Re: [Elecraft] K3: use of 1.8 filter - clarification
Hi Doug, # You asked: Bill...I do have a question or two, with respect to your statement below. 1. Just how often do you find that you run into a situation such as you describe below? I don't mean simply, during every a contest, I mean more like how often during a contest? For how many Q's? # Fortunately not very often. I operate 10m almost exclusively in SSB contests. If a hippo comes near my watering hole, I first make my presence known (ask him to QSY, etc). But rather than pointlessly (pun intended) slugging it out, I'll move (lots of room on 10m). Of course moving is not an option on many bands (e.g. 20m) in SSB contests, otherwise you'll not make many QSOs at all. 2. If the really close and really strong signal is pumping your AGC, why not just turn off the AGC and ride the RF? This is not a rhetorical question, because I know you do this. So I'd like to learn why you would, in some situations, prefer to not do that. I would love to learn a new trick! # Remember that you CANNOT turn the hardware AGC off because it's always on to protect the ADC in the DSP stage. HAGC will still cause pumping even if the DSP AGC is turned off. Of course you can use an attenuator but that also has consequences for copying weaker signals on your frequency. 3. And just out of curiosity (on SSB), how long would you tolerate being so close to someone who would pump your AGC? Of course, for me (QRP), the answer is zero seconds. :-) # It depends. If I think someone is intentionally trying to steal my run frequency, I may stay longer than if I think it's accidental. In the recent CQ WW, I had one station try this twice but they left after ~5 minutes each time. The top operators NEVER do this but I keep a mental list of some folks who routinely try it and sometimes return the favor. ;-) It often helps to point one antenna in my 3-stack toward someone who accidentally lands on my run frequency, so they can hear me better. :-) Fortunately this does not happen often on 10m (unlike more crowded bands). 73, Bill W4ZV said: I agree IMD reduction is not a big issue on SSB but blocking dynamic range (BDR) is the primary reason I sometimes need a narrower filter. If you have an S9+25 SSB signal CQing next to you (sometimes the case in crowded contests), a narrower filter will prevent it from de-sensing your receiver. If part of the interfering signal falls inside your 2.7k filter, signals on your frequency will be gain modulated by his signal (commonly called AGC pumping). In this case a narrower filter will prevent the problem. Of course when this happens, we still have to contend with his transmitted splatter (typical SSB TXs run -35 dB IMD which would result in ~S7 splatter from an S9+25 signal), but at least you can still copy signals at S7 or above (and lower when he's not transmitting). 73, Bill -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-use-of-1-8-filter-clarification-tp7188854p7189480.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
[Elecraft] K3: use of 1.8 filter - clarification
I've received emails replies (direct and otherwise) that, for me, indicate that I should elaborate/clarify what I am referring to. Let's assume that you have a 2.7 and 2.1 roofing filter. If you set up your narrower SSB filter according the the manual, which is what the majority of K3 ops do, as you transition from, 2.7 to 2.1 using the width knob, you are doing two separate, but linked things. First, you are reducing the DSP BW. Sync'ed to that (you have no choice without manual intervention, ie faking out the K3), as you get to 2.1 kHz in the DSP BW, you simultaneously switch from the 2.7 to the 2.1 roofing filter. Unless you unhook this coupling between the DSP BW and the Roofing Filter BW, you simply cannot tell which one is influencing what you hear (what I called feel). So when you get down to 2.1 (from 2.7) are you appreciating the impact of the DSP or the roofing filter - or maybe both? How would you know? I am saying that unless you are operating in extremely crowded band conditions (not with just one interfering, very near-by station) you are appreciating the impact due to the DSP BW and certainly NOT the roofing filter. It is possible to manually intervene to alter (even temporarily turn off) the (point of) sync between the DSP BW and the roofing filter (narrower) BW. And I am saying that unless you actually do this de-linking, that you won't be able to know/confirm the true source of what you are hearing / feeling. I'm betting that for the vast majority, especially non-contesters and non-160 serious DXers, what you hear is due to the DSP BW. The roofing filters are used for reducing IMD. A receiver with poor IMD will experience phantom signals due to the mixing of other very strong signals (multiple) on the band and these phantom signals can potentially cover up real, but weak, signals. You can usually identify such IMD as received squeaks, pops, whines, groans, etc. The band will sound like it is covered with garbage - even somewhat musical. The addition of the appropriate roofing filter can reduce or eliminate this. This is esp true (for me) on CW and especially (for me) on the low bands (lots of very strong signals) during a contest. In the old days, I've had many receivers that would simply collapse under the strain. It made tuning across the band painful and arduous when trying to pick out weaker signals. After hours and hours of this, it is very fatiguing. I use the 5 pole 500hz filter on CW for both of my K3s. Is it wrong to get a narrow filter? Of course not. But unless you are planning on operating in the midst of multiple, super strong signals, then I do not see much logic in getting a narrower CW filter...and certainly not a narrower SSB filter for SSB use. At least on CW, you can fit another signal inside the passband (very rare) when going from 500 to 200hz, but on SSB, going from 2.7 to 2.1? No way that will fit another signal in that delta (which is half of the difference or just 300hz.). Now, if you have the sub-receiver and want to match filters, then I see nothing wrong with buying one of the narrower (or even wider) SSB filters. But that would be motivated by a different reason. If you're spending money frugally or even just being thrifty, (however you want to define that) you can stick with the 2.7 stock filter. If money isn't an issue (the cost isn't that much different), you sure can't be hurt by getting a narrower SSB filter, except as cited by others, when it comes to ease of tuning in a station (though I have never experienced such difficulty). Lots of folks simply like to load up the open the slots. That is yet another motivation...not much to do with operating. Hope this helped to clarify what I was trying to get across. de Doug __ 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] K3: use of 1.8 filter - clarification
Hi Doug, DOUGLAS ZWIEBEL wrote The roofing filters are used for reducing IMD. I agree IMD reduction is not a big issue on SSB but blocking dynamic range (BDR) is the primary reason I sometimes need a narrower filter. If you have an S9+25 SSB signal CQing next to you (sometimes the case in crowded contests), a narrower filter will prevent it from de-sensing your receiver. If part of the interfering signal falls inside your 2.7k filter, signals on your frequency will be gain modulated by his signal (commonly called AGC pumping). In this case a narrower filter will prevent the problem. Of course when this happens, we still have to contend with his transmitted splatter (typical SSB TXs run -35 dB IMD which would result in ~S7 splatter from an S9+25 signal), but at least you can still copy signals at S7 or above (and lower when he's not transmitting). 73, Bill -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-use-of-1-8-filter-clarification-tp7187876p7187921.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] K3: use of 1.8 filter - clarification
That really IS the kicker. I guess the point is how bad do you want/need the cost of an extra filter. How important would it be in the 1% condition where the signal up or down is INSIDE the roofing filter. In my experience from home (not the monster antennas out at N4AF), in ANY phone contest, changing the width from 1.8 to 1.9, thus changing to the 2.7 roofer, always is a large jump in crap inside the DSP. This is because I just went from DSP and roofer ALIGNED SKIRTS, that drop 100+ dB in a given width (combined) to a composite skirt that only drops 50 in the same range. This means that the loudness of what is just up and down JUST GOT 50 DB LOUDER at the roofer change, because the close in skirt is now ONLY DSP instead of DSP+roofer. The DSP is great, but hear this, at 400 Hz, the straight selectivity of DSP plus a CAREFULLY ALIGNED 8 pole roofer is still less than my MP with INRAD 400 Hz 8 pole filters at the 8 and 455 IF slots. The presumption with no tight filters is that the selectivity of the DSP by itself is enough. Personally, my experience is that the K3 DSP, by itself, as very excellent as it truly is, is NOWHERE near enough to deal with contests and situations where one is trying to listen to a 0.05 uV signal next to a 500 or 5000 millivolt signal that is JUST BARELY OUTSIDE the passband. It takes the DSP, as excellent as it is, TOO MANY Hz to reach the ultimate 100 dB. I need the FASTER DIVING COMBINED skirts of a matched roofer and DSP skirt to knock off the content just barely up and down. While my MP has faster diving skirts at 400 Hz using the matched INRADs, the K3 nearly matches the skirts AND has vastly superior IMD and internal noise. ***BUT*** without the matched DSP and roofer skirts, particularly if the roofer is significantly wider, there will be so much stuff let in by the missing 50 dB of skirt inside ultimate rejection that the advantages of the superior IMD are quashed by all the stuff now let in, and in fact, in that particular situation, the MP would be the superior rig. Credit where credit is due. When I am running at NY4A on 40 with the overwhelming signals from Europe on the monster quad, I use the 400 roofer and DSP at 450 and the 250 roofer and DSP at 350 to get sharp aligned hard-diving skirts just above and below. Don't bother to tell me that some of those Italian signals are running anywhere near 1.5 kW because I've rechecked the S meter countless times, and something that tickles 40 over is an issue. You COULD say, just reduce the width, and I would agree **IF** it weren't for so very many people calling fairly well off frequency. There are times where I have to reduce the width from 350 to 300 or 250, where the up or down signal is just too strong and too close and overwhelms the excellent roofer/DSP combo at 350. But I know I'm losing contacts. I know this is more like a NASCAR take on tires, and some of you may be driving the K3 like the family car. But if you understand the NASCAR (severe contest) issues regarding roofer selection, then you know what it's about and can choose one way or another and know it's right for you without being snookered. If you occasionally take the K3 down to the race track and want it to perform out there, you need to match DSP and roofer skirts, and align them. 73, Guy. On Sat, Jan 14, 2012 at 11:43 AM, DOUGLAS ZWIEBEL doug...@gmail.com wrote: But unless you are planning on operating in the midst of multiple, super strong signals, then I do not see much logic in getting a narrower CW filter...and certainly not a narrower SSB filter for SSB use. __ 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] K3: use of 1.8 filter - clarification
`Guy, That is a very true statement. Thanks. 73 Arie PA3A Op 14-1-2012 21:22, Guy Olinger K2AV schreef: SNIP If you occasionally take the K3 down to the race track and want it to perform out there, you need to match DSP and roofer skirts, and align them.SNIP __ 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] K3: use of 1.8 filter - clarification
IMHO, there are few folks in the contest world that are better technically than Bill (W4ZV), so I would suggest that everyone take his comments very seriously. Bill...I do have a question or two, with respect to your statement below. 1. Just how often do you find that you run into a situation such as you describe below? I don't mean simply, during every a contest, I mean more like how often during a contest? For how many Q's? 2. If the really close and really strong signal is pumping your AGC, why not just turn off the AGC and ride the RF? This is not a rhetorical question, because I know you do this. So I'd like to learn why you would, in some situations, prefer to not do that. I would love to learn a new trick! 3. And just out of curiosity (on SSB), how long would you tolerate being so close to someone who would pump your AGC? Of course, for me (QRP), the answer is zero seconds. :-) W4ZV said: I agree IMD reduction is not a big issue on SSB but blocking dynamic range (BDR) is the primary reason I sometimes need a narrower filter. If you have an S9+25 SSB signal CQing next to you (sometimes the case in crowded contests), a narrower filter will prevent it from de-sensing your receiver. If part of the interfering signal falls inside your 2.7k filter, signals on your frequency will be gain modulated by his signal (commonly called AGC pumping). In this case a narrower filter will prevent the problem. Of course when this happens, we still have to contend with his transmitted splatter (typical SSB TXs run -35 dB IMD which would result in ~S7 splatter from an S9+25 signal), but at least you can still copy signals at S7 or above (and lower when he's not transmitting). 73, Bill __ 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] K3: use of 1.8 filter - clarification
Pardon the misstatement in the paragraph below, I accidentally switched units. It should read: On Sat, Jan 14, 2012 at 3:22 PM, Guy Olinger K2AV olin...@bellsouth.netwrote: The presumption with no tight filters is that the selectivity of the DSP by itself is enough. Personally, my experience is that the K3 DSP, by itself, as very excellent as it truly is, is NOWHERE near enough to deal with contests and situations where one is trying to listen to a 0.05 uV signal next to a 500 or 5000 ***[ uV ]*** signal that is JUST BARELY OUTSIDE the passband. It takes the DSP, as excellent as it is, TOO MANY Hz to reach the ultimate 100 dB. I need the FASTER DIVING COMBINED skirts of a matched roofer and DSP skirt to knock off the content just barely up and down. __ 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] K3: use of 1.8 filter - clarification
Can't speak for Bill, but for myself, all night long on 75 and 40 meters. There are people that show up with amps and antennas that you almost never hear outside of a contest. NQ4I near Atlanta has a 12 element LPDA for 80/75 meters fixed northeast. 4 or 5 elements active on any given frequency. What do you suppose that's like downwind? 73, Guy. On Sat, Jan 14, 2012 at 9:06 PM, DOUGLAS ZWIEBEL doug...@gmail.com wrote: IMHO, there are few folks in the contest world that are better technically than Bill (W4ZV), so I would suggest that everyone take his comments very seriously. Bill...I do have a question or two, with respect to your statement below. 1. Just how often do you find that you run into a situation such as you describe below? I don't mean simply, during every a contest, I mean more like how often during a contest? For how many Q's? 2. If the really close and really strong signal is pumping your AGC, why not just turn off the AGC and ride the RF? This is not a rhetorical question, because I know you do this. So I'd like to learn why you would, in some situations, prefer to not do that. I would love to learn a new trick! 3. And just out of curiosity (on SSB), how long would you tolerate being so close to someone who would pump your AGC? Of course, for me (QRP), the answer is zero seconds. :-) W4ZV said: I agree IMD reduction is not a big issue on SSB but blocking dynamic range (BDR) is the primary reason I sometimes need a narrower filter. If you have an S9+25 SSB signal CQing next to you (sometimes the case in crowded contests), a narrower filter will prevent it from de-sensing your receiver. If part of the interfering signal falls inside your 2.7k filter, signals on your frequency will be gain modulated by his signal (commonly called AGC pumping). In this case a narrower filter will prevent the problem. Of course when this happens, we still have to contend with his transmitted splatter (typical SSB TXs run -35 dB IMD which would result in ~S7 splatter from an S9+25 signal), but at least you can still copy signals at S7 or above (and lower when he's not transmitting). 73, Bill __ 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
