Rich, Many thanks for your reply.
>From your description, it then sounds as if I'm hearing a real signal. I do have a theory that there may be some sort of electronic signal getting into my feedline. My coax isn't routed ideally, as a good portion of it runs between two entertainment centers chock full of transformers, etc. These birdies or signals as I hear them change in pitch over a wide range, not just 100Hz. For example, if I start at 28.375, I can hear a solid tone. As I go to 28.376, the tone pitch increases and so on until it peaks at 28.380. At 28.381, I can no longer hear it. If I go back down in frequency, the pattern repeats itself with the tone pitch decreasing. I seem to hear these "birdies" spaced every 500-700 KHz. I'm going by memory now as I don't have the rig in front of me. If I remove the antenna, most of them go away. When I say most, I'd guess about 98% of them. Only some which are very strong are still barely audible, but their behavior doesn't change as I tune around. They are not by your description fast tuning. With the antenna connected, the loudest of these signals will peak my S-meter at S3. With no antenna, it may be an S0-S1. Interestingly, removing the antenna does not affect the sub receiver as I can still hear them a little bit when the sub is set to ANT1. Switching the sub to the BNC though, and all remaining signals disappear. I'll have to play around a little bit more to determine the origin, but I was surprised to suddenly hear all of these signals spaced quite evenly apart. I began to think that this was synthesizer noise, as it does sound similar to the DDS signals. I remember telling Wayne over the phone that I was pleasantly surprised after the build, because the first thing I did was to tune around the entire frequency range with no antenna attached to test for birdies, and I did not hear any at all. 73, James KC2UEE On Wed, Mar 4, 2009 at 10:07 AM, Richard Ferch <[email protected]> wrote: > James, > > Any signal coming in from the antenna will change pitch when you tune the > radio in CW, SSB or DATA mode. That's not how you tell a birdie from a real > signal - it's removing the antenna that distinguishes them. A real signal > will either disappear entirely or at least become much weaker when the > antenna is removed. Internal birdies, on the other hand, usually sound > louder when the antenna is removed, because the noise floor surrounding > them > drops. > > Note also that there is a difference between the situation with nothing > connected to any of the K3's antenna connectors, and having anything at > all, > such as an antenna switch or a dummy load or just a short piece of coax, > connected to one of the connectors. If the signal is still there with > nothing whatsoever touching any of the antenna connectors, then it is > likely > a birdie internal to the radio. From your description, it sounds as if you > are hearing external signals, not birdies. > > There are different kinds of birdies. Some are on fixed frequencies, just > like real signals, and others are harmonics that tune more rapidly than > real > signals. The birdies that are removed by the new signal removal feature are > the ones that change pitch abnormally rapidly as you tune the radio. > > With a real signal, if you change the receiver's frequency by 10 Hz, the > pitch of the signal changes by 10 Hz. With one of these "fast" birdies, > changing the tuning of the radio by 10 Hz might cause the pitch of the > birdie to change by 300 Hz. These "fast" birdies also change pitch when you > rotate the Shift control - real signals do not. > > Using a 2.7 kHz roofing filter, as you tune past a real signal it will be > audible over a tuning range of about 2.7 kHz, and will sweep steadily from > very low to very high pitch (or vice versa) as you tune past it. In > contrast, a "fast" birdie might only be audible over a tuning range of > about > 100 Hz, i.e. as you tune the radio past the birdie it will jump right > across > the audible range of pitches within only 100 Hz of dial movement. These are > the birdies that the signal removal feature works on. It doesn't work on > birdies that are on fixed frequencies and tune like real signals. > > 73, > Rich VE3KI > > > > ______________________________________________________________ > 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
