filters and contests and interference question/opinions
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After spending time in two DX contasts this year and also dealing with
lots of splatter from other stations during non contest conditions I find myself continually dialing down tighter and tighter filter settings on phone (ssb) Currently I have a 2.7, and 2.1 filter plus the narrow ones for digital. My brain is starting to tell me to stop using the 2.1 and get either a 1.8 or even a 1.5 or possibly both. My thoughts are that the dsp would work much better if some of the interference can be directly blocked out by the filter. These thoughts are guided by past readings on the list that this is the case. What is the collective wisdom of these filter changes I am thinking about. I am curious about others who may have tried these and if they kept them or if they thought it made no difference at all. Again thanks in advance for your help. ~73 Don KD8NNU ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: filters and contests and interference question/opinions
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Don,
The DSP filters can deal with all the interference as long as it is not overloaded - and overload is what the Hardware AGC prevents. What I am saying is - turn Hi-Cut down so you have the equal of a 1.8 or 1.5 filter - then if you begin to hear the Hardware AGC pumping from the nearby signals, you can conclude you need one of the narrow filters. The DSP filters do not need any filtering help, they are quite good all by themselves, but observe for AGC pumping, and if present under your contest conditions, then the only cure is a more narrow roofing filter. 73, Don W3FPR On 3/25/2012 8:33 AM, [hidden email] wrote: > After spending time in two DX contasts this year and also dealing with > lots of splatter from other stations during non contest conditions I > find myself continually dialing down tighter and tighter filter settings > on phone (ssb) > > Currently I have a 2.7, and 2.1 filter plus the narrow ones for digital. > > My brain is starting to tell me to stop using the 2.1 and get either a > 1.8 or even a 1.5 or possibly both. My thoughts are that the dsp would > work much better if some of the interference can be directly blocked out > by the filter. These thoughts are guided by past readings on the list > that this is the case. > > What is the collective wisdom of these filter changes I am thinking > about. I am curious about others who may have tried these and if they > kept them or if they thought it made no difference at all. > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Hi Don,
Every now and then on this subject, I have to throw in this rather significant (IMHO) caveat on all this talk about how good the DSP bandwidth is. I have an old MP, INRAD 8 pole filters in 8 and 455 IF's, that has selectivity just barely matched by a K3 with 8 pole roofing filter AND DSP set for skirt alignment. The DSP by itself is nowhere near the MP's selectivity, sorry. Not close. There is a point in CW contesting, where if you want to continue on a run frequency, you will have to be able to deal with a MUCH louder signal just a few hundred Hz up or down, and try to copy a MUCH weaker signal in band. And since the K3 is so clean in matters intermod, it really IS possible to deal with a 35 over 9 signal just up and copy an S1 signal in band, a mere 80 dB difference. IF you also want the desired signal to be 20 dB louder than the undesired signal in the audio, you are trying to create a separation of 100 dB !! IF you also want to be able to hear the forever present off-frequency callers, who to be kind, may actually be physically incapable of closely matching two tones (quite common actually), or to not be kind, don't have enough sense to listen first off a packet spot... if all of these, you will NOT be able to narrow down to super narrow to get rid of Mr 35over9 without giving up on all the +/- callers. Once you have figured out that 1/4 of all your contacts are "off frequency" then you have to maintain a barely adequate bandwidth. In my experience that is done using the 8 pole "250" roofing filter (really 330), and very carefully aligning the offset in setup, so that the roofing filter skirts are centered on the DSP skirts with width at 350, MEASURING AT THE -30 dB POINTS ON BOTH SIDES. This produces a remarkably sharp, very steep skirt, that equals the remarkable selectivity of my MP with INRAD 400 and 250 8 pole filters in the 8 and 455 IF's. Of course the MP never had the IMD performance. With aligned skirts, the K3 delivers the selectivity of the MP WITHOUT the 6 dB of IMD crud down at the bottom covering up 6 dB of Russians on 40 meters. And then there's key click cancelling, see below. With the shift control set for 10 Hz increments, Mr 35over9 can be edged out with just a tick or two up or down on the shift, and STILL have enough band width to get the other 25% of the callers. You will not accomplish this on a good antenna without a roofing filter that matches your preferred operating bandwidth. For those who can't stand key clicks, this procedure has another benefit. This very sharp combination skirt turns a key click from up or down into an amplitude-reduced very sharp waveform that has a very quick onset and very quick drop out, e.g. a ** PULSE **. Because the AGC can now reach down farther, some mistakenly think this is making the click WORSE. But it's only turned the click into a REDUCED AMPLITUDE pulse. The K3 is WONDERFUL at dealing with pulses, so the DSP NB settings of T1-7 T2-7 and T3-7, IF NB **off**, with AGC set to skip pulses, kills the clicks from the guy up above or down below. The K3 is the only radio I know of that can deal with serious clicks and maintain a satisfactory run frequency bandwidth in such ghastly conditions. But you CANNOT do this just with the DSP bandwidth. You need a matching 8 pole roofing filter with offset adjusted to make roofing and DSP skirts align 30 dB down. That said, conversational use outside of contests, where you don't have super signals just up and down, you might be hard pressed to hear the pumping, even using the 5 pole standard 2.7 filter on CW. The DSP AGC will suck up a lot of the hardware variation if you are on FAST AGC and don't run PRE on and RF gain wide open all the time on low bands. 73, Guy. On Sun, Mar 25, 2012 at 8:53 AM, Don Wilhelm <[hidden email]> wrote: > Don, > > The DSP filters can deal with all the interference as long as it is not > overloaded - and overload is what the Hardware AGC prevents. > What I am saying is - turn Hi-Cut down so you have the equal of a 1.8 or > 1.5 filter - then if you begin to hear the Hardware AGC pumping from the > nearby signals, you can conclude you need one of the narrow filters. > > The DSP filters do not need any filtering help, they are quite good all > by themselves, but observe for AGC pumping, and if present under your > contest conditions, then the only cure is a more narrow roofing filter. > > 73, > Don W3FPR > > On 3/25/2012 8:33 AM, [hidden email] wrote: >> After spending time in two DX contasts this year and also dealing with >> lots of splatter from other stations during non contest conditions I >> find myself continually dialing down tighter and tighter filter settings >> on phone (ssb) >> >> Currently I have a 2.7, and 2.1 filter plus the narrow ones for digital. >> >> My brain is starting to tell me to stop using the 2.1 and get either a >> 1.8 or even a 1.5 or possibly both. My thoughts are that the dsp would >> work much better if some of the interference can be directly blocked out >> by the filter. These thoughts are guided by past readings on the list >> that this is the case. >> >> What is the collective wisdom of these filter changes I am thinking >> about. I am curious about others who may have tried these and if they >> kept them or if they thought it made no difference at all. >> >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: filters and contests and interference question/opinions
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Guy,
I will agree with you for CW - cascaded filters of approximately the same width can be necessary. However, the question had to do with SSB width filters, and there I believe the answer is different. 73, Don W3FPR On 3/25/2012 10:05 AM, Guy Olinger K2AV wrote: > a K3 with 8 pole > roofing filter AND DSP set for skirt alignment. The DSP by itself is > nowhere near the MP's selectivity, sorry. Not close. > > There is a point in CW contesting, where if you want to continue on a > run frequency, you will have to be able to deal with a MUCH louder > signal just a few hundred Hz up or down, and try to copy a MUCH weaker > signal in band. And since the K3 is so clean in matters intermod, it > really IS possible to deal with a 35 over 9 signal just up and copy an > S1 signal in band, a mere 80 dB difference. IF you also want the > desired signal to be 20 dB louder than the undesired signal in the > audio, you are trying to create a separation of 100 dB !! > > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by KD8NNU
dalej wrote:
> >I debated between the 2.1 and 1.8, I decided on the 1.8 and am glad I >did. This is the first radio I've had with a 1.8 filter that doesn't >sound like tweety bird on SSB. It is a good and tight filter while >still bringing in some good audio. I used that same 1.8kHz Inrad filter in the old FT-1000MP, where it was very much needed for SSB contesting. Because that filter is also compatible with the K3, I decided to make a new adapter board and try it... and am very glad I did! The K3 is configured to switch in the filter at a DSP bandwidth of 1.9kHz, and with the center frequency set to 1.25kHz it gives a very good balance between selectivity and intelligibility - so good, in fact, that the SHIFT and WIDTH controls hardly ever need to be touched for the duration of an entire contest. That isn't just one person's opinion; my wife and guest operators also find those same filter settings immediately comfortable, so they can go straight ahead and operate. >You won't be displeased. > I agree with Dale. Although a narrower roofing filter isn't essential (we all understand that), the 1.8kHz filter does make a difference to SSB contesting. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: filters and contests and interference question/opinions
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In reply to this post by KD8NNU
Sadly if the splatter is real (not an artifact generated in the receiver)
and the splatter is in the passband, no amount of filtering is going to help get rid of it. If the other guy's signal is broad then there isn't much that can be done to get rid of it given today's technology. Pete, W1RM -----Original Message----- From: [hidden email] [mailto:[hidden email]] Sent: Sunday, March 25, 2012 8:34 AM To: [hidden email]; [hidden email] Subject: [Elecraft] filters and contests and interference question/opinions After spending time in two DX contasts this year and also dealing with lots of splatter from other stations during non contest conditions I find myself continually dialing down tighter and tighter filter settings on phone (ssb) Currently I have a 2.7, and 2.1 filter plus the narrow ones for digital. My brain is starting to tell me to stop using the 2.1 and get either a 1.8 or even a 1.5 or possibly both. My thoughts are that the dsp would work much better if some of the interference can be directly blocked out by the filter. These thoughts are guided by past readings on the list that this is the case. What is the collective wisdom of these filter changes I am thinking about. I am curious about others who may have tried these and if they kept them or if they thought it made no difference at all. Again thanks in advance for your help. ~73 Don KD8NNU ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: filters and contests and interference question/opinions
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In reply to this post by Don Wilhelm-4
On 3/25/2012 5:53 AM, Don Wilhelm wrote:
> The DSP filters can deal with all the interference as long as it is not > overloaded - and overload is what the Hardware AGC prevents. And as long as the interference is not on YOUR frequency, which is sadly all too common during contest stations heavily overdriving their rigs with their computers and turning their microphone gains up way too high. I've been part of a casual multi-op for WPX this weekend, and I've heard dozens of stations whose audio was so badly distorted that I could not copy their call, even listening to it many times. And when they do that, they're also usually creating lots of sideband splatter. One of these times I'm going to make a list of the most awful ones and post it far and wide. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by KD8NNU
Thanks for all the replies.
I did forget about playing with the AGC so I went back and did some adjustments and was able to make things better. I think that the problem is that there is too much junk in the passband during contests and asking the dsp to take it all out just does not work. So I think that I will be looking for either a 1.8 or 1.5 filter. I did pay attention to the pc screen to see how wide I was running the filter and most of the time I was below 1.8 in width and a fair amount at 1.4 to try and reduce the splatter. Thus until I have more filters to play with I wont know for sure. Cheers Don ~73 Don KD8NNU On Sun, Mar 25, 2012 at 11:10 AM, Peter Chamalian wrote: > Sadly if the splatter is real (not an artifact generated in the > receiver) > and the splatter is in the passband, no amount of filtering is going > to help > get rid of it. If the other guy's signal is broad then there isn't > much > that can be done to get rid of it given today's technology. > > Pete, W1RM > > -----Original Message----- > From: [hidden email] [mailto:[hidden email]] Sent: Sunday, > March 25, 2012 8:34 AM > To: [hidden email]; [hidden email] > Subject: [Elecraft] filters and contests and interference > question/opinions > > After spending time in two DX contasts this year and also dealing with > lots > of splatter from other stations during non contest conditions I find > myself > continually dialing down tighter and tighter filter settings on phone > (ssb) > > Currently I have a 2.7, and 2.1 filter plus the narrow ones for > digital. > > My brain is starting to tell me to stop using the 2.1 and get either a > 1.8 or even a 1.5 or possibly both. My thoughts are that the dsp > would work much better if some of the interference can be directly > blocked out by the filter. These thoughts are guided by past > readings on the list that this is the case. > > What is the collective wisdom of these filter changes I am thinking > about. I am curious about others who may have tried these and if > they kept them or if they thought it made no difference at all. > > Again thanks in advance for your help. > > ~73 > Don > KD8NNU > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by KD8NNU
The answer is...it depends. :-) I believe you're fairly new to radio and contesting. Therefore I'm assuming you mostly tune for DX stations and call them rather than running a pileup yourself, which requires good antennas and high power on SSB. For DXing or Search and Pounce (S&P) contesting, you normally have plenty of time to tune in stations carefully before calling. In this case narrow filters (either XFIL or DSP) will work even with bandwidths down to 1.5 kHz. BUT...this assumes you have time to carefully tune in the station you want to call. In the case of someone running a pileup at fairly high rates (e.g. 150-200 per hour), it's a different situation. You want to copy callers correctly the first time without any tuning, send your exchange and get his exchange in the space of 15 seconds and go on to the next one. The problem with extremely narrow SSB filters is that many callers will be slightly off frequency (e.g. 100 Hz) which renders them unintelligible when using narrow filters. With a little wider filter, your ears can still copy the off-frequency guys without needing to touch the VFO. I had a 1.8k filter in the CQ WW last October and gave up using it because of this problem...and a 1.5k would be even worse. Instead I found myself using a DSP setting of 2.0-2.1k with the stock 2.7k XFIL, so after the contest I traded my 1.8k XFIL for a 2.1k. Unfortunately conditions on my favorite SSB band (10m) have been so poor that I opted not to enter the ARRL DX SSB or CQ WPX SSB and really haven't had a chance to try it under fire, but I believe it will be better than the 1.8k for my purposes. As Don said earlier, the major advantage of a narrow XFIL is to prevent AGC pumping from strong stations nearby. In extremely crowded contests this can be a major problem. However a narrower filter WILL NOT remove the splatter from nearby stations...nothing can do that short of using phased antennas to null their signal. 73, Bill |
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In reply to this post by KD8NNU
Hi Bill,
Thanks for the reply. You are correct that I am new to contesting and do the S&P method. So yes I try to dial in the frequency and tighten the filters as much as possible. Yes I was getting some AGC pumping and after emails stating this I went and played with my settings on low and high signals and eleminated this problem For running one frequency and trying to create my own pile up has not been sucessful. Michigan is just not that rare I guess :-). However, your point of running your DSP at about 2.0 ish tells me that I might want to keep that filter also incase this ever changes. Or maybe I need to spend more time on one frequency making calls. I have room in the K3 for 1 more filter so I just may go ahead and get a 1.8 to try it out to keep some noise out of the passband when I do the fine tuning. ~73 Don KD8NNU On Sun, Mar 25, 2012 at 9:20 PM, Bill W4ZV wrote: > goldtr8 wrote >> >> Currently I have a 2.7, and 2.1 filter plus the narrow ones for >> digital. >> >> My brain is starting to tell me to stop using the 2.1 and get either >> a 1.8 or even a 1.5 or possibly both. My thoughts are that the dsp >> would work much better if some of the interference can be directly >> blocked out by the filter. These thoughts are guided by past >> readings on the list that this is the case. >> >> What is the collective wisdom of these filter changes I am thinking >> about. I am curious about others who may have tried these and if >> they kept them or if they thought it made no difference at all. >> > > The answer is...it depends. :-) > > I believe you're fairly new to radio and contesting. Therefore I'm > assuming > you mostly tune for DX stations and call them rather than running a > pileup > yourself, which requires good antennas and high power on SSB. For > DXing or > Search and Pounce (S&P) contesting, you normally have plenty of time > to tune > in stations carefully before calling. In this case narrow filters > (either > XFIL or DSP) will work even with bandwidths down to 1.5 kHz. > BUT...this > assumes you have time to carefully tune in the station you want to > call. > > In the case of someone running a pileup at fairly high rates (e.g. > 150-200 > per hour), it's a different situation. You want to copy callers > correctly > the first time without any tuning, send your exchange and get his > exchange > in the space of 15 seconds and go on to the next one. The problem > with > extremely narrow SSB filters is that many callers will be slightly off > frequency (e.g. 100 Hz) which renders them unintelligible when using > narrow > filters. With a little wider filter, your ears can still copy the > off-frequency guys without needing to touch the VFO. > I had a 1.8k filter in the CQ WW last October and gave up using it > because > of this problem...and a 1.5k would be even worse. Instead I found > myself > using a DSP setting of 2.0-2.1k with the stock 2.7k XFIL, so after the > contest I traded my 1.8k XFIL for a 2.1k. Unfortunately conditions on > my > favorite SSB band (10m) have been so poor that I opted not to enter > the ARRL > DX SSB or CQ WPX SSB and really haven't had a chance to try it under > fire, > but I believe it will be better than the 1.8k for my purposes. > As Don said earlier, the major advantage of a narrow XFIL is to > prevent AGC > pumping from strong stations nearby. In extremely crowded contests > this can > be a major problem. However a narrower filter WILL NOT remove the > splatter > from nearby stations...nothing can do that short of using phased > antennas to > null their signal. > > 73, Bill > > > > > -- > View this message in context: > http://elecraft.365791.n2.nabble.com/filters-and-contests-and-interference-question-opinions-tp7403392p7404470.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:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: filters and contests and interference question/opinions
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In reply to this post by Bill W4ZV
On 3/25/2012 6:20 PM, Bill W4ZV wrote:
> so after the contest I traded my 1.8k XFIL for a 2.1k. I'm also thinking of doing that. A major reason is that when the station you're trying to work is so badly distorted that it's turned to mush and hard to copy, a narrower filter seems to make it even worse. I've set my 1.8 kHz filters to switch in at 2kHz, and mostly run the DSP around 2.2 kHz, narrowing it up to 2kHz when needed. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On 3/26/2012 10:30 AM, Jim Brown wrote:
> A major reason is that when the station > you're trying to work is so badly distorted that it's turned to mush and > hard to copy, a narrower filter seems to make it even worse. Well, that's a relief! I dabbled in the WPX SSB, S&P only, and figured my inability to copy many signals was just because I am close to deaf. Maybe they really *were* bad. Wider seemed to help intelligibility a little, but the band was way too crowded for anything over about 2.0 KHz. I lost count of the number of stations I chose not to call because I couldn't get the call sign. First SSB contest with the P3 and monochrome waterfall [that I can actually see :-) Thanks Alan]. The really distorted signals were noticeably wider on the waterfall. CQ's from the DVK's were also a problem ... heavily compressed, way too low a signal-to-bacground ratio, and often unintelligible. However, with QSO # still in single digits, I got the first of several unsolicited, "Really clean and nice audio" reports. I've tested with a couple of locals and they cannot tell the difference between live mic and the K3DVR. I'm using the Heil Pro with electret element from Elecraft and the K9YC recommended TX EQ settings. I need to find a local with a K3 and trade stations to see what mine sounds like. 73, Fred K6DGW - Northern California Contest Club - CU in the 2012 Cal QSO Party 6-7 Oct 2012 - www.cqp.org ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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