Mark, This question is asked over and over, and you will get answers all over the board. The real answer is that a lot of your filter choices will depend on what kind of operating you will do and in what modes. If you do a lot of contesting or work DX in heavy pileups where there are a lot of strong stations close to what you want to hear. then you should have only the 8 pole filters, their skirts are a little bit steeper - BUT - these are only roofing filters, the DSP takes care of most of the filtering, and does it quite well. If you will be adding the KRX3, the filters must be matched for diversity reception, so the simple way is just to use the 2.8 kHz filters.
In fact, the DSP filtering is good enough to be used alone, it goes down to 50 Hz width - but the DSP can only do its job if the ADC is not being overdriven - the hardware AGC does protect from that, but will result in "pumping" of that hardware AGC if there a quite strong (S-9 +20 or more) nearby signals. The K3 roofing filters will knock down the strength of those nearby signals to a point where the hardware AGC is not activated. Eric Swartz has posted some information for making filter choices on the Elecraft website, I suggest you read that too. Bottom line is that you will have to review the type of operating that you will do with the K3 and select your filters from that information. If your operation is rather casual, you may only need the stock 2.7 kHz filter. If you want to transmit either AM or ESSB or you want wide bandwidth SWL reception, you will need the 6 kHz filter, and if you want to either transmit or receive FM, you will need the 13 kHz filter. Another option is to wait and see - order your K3 with the stock filter (or perhaps the optional 2.8 8 pole filter), and operate for a while to determine your usual DSP-set bandwidths for each mode you use - that information will reveal the filters that you will derive most benefit from. A word of caution on my above suggestion - if you will install the KRX3 immediately, you must remove it to add more filters, and that operation has been referred to as a "shoehorn operation", so your choice is to guess at the filters needed and order them up front or delay the installation of the KRX3. Without the KRX3 installed, the filters are a breeze to change. 73, Don W3FPR On 10/3/2010 7:27 PM, [email protected] wrote: > Hi Guys, in my quest to purchase a new K3 I am worndering about 8 pole filter > choices. I see that there is a 1.8 KHZ 8 pole ssb filter and a 250 HZ 8 pole > cw filter that is avaiable. If one purchases one of these filters wouldn't > that basically solve the problem of not needing all the other filters at > different KHZ? This probably is a stupid question, but would really like to > learn. Mark KB3Z > ______________________________________________________________ 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
