[Elecraft] CW filter and Roofing filter
Trying to sort this out... 1) with any filter selected using the XFIL button on the K3, there is only ONE crystal IF filter in the signal path. In other words, there is no cascading or tail ending of the filters before and after the IF. 2) if I select a 400 Hz filter with the XFIL button then adjusting the DSP WIDTH control to any WIDER than 500 Hz is pointless. 3) can the DSP be bypassed to produce a purely analog demodulated audio to the speaker? As I recall years ago, some early DSP radios had this feature. I am pretty sure the answer is no but still, had to ask. It is interesting to note that there are new hams out there who have never listened to an analog receiver before. It can be an eye opening experience! __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] CW filter and Roofing filter
Cascading: The only cascading filtering is first the xtal filter and then the DSP filter. (So there's only one xtal filter) 400Hz-500Hz: Yes listening to a wider DSP filter than Xtal filter is pointless. Although (if configured correctly) the K3 will switch to a wider Xtal filter (if there is one) if you widen up the DSP. Analog demodulation: Demodulation in the K3 is DSP. There is not menu setting to get around this. 73 Arie PA3A Gee schreef op 24-6-2015 om 14:55: Trying to sort this out... 1) with any filter selected using the XFIL button on the K3, there is only ONE crystal IF filter in the signal path. In other words, there is no cascading or tail ending of the filters before and after the IF. 2) if I select a 400 Hz filter with the XFIL button then adjusting the DSP WIDTH control to any WIDER than 500 Hz is pointless. 3) can the DSP be bypassed to produce a purely analog demodulated audio to the speaker? As I recall years ago, some early DSP radios had this feature. I am pretty sure the answer is no but still, had to ask. It is interesting to note that there are new hams out there who have never listened to an analog receiver before. It can be an eye opening experience! __ 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 Message delivered to p...@xs4all.nl __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] CW filter and Roofing filter
Gee, The K3 DSP cannot be bypassed, it is part and parcel of the K3. The DSP mathematical computations are what does the modulation, demodulation, and forms the filters as well as doing a lot of other tasks. The K3 DSP processing in the K3 is done at a frequency of 15kHz. There is no parallel to an analog receiver. The front end of the K3 is analog, but as soon as the signal is converted to 15kHz, it goes through an ADC and becomes 'mathematical soup' - after processing, the math result is fed to a DAC where it emerges as audio. In other words, the K3 is an SDR with an analog front end and a built-in processor. The K3 must have the 2.7 or 2.8kHz filter installed. If you have additional hardware filters installed, they are not cascaded - BUT the roofing filter can cascade with the DSP filter. Even if you select a narrow filter with the XFIL button, if you widen the DSP bandwidth beyond the width of that narrow filter, the K3 will switch to a wider filter. I hope that helps your understanding. 73, Don W3FPR On 6/24/2015 8:55 AM, Gee wrote: Trying to sort this out... 1) with any filter selected using the XFIL button on the K3, there is only ONE crystal IF filter in the signal path. In other words, there is no cascading or tail ending of the filters before and after the IF. 2) if I select a 400 Hz filter with the XFIL button then adjusting the DSP WIDTH control to any WIDER than 500 Hz is pointless. 3) can the DSP be bypassed to produce a purely analog demodulated audio to the speaker? As I recall years ago, some early DSP radios had this feature. I am pretty sure the answer is no but still, had to ask. It is interesting to note that there are new hams out there who have never listened to an analog receiver before. It can be an eye opening experience! __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] CW filter and Roofing filter
On 6/24/2015 5:55 AM, Gee wrote: with any filter selected using the XFIL button on the K3, there is only ONE crystal IF filter in the signal path. Correct In other words, there is no cascading or tail ending of the filters before and after the IF. Semi-correct. If by filter you mean crystal roofing filter, and if by IF you mean 1st IF [8 MHz], correct. One roofing filter followed by 2nd IF filtering provided by the DSP. 2) if I select a 400 Hz filter with the XFIL button then adjusting the DSP WIDTH control to any WIDER than 500 Hz is pointless. Sort of. The K3 will automatically select a roofing filter from whatever you have that is wider than what the DSP is set to ... if it can. 3) can the DSP be bypassed to produce a purely analog demodulated audio to the speaker? No. Once the 15 KHz 2nd IF becomes number soup in the DSP, there are only two analog things left in the chain: The AF amplifier and you. The DSP contains a lot more than just adjustable filtering, such as AGC and demodulation. It is interesting to note that there are new hams out there who have never listened to an analog receiver before. True It can be an eye opening experience! Possibly, although I doubt most would find that. 73, Fred K6DGW - Northern California Contest Club - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015 - www.cqp.org __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] CW Filter and Roofing Filter
Hi Robert, For best overall performance in CW mode with the K3S, I suggest using our 400-Hz 8-pole filter. The 250-Hz 8-pole filter is a further optimization, with very steep skirts to help with close-in QRM. 5-pole filters are also available but they won't have as steep skirts. (The 500-Hz 5-pole is not appreciably wider than the 400-Hz 8-pole.) With either filter selected, high-performance, variable-bandwidth DSP filtering is applied within the crystal filter passband. As you adjust the bandpass controls, the K3S will automatically select the right crystal filter. The DSP filtering can go to as narrow as 50 Hz, and as wide as the widest crystal filter installed that is compatible with CW mode (up to 2.8 kHz, another one of our 8-pole filters.) In addition, the DSP also provides a switchable audio peaking filter in CW mode (APF). This is a special filter type that can make signals very close to noise floor seem to emerge from the noise (magically, some have said), without adding the ringing associated with traditional brick-wall filters. Other weapons in the K3S's weak-signal arsenal include CW REVerse mode, DSP and IF noise blankers, noise reduction, and both auto- and manual notch. 73, Wayne N6KR On Jun 23, 2015, at 11:42 AM, rclar...@comcast.net wrote: Hi all: I currently own a Yaesu FT-950 and am considering selling it to move the the Elecraft K3S line. My question is about filters. My FT-950 has a roofing filter and a variable CW filter down to 200hz. Quite frankly, I can't tell much different when I switch in the roofing filter but the variable CW filter makes a big difference. I also have a 1970's TenTen Century 21 which has a 500Hz filter that, to me, seems to do a better job than the FT-950. So..when I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? Are they adjusting the roofing filter or the cw filter? And...is the cw filter variable (like my FT-950) or fixed (like the Century 21)? Thanks! Robert NJ4j __ 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 Message delivered to n...@elecraft.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 Message delivered to arch...@mail-archive.com
[Elecraft] CW Filter and Roofing Filter
Hi all: I currently own a Yaesu FT-950 and am considering selling it to move the the Elecraft K3S line. My question is about filters. My FT-950 has a roofing filter and a variable CW filter down to 200hz. Quite frankly, I can't tell much different when I switch in the roofing filter but the variable CW filter makes a big difference. I also have a 1970's TenTen Century 21 which has a 500Hz filter that, to me, seems to do a better job than the FT-950. So..when I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? Are they adjusting the roofing filter or the cw filter? And...is the cw filter variable (like my FT-950) or fixed (like the Century 21)? Thanks! Robert NJ4j __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] CW Filter and Roofing Filter
Robert, Actually there is no good comparison with either your Yaesu or the TenTec. The DSP sets the ultimate signal bandwidth and is continuously variable from greater than 2.8kHz down to 50 Hz. There is no specific CW filter. Adjust for a width that is appropriate for your mode, band conditions and your personal choice of a good filter width. That leaves the question of the roofing filter(s) unanswered. The K3 (or K3S) will work with only the stock 2.7kHz or the 8 pole 2.8kHz filter - you must have one or the other in the K3. Other roofing filters may be desirable in your K3 when you are working in crowded band conditions where there may be strong nearby signals that are outside your DSP filter, yet are within the passband of the roofing filter - in other words, you may not hear them. Those strong signals will activate the hardware AGC (which is there mainly to protect the A to D converter from overload). If those signals activate the Hdwr AGC, you will hear AGC Pumping in the receiver and the receiver sensitivity will be reduced when that strong signal transmits. The cure for the effects above is to add narrow roofing filters to reduce the K3 response to those nearby strong signals. The roofing filters are automatically switched in as you narrow the DSP filter bandwidth. 73, Don W3FPR On 6/23/2015 2:42 PM, rclar...@comcast.net wrote: Hi all: I currently own a Yaesu FT-950 and am considering selling it to move the the Elecraft K3S line. My question is about filters. My FT-950 has a roofing filter and a variable CW filter down to 200hz. Quite frankly, I can't tell much different when I switch in the roofing filter but the variable CW filter makes a big difference. I also have a 1970's TenTen Century 21 which has a 500Hz filter that, to me, seems to do a better job than the FT-950. So..when I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? Are they adjusting the roofing filter or the cw filter? And...is the cw filter variable (like my FT-950) or fixed (like the Century 21)? __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] CW Filter and Roofing Filter
Hi Robert, K3(S) operators often set the DSP bandwidth to the roofing filter width having bought the filter with operating at that bandwidth in mind. However the DSP bandwidth is variable. As this is varied the radio will use the roofer equal to or next larger than the DSP bandwidth. Operating a K3(S) roofing filter and DSP with coinciding skirts produces exceptional quick rejection of close interference, which is very useful running in a contest, particularly on CW. Hope this helps. 73, Guy K2AV On Tuesday, June 23, 2015, rclar...@comcast.net wrote: Hi all: I currently own a Yaesu FT-950 and am considering selling it to move the the Elecraft K3S line. My question is about filters. My FT-950 has a roofing filter and a variable CW filter down to 200hz. Quite frankly, I can't tell much different when I switch in the roofing filter but the variable CW filter makes a big difference. I also have a 1970's TenTen Century 21 which has a 500Hz filter that, to me, seems to do a better job than the FT-950. So..when I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? Are they adjusting the roofing filter or the cw filter? And...is the cw filter variable (like my FT-950) or fixed (like the Century 21)? Thanks! Robert NJ4j __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net javascript:; This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to k2av@gmail.com javascript:; -- Sent via Gmail Mobile on my iPhone __ 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 Message delivered to arch...@mail-archive.com
Re: [Elecraft] CW Filter and Roofing Filter
Robert, I don't think you can make the comparison as you suggest, very different radios. I don't remember when the term roofing filter entered the ham vocabulary but it has caused a lot of confusion, some angst, and possibly some over-buying of filters. In the K3 and K3S, the bandwidth that you actually hear in your headphones or speaker is set by the DSP with the WIDTH knob. It's essentially a brick-wall filter, built with binary arithmetic. If the signal is not inside the passband, you don't hear it. Our bands are full of signals, some very strong which will activate the hardware AGC and reduce the level of *all* signals at the input to the ADC ... including the one weak one you're listening to. All the roofing filter does is restrict the BW of the energy applied to the ADC to exclude most of the other signals on the band. I'm not at all surprised that you don't notice much effect from the 1st IF filter, you won't unless there are very strong signals that will activate the AGC. Matching the roofer BW and DSP BW offers a small benefit since two filters are cascaded. But, since the roofers are not adjustable, you have to find a happy compromise for your operating style. My K3 came with a 2.7 KHz 5-pole filter for SSB and I added a 500 Hz for CW. That's all I have. I contest some [not anywhere near hard core], nearly all CW, and I operate casually, nearly always at 250 or 200 Hz DSP BW. For SSB, I usually run the DSP BW at 2.1 KHz, that's what the Collins mech filter was in my S-Line and I'm used to the sound. I've never noticed a strong signal, outside the DSP BW but inside the roofer activate the K3's hardware AGC. Now, you asked questions ... When I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Elecraft offers a 500 Hz filter [and maybe a 250 Hz] for narrow-band modes which will restrict the BW of the energy presented to the ADC. If you operate CW or other narrow-band modes a lot, I think it's a good buy. If you're mainly a phone guy, you might not ever encounter a situation where it would make a difference. I think the filters are really Inrads, I had a 250 Hz Inrad in a TS-850, and it was pretty ringey. Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? K3? If so, no, they are not the same if 500Hz CW filter means what you set in the DSP. You can have a 500 Hz roofer, I do. You can set the DSP BW on CW to 500 Hz [you can set it much wider than that in fact]. The K3 will select the 500 Hz roofer, and you'll have two cascaded filters. Keep in mind, the roofers are analog crystal filters, not adjustable. They are nominally Hz wide, but the skirts are not vertical. In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? If they're using a K3, they're adjusting the DSP WIDTH control. is the cw filter variable (like my FT-950) or fixed (like the Century 21)? There is no CW filter in a K3/K3S. There is a roofing filter that restricts the BW going into the ADC, and there is a DSP filter controlled by knobs on the front panel which can be set to anything within its range, regardless of operating mode. The roofer isn't adjustable. The knobs do the same thing whether your listening to CW, RTTY, PSK31, SSB, or anything else. Small exception to the above: Separate from the roofing and DSP filters, the K3/K3S has a switchable [on/off] audio peaking filter for CW. It too is done in binary arithmetic, is totally separate and only good for CW, and under some conditions it can render an unreadable signal quite readable. Hope this helps, 73, Fred K6DGW - Northern California Contest Club - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015 - www.cqp.org On 6/23/2015 2:42 PM, rclar...@comcast.net wrote: Hi all: I currently own a Yaesu FT-950 and am considering selling it to move the the Elecraft K3S line. My question is about filters. My FT-950 has a roofing filter and a variable CW filter down to 200hz. Quite frankly, I can't tell much different when I switch in the roofing filter but the variable CW filter makes a big difference. I also have a 1970's TenTen Century 21 which has a 500Hz filter that, to me, seems to do a better job than the FT-950. So..when I read that a 500 Hz roofing filter is an option for the Elecraft K3S, what am I actually reading? Could there be a 500Hz roofing filter and a 500Hz CW filter or are they the same? In several Youtube videos, I've seen operators using the variable width the filter signals. What am I seeing? Are they adjusting the roofing filter or the cw filter? And...is the cw filter variable (like my FT-950) or fixed (like the Century 21)? __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post:
