15625hz oscilator

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Marmelado

Joined: 06 Apr 2002
Posts: 46

12 Jan 2003 3:12 15625hz

Hi!
How can i make a 15625hz oscilator?
i want to put a ne565 or a 4046 oscilating at that precise frequency, with very small deviation +-10hz

Thanks!

E-design

Joined: 01 Jun 2002
Posts: 947
Helped: 68

12 Jan 2003 8:38 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

Kripton2035

Joined: 19 Jul 2001
Posts: 587
Helped: 20
Location: Earth

12 Jan 2003 11:37 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 !

flatulent

Joined: 19 Jul 2002
Posts: 4876
Helped: 324
Location: Middle Earth

13 Jan 2003 1:15 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.

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13 Jan 2003 1:15 Ads

MCRF

Joined: 10 Apr 2002
Posts: 30

13 Jan 2003 3:24 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
---------------------------------------------

thomaz

Joined: 04 May 2001
Posts: 54
Location: atlantis

13 Jan 2003 3:31 ne565 schematic

quartz oscillator 4MHz
divide 8 times by 2 = 15625 Hz
divider: 74xx393

quartz 4MHz is cheaper than 1MHz

TurboPC

Joined: 14 Mar 2002
Posts: 151
Helped: 1

13 Jan 2003 4:04 ne567 15,625

Marmelado wrote:

Hi!
How can i make a 15625hz oscilator?
i want to put a ne565 or a 4046 oscilating at that precise frequency, with very small deviation +-10hz

Thanks!

He! He! You are right! More than 10 Hz and you lose the color... Some very interesting solutions here... Good job to all.

MCRF

Joined: 10 Apr 2002
Posts: 30

13 Jan 2003 4:58 tv oscilator

Low Cost shematic under 1$ , = 15625 Hz Osc
CMOS 4060 or 74hc4060 ......

If you use 4MHz then get OUT Q8.

Marmelado

Joined: 06 Apr 2002
Posts: 46

13 Jan 2003 14:37

Hi!

Many thanks for that schematic:)

But if i want that +-10hz deviation, do i have to use a pll like the 4046 with that schematic as an oscillator?

MCRF

Joined: 10 Apr 2002
Posts: 30

13 Jan 2003 16:57 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.

MCRF

Joined: 10 Apr 2002
Posts: 30

13 Jan 2003 17:06 Calculation

Calculation

MCRF

Joined: 10 Apr 2002
Posts: 30

13 Jan 2003 17:15 Hi stability osc

hi stability osc

TurboPC

Joined: 14 Mar 2002
Posts: 151
Helped: 1

14 Jan 2003 4:16

Marmelado:

What's your design? There may be other solutions to help you if we knew what's the goal?

Regards,

TurboPC

TurboPC

Joined: 14 Mar 2002
Posts: 151
Helped: 1

14 Jan 2003 5:27

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

Joined: 27 Jun 2001
Posts: 14

14 Jan 2003 23:19 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