K3 6m pre-amp
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I've just done an A/B comparison between my K3 and my Kenwood TS-480SAT.
I had the pre-amp switched on in both transceivers. On the 480 I was able to comfortably hear a signal from my signal generator some 10 dB lower in level on the 480 than I could on the K3, which is quite a difference. I think the often quoted MDS (minimum discernible signal) makes the specification appear "better" than it really is and is not realistic. MDS is a measure of the signal that increases the output of the receiver by 3 dB when the signal generators output is turned on. You couldn't copy by ear a signal of that level except for the slowest of Morse keying and then it would be very hard going. The "old fashioned" signal level that gives a signal to noise ratio of 10 dB is more meaningful, as a 10 dB above the noise signal is a comfortable listening level that we can all equate to. I had done earlier A/B comparisons between the K3 and 480 where I didn't think there was a difference, I must have mistakenly not use the 480 pre-amp... 73 Dave, G4AON K3/100 #80 _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Dave,
If I do the conversion to microvolts, it indicates 0.8 microvolts for no preamp and 0.04 microvolts for a preamp (I think the column headings are reversed) I believe MDS is a 3db s/n ratio. For comparison. My IC706IIG has the following 50MHz specs 0.12 microvolts for 10 db s/n ratio. Filter unspecificed, mode SSB/CW, preamp on. My guess it is the stock (2.7KHz?) filter What it really measures, I don't know. I know why they didn't use the narrower available CW filters for the ICOM specs. The 300Hz filter has a lot of uncompensated for loss. So much so I can't use it on 6M CW for any weak signal work. All that aside. Trying to put the two on an equal footing. Say 400Hz, 3db S/N indicates the 706 would come in at about (preamp on, 400Hz lossless filter, 3db S/N) yields -131 dbm (if I did the math right) One thing for sure, one can't compare S-meter readings from rig to rig. It has to be some kind of measurement with attenuators or lab equipment- - like you did with the lab generator. What are the 480 specs on 6M? I do disagree with a CW op not being able to copy a signal with a 3db s/n ratio. In fact, decent operators can copy CW signals several db below the noise. 73 de Brian/K3KO ------------------------------------------------------------------------------ Hallo, > I can't see any comment made by the BCC re the 6m sensitivity, only Wayne's response. I am working on the translation of a much delayed update of the BCC report. In the mean time we have done MDS measurements for various bands: ----------------------------------------- Band w Preamp w/o Preamp 160m -129dBm -137dBm 80m -133dBm -138dBm 40m -133dBm -138dBm 20m -134dBm -138dBm 15m -132dBm -137dBm 10m -130dBm -137dBm 6m -129dBm -134dBm Table 2: MDS of the K3 at 400Hz ----------------------------------------- vy 73 de toby -- DD5FZ (ex 4n6fz, dj7mgq, dg5mgq, dd5fz)
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Not 0.8 it is 0.08 microvolts for no preamp
K3KO
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