Hi, Roy.
I've had the 1500 Hz 8-pole Inrad filter in my K3 for at least 18 months now, and while I don't do a lot of SSB contesting I certainly appreciate that filter when I do. It works fine and gives just a bit extra margin of protection against really loud adjacent stations. What DSP bandwidth you use is up to you. Of course there isn't much point in setting it much wider than 1.5/1.6/1.8 KHz or so because the filter will chop it off anyway. I have often set my DSP as narrow as 1.2 KHz or even sometimes 1.0/1.1 KHz, but the key to decent intelligibility with any of those really narrow bandwidths is to shift the center frequency much lower than the K3 default 1.5Khz. I typically set the center frequency to about 1.1 KHz when I have the bandwidth at 1.5 KHz, and I drop down to a center frequency about 0.9 KHz when I have the bandwidth set to 1.1 KHz. A few caveats to all of that: a. The optimum center frequency will probably be different depending on the voice you are listening to. I sometimes have to adjust the center frequency depending upon the caller, occasionally as low as 700 Hz but usually higher than normal. A few voices seem difficult to copy at 1.5 KHz or less bandwidth no matter what center frequency I use. b. No filter on this earth is going to protect you from in-band splatter. Somebody 3 KHz away with a 5 KHz wide signal is going to mess you up even if you're using the 1.5 KHz filter. I'm always amazed at the incredibly bad, almost unintelligible signals we have to put up with during a major SSB contest, many of them coming from long time high profile contesters. I find it to be simply pathetic. My voice won't hold up during a SSB contest anymore, so I'm honestly tempted to spend the next CQ WW DX SSB contest just recording audio samples (both good and bad) identified by callsign. c. I bought the 1.5 KHz filters instead of buying the 1.8 KHz filters. If you already own the 1.8 KHZ filters I'm not sure it would be worth the hassle to switch, especially considering the in-band splatter issue. The only thing you gain from the 1.5 KHz filters is 150 Hz additional protection from strong signal overload either side of you since the DSP can give you whatever narrow bandwidth you might want for moderate signal strengths. 73, Dave AB7E On 5/12/2010 1:08 PM, Roy Morris wrote: > I would like to hear from anyone who is using the #727 Inrad 1500 Khz roofing > filter. I wonder if this filter adds to razor sharp clear SSB reception when > properly set in the DSP bandwidth. What DSP bandwidth setting should be > used to insert this filter? Any comments will be appreciated. Thanks. Roy > Morris W4WFB > ______________________________________________________________ > 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 > > ______________________________________________________________ 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
