> Anyway, the "noise/distortion" is still there coming out of the > headphone socket.
The spectrum display you sent me shows an excessive level of 50 Hz harmonics - some 15 dB above the noise floor and only 40 dB below the desired signal from 150 Hz to above 3 KHz. That strongly indicates serious grounding issues, power supply filtering problems, improper power supply decoupling and/or soundcard instability. I suggest you read K9YC's information on interfacing and RFI www.audiosystemsgroup.com/publish.htm and resolve that noise issue first. I have seen the K3 audio output "go spurious" when presented a bad load or encountering regeneration (feedback from powered speakers) due to bad grounds. > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Berni G0IDA > Sent: Monday, September 01, 2008 7:13 PM > To: elecraft@mailman.qth.net > Subject: Re: [Elecraft] K3 Harmonic Distortion > > > Yes indeed it would be a sorry situation if an operator can't > tell the difference between a desired signal and an audio > harmonic, fortunately > my thread is not about that. > > Anyway, the "noise/distortion" is still there coming out of the > headphone socket. > > Berni > > Joe Subich, W4TV wrote: > > Jim, > > > > > >> Insignificant depends on the decoder, what you are decoding (PSK > >> or RTTY), band conditions, and the operator. If a PSK operator is > >> using the IF with a broadband setting and tries to work a signal > >> that's really a harmonic, it won't work -- he'll be transmitting > >> on a frequency displaced from the signal he thinks he's working > >> (displaced by 2X the audio frequency of the actual signal if it's > >> a third harmonic, 1X if it't the second harmonic). If it's a > >> crowded RTTY contest, there can be lots of big signals creating > >> that IM. Or the operator could be using a narrow roofing filter > >> and those other signals are not there or heavily suppressed, so > >> can't cause IM. > >> > > > > It would be a sorry situation if an operator can't tell the > > difference between a desired signal and an audio harmonic down > > 50 dB. K3_Line_out.jpg shows the line out spectrum of my K3 > > at 1 KHz, Data_A, 2.8 KHz 1st IF filter and 4 KHz filter. The > > third harmonic is -62 dB and the fifth harmonic is - 80 dB. > > See: www.microHAM-USA.com/Downloads/K3_Line_Out.jpg. > > > > A typical waterfall does not show the spurious signals at the > > soundcard input (noise on the cables) which is well below the > > "band noise" - typically around -60 dBu. > > > > 73, > > > > ... Joe, W4TV > > > > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
