On Mon, 1 Sep 2008 12:38:31 -0400, Joe Subich, W4TV wrote: >Jim is entirely correct although we will disagree a bit about >the need to keep the line out as low as he suggests. My own >measurements say the harmonic distortion is insignificant as >long as the Line Out levels stay below .5V RMS.
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. >The headphone outputs are exceptionally clean as long as the >audio amplifier level is kept below 2V peak (1.4V RMS) and >the output impedance is not too low. In fact, noise in the >audio amplifier (headphones) is 70 dB below the desired (CW >at 500 Hz) signal +/- 250 Hz and 80 dB below the desired >signal above that. All harmonics are down more than 60 dB >as long as the headphone level is not at levels that could >damage hearing (> 1.4V RMS). YES! My measurements of the headphone output, taken at about 1 volt RMS, show harmonic distortion at about 0.02% and IM at less than 0.1%. That is VERY VERY good! 1VRMS is LOUD! >The headphone output in the K3 is cleaner than any amateur >receiver I have seen and certainly better than the current >crop from Ikensu or Yaecomwood. Yes. 73, Jim _______________________________________________ Elecraft mailing list Post to: [email protected] 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
