On Wed, 6 Aug 2008 11:14:51 -0600, Bob Cunnings wrote: >It's a 600 ohm transformer, rated for 7dBm max (about 1.7 Vrms >across 600 ohms).
This datasheet does not show a graph of distortion vs level vs frequency, but it is specified for 300Hz - 3.5 kHz, and its frequency response is specified at 0 dBm (0.78 vrms). It is well known that saturation in transformers is a function of the core, and increases rapidly at lower frequencies below the design limits of the core. As audio transformers go, these are small transformers. They are specifically designed for telecom, where levels are generally well controlled and there's no energy below 300 Hz. They're fine at low levels, but if you overdrive them or feed them LF, the DO saturate, and both IM and harmonic distortion can get nasty. They ARE big enough for the intended use -- driving a sound card to decode RTTY and PSK -- but you've got to keep the level down in the range where they're designed to operate. See http://audiosystemsgroup.com/FilterTestNotes.pdf for my measurements with a high quality professional FFT analysis system. BTW -- Jensen Transformers are pretty much the accepted standard for professional audio transformers, and their data sheets are quite detailed. You can learn a lot about how transformers behave by studying them. http://www.jensen-transformers.com/ 73, Jim Brown K9YC _______________________________________________ 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
