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Topic: Roofing filter

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	Roofing filter - Wikipedia, the free encyclopedia
		A roofing filter, is a type of audio filter, used in a HF receiver (shortwave radio).
		The goal of a roofing filter is to reduce the passband of the 1.
		The receiver's bandwidth is not performed by the roofing filter but by a following crystal filter, mechanical filter or DSP filter.
	en.wikipedia.org /wiki/Roofing_filter (133 words)

	Radio-Electronics.Com :: Radio Receiver Filter Options
		Ceramic filters are made from a specialised family of ceramics, and the elements for filters are normally in the form of a small disc.
		At either end of the filter assembly there are transducers which convert the signals from their electrical form to mechanical vibrations, and back again at the other end.
		Roofing filters are often found in multi-conversion superhet receivers where the main filter is found after two or possibly three conversion stages.
	www.radio-electronics.com /info/receivers/filters/filter_options.php (2208 words)

	50 MHz Noise Cancelling Receiver Front End
		The 1st I.F. crystal filter is sometimes called a "roofing filter" and it sets the maximum bandwidth into the rest of the receiver.
		Noise pulses (ignition and power line) pass through the mixer and 1st I.F. filter and are split into two channels: one to the noise amplifier and the other to the delay line and the noise gate (an on and off switch).
		Filtering and gain are required to have enough "noise" signal to control and thus cancel.
	www.ham-radio.com /n6ca/50MHz/50appnotes/noiz_rx/noizcancelRx.html (1830 words)

	List of telecommunications filter terms - Wikipedia, the free encyclopedia
		This is a list of filter-related terms initially derived from the Glossary of Telecommunication Terms published as Federal Standard 1037C.
		Please see the Federal Standard article for copyright-related issues, as not all parts of the source document are in the public domain.
		bandpass filter -- bandpass limiter -- band-stop filter -- character filter -- dichroic filter -- digital filter -- filter -- Hanning filter -- high-pass filter -- interference filter -- Kalman filter -- loop filter -- low-pass filter -- mode filter -- optical filter -- roofing filter -- security filter
	en.wikipedia.org /wiki/List_of_filter_terms (127 words)

	W5YR's Notes on Filtering & DSP (Site not responding. Last check: 2007-11-06)
		There is a widely-held misconception that "a filter is a filter" and "you can't have too many of them." Nothing could be further from the truth.
		Every conventional crystal lattice or ladder filter in the signal path contributes attenuation, varying response within the passband, relatively poor adjacent-frequency rejection (shape factor), comparatively poor ultimate rejection, substantial phase distortion at and near the passband "edge" frequencies, and non-trivial frequency-dependent time delay.
		The effect of the 6 kHz filter is to reduce the broadband noise input to the ADC by 4 dB, as compared to the 15 kHz filter.
	www.qsl.net /ab4oj/icom/dspfilter.html (853 words)

	Active Filters for Video - Maxim/Dallas
		Such filters are categorized by their amplitude-vs-frequency characteristic, or the name of the person whose polynomial describes it, e.g.; Bessel, Butterworth, Chebyshev, or Cauer.
		is the cutoff frequency of the filter in radians.
		Response of the 20MHz, 3-pole Butterworth filter with sin(x)/(x) amplitude compensation for the DAC using the MAX4450/51.
	www.maxim-ic.com /appnotes.cfm/appnote_number/2159/ln/en (4363 words)

	INRAD Filters (Site not responding. Last check: 2007-11-06)
		This means that the roofing filter can be up to 25 KHz wide, effectively offering a barn-door for other unwanted signals to drive the other parts of the receiver.
		The wider trace is the unmodified board, and the narrow is with the roofing filter.
		Not with the main receiver - the filter is designed for regular SSB and narrower modes such as CW and the data modes.
	www.vinecom.co.uk /roofing.html (520 words)

	ICOM 756Pro3 Roofing Filter (Site not responding. Last check: 2007-11-06)
		The Icom 756 ProIII uses a fundamental-mode monolithic crystal filter for the roofing filter.
		Although it is more expensive than overtone-mode filters, the fundamental-mode filter has a better shape factor and is less susceptible to intermodulation distortion under strong-signal conditions.
		This is the same 15kHz crystal filter used in the IC-7800.
	www.universal-radio.com /catalog/hamhf/3756roof.html (51 words)

	HF Decoding \| Code 30
		After this 'roofing filter', the signal is then ready to be demodulated by one of many demodulation methods, some of which are user selectable as follows.
		Therefore a special and optimized low pass filter is constructed in software which, just like the roofing filter, is dependant on the set baud speed and shift.
		Because the roofing filter and the post detection low pass filter are both set up from parameters derived by measuring the signal being received, this frequency discriminator will give a much better performance than the frequency discriminators you may be used to working with up to now.
	hoka.defiant.co.uk /Code30 (1566 words)

	Real-time Spectrum Analyzer in WiNRADiO WR-G313 Receiver
		The real-time spectrum display shows the actual situation on the band within the "roofing filter" bandwidth of the receiver.
		This highlighted filter passband can be shifted, or its width altered, by simply dragging its center or edges using a mouse, to exactly match the received signal, maximize the signal-to-noise ratio and achieve the best possible signal clarity.
		One of the demonstrable advantages of software-defined receivers is the enormous flexibility and a potential for development of new features, or innovative and improved implementations of existing features.
	www.winradio.com /home/g313-realtime.htm (406 words)

	Rooftop Resource
		This has spawned a whole new industry which specializes in light-weight growing mediums, filter cloths, roofing membranes, plant stock, and how-to books and kits; nurseries, designers, consultants, and contractors have been forced to relearn and re-adjust in order to compete in the new market, with the result that they now have more and varied work.
		Soil, decking, people, planters - and where they are placed on your roof deck - all have an impact on the existing structural/carrying capacity of the roof, as well as that of the rest of the building.
		The main thing to remember is that each roof is as different as the gardener who uses it.
	www.cityfarmer.org /roofmonica61.html (828 words)

	International Radio: Enhancement Kits for Amateur Radio
		These roofing filters can substantially reduce the third order Intermodulation from multiple strong signals in the 2 to 20 kHz region either side of the tuned frequency.
		Roofing filter mod boards and filters can now be ordered for the Omni series radios.
		The filters are 4 poles and the 600 Hz is #763 while the 2400 Hz is #764.
	www.qth.com /inrad/kits.htm (1647 words)

	Comments from John Thorpe
		A gradual elimination of components that may cause the effect pointed to the roofing filter being the guilty party and indeed slight warming or cooling of that part caused significant changes in the IMD level virtually confirming it as the culprit.
		Whatever is happening in the roofing filter cannot be described with a standard polynomial transfer function - indeed the input / output characteristic must actually change with the applied signal level and as such its IMD performance cannot be characterised with an IP3 figure.
		To summarise the observations - the roofing filter produces IMD products when one or both of the test signals are in the transition band of the filter (between pass-band and stop-band) and the level of these products does not obey the expected 1:3 input / output level ratio.
	www.aoruk.com /comments.htm (6272 words)

	Analog Devices: Analog Dialogue: Othello™: A New Direct-Conversion Radio Chip Set Eliminates IF Stages
		The signal then passes through an RF band filter (a so-called "roofing filter") that serves to pass the entire desired frequency band while attenuating all other out-of-band frequencies (blockers-including frequencies in the transmission band) to prevent them from saturating the active components in the radio front end.
		The roofing filter is followed by the low-noise amplifier (LNA).
		The output of the loop filter drives the tuning port of a voltage-controlled oscillator (VCO), with frequency ranges that cover the GSM and DCS transmit bands.
	www.analog.com /library/analogDialogue/archives/33-10/othello (2867 words)

	Images > Orion > HF Transceivers > Amateur Radio > Ten-Tec, Inc.
		Selectable roofing filters allow the transceiver to reject any unwanted signals outside the target frequency that will have a negative impact on receiver performance.
		As the BW control for the DSP filters is tuned from 2410 Hz to 2400 Hz, the 2.4 kHz roofing filter automatically is switched in line.
		You can manually select the desired roofing filter for any of the available bandwidths (stock: 15 kHz, 6 kHz, 2.4 kHz, 1 kHz) or optional (1.8 kHz, 500 Hz, 250 Hz) and have that filter always be in line regardless of where the DSP filter bandwidth is set.
	radio.tentec.com /Amateur/Transceivers/TT565/Images (2120 words)

	Inrad #762 Filter
		In December, ARRL published their Expanded Test Report results which indicated that the standard 1000 Hz roofing filter had much better IMD performance than the 500 Hz.
		These filters have higher insertion loss than the 4-pole filters used in the 1000 and above positions, so an additional amplification stage for the 250/500 was added to compensate for the increased insertion loss of the narrow filters, and this extra amplification stage apparently causes IMD degradation.
		Further complicating the issue, the 250/500 Hz filters use a slightly different IF frequency (9.000750) than the 1000 and higher filters (9.001500), so you cannot simply move the 500 Hz filter to the 1000 position.
	users.vnet.net /btippett/inrad_.htm (1138 words)

	Welcome to Yaesu.com
		As a result, you may visually observe the effects of filter adjustments you make (using the Contour or Notch filters, for example), and it is an especially effective tool for building your intuition as to the effects and benefits of the various filter systems of the FT DX 9000.
		The Contour filter in the '9000 now allows you to define whether it will act as a low-Q Notch filter, or alow-Q peaking filter, to be used for enhancement of the receiver passband response.
		Roofing Filters of 15 kHz, 6 kHz, and 3 kHz are provided on the Main and Sub receivers (separate filters, of course), and they are automatically selected according to the operating mode.
	www.yaesu.com /indexVS.cfm?cmd=DisplayProducts&ProdCatID=102&encProdID=LGAPdoibciM=&DivisionID=65&isArchived=0 (2357 words)

	Comments on 8845 \| Ask MetaFilter
		Run-off from your roof will result in tar-water in your garden, not, if you are growing any vegatables or fruits, what you want to eat.
		I roofed a small section of my house with a friend who used to do it for a living.
		And then there is flashing, gutters, boots for vent pipes, and so on; unless your roof is very simple and you live in a cool climate, stick to something like wallpaper as a husband and wife project.
	ask.metafilter.com /mefi/8845 (2245 words)

	Re: [Elecraft] K6SE Sprint Summary for Team Elecraft (Site not responding. Last check: 2007-11-06)
		Most ham rigs use a 15 kHz roofing filter as they have a FM mode and need it, or the designers follow the lead of designers of FM mode rigs and continue to use 15 kHz roofing filters, or else they haven't figured out how to do it yet, or worse, don't care.
		I think the main reason for the use of wide roofing filters is the desire for general coverage reception.
		The secondary receiver in the Orion is more typical of current transceiver design, using up-conversion and a wide roofing filter; it does have general coverage.
	www.ac6rm.net /mailarchive/cgi-bin/mesg.cgi?a=elecraft-list&i=3D7F4D45.2060908@buttery.org (597 words)

	testing close wide spaced selectivity R4C Yaesu Icom Kenwood Drake
		R4C's have far too much filter leakage to be useful on crowded bands using CW with a wide roofing filter.
		In the case of CW a roofing filter, to be useful, needs to be about 500Hz wide or less.
		A roofing filer really needs to eliminate the adjacent channel up and/or down, and that means a roofing filter that passes only 3kHz or less.
	www.w8ji.com /receivers.htm (2064 words)

	FW: RE: SSB (Leif Åsbrink Oct 14 2002) (Site not responding. Last check: 2007-11-06)
		For short delay times through the filter, use the buttons in the upper left corner of the baseband graph to display the filter function with few points.
		The reason is that some fft implementations are approximate and they contribute to the total filter response that the calibration is intended to cancel out.
		Another thing is that the filters you use on HF bands may be narrow enough to affect calibration.
	www.nitehawk.com /sm5bsz/linarch/msg01555.html (677 words)

	DRS Technologies Inc. - SI-8616 VME Digital Receiver
		The standard configuration (/BW1), which is optimized for narrowband applications, has a 500 kHz roofing filter in front of the digitizer and therefore supports IF bandwidths up to 500 kHz.
		The /BW2 configuration has a 1.23 MHz roofing filter in front of the digitizer and therefore supports IF bandwidths up to 1.23 MHz.
		Typical filter shape factors are better than 1.35:1.
	www.drs.com /products/index.cfm?gID=17&productID=678 (938 words)

	WiMo: Yaesu Desktop radios
		Three selectable roofing filters (3, 6 and 15kHz wide) work on the first IF level and are vital for providing an excellent blocking dynamic range.
		The VRF filter is engaged using mechanical relays, not diodes that can contribute IMD, and it may be manually adjusted from the front panel.
		The Bandpass Filter is particularly effective in weak signal work, such as EME (Moonbounce), as the CW bandwidth may be reduced to a razor-sharp 25 Hz, with a variable center frequency.
	www.wimo.com /yaesufix_e.htm (2843 words)

	Unknown Impedance
		Another way would be to do a roofing filter, then an amplifier, then the filter using the amplifier known parameters.
		The roofing filter would be so wide band that any ripple in it would be minimal in the IF frequency range.
		By roofing I mean one that cuts out the sum mixer product at 3 GHz or so and the LO feed through at 1.5 GHz or so but lets through your IF.
	www.edaboard.com /ftopic35710.html (375 words)

	Nws-699.htm
		A “quasi-optimum” filter is defined as one having some of the characteristics of the optimum network.
		One example is a direct opening between the input portion of the filter and the output.
		Those examples show that filter networks are approaching optimality, but that advances in technology will still provide plenty of room for improved performance in the future.
	www.rsmicro.com /nws-699.htm (1075 words)

	Japan Radio NRD-545 Comments
		This filter along with some narrowing of the filter setting (about 2.2 to 2.4) and using the passband tuning cleans audio up significantly.
		Since the receiver has a DSP function, and the bandpass filter is variable, I would not expect it to have switched filters, but I could be wrong.
		In fact, I had to use the SSB filters on the Yaesu and JST, to get the same results as I was getting on the 545 with the 6.0 khz bandwidth settings.Particularly, this was snagging a close in AM ham signal on 75 meters.
	www.ticon.net /~n9ewo/545old.html (4760 words)

	N1EU's Orion Setup Page (Site not responding. Last check: 2007-11-06)
		Typical setup for tough contesting condx: 1650hz BW with 1.8Khz roofing filter, +300hz PBT, RX EQ -10dB CW Roofing Filter Replace the stock 1000hz roofing filter with the Inrad 600hz roofing filter.
		If you do install the narrower roofing filters (you really don't need them, even in the worst contest condx) then one trick to set the center freq adjustment in the Filter menu is to feed the Orion audio into a soundcard and use spectrum analysis software.
		Set the dsp selectivity wide (2000hz) and manually select the xtal filter (Filter menu) and tune to band noise.
	www.qsl.net /n1eu/orion/Osetup.htm (603 words)

	Radioworld Canada Icom Amateur Ham Radio Equipment (Site not responding. Last check: 2007-11-06)
		While a 15 KHz or more filter is used in almost all current amateur transceivers, it is not the "optimal design" for SSB, CW or AM operation.
		The IC-7800 utilizes two 1st IF roofing filters, one for FM operation and the second with a 6 KHz bandwidth for SSB, CW, AM and data modes.
		Fundamental-type 64MHz roofing filter The IC-756PROIII uses a fundamental-mode monolithic crystal filter for the roofing filter.
	www.radioworld.ca /ham/icom/icomhf.php (2074 words)

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