Filters - Revision history

Carlb: /* Filter Types */

2009-04-09T01:24:20Z

Filter Types

← Older revision		Revision as of 18:24, 8 April 2009
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	==Filter Types==		==Filter Types==
			* [[What is a cavity filter? \| Cavity Filter]]
			* [[LC filters]]
			* [[Saw Filter]]

	~~[[What is a cavity filter? \| Cavity Filter]]~~

	~~[[LC filters]]~~		{{electronics}}

	~~[[Saw Filter]]~~

TimVK4YEH at 22:14, 18 December 2008

2008-12-18T22:14:12Z

← Older revision		Revision as of 15:14, 18 December 2008
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	~~rleated~~ wiki pages : [[Electronic Theory]], [[capacitors]]. [[Inductors]], [[Voltage]], [[Current]]		related wiki pages : [[Electronic Theory]], [[capacitors]]. [[Inductors]], [[Voltage]], [[Current]]

	A filter is an electric circuit (often called a network) that allows certain frequencies to pass but rejects (attenuates) other unwanted frequencies.		A filter is an electric circuit (often called a network) that allows certain frequencies to pass but rejects (attenuates) other unwanted frequencies.

TimVK4YEH: added info about bpf types

2008-10-25T07:52:57Z

added info about bpf types

← Older revision		Revision as of 00:52, 25 October 2008
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	===Band Pass Filters===		===Band Pass Filters===

	Band Pass filters allow a specific band of frequencies to pass and block all those above and below. ~~these~~ are typically used in repeater instalations to "notch" the frequency of the repeater and reject all unwanted frequencies.		Band Pass filters allow a specific band of frequencies to pass and block all those above and below. These are typically used in repeater instalations to "notch" the frequency of the repeater and reject all unwanted frequencies.

	[[Image:Vk4yeh_bandpass_block.jpg \|600px]]		[[Image:Vk4yeh_bandpass_block.jpg \|600px]]

			As the diagram above indicates, a bandpass filter is created by combining a low-pass and a high-pass filter. Obly desired frequencies are allowed to pass.

	====Capacitive====		====Capacitive====

	[[Image:Vk4yeh_capacitive_bpf.jpg \|500px]]		[[Image:Vk4yeh_capacitive_bpf.jpg \|500px]]

			The components R1 and C1 fulfill the low-pass features of the filter. C2 then becomes the high pass section of the filter.

	====Inductive====		====Inductive====

	[[Image:Vk4yeh_inductive_bpf.jpg \|500px]]		[[Image:Vk4yeh_inductive_bpf.jpg \|500px]]

			Components R1 and L1 complete the high=pass section of the filter, while L2 filters out low frequencies.

	===Band Stop Filters===		===Band Stop Filters===

TimVK4YEH: added bpf diags

2008-10-25T06:31:19Z

added bpf diags

← Older revision		Revision as of 23:31, 24 October 2008
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	High Pass filters allow the transmission of high frequency transmissions and block frequencies below the design frequency.		High Pass filters allow the transmission of high frequency transmissions and block frequencies below the design frequency.

	~~'''~~Capacitive~~'''~~		====Capacitive====

	[[Image:VK4YEH_capacitive_HPF.jpg \| 400px]]		[[Image:VK4YEH_capacitive_HPF.jpg \| 400px]]
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	The impedance of the capacitor C1 increases with decreasing frequency. High impedance at the capacitor blocks low frequency signals.		The impedance of the capacitor C1 increases with decreasing frequency. High impedance at the capacitor blocks low frequency signals.

	~~'''~~Inductive~~'''~~		====Inductive====

	[[Image:Vk4yeh_inductive_HPF.jpg \| 400px]]		[[Image:Vk4yeh_inductive_HPF.jpg \| 400px]]
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	Band Pass filters allow a specific band of frequencies to pass and block all those above and below. these are typically used in repeater instalations to "notch" the frequency of the repeater and reject all unwanted frequencies.		Band Pass filters allow a specific band of frequencies to pass and block all those above and below. these are typically used in repeater instalations to "notch" the frequency of the repeater and reject all unwanted frequencies.

			[[Image:Vk4yeh_bandpass_block.jpg \|600px]]

			====Capacitive====

			[[Image:Vk4yeh_capacitive_bpf.jpg \|500px]]

			====Inductive====

			[[Image:Vk4yeh_inductive_bpf.jpg \|500px]]

	===Band Stop Filters===		===Band Stop Filters===

TimVK4YEH: added hpf diags and brief info

2008-10-25T06:03:59Z

added hpf diags and brief info

← Older revision		Revision as of 23:03, 24 October 2008
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	High Pass filters allow the transmission of high frequency transmissions and block frequencies below the design frequency.		High Pass filters allow the transmission of high frequency transmissions and block frequencies below the design frequency.

			'''Capacitive'''

			[[Image:VK4YEH_capacitive_HPF.jpg \| 400px]]

			The impedance of the capacitor C1 increases with decreasing frequency. High impedance at the capacitor blocks low frequency signals.

			'''Inductive'''

			[[Image:Vk4yeh_inductive_HPF.jpg \| 400px]]

			The impedance of the inductor L1 decreases with decreasing frequency. Low frequency signals are in effect shorted out by the inductor with most of the voltage drom occuring at the series resistor R1.

			the cut-off frequency of a high pass filter is the frequency below which the voltage across the load is 70.7% of the input voltage.

	===Band Pass Filters===		===Band Pass Filters===

TimVK4YEH: added links to other wiki pages

2008-10-20T22:08:01Z

added links to other wiki pages

← Older revision		Revision as of 15:08, 20 October 2008
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			rleated wiki pages : [[Electronic Theory]], [[capacitors]]. [[Inductors]], [[Voltage]], [[Current]]

	A filter is an electric circuit (often called a network) that allows certain frequencies to pass but rejects (attenuates) other unwanted frequencies.		A filter is an electric circuit (often called a network) that allows certain frequencies to pass but rejects (attenuates) other unwanted frequencies.

TimVK4YEH: /* What is cut-off frequency? */

2008-10-20T22:05:07Z

What is cut-off frequency?

← Older revision		Revision as of 15:05, 20 October 2008
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	<math> f_{cutoff} = \frac{1}{2\pi RC}</math>		<math> f_{cutoff} = \frac{1}{2\pi RC}</math>

			R = the resistance of the series resistor R1

			C is the capacitance of the capacitor C1

	===High Pass Filter===		===High Pass Filter===

TimVK4YEH: added info on cut-off frequency

2008-10-20T22:03:54Z

added info on cut-off frequency

← Older revision		Revision as of 15:03, 20 October 2008
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	==Filter Design==		==Filter Design==

	===Low Pass Filter===		===Low Pass (LP) Filter===

	A low pass filter is designed to pass low frequency signals and to block those above a certain design frequency. In ham radio these are typically used to block [[VHF \| VHF]] [[Harmonics \|harmonics]] of [[HF\|HF]] transmissions that interfere with TV reception.		A low pass filter is designed to pass low frequency signals and to block those above a certain design frequency. In ham radio these are typically used to block [[VHF \| VHF]] [[Harmonics \|harmonics]] of [[HF\|HF]] transmissions that interfere with TV reception.

	~~'''~~Inductive~~'''~~		====Inductive====

	[[Image:Vk4yeh_lowpass_inductive.jpg \| 400px]]		[[Image:Vk4yeh_lowpass_inductive.jpg \| 400px]]
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	The [[Impedance \|impedance]] of the [[Inductors \|inductor]] L1 increases with increasing frequency. The increase in impedance blocks high frequency signals from reaching the load.		The [[Impedance \|impedance]] of the [[Inductors \|inductor]] L1 increases with increasing frequency. The increase in impedance blocks high frequency signals from reaching the load.

	~~'''~~Capacitive~~'''~~		====Capacitive====

	[[Image:Vk4yeh_lowpass_capacitive.jpg \| 400px]]		[[Image:Vk4yeh_lowpass_capacitive.jpg \| 400px]]

	The [[Impedance \|impedance]] of the [[Capacitors \| capacitor]] C1 decreases with increasing frequency. High frequencies are shorted out by this low impedance in parallel with the load. Most of the source voltage is dropped across the serier resistor R1.		The [[Impedance \|impedance]] of the [[Capacitors \| capacitor]] C1 decreases with increasing frequency. High frequencies are shorted out by this low impedance in parallel with the load. Most of the source voltage is dropped across the serier resistor R1.

			====Which one do I use?====

			The inductive LP filter is often the preferred filter in AC - DC power supply design. It is used here becasue of its ability to filter out the left over "ripple" created when AC is converted to DC in a [[rectifier \| Rectifier Circuits]] circuit. The addition of a series resistor in the capacitive LP filter is often undesirable in this application as it increases the internal resistane of the power supply circuit.

			Capacitive LP circuits in situations where it is desirable for the resistive reactance is to be a minimum. In addition, capacitors tend not to "couple" with other components (generate interference in or receive interference from other components in the form of electric or magnetic fields).

			====What is cut-off frequency?====

			The cut-off frequency of a capacitive LP filter is the frequency above which the output voltage falls below 70.7% of the input voltage. For a simple capacitive filter as described above, the cutoff frequency is given by:

			<math> f_{cutoff} = \frac{1}{2\pi RC}</math>

	===High Pass Filter===		===High Pass Filter===

TimVK4YEH: /* Low Pass Filter */

2008-10-20T21:10:37Z

Low Pass Filter

← Older revision		Revision as of 14:10, 20 October 2008
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	===Low Pass Filter===		===Low Pass Filter===

	A low pass filter is designed to pass low frequency signals and to block those above a certain design frequency. In ham radio these are typically used to block [[VHF \| VHF]] [[Harmonics \|harmonics]] of [[HF\|HF]]transmissions that interfere with TV reception.		A low pass filter is designed to pass low frequency signals and to block those above a certain design frequency. In ham radio these are typically used to block [[VHF \| VHF]] [[Harmonics \|harmonics]] of [[HF\|HF]] transmissions that interfere with TV reception.

	'''Inductive'''		'''Inductive'''

TimVK4YEH: added internal links

2008-10-20T21:10:02Z

added internal links

← Older revision		Revision as of 14:10, 20 October 2008
Line 7:		Line 7:
	===Low Pass Filter===		===Low Pass Filter===

	A low pass filter is designed to pass low frequency signals and to block those above a certain design frequency. In ham radio these are typically used to block VHF harmonics of HF transmissions that interfere with TV reception.		A low pass filter is designed to pass low frequency signals and to block those above a certain design frequency. In ham radio these are typically used to block [[VHF \| VHF]] [[Harmonics \|harmonics]] of [[HF\|HF]]transmissions that interfere with TV reception.

	'''Inductive'''		'''Inductive'''