There are recommendations in the K3 Owner's manual (see "Crystal Filter Setup", indexed, on page 46) :
Use VFO A to set the gain in dB. In general, you'll want to add 1-2 dB for 400-500 Hz filters, and 3-4 dB for 200-250 Hz filters. and there is a table (with essentially the same guidance) in K3 Utility Help for the Filter Configuration page. I've lost the table formatting in cut/paste from Help, but here's the information: Narrow crystal filters tend to have more passband loss than wide filters. You can compensate for this effect by specifying an amount of added gain to use for each filter in receive mode. Enter the desired gain "boost", in decibels, for each filter. You may specify a value between 0 and 8 dB. Elecraft recommends using the initial loss compensation values below. You may wish to further adjust the values for your particular filters. Part Number Bandwidth Gain KFL3A-200 0.20 kHz 3-4 dB KFL3A-250 0.25 kHz 3-4 dB KFL3A-400 0.40 kHz 1-2 dB KFL3A-500 0.50 kHz 1-2 dB KFL3A-1.0K 1.00 kHz 0 dB KFL3A-1.8K 1.80 kHz 0 dB KFL3A-2.1K 2.10 kHz 0 dB KFL3A-2.7K 2.70 kHz 0 dB KFL3A-2.8K 2.80 kHz 0 dB KFL3A-6K 6.00 kHz 0 dB KFL3B-FM 13.00 kHz 0 dB 73 de Dick, K6KR -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of [email protected] Sent: Saturday, May 28, 2011 12:17 PM To: Elecraft Subject: [Elecraft] K3 Roofing Filter Gain Setup Gents, I am searching without much luck for recommendations for the gain setting recommendations for roofing filters. Specfically I have a 700 hz 8 pole and a 200 hz filter 5 pole. There is a gain setting in the k3 setup menue and I remember there were recomendations on how to choose this setting. However, I have not been able to find reference on the net. Please can anyone provide some guidance as the performance when these filters are engaged with digital modes is rather disapointing. What I mean by this is that a signal can be very clean with the 2.7 or 2.1 filter engaged but if I use on of these filters the signal becomes very poor. I want to use these to isolate close in signals but there appears to be a lot of distortation so they are basically of little use. I am betting that there is more to this gain setting than meets the eye and that is where my problem is. I have put the gain for these two filters at 1 and the 2.1 & 2.7 at zero. I will be playing around with the settings, but there is a method to set this parameter so I need to learn what and why so I can make them work the way they are supposed to work. Thanks and have a great holiday. Don KD8NNU ______________________________________________________________ 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
