Roofing Filters, Transmitted IMD And Receiver Performance .

Sherwood Engineering1What’s important when it comes tochoosing a radio?Rob SherwoodNCØBRoofing Filters,Transmitted IMD andReceiver Performance

2 Was the wrong thing being tested or did the test notapproximate a real amateur environment,environment especiallya CW contest environment? R-4C tested well for Dynamic Range, but flunked CWcontest 101101. 70s: League expanded testing to include Noise Floor &Dynamic RangeRange, new concepts for the amateuramateur. RadioR di performedfd miserably,ibl yett SpecsSWWereGoodG d Used it during the ARRL 160m CW contest Purchased a new Drake R-4C in 1975Wh Did I StartWhySt t TTestingtiRRadiosdi?

3 Close-in dynamic range numbers are ALWAYS worsethan the wide-spaced numbers, for a radio with a singlewide roofing filterfilter. Solution:Solution Place test signals close together so they passthrough 1st IF Filter the Next Amplifier Mixer 20 kHz test showed no hint of the problem If the first IF was 6 - 20 kHz wide, be it at 5 MHz, 9 MHzor 45 - 70 MHz,, the radio would overload in a CW pilep up.p 20 kHz Dynamic Range test showed that in a multig the radio’s front end.conversion radio,, it was onlyy testing

4 Close-in DynamicyRangeg Noise FloorWhat 2 Numbers are Most Importantfor a CW Contester?

5League normally only publishes noise floor for a CWb d idth ttypicallybandwidth,i ll 500 HHz CW filtfilter.Noise floor can be measured at any filter bandwidth, CW orSSB, for example.Sensitivity 10 dB Signal Noise / Noise (10 dB S N/N)Noise Floor 3 dB Signal Noise / Noise (3 dB S N/N)Sensitivity is a familiar number, normally applies to SSB.What is Noise Floor?

6Why is it less important for SSB operators?Why is Close-in Dynamic so important for CW ops?Whatt isWhi Close-inCli DynamicDi RangeRvs. Wide-SpacedWid SdDynamic Range?What is Dynamic Range?

7IMDSignalThird Order IMDSignalIMD

8Filter600 HzWideAmplifierMixerFilter500 HzWideThis keeps the undesired strong signals from progressingdown stream to the next stagesMixerFilter6–12 kHzWideWhatt if we couldWhld switchit h iin a narrow RRoofingfi FiltFilter onlylslightly wider than the final selectivity?

9First IF Filter at 7070.455455 MHz12 kHz WideIMD 20 kHz Away20 kHz SpacingFirst IF Filter at 7070.455455 MHMHz12 kHz WideIMD 2 kHz Away2 kHz SpacingWide & Close Dynamic Range

10 Dynamic Range55 dB60 dB65 dB70 dB75 dB80 dB85 dB90 dB95 dB100 dB500 Hz CW filter Signal Level Causing IMD Noise FloorS9S9 5 dBS9 10 dBS9 15 dBS9 20 dBS9 25 dBS9 30 dBS9 35 dBS9 40 dBS9 45 dBNoise Floor of -128 dBm Assume S9 50 V which is –7373 dBm Assume a typical radio:Preamp OFF If you knowktheth close-inli ddynamici range off a radio,di att whath tsignal level will IMD start to be a problem?When are 2 Out of Pass BandSignals a Problem?

11Transmitted IMD Collins 32S-3

129 dB12 dB17 dB20 dB-3030 dB-37 dB-4242 dB-48 dB3rd5th7th9th-3939 dB-49 dB-5959 dB-68 dBDifferencein dBOrder Collins YaesuIMD32S-3 FT-450Compare the Old vs. New

13IF FiltFilter vs. AdjAdjacentt SiSignall andd IMD SSplatterl ttSignal 5 kHz AwayClose in Signal and SplatterClose-in

14 (Some key click and phase-noise energy may be heard.)CW signals do not have IMD products, thus strong adjacent signalsdo not have much energy in the CW passband of your filter.On CW,OC , a singles g e widede roofingoo g filterte iss notot adequateadequate. Would a 3 kHz roofing filter be better? Yes, a fairly new concept.Other radios, old and new with similar performance: Drake R7/TR7,Collins 75S-3B/C, Icom 781, TS-830/930, FT-1000X, T-T Omni-VFor SSB, a single 15 kHz roofing filter is adequate, such as in theIcom 756 Pro II / Pro III with a close-in dynamic range of 75 dBdB.It depends on your mode of operation. How Many Roofing Filters are Needed?

15 The Sherwood 600 Hz CW roofing filter fixed theR 4C iin 1976R-4C1976, andd ththe TTen-TecT OrionO i putt thatth tconcept in a commercial design in 2003. Nowthe Elecraft K3 also offers multiple roofing filtersof AM, SSB & CW bandwidths. Contesters – DXers – Pileup operators need thebest receiver possible, especially for CWoperationConclusions

16 IC-7800 3-kHz filter is 5 kHz wide. FT-2000 3-kHzfilter is 7 kHz wide, with worse IMD than its 6 kHz filter. Now the buzz word is a 3-kHz roofing ffilterfin upconversion radios, though some are pure hype. 25 yyears of upp conversion radios have ggenerallyyoffered a 20 kHz dynamic range in the 90s but a 2 kHzclose-in dynamic range in the 70s. Typical degradation ofdynamic range within the up conversion filter bandwidthis 25 dB.

17The only radios with no roofing filters at allare from Flex, like the 5000A. It basicallyconverts everything to audio and filters it inDSP.DSPThe Orion II and the K3 roofing filters are inthe 8 to 9 MHz rangerange, similar to the RR-4C4C at 5MHz.It is not possible to offer CW bandwidthRoofing Filters at VHF (up-conversion)ffrequencies.i

182008 Elecraft K3: 101 dB (with 200 Hz roofing filter)2007 Ten-Tec Omni-VII: 80 dB2007 Flex 5000A: 96 dB2005 Ten-Tec Orion II: 95 dB2001 Ten-Tec Omni-VI : 80 dB1976 Sherwood / Drake RR-4C:4C: 84 dB80 dB or better @ 2 kHz.What dynamicyrangeg is ppossible and needed for CW?

1972 dB69 dB63 dB63 dB63 dBCollins 75S-3B/C:Kenwood TS-870S:Yaesu FT-2000:Icom IC-7000:Yaesu FT-One:58 dB56 dB49 dBDrake R-4C Stock:Yaesu FT-757:Yaesu VR-5000:Yaesu FT-101E:59 dB77 dBKenwood TS-850S:Other radios for comparison,p, 2 kHz data:

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Kenwood TS-850S: 77 dB Collins 75S-3B/C: 72 dB Kenwood TS-870S: 69 dB Yaesu FT-2000: 63 dB Icom IC-7000: 63 dB Yaesu FT-One: 63 dB Yaesu FT-101E:59 dB Drake R-4C Stock: 58 dB Yaesu FT-757: 56 dB Yaesu VR-5000: 49 dB 19