[Elecraft] KRX3 roofing filter matching for diversity receive
Stan, you asked a good question-- one I asked about some time ago. When I worked in the aerospace industry, I designed and used analog and digital filters for measurement applications. Most textbook design formulas and procedures are based on 3 dB bandwidths, although sometimes our measurement requirements demanded 0.5 dB bandwidth. Amateur radio IF bandwidths seem to have been standardized at the 6dB points. If the filter designers are reporting 3 dB points, this might account for the difference you asked about. BTW, I just checked the INRAD website and looked for the filter curves for the K3 roofing filters and couldn't find them. They used to be available there. 73, Chuck NI0C K2-10 s/n 5853 K3 s/n 1061 Stan Rife, W5EWA, wrote: I'm not sure why a filter would be advertised as a 250hz filter but actually have a (usable?) bandwidth of 370hz. Is this just a difference in how it's measured? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] KRX3 roofing filter matching for diversity receive
W5EWA wrote: So is the information in the manual just the easy way to set it up, and you can actually put them in whatever slots you want? From reading the manual I understood that they had to be in decending order starting from FL1, and the filters in both receivers had to match for diversity receive. You should always follow the manual carefully. The manual says that filters should be in descending order of width, but they do not have to be in consecutive slots. For example, in my main RX I have a 2.7 kHz in slot 2, a 500 kHz in slot 4, and a 250 Hz (configured to switch in at 350 Hz) in slot 5. Slots 1 and 3 are open. In the sub-RX I have 2.7 kHz and 500 Hz filters. I could have installed the sub-RX filters in slots 1 and 2, or 4 and 5, or 1 and 5, or ..., but I chose to install them in slots 2 and 4 simply to reduce confusion. For diversity receive, you should have similar filters in both receivers, e.g. matched pairs at the bandwidths you usually use during diversity receive. If the filters are 5-pole filters, the offsets should be matched as well. Note that during diversity receive, if the filters in each receiver are not identical (as in my case below 350 Hz widths) you may hear phase modulation, although in my case I can't say that this has ever been a serious problem - to me it sounds rather similar to the AFX feature. There is one other restriction: if you plan to transmit in FM, you must have an FM filter in slot 1 on the main board. 73, Rich VE3KI __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
[Elecraft] KRX3 roofing filter matching for diversity receive
Hi folks, I’m trying to configure the K3 receiver for diversity receive. I’m populating the roofing filter slots in both receivers with matched filters, and the question came up: When the K3 automatically selects the correct roofing filter to match DSP filter bandwidth, does the K3 do this by filter bandwidth, or by FLx number? In other words; when I use the “width” control, and decrease DSP bandwidth from 3.0 Khz to 2.0 Khz on the front panel, the K3 switches from the 2.8 Khz roofing filter located in FL3 to the 2.1 Khz roofing filter located in FL4. With the sub-receiver on, and in diversity receive, does the K3 switch the sub-receiver roofing filter from FL3 to FL4, like the main, or is it smart enough to know that my sub-receiver has it’s 2.8, and 2.1 Khz roofing filters in FL1 and FL2 respectively? Does the K3 select the correct roofing filter by bandwidth, or by FLx number? Is the selection logic the same for main and sub-receiver? The KRX3 manual is a little foggy on this. It says you have to have at least one roofing filter, and if that happens to be the KFL3B FM filter, it MUST be in the FL1 location. It also says that you must have the widest bandwidth nearest FL1, but does not say it must be located at FL1. Bill, W7QQ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] KRX3 roofing filter matching for diversity receive
Roofing filters are selected by either of two ways. One is by directly selecting FLx on the K3 front panel. The other is by changing the DSP bandwidth via WIDTH, LO CUT or HIGH CUT. When the DSP bandwidth is decreased to the crystal filter bandwidth, then that roofer is selected. (Or, when the DSP increases beyond the current roofer's bandwidth, then the next wider roofer is selected.) It is important to note that the roofer bandwidth is specified by the user in the K3 CONFIG menu, and you are not constrained to use either the marketing bandwidth or the actual bandwidth of the filter. You can put in any bandwidth you want because all you are doing is telling the K3 what DSP bandwidth to engage that particular crystal filter. Most users specify the marketing bandwidth of the filter, e.g., 250 Hz for the 250 Hz 8-pole filter. So, as you decrease the DSP bandwidth and reach 250 Hz, that crystal filter will engage. (Or, if you select FLx, then crystal filter 'x' is selected and the DSP bandwidth is set to 250 Hz.) But you can specify 350 Hz, which is actually rational since the real bandwidth of this filter is 370 Hz. Some people even specify a wider DSP bandwidth engagement point such as 400 or 450 Hz, because they want their crystal filter bandwidth INSIDE the DSP bandwidth. So, think about the relationship of the two filters (crystal and DSP), the resultant cascade bandwidth of the two, the shape factor of the two filters, and the passband shape. Decide the DSP bandwidth at which you want your particular crystal filters to engage. There are arguments for keeping the roofer wider than the DSP at all times and vice versa. Remember that when the DSP bandwidth is near the roofer's actual bandwidth, the cascade bandwidth will be significantly less. When one is much narrower than the other then the narrow bandwidth dominates the IF bandwidth, but other RX characteristics like IMD performance will be determined by the roofer bandwidth. Setting the DSP engagement bandwidths for your crystal filters affects both the resultant IF passband width, shape and sound of the audio, as well as the RX performance characteristics such as IMD. If your head hurts thinking about all this, just specify the bandwidth number in the part number of the filter! That is a good default and the radio will work great. Ed - W0YK --- Ed Muns Muns Vineyard - www.munsvineyard.com FaceBook - www.facebook.com/munsvineyard W7QQ wrote: Im trying to configure the K3 receiver for diversity receive. Im populating the roofing filter slots in both receivers with matched filters, and the question came up: When the K3 automatically selects the correct roofing filter to match DSP filter bandwidth, does the K3 do this by filter bandwidth, or by FLx number? In other words; when I use the width control, and decrease DSP bandwidth from 3.0 Khz to 2.0 Khz on the front panel, the K3 switches from the 2.8 Khz roofing filter located in FL3 to the 2.1 Khz roofing filter located in FL4. With the sub-receiver on, and in diversity receive, does the K3 switch the sub-receiver roofing filter from FL3 to FL4, like the main, or is it smart enough to know that my sub-receiver has its 2.8, and 2.1 Khz roofing filters in FL1 and FL2 respectively? Does the K3 select the correct roofing filter by bandwidth, or by FLx number? Is the selection logic the same for main and sub-receiver? The KRX3 manual is a little foggy on this. It says you have to have at least one roofing filter, and if that happens to be the KFL3B FM filter, it MUST be in the FL1 location. It also says that you must have the widest bandwidth nearest FL1, but does not say it must be located at FL1. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] KRX3 roofing filter matching for diversity receive
bill4570 wrote: In other words; when I use the “width” control, and decrease DSP bandwidth from 3.0 Khz to 2.0 Khz on the front panel, the K3 switches from the 2.8 Khz roofing filter located in FL3 to the 2.1 Khz roofing filter located in FL4. With the sub-receiver on, and in diversity receive, does the K3 switch the sub-receiver roofing filter from FL3 to FL4, like the main, or is it smart enough to know that my sub-receiver has it’s 2.8, and 2.1 Khz roofing filters in FL1 and FL2 respectively? Does the K3 select the correct roofing filter by bandwidth, or by FLx number? Is the selection logic the same for main and sub-receiver? Is there some reason you don't want to put the main and subrx filters in corresponding slots? 73, Barry N1EU -- View this message in context: http://n2.nabble.com/KRX3-roofing-filter-matching-for-diversity-receive-tp4200536p4200926.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] KRX3 roofing filter matching for diversity receive
Bill, it's simpler than what you're looking for. You can put your widest filter in FL1 and install them from there in descending bandwidth. Use the K3 utility to set up the filters, much easier than doing it with the config menu. The radio automatically switches in the matching filter that matches WIDTH going down. This will be done separately in each RX regardless of what filter slots were used. You do not have to make slot assignments identical. 73, Guy. On Mon, Dec 21, 2009 at 3:57 PM, bill4...@comcast.net wrote: Hi folks, I’m trying to configure the K3 receiver for diversity receive. I’m populating the roofing filter slots in both receivers with matched filters, and the question came up: When the K3 automatically selects the correct roofing filter to match DSP filter bandwidth, does the K3 do this by filter bandwidth, or by FLx number? In other words; when I use the “width” control, and decrease DSP bandwidth from 3.0 Khz to 2.0 Khz on the front panel, the K3 switches from the 2.8 Khz roofing filter located in FL3 to the 2.1 Khz roofing filter located in FL4. With the sub-receiver on, and in diversity receive, does the K3 switch the sub-receiver roofing filter from FL3 to FL4, like the main, or is it smart enough to know that my sub-receiver has it’s 2.8, and 2.1 Khz roofing filters in FL1 and FL2 respectively? Does the K3 select the correct roofing filter by bandwidth, or by FLx number? Is the selection logic the same for main and sub-receiver? The KRX3 manual is a little foggy on this. It says you have to have at least one roofing filter, and if that happens to be the KFL3B FM filter, it MUST be in the FL1 location. It also says that you must have the widest bandwidth nearest FL1, but does not say it must be located at FL1. Bill, W7QQ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] KRX3 roofing filter matching for diversity receive
H... Ed, I almost tried using the built in translator in Outlook...but then I recognized some of those words, like is and the. :-() It almost let the smoke out of my head. Seriously though, I don't understand the filter setup technicalities. I can get through setting them up per the defaults in the manual, but I would like to understand more about what you said. I'm not sure why a filter would be advertised as a 250hz filter but actually have a (usable?) bandwidth of 370hz. Is this just a difference in how it's measured? I have SN/0690 and am just now installing the KRX3. It arrived a few months after the radio, back in mid to late 08, and I just never got around to installing it. I have identical filters in both the main and sub receiver (13khz, 6khz, 2.8 400 respecitively, with # 5 empty) so I can try out diversity receive. I don't do much CW so didn't figure I needed a 250hz. I'm sure I'll be asking some questions about this in short order, once I get the rig back together. I am doing some of the mods and am currently waiting on some parts and the REV C or D (or whatever it's up to now) DSP board. Stan Rife W5EWA -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Ed Muns Roofing filters are selected by either of two ways. One is by directly selecting FLx on the K3 front panel. The other is by changing the DSP bandwidth via WIDTH, LO CUT or HIGH CUT. When the DSP bandwidth is decreased to the crystal filter bandwidth, then that roofer is selected. (Or, when the DSP increases beyond the current roofer's bandwidth, then the next wider roofer is selected.) It is important to note that the roofer bandwidth is specified by the user in the K3 CONFIG menu, and you are not constrained to use either the marketing bandwidth or the actual bandwidth of the filter. You can put in any bandwidth you want because all you are doing is telling the K3 what DSP bandwidth to engage that particular crystal filter. Most users specify the marketing bandwidth of the filter, e.g., 250 Hz for the 250 Hz 8-pole filter. So, as you decrease the DSP bandwidth and reach 250 Hz, that crystal filter will engage. (Or, if you select FLx, then crystal filter 'x' is selected and the DSP bandwidth is set to 250 Hz.) But you can specify 350 Hz, which is actually rational since the real bandwidth of this filter is 370 Hz. Some people even specify a wider DSP bandwidth engagement point such as 400 or 450 Hz, because they want their crystal filter bandwidth INSIDE the DSP bandwidth. So, think about the relationship of the two filters (crystal and DSP), the resultant cascade bandwidth of the two, the shape factor of the two filters, and the passband shape. Decide the DSP bandwidth at which you want your particular crystal filters to engage. There are arguments for keeping the roofer wider than the DSP at all times and vice versa. Remember that when the DSP bandwidth is near the roofer's actual bandwidth, the cascade bandwidth will be significantly less. When one is much narrower than the other then the narrow bandwidth dominates the IF bandwidth, but other RX characteristics like IMD performance will be determined by the roofer bandwidth. Setting the DSP engagement bandwidths for your crystal filters affects both the resultant IF passband width, shape and sound of the audio, as well as the RX performance characteristics such as IMD. If your head hurts thinking about all this, just specify the bandwidth number in the part number of the filter! That is a good default and the radio will work great. Ed - W0YK __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
Re: [Elecraft] KRX3 roofing filter matching for diversity receive
So is the information in the manual just the easy way to set it up, and you can actually put them in whatever slots you want? From reading the manual I understood that they had to be in decending order starting from FL1, and the filters in both receivers had to match for diversity receive. Stan Rife W5EWA -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Guy Olinger K2AV Sent: Monday, December 21, 2009 8:06 PM To: bill4...@comcast.net Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] KRX3 roofing filter matching for diversity receive Bill, it's simpler than what you're looking for. You can put your widest filter in FL1 and install them from there in descending bandwidth. Use the K3 utility to set up the filters, much easier than doing it with the config menu. The radio automatically switches in the matching filter that matches WIDTH going down. This will be done separately in each RX regardless of what filter slots were used. You do not have to make slot assignments identical. 73, Guy. On Mon, Dec 21, 2009 at 3:57 PM, bill4...@comcast.net wrote: Hi folks, Im trying to configure the K3 receiver for diversity receive. Im populating the roofing filter slots in both receivers with matched filters, and the question came up: When the K3 automatically selects the correct roofing filter to match DSP filter bandwidth, does the K3 do this by filter bandwidth, or by FLx number? In other words; when I use the width control, and decrease DSP bandwidth from 3.0 Khz to 2.0 Khz on the front panel, the K3 switches from the 2.8 Khz roofing filter located in FL3 to the 2.1 Khz roofing filter located in FL4. With the sub-receiver on, and in diversity receive, does the K3 switch the sub-receiver roofing filter from FL3 to FL4, like the main, or is it smart enough to know that my sub-receiver has its 2.8, and 2.1 Khz roofing filters in FL1 and FL2 respectively? Does the K3 select the correct roofing filter by bandwidth, or by FLx number? Is the selection logic the same for main and sub-receiver? The KRX3 manual is a little foggy on this. It says you have to have at least one roofing filter, and if that happens to be the KFL3B FM filter, it MUST be in the FL1 location. It also says that you must have the widest bandwidth nearest FL1, but does not say it must be located at FL1. Bill, W7QQ __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
