Wayne, Won't the birdies still show up on a panadapter? They'll be mysterious blips that disappear when you click on them to tune them in?
--Oliver Johns, W6ODJ On 10 Feb 2009, at 9:09 AM, wayne burdick wrote: > The K3 is a down-conversion superhet that uses high-level signal > injection to achieve its excellent dynamic range. Short of adding many > more pounds of shielding and elaborate cable dressing, there's no way > to completely eliminate the few spurious signals that rise above the > noise floor. > > These "Fast-tuning" birdies result from UHF harmonics of the signal > sources that leak back into the main mixer. In some cases they combine > and end up in either the I.F. or R.F./image range of the receiver. > Typically, they involve 9th-order or higher harmonics of the VFO. > That's what makes them "fast": if you move the VFO 100 Hz, the pitch > of > the birdie will shift on the order of 1 to 2 kHz. > > While it is possible to attenuate some spurious responses by moving > coax cables around, there is a firmware-based approach that we're > working on. The general idea is to shift the 1st LO and BFO a small > amount, simultaneously, when the VFO is tuned to specific frequencies. > If the shift is small relative to the communications bandwidth in use, > it will hardly be noticeable when the VFO is tuned over a "mapped out" > spot in the tuning range. > > I have this new firmware nearly completed, and in early tests, it > appears to work very well. Fast-tuning birdies that are mapped out > pretty much disappear as the VFO is tuned over them. The upshot is > that > you can have your cake (outstanding dynamic range in a rig that weighs > less than 10 pounds) and eat it, too (no annoying birdies). > > If you'd like to try a field-test version of K3 firmware that includes > this new feature, please e-mail me directly. > > 73, > Wayne > N6KR > > --- > > http://www.elecraft.com > > ______________________________________________________________ > 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
