XO controlled 480Hz Oscillator
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From: Chris on 16 Feb 2010 15:57 On Feb 4, 7:00 pm, Ross Herbert <rherb...(a)bigpond.net.au> wrote: > On Tue, 2 Feb 2010 08:29:47 -0800 (PST), Chris <christopher.man...(a)gmail.com> > wrote: > > :What is the simplest way to get480Hzfrom a crystal controlled > :oscillator? Looks like most of the pre-packaged XO's and VCXO, seem > :to put out much higher frequencies. Would a series of dividers be the > :best way? > : > :Thanks, > :Chris KQ6UP > > You might be able to still pick up this surplus itemhttp://surplussalespa..com/catalog/product_info.php?products_id=7474 > > With a bit of trimming I'm sure it could be pulled to 3.360kHz and then you can > use a divide by 7 counter using the HCF4018 to get480Hz.http://www.jaycar..com.au/images_uploaded/CD4018B.PDF It is already built and installed. I just need to solve the little hum problem that it created. However, overall it is working good. Thanks, Chris
From: RFI-EMI-GUY on 17 Feb 2010 23:08 On 2/16/2010 11:46 AM, Chris wrote: > I finished the this part of the project. The design with the 3.9Mhz > crystal with a CD4060 works perfectly. My tape deck is running > again. However, there is a small 480Hz hum in the record/play audio > now. This is very slight hum, not noticeable when there is dialog. I > did not notice this when the unit was running from a tuning fork time > reference. However, the tuning fork itself was audible outside the > chassis, and maybe masking my ability to hear the hum through the > headphones. > > There is a voltage divider resistor (1k) in series with the circuit. > This was in place because the tuning fork ran off of 12V and the > supply was 24V. My circuit is using a voltage regulator to drop the > voltage down to 12V. There is now about a 8V drop across the > resistor. If I remove the resistor, the hum gets much louder. If I > shunt the power with a 1000uF cap after the resistor the hum gets > louder. If I shunt before the resistor the hum drops into the Nyquist > noise when I monitoring through the preamp. It is still there, but > buried. Is there a better way to get rid of this hum/ripple? The cap > is rather big and not as effective as I would like. > > Thanks, > Chris Maness Problem could be that when using a tuning fork oscillator, the signal was a sine wave. Now dealing with digital divider you have a square wave and what you are hearing are harmonics. Look up 'super filters' these are capacitor/pass transistor arrangement to effectively increase capacitance through gain of the transistor. -- Joe Leikhim K4SAT "The RFI-EMI-GUY"� "Use only Genuine Interocitor Parts" Tom Servo ;-P
From: JosephKK on 18 Feb 2010 22:41 On Wed, 17 Feb 2010 23:08:16 -0500, RFI-EMI-GUY <Rhyolite(a)NETTALLY.COM> wrote: >On 2/16/2010 11:46 AM, Chris wrote: >> I finished the this part of the project. The design with the 3.9Mhz >> crystal with a CD4060 works perfectly. My tape deck is running >> again. However, there is a small 480Hz hum in the record/play audio >> now. This is very slight hum, not noticeable when there is dialog. I >> did not notice this when the unit was running from a tuning fork time >> reference. However, the tuning fork itself was audible outside the >> chassis, and maybe masking my ability to hear the hum through the >> headphones. >> >> There is a voltage divider resistor (1k) in series with the circuit. >> This was in place because the tuning fork ran off of 12V and the >> supply was 24V. My circuit is using a voltage regulator to drop the >> voltage down to 12V. There is now about a 8V drop across the >> resistor. If I remove the resistor, the hum gets much louder. If I >> shunt the power with a 1000uF cap after the resistor the hum gets >> louder. If I shunt before the resistor the hum drops into the Nyquist >> noise when I monitoring through the preamp. It is still there, but >> buried. Is there a better way to get rid of this hum/ripple? The cap >> is rather big and not as effective as I would like. >> >> Thanks, >> Chris Maness > >Problem could be that when using a tuning fork oscillator, the signal >was a sine wave. Now dealing with digital divider you have a square wave >and what you are hearing are harmonics. Look up 'super filters' these >are capacitor/pass transistor arrangement to effectively increase >capacitance through gain of the transistor. You could use a parallel T (sometimes called twin T) filter with a high Q to get the sine wave back.
From: MooseFET on 20 Feb 2010 10:03 On Feb 18, 7:41 pm, "JosephKK"<quiettechb...(a)yahoo.com> wrote: [....] > > >Problem could be that when using a tuning fork oscillator, the signal > >was a sine wave. Now dealing with digital divider you have a square wave > >and what you are hearing are harmonics. Look up 'super filters' these > >are capacitor/pass transistor arrangement to effectively increase > >capacitance through gain of the transistor. > > You could use a parallel T (sometimes called twin T) filter with a high Q > to get the sine wave back. If you use a couple of flip-flops to make a 45 and 90 degree delayed version, making the filter can be a lot easier. If you combine the 3 signals with 14K,10K,14K resistors, the 3rd harmonic drops to zero. 0 * 3 = 0 45 * 3 = 135 AKA 180-45 90 * 3 = 270 AKA -90 If you draw the 3 vectors, you will see why the 3rd harmonic is zero.
From: Chris on 23 Feb 2010 13:30
On Feb 17, 8:08 pm, RFI-EMI-GUY <Rhyol...(a)NETTALLY.COM> wrote: > On 2/16/2010 11:46 AM, Chris wrote: > > > > > I finished the this part of the project. The design with the 3.9Mhz > > crystal with a CD4060 works perfectly. My tape deck is running > > again. However, there is a small 480Hz hum in the record/play audio > > now. This is very slight hum, not noticeable when there is dialog. I > > did not notice this when the unit was running from a tuning fork time > > reference. However, the tuning fork itself was audible outside the > > chassis, and maybe masking my ability to hear the hum through the > > headphones. > > > There is a voltage divider resistor (1k) in series with the circuit. > > This was in place because the tuning fork ran off of 12V and the > > supply was 24V. My circuit is using a voltage regulator to drop the > > voltage down to 12V. There is now about a 8V drop across the > > resistor. If I remove the resistor, the hum gets much louder. If I > > shunt the power with a 1000uF cap after the resistor the hum gets > > louder. If I shunt before the resistor the hum drops into the Nyquist > > noise when I monitoring through the preamp. It is still there, but > > buried. Is there a better way to get rid of this hum/ripple? The cap > > is rather big and not as effective as I would like. > > > Thanks, > > Chris Maness > > Problem could be that when using a tuning fork oscillator, the signal > was a sine wave. Now dealing with digital divider you have a square wave > and what you are hearing are harmonics. Look up 'super filters' these > are capacitor/pass transistor arrangement to effectively increase > capacitance through gain of the transistor. > > -- > Joe Leikhim K4SAT > "The RFI-EMI-GUY"© > > "Use only Genuine Interocitor Parts" Tom Servo ;-P The output of this tuning fork was digital (square). Chris |