Joe, Fine business on those measurements, and thank you for providing the data. I note that all except the K3 show the taper from 1600 Hz to the upper passband edge that follows something similar to a "pink noise" spectrum. The K3 is flat without EQ. It is interesting that the K3 Norm does show some falloff, but not nearly as much as either the FT-2000 or the MK V or IC-706.
I am ready to conclude that the K3's ultra-flat in-passband response is the cause of several of the "noisy" responses. That can be easily handled by shaping with the RX EQ if one desires. I do data modes frequently, and prefer the flat response of the K3. The audio response above the filter passband apparently has less influence than I had originally expected. 73, Don W3FPR Joe Subich, W4TV wrote: >> It would be interesting (at least to me) for someone to make similar >> measurements on an FT-1000 - perhaps with the INRAD filter. I am >> especially interested to know if the in-passband response shows a >> similar taper at 2 kHz and above, and what is the response for the >> FT-1000 above the filter passband. >> > > Here are some measurements using Spectrogram and broadband noise: > > FT-2000 --- MK V --- IC-706 ------ K3 ------ > > Analog DSP MKIIG Norm BW=4 EQ > > 50 -34 -44 -49 -46 -35 -7 -35 > 100 -31 -24 -27 -40 -18 -6 -18 > 200 -17 -10 -9 -21 -5 -2 -5 > 300 -6 -4 -4 -11 -1 0 -1 > 400 -3 -2 -1 -5 0 0 0 > 600 -2 -1 0 -1 0 0 2 > 800 -1 -1 0 0 0 0 1 > 1000 -1 -1 0 -1 0 0 0 > 1200 0 -1 0 -2 0 0 0 > 1400 0 0 0 -1 0 0 -2 > 1600 -1 -2 -1 -2 0 0 -3 > 1800 -2 -3 -2 -3 0 0 -4 > 2000 -5 -5 -2 -4 -1 0 -5 > 2200 -7 -6 -3 -6 -2 0 -7 > 2400 -8 -8 -4 -8 -2 0 -8 > 2600 -10 -10 -6 -15 -3 0 -9 > 2700 -23 -13 -7 -27 -4 0 -10 > 2800 -34 -19 -11 -31 -8 0 -14 > 2900 -41 -32 -24 -33 -18 0 -24 > 3000 -50 -43 -36 -35 -58 0 -60 > 3100 -42 -67 0 > 3200 -58 0 > 3300 0 > 3400 0 > 3500 0 > 3600 -1 > 3700 -2 > 3800 -4 > 3900 -5 > 4000 -13 > 4100 -34 > 4150 -66 > > All measurements were made at the speaker output for consistency. > All measurements were made in USB mode with the default filter > settings. FT-1000MP Mark V was measured with both the analog > and DSP (100-3100 Hz setting) detectors. > > The two additional K3 measurements are 1) FM filter, BW=4.00 > and FC=2.00 and 2) "NORM" using the "pink EQ" settings (1.60=-3, > 2.40=-5, 3.20=-6). > > Note the K3 audio amplifier is the cleanest hands down. The other > transceivers had noise floors at about -120 dBV (IC-706 mkIIg was > -100 dBV). Except for what appear to be artifacts of the ADC > clock at 4, 8, 12, 16, 18 and 20 KHz the K3 out of band audio > noise is <140 dBV. > > 73, > > ... Joe, W4TV > > > > > > > > > >> -----Original Message----- >> From: Don Wilhelm [mailto:[email protected]] >> Sent: Saturday, December 19, 2009 5:14 PM >> To: [email protected] >> Cc: [email protected] >> Subject: Re: [Elecraft] : K3 receiver noise - my test results (long) >> >> >> Joe, >> >> I think you may have hit on some major part of the "problem" here. I >> measured the passband (and out of passband) response of my K3 >> and my K2, >> Yaesu FT-900 and Yaesu FT-817. All measurements were with the SSB >> filter in all transceivers, and the K3 DSP width was set to >> maximum. My >> K2 has the 2.4 kHz filter and the Yaesu transceivers have the >> stock SSB >> filter. >> >> The test setup consisted of an Elecraft broadband noise generator >> feeding that receiver and the output was observed with >> Spectrogram. The >> receiver gain controls were adjusted to place the peak in-passband >> response at -30 dB. >> I also connected an antenna and listened to several signals >> participating in a 40 meter roundtable, and made my own 'quality of >> sound' assessment. >> >> Several things became apparent as a result of these tests. >> 1) the K3 in-passband response is almost flat - from 500 Hz >> to 2500 Hz >> it showed less than 1 dB variation. >> 2) All the other passband responses were down about 5 dB at >> 500 Hz and >> essentially flat from 1 kHz to 1600 Hz, then began a gradual falloff, >> being down 3 dB at 2 kHz, down 8 dB at 2.5 kHz, the Yaesus >> were down 17 >> dB while the K2 was down 36 dB (this is the effective high end of the >> passband). So within the passband, there is a rolloff >> similar to that >> which you suggested for the receive EQ settings on all but the K3. >> 3) The response outside the passband on the low end was also >> interesting. The K3 at 200 Hz was only down 3 dB, but >> dropped steeply >> at lower frequencies (I do not have the low frequency mod on my K3). >> The K2 was down 26 dB at 200 Hz while the Yaesus were down 20 dB. >> 4) On he high frequency side out of the passband, the K2 and K3 had >> almost no audio response that showed on Spectrogram - in other words >> greater than 60 dB down from the passband peak. The Yaesu FT-900 had >> audio artifacts that were only 44 dB down at 4 kHz and for the FT-817 >> were only 35 dB down. At 5 kHz the FT-900 had audio content >> at -50 dB >> and the FT-817 had content only 40 dB down. >> >> Summary of my observations - the in-passband response of both Yaesu >> filters and the K2 filter tapered off above 1800 Hz, similar >> to a "pink >> noise" response, while the K3 response was remarkably flat with very >> steep filter skirts. The skirt slope of the other filter >> passbands were >> more gentle. >> >> On the high frequency end, both Yaesu transceivers had considerable >> audio content while the K2 and K3 content was much lower. >> >> My conclusions: I am not certain what K3 owners are >> perceiving as noise >> any more than I had been before these tests. The flatter >> passband of >> the K3 may be sub-consciously perceived as being more 'harsh', but I >> could not equate that to 'noise'. The other filters with a high end >> in-passband response that drops off similar to a "pink noise" >> response >> *could* be causing a perception of additional noise *if* their local >> noise has significant content in the 2 kHz to 3 kHz range - >> yes, the K3 >> will make this section of the audio spectrum louder than the other >> receiver I measured. The "audio hiss" is not coming from the high >> frequency spectrum outside the passband because in that area, >> the K3 and >> the K2 are much more quiet than the others measured. >> >> It would be interesting (at least to me) for someone to make similar >> measurements on an FT-1000 - perhaps with the INRAD filter. I am >> especially interested to know if the in-passband response shows a >> similar taper at 2 kHz and above, and what is the response for the >> FT-1000 above the filter passband. >> >> For those trying the "pink noise rolloff", my measurements >> suggest that >> you should set the RX EQ bands from 100 Hz through 1600 Hz at >> 0 dB, 2400 >> at -3 dB, and 3200 at -5 dB. The 50 Hz band can be set at -16 dB for >> the reasons Joe has stated. >> >> 73, >> Don W3FPR >> >> Joe Subich, W4TV wrote: >> >>> If one is going to attempt to mimic the "pink noise" behavior, >>> there is no need to bother with the low frequency boost. It >>> simply puts more strain on the audio amplifier, increasing the >>> amount of IMD products, with little or no aural benefit. A >>> better RX EQ configuration with essentially the same perceived >>> sound: >>> >>> 50: -16 dB (reduce sub-vocal noise and hum) >>> 100: 0 dB >>> 200: 0 dB >>> 400: 0 dB >>> 800: 0 dB >>> 1600: -3 dB >>> 2400: -5 dB >>> 3200: -6 dB >>> >>> >>> >>> > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ------------------------------------------------------------------------ > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.717 / Virus Database: 270.14.114/2575 - Release Date: 12/19/09 > 03:33:00 > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
