signal spacing more. signal spacing decreases, some point they will fa

The Datasheet Archive - 100 Million Datasheets from 7500 Manufacturers.

signal spacing more. signal spacing decreases, some point they will fa

Datasheet Thumbnail

Top Searches for this datasheet

words about intermodulation dynamic range roofing filters: "Roofing filter" current buzzword high-end radios. Just what does mean? Basically, roofing filter simply first filter radio. usually placed close first mixer possible order effective. term "roofing" stems from fact that protects rest radio following from passband signals. There basic designs modern radios. There radios with only bands that first region, typically between MHz, there radios that have their first region, well above MHz. latter usually called Conversion" radios. There advantages either way, lets examine some them. Orion, Omni like first type. Yaesu, Kenwood Icom radios like second. first Orion, etc., region. These filters easy make have been available many years. conversion radios first VHF, somewhere region. crystal filters, either discrete monolithic types. Narrow bandwidth filters have been available until recently, radios with typically wide filters. ability radio ignore strong signals near tuned frequency greatly enhanced roofing filter. Ideally, final desired selectivity should first protect following high gain stages from strong band signals. lower possible filters narrow possible make practical filters that narrow. Three four about narrow they region. Roofing filters dynamic range: Following antenna connection, most radios have bandpass filter. This filter usually wide amateur band even wider. first mixer have tens hundreds signals input while trying separate signal copy. ability first mixer handle these signals without excessive intermodulation function circuit design. does have limit, above which there intermodulation which becomes stronger than noise floor radio. difference between these levels known dynamic range. This characteristic generally measured with just signals same strength some particular frequency spacing. signals within operating band, this called third order dynamic range. When signal spacing much greater than roofing filter bandwidth, dynamic range radio determined first mixer other early stages. Most high-end radios today have dynamic range area
signal spacing more. signal spacing decreases, some point they will fall into passband roofing filter. They will then impinge following second mixer stages, which will create intermodulation much lower levels. Thus closely spaced signals receiver dynamic range drops dramatically maybe transition width from first mixer dynamic range limit second mixer limit determined bandwidth roofing filter. Let's make some guesses signal levels involved here. Assume have radio with dynamic range noise floor -135 signals spaced kHz. This means there signals tune second tune they create false response tuned frequency when their level dBm, above noise floor. strong that? Well, typical radio dBm, these signals above signals weaker that that will cause problem these wider signal spacings. Now, suppose dynamic range within roofing filter bandwidth only filter wide FT-1000MP). signals spaced less will fall inside this filter, they stronger, they will cause intermodulation signals passband. This only signal. radio contest possible have several signals band around your tuned frequency which stronger than this hear false signals under those conditions. Narrowing roofing filter effect widely spaced signals, intermodulation takes place earlier signal chain receiver. However, improve receiver performance close-in signals. above example, reduce roofing filter bandwidth kHz, Inrad Roofing Filter does, widest separation which will cause problem becomes instead This reduce interference substantially crowded band conditions. it's apparent that signals spaced roofing filter bandwidth divided minimum spacing which dynamic range radio will improved. Shall narrow possible? Suppose roofing filter. Signal spacings down 62.5 will improved. Doesn't this seem close operate next your neighbor contest? think station would have some difficulty trying copy other. What reasonable? Maybe something which starts attenuating signal spacings makes sense. This roofing filter with bandwidth. other advantage making filter wider that insertion loss great. Insertion loss reduce sensitivity radio. pole filter necessary? does pole filter compare? difference between filters insertion loss. filter this difference difference about filter. receiver overall gain should kept fairly constant filter bandwidths change preserve
characteristics keep meter reading constant. Also, receiver noise floor suffer there gain reduction close front end. need insert amplifier otherwise change gain make extra filter loss when narrow pole filter selected. This reduce dynamic range radio, been seen Orion performance numbers ARRL review. pole filters have advantage, particularly narrow bandwidths, even though selectivity good signals falling down skirts. There less advantage going wider filter such 2400 bandwidth. example, Inrad's pole, 2400 filter insertion loss about while pole filter with same bandwidth loss difference small enough that could ignored pole filter would provide better off-channel rejection. Thus bandwidths good pole filter will outperform pole filter, narrow bandwidths simpler filter best. Roofing filter products: Orion: Some time ago, after much discussion with W4ZV, introduced pole, bandwidth filter centered 9001.5 Orion. This filter centered frequency could into slots Orion, allowing narrow roofing filter without needing extra amplifier which switched when selecting bandwidths. result dynamic range close signals dramatically improved. Here what Sherwood said about this filter compared unit. spacing, improvement dynamic range) order spacing improvement closer dB." have discontinued reference #352) favor completely assembled unit which ready plug reference #762. (See page.) Yaesu FT-1000MP series: Earlier this year located source which produce good filters 70.455 other frequencies. procured some numerous tests. Initial results were promising board designed before Dayton Hamvention. units completed tested documented each unit. Customers receiving these filters were asked report their findings. Some those comments reproduced below.
have been doing tests with Orion FT1000MP crowded large interfering signal conditions. must FT1000MP doing very cellent earlier tests clearly showed superiority Orion those kinds conditions."
real eye-opener when tuned across neighbor ham's signal, which pegging S-meter over. been listening just below frequency awhile even realized air. have turned noise blanker presence local strong signals, hear products when they tuned outside passband filter. consider price real bargain. disproved prevailing theory that roofing filters were impractical. Keep good work." appears that less touchy signals when tuning around band with wide filter open. Looks like keeper." About noise blanker."I notice shotgun effect used from almost totally gone. difference here phenomenal!!" "Without attenuation receiver course still shows intermod main clean. very happy customer." Europe."initial subjective listening with over European signals crowding band indicates improved close-in strong signal capabilities." During Field Day: could walk over other stations hear difference between stock FT-1000's Inrad equipped FT-1000. Does roofing filter make difference.YES! Would again.YES! Does Roofing Filter give advantage? YES! Don't tell competition about your Roofing Filter, need advantages get."
Testing also done independent laboratory (not ours) sample performance obtained with installed shown below. Signal Spacing Blocking
these performance parameters important you, indications that save from $1500 almost $9000 keeping your 1000MP, installing this buying radio. Performance data original radio modified shown plot below. These curves plots made injecting signal into radio antenna connector detecting resulting signal output board 70.455 MHz.
wider trace unmodified board response narrow trace after Inrad installed. There small increase gain which slight effect lowering noise floor. What expect from this mod? Less crowded band conditions, particularly from stations offset frequencies either side operating frequency. Will defeat noise blanker? roofing filter circuit before noise blanker sample taken. filter delay added both signal noise. Will this allow wide band SSB? roofing filter will determine overall widest bandwidth receiver, which about wide. will also limit bandwidth signals when
both sidebands being detected. receiver altered still used wider bandwidth modes. make bandwidth narrower use? quite difficult make narrow filters MHz. There quite variation from unit unit, have chosen bandwidth that will work even with worst-case variation bandwidth. poles work well, poles? most important part filter characteristic from pass-band down about either side center. Eight poles would provide much better stop-band isolation, it's required roofing filter would make noticeable improvement performance. benefit from installing this mod? Operators experience lots strong signals which close together frequency. This would include contesters with antennas, people with really good antennas good location, dxpeditioners large pileups. Casual operators probably notice difference receiver performance. Omni series: presently working roofing filter Omni radios. Plans quite formalized yet, some preliminary data from shown below. Signal Spacing Filter Bandwidth 2800 2800
hope make this unit available late fall winter this year. IC-765 IC-781: Sample filters feasibility testing order will here August. Stay tuned. Other radios: time permits.

signal spacing more. signal spacing decreases, some point they will fa

Top Searches for this datasheet

Other recent searches