There's something about Cookie's description of how one can hear noise that makes me think that perhaps some of these "noisy" K3 comments are due to having an expectation that is simply not realistic.
I get the impression that the expectation may be that at some point, with a given signal strength, and enough signal to noise ratio, you will hear no noise at all. I know this is false - unless you are using FM and the receiver is locked on that one signal. Even under such a "full quieting" situation, you can still hear lightning crashes through the FM signal if they're strong enough. The only other way that this would happen is if we were removing the noise using DSP techniques, and re-creating the desired signal absent of the noise that will always be there. I have tried such DSP stuff, and what remains does not sound all that good to me, and it needs to be used sparingly. When we're listening to CW or SSB, the level of the signal is constantly changing in amplitude from both fading and just from the constant waveform variance. If the AGC is set to a value (slow) that holds the gain down during the variances, it will mask the apparent amount of noise that we hear. Its not gone, but we don't hear it as much. To confirm this just switch from fast to slow AGC and back to fast on most any receiver and you will notice this phenomena. The point is that there will be noise within your pass band regardless of how narrow it may be and how strong the signal may be that you are listening to. Am I recognizing an unrealistic expectation by users of the K3 (or most any receiver) or am I just misinterpreting this comment? 73, Bob W5OV -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of WILLIS COOKE Sent: Saturday, December 19, 2009 11:37 AM To: [email protected]; Elecraft Reflector Subject: Re: [Elecraft] [K3] Noisy K3 receiver There are two ways to hear noise that comes from the antenna. If you are hearing it while hearing a CW tone, it is strong enough to compete with the signal and about all you can do is narrow the band width or mentally filter it. If the noise is blanked by the key down signal, but you are hearing it in the pauses it can still be annoying and you can still perceive the receiver to be noisy. In the latter case, changes in the AGC, or RF gain can be effective and reduce the annoyance. This is primarily why I like my slope at about 6 instead of 10. But, I am mostly a CW operator with some SSB. I don't operate AM or FM with my K3 which would certainly have different requirements. Also there is a difference in what is appropriate for weak signal operation or strong signal operation. In a contest situation you repidly switch between strong and weak signals so you probably would prefer a compromise setting. Willis 'Cookie' Cooke K5EWJ ________________________________ From: Don Wilhelm <[email protected]> To: [email protected] Sent: Sat, December 19, 2009 9:23:08 AM Subject: Re: [Elecraft] [K3] Noisy K3 receiver Maarten (and all), There are two separate noise sources to be considered here, and it is important to separate them. One is the internal receiver noise, and the second is demodulated noise that comes into the receiver via the antenna port. For anyone who suspects that the K3 itself is noisy (because of internal noise), I encourage those owners to do an MDS measurement. If the internal noise is excessive, the MDS will be greatly reduced - MDS is the minimum signal level that can be detected above the receiver noise floor. The Elecraft XG1 or XG2 is an inexpensive signal generator that will do the task - and the instructions for measuring MDS are in the manual. If your K3 is not 'up to par', then that problem can be fixed. OTOH, if the noise is coming into the receiver on the antenna port, there is not much that can be done to eliminate it - it is just like any other "signal" coming in from the antenna. The K3 does offer tools such as the attenuator and AGC adjustments that can better handle than noise. Unfortunately, there is not a "one size fits all" solution because each source of noise is different in its character and amplitude. I cannot comment intelligently to those who are comparing the K3 audio noise output with that of another receiver because I do not have access to the receivers they are comparing. I can only guess that the difference may be due to differences in receiver gain, AGC action, bandpass width, or the shaping of the audio spectrum. Without doing actual measurements, these variables cannot be quantified. 73, Don W3FPR Maarten van Rossum wrote: > I hope that with the help of this topic on the reflector, I too am able to > set my K3 correctly for my circumstances so I too can enjoy noise free > reception. > > ______________________________________________________________ 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 ______________________________________________________________ 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 ______________________________________________________________ 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
