> A while ago, I bought a 6 KHz AM filter. I was a little confused > when I could only open the filter width up to 5.0 KHz in AM mode.
A little study of the Owner's Manual will reveal that the displayed bandwidth is the "audio" bandwidth (High - Low). In AM, RF bandwidth is *twice* the audio bandwidth because AM is a DOUBLE SIDEBAND mode. While one can, in fact "open up" the DSP to 5 KHz even with the 6 KHz IF filter installed, the received bandwidth will be limited to about 3 KHz (carrier +/- 3 KHz) by the IF filter unless one selects Sync AM mode which used only one sideband (again, study the Owners Manual).
So, I just bought the FM filter and installed it. To my dismay, I still can only widen the bandwidth to 5.0 KHz in AM mode. I have AM mode checked in the mode list for the FM filter.
That is correct, the DSP is limited to 5 KHz (and the audio chain contains a 4.2 KHz "brickwall" lowpass filter in any case). The FM filter still provides 13 KHz (carrier +/- 6.5 KHZ) selectivity in the IF stages which allows the full 5 KHz maximum detection bandwidth in the DSP (demodulator). However, again AM is a *double sideband* mode - the detected audio bandwidth will always be no more than *one half* of the IF/RF bandwidth. > The 6.0 KHz filter is still configured for TX on AM. Correct, transmit *audio* bandwidth is limited to 3 KHz and that requires an IF filter *at least* 6 KHz wide. > Also, when increase the audio in the AM mode to more than half, What do you mean by "increase audio ... to more than half"? Half of what? What audio - transmit or receive? 73, ... Joe, W4TV On 9/1/2013 11:48 PM, Michael Marx wrote:
Hi to the group! I have been slowly loading my K3 up. I concentrated on CW at first, but now I am adding other stuff. A while ago, I bought a 6 KHz AM filter. I was a little confused when I could only open the filter width up to 5.0 KHz in AM mode. I called the factory and they told me that, yes, you could only open it up to 5 KHz with the 6 KHz AM filter. They told me that if I bought the 13 KHz FM filter, then I could open the bandwidth all the way to 13 KHz. So, I just bought the FM filter and installed it. To my dismay, I still can only widen the bandwidth to 5.0 KHz in AM mode. I have AM mode checked in the mode list for the FM filter. The 6.0 KHz filter is still configured for TX on AM. Also, when increase the audio in the AM mode to more than half, the audio becomes distorted and just a little more advanced from that, the audio shuts off altogether. Any ideas are appreciated. 73 Mike WB0SND Michael Marx [email protected] ______________________________________________________________ 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
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