James When you start looking around for sources of these external signals, be prepared for some surprises. I had a fairly strong signal on 10m that was a real nuisance. I turned off the power to my house and it went away. I finally found it in the controller for our air mattress in the bedroom. Now, during a serious 10m effort, like the ARRL 10m contest, I just unplug the controller until after the contest. 73, Bob N6WG
----- Original Message ----- From: "KC2UEE" <[email protected]> To: "Richard Ferch" <[email protected]> Cc: <[email protected]> Sent: Wednesday, March 04, 2009 8:15 AM Subject: Re: [Elecraft] K3 birdies - question? > 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 ______________________________________________________________ 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
