> MCU 1.87 / DSP 1.69, 5-3-08
> * AM RECEIVE WIDTH RANGE INCREASED: The WIDTH control in AM > mode now has a range of 2.8 to 10.0 kHz. Wider settings provide > outstanding fidelity for hi-fi speech and other wide-band signals. > This is the *IF* filter bandwidth -- the traditional way to show > bandwidth for AM, because the required IF bandwidth is twice the > modulation bandwidth. > NORM selects an IF bandwidth of 6.0 kHz in this mode. WIDTH > settings above 6.0 kHz will not be useful unless you have an FM- > bandwidth crystal filter installed (at FL1). Audio response is limited to 4.2 KHz with either the FM filter (13 KHz) or AM filter (6 KHz) at FL1. With the AM filter, 4.2 KHz is wider than necessary. With the FM filter, the 4.2 KHz high cut is less than the 10 KHZ of IF bandwidth. Why is the IF bandwidth and audio response excessively restricted with the FM filter? It should be possible to achieve at least 12 KHz of IF bandwidth and 6 KHz or more of audio bandwidth depending on the filter skirts. > * IF A 2.8 KHZ FILTER IS INSTALLED, SSB "NORM" BW is 2.8 kHz > (was fixed at 2.7 kHz). Can this be extended to CW and Data? It appears that "NORM" is currently fixed at 400 Hz regardless of mode and filter. 500 Hz would be more appropriate for CW with the 500 Hz crystal filter and even wider values might be appropriate for some DATA A modes with a 1000 Hz or 1.8 KHz filter. > * AUTO-SPOT (SPOT with CWT ON) now works with both very > weak and very strong signals. Auto-spot consistently tunes to a tone 50 Hz low (50 Hz below the value set for pitch). > * SSB TRANSMIT BANDPASS EXTENDED AT LOW END. Improvement > is about 2 dB at 300 Hz, 3 dB at 200 Hz, and 6 dB at 100 Hz. Can this be made optional? Excess LF response only wastes power at low frequencies and occupies excess bandwidth. > Additional improvement possible via TX EQ. Will TX EQ be made mode and/or input dependent? Setting TX EQ for voice screws up the audio response for digital mode (AFSK A and DATA A) operation. The same is true for RX EQ. 73, ... Joe, W4TV _______________________________________________ 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
