etc. against a Cesium standard.
Well I took a 10MHz crystal with a 4060 and took the /64 output and then another /10 chip to get to the 15625 Hz that I needed as a ref for the 4046 to compare the line freq from the TV with. I then also had a varicap acting on one of the crystal's capacitors that connects it to the 4060 which was fed from the 4046 o/p.
This way I could vary the crystals freq slightly to get it to lock to the 15625
So you should be able to get enough swing on the 15625 side from changing the 10MHz
Kripton2035
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cmos 4060 4mhz
You can also use the direct digital synthesis (dds) chips from analog design. these are small but precise.
look at their ad9833, ad9834, or ad9835.
some of them are available as free sample.
http://www.analog.com
you need only a quartz (around 25 or 50 Mhz) and it's precise as the milli-hertz... you program it via a parallel or serial pins on the chip.
have a good day !
You can also use the direct digital synthesis (dds) chips from analog design. these are small but precise.
look at their ad9833, ad9834, or ad9835.
some of them are available as free sample.
http://www.analog.com
you need only a quartz (around 25 or 50 Mhz) and it's precise as the milli-hertz... you program it via a parallel or serial pins on the chip.
have a good day !
flatulent
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15625hz filter
If it is the sweep frequency of your TV set you want to lock to, you can make a pick up coil to place near your TV set. Then follow the coil with an amplifier and a narrow band active filter. This should be good enough. You can further clean the signal by locking a PLL chip running at this frequency. The NE567 types (also called tone decoders) work very well. Select in the design a narrow loop bandwidth. If you want to adjust the phase relationship, you can preceed the PLL with a RC low pass filter and adjust the time constant. You can also use several RC sections if you want a wide phase adjustment without very much signal amplitude reduction. You should orient the pick up coil with its axis on line with your CRT ppicture tube deflection coil axis. Your coil should be only a few times larger diameter than the tube coil. At these low frequencies there is no resonance limit on the number of turns resonating with the inter wire capacitance. You will probably run out of stamina in winding the coil before you reach the self resonance frequency being above the swee frequency.
If it is the sweep frequency of your TV set you want to lock to, you can make a pick up coil to place near your TV set. Then follow the coil with an amplifier and a narrow band active filter. This should be good enough. You can further clean the signal by locking a PLL chip running at this frequency. The NE567 types (also called tone decoders) work very well. Select in the design a narrow loop bandwidth. If you want to adjust the phase relationship, you can preceed the PLL with a RC low pass filter and adjust the time constant. You can also use several RC sections if you want a wide phase adjustment without very much signal amplitude reduction. You should orient the pick up coil with its axis on line with your CRT ppicture tube deflection coil axis. Your coil should be only a few times larger diameter than the tube coil. At these low frequencies there is no resonance limit on the number of turns resonating with the inter wire capacitance. You will probably run out of stamina in winding the coil before you reach the self resonance frequency being above the swee frequency.
MCRF
Junior Member level 3
15625hz lc oscillator schematic
First build any 1Mhz Quartz oscilator
you may using two inverter , very simple
and devide this with any low cost
prescaler/divider /64 then result
find it on Internet , many types exist.
---------------------------------------------
frq 15625Hz.
---------------------------------------------
1000000Hz / 64 ->15625Hz
---------------------------------------------
First build any 1Mhz Quartz oscilator
you may using two inverter , very simple
and devide this with any low cost
prescaler/divider /64 then result
find it on Internet , many types exist.
---------------------------------------------
frq 15625Hz.
---------------------------------------------
1000000Hz / 64 ->15625Hz
---------------------------------------------
MCRF
Junior Member level 3
Capacitor Shift Frq
you may use 2Xpairs capacitors on quartz pins, this named
two point modulation or make deviaton on PLL (4046).
Calculation for +/- 350Hz deviation you get +/-5Hz on 15625
If you need high stability use oscilators Like this.
you may use 2Xpairs capacitors on quartz pins, this named
two point modulation or make deviaton on PLL (4046).
Calculation for +/- 350Hz deviation you get +/-5Hz on 15625
If you need high stability use oscilators Like this.
TurboPC
Advanced Member level 4
While we are at numbers... Here's the ITU 624-4 spec that specifies some numbers for PAL-BGHI, PAL-M, PAL-M, NTSC and so on... including the frequency tolerances...
alterego
Newbie level 6
Genlock
Hi all,
I've built a genlock at 15625 Hz sur TV digitalisation using an ELANTEC chip : see EL4585C. It's distribute by Radiospares
you can use LC oscillator + varicap or Quartz + varicap.
Good luck
Hi all,
I've built a genlock at 15625 Hz sur TV digitalisation using an ELANTEC chip : see EL4585C. It's distribute by Radiospares
you can use LC oscillator + varicap or Quartz + varicap.
Good luck
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