It seems to me, and apparently to some others, that an important metric of receiver performance is the ability to fight noise. ARRL has promoted dynamic range, because they can measure it, and the manufacturers have stampeded to win the dynamic range sweepstakes. With the K2, Elecraft jumped to the top of the charts with a bullet, and the K3 cemented their spot at the summit. This is great, and we all love lots of dynamic range and close-in signal rejection.
However, there are big differences in the noise-fighting ammo inside each receiver. I suspect that the DSP chips in some radios are a lot more capable than in others. And I'm pretty sure that there are substantial differences in the algorithms programmed into those chips by various radio manufacturers. As someone on this list pointed out, there are lots of interesting developments in the highly technical and difficult field of DSP research (cf http://www.dspalgorithms.com/products/nr.html ). Ham manufacturers can't carry on this R & D on their own, so they should be doing what manufacturers in other tech fields routinely do, licensing technologies from specialty research companies. But again, we don't know who does and who doesn't. Of course, what we care about is the end result, the S/N as we perceive it. I have corresponded at some length with the receiver test guys at ARRL on this topic. I think it would be cool to develop some sort of test of noise rejection, so I proposed the following: set up a system to measure the S/N of a series of dits (say 3 dits/second with 1-dit spaces between); then add noise until the S/N is degraded to some determined threshold. Try it for various kinds of noise, with dits at various audio frequencies. Their response was to point out that this test, and just about any other one you can propose, has lots of flaws. In particular, the S/N detector is part of the system, so you're testing it jointly with the receiver. Then there are question about what noises to use, etc. etc. The bottom line was that I didn't get anywhere with my proposal. I accept all that. Nonetheless, I am in a location that suffers from various kinds of noises, depending on time of day, day of the week, and band conditions. The best receiver for me would be the one that does the best job of pulling the signals through the noise. Nowadays they all have enough strong-signal rejection for my particular situation, but among the various receivers I have here (K3, K2, Mark V, K1, KX1) there are significant differences in ability to read signal through noise. Whenever someone posts a comment to the effect that receiver X does a better job than Y, I make a note of it. No matter how subjective or casually done these tests may be, they're all we have until somebody devises a more rigorous approach. If such an approach ever does appear on the scene, the manufacturers can go into another competitive scramble, and we'll all be the winners. 73, Tony KT0NY ______________________________________________________________ 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
