I have been making some critical listening tests of the K3 receiver which are completely subjective and non-repeatable by anybody else, but for what it's worth I would like to share my observations.
In my opinion, the three biggest factors governing the "noisiness" of the receiver are: 1. Headphone response 2. Receiver gain 3. AGC settings 1. Headphone response. It was almost shocking to me how different the receiver sounds with different types of headphones. It may be that most folks could solve 80% of their noisiness just by changing headphones. It seems to me that using very hi-fi headphones (or ear buds) can increase the white noise hiss above 10 kHz significantly. There is a night-and-day difference between some iPod-style ear buds and a computer headset that I own, for example. I am not here to recommend one brand over another, but simply to warn folks that a lot of what you are hearing might be eliminated just by switching to another (perhaps cheaper!) headphone or ear bud. If you can hear 12 kHz, that pair of iPod/Walkman/MP3 ear phones may be doing you more harm than good. 2. Receiver gain. Bill, W4ZV, and Barry, N1EU, have already said this well enough, but I can't stress enough how critical it is not to use too much gain. This means turning off the preamp-- which for some reason a lot of folks are very resistant to doing-- or leaving the front end attenuator on, or turning down the RF gain. If you can't imagine leaving the attenuator on (and the preamp off) all the time below 10 MHz, you are probably just the person who can most benefit by doing so. You will not lose any sensitivity. Things will get *quieter*, but they won't disappear completely. On a very related note, I once wrote about my experience with well-known QRPer and author Rick Campbell, KK7P, and though I can no longer find it in the Elecraft archives it appears to have been preserved here, on page 7 of this document: http://www.larclub.net/history/document/2000-/2003-10%20HI-Q%20October%202003.pdf 3. AGC settings. There are two pertinent parameters here: AGC THR (threshhold) and AGC SLP (slope). AGC THR, which goes from 002 to 008 (with a default of 005) has a major effect on noise level at the audio output. If you turn it down to 002, the AGC kicks in at a much lower level-- even on the noise when no signal is present-- and this tends to quiet the receiver. Tune to noise, change this parameter from 002 to 008 and listen to the difference. AGC SLP, which is adjustable from 000 to 015, with a default of 012, has a lesser effect on the noise. Lower numbers allow a wider audio dynamic range... loud signals sound louder. Higher numbers compress or hard limit the audio into a smaller dynamic range... weak signals and strong signals tend to sound equally loud. As a final thought, why wouldn't the folks who object to the noisiness leave NR on all the time at a relatively unagressive level such as F5-1? You paid for it; why not use it? I'm not saying you shouldn't pursue other remedies such as low pass filters, etc., but simply suggesting there may be a better way to use what's already there. Just a few observations. Al W6LX P. S. As a final final thought, consider that I cannot listen to MP3 recordings (or satellite radio) because of the digital artifacts in the audio that drive my psycho-acoustical brain crazy, yet which many people can't hear or don't mind. I believe this gives me a certain empathy for the folks who feel the same about the K3 audio, as well as empathy for one possible objection to my NR suggestion above. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
