K3: KRX3 question
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I note in the new KRX3 manual the comment that diversity reception may be enhanced by using filters with matched offsets for the main and sub-receivers. I'm a 160M nut and this is certainly an important point to me... I have these filterson backorder:
KFL3A-200 2 K3 200 Hz, 5 pole filter KFL3A-500 2 K3 500 Hz, 5 pole filter I'm wondering if Elecraft has plans for shipping these as matched sets or if I should scramble to change my order for 8 pole filters which should not need the offset. Heads up and anyone know the answer? Tom N5TW _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Yes Elecraft is *supposed* to match these...but I would certainly remind them via an email to Lisa. They are also *supposed* to have a process to match existing filters already in the field (i.e. matching the Sub filters to Main filters already installed). I would think this could be as simple as sending them the offsets for existing filters so they could choose units with identical offsets one from production. But only Eric or Wayne can truly answer your question, which is a very timely one! 73, Bill |
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In reply to this post by Tom Whiteside
H Tom,
We will match the 5 pole filters (to within 40 Hz) on request. If your filters are already that close you are in good shape. We can't guarantee a good enough yield on filter offsets to get closer than that, though most will be closer. Fortunately 40 Hz is more than adequate as you can set the K3 menu offsets for the two filters the same at the mean between them and both will be within 20 Hz or less of their ideal center. The $30 option is per matched set (not per filter) and will be on the web order form next week. (We're officially on national holiday today :-) We just put it into the in-house ordering system yesterday. This applies to either matching two of the same bandwidth filter at time of shipment or matching a second same b/w filter to one you already have in your radio. For everyone else, if you are not planning on doing 2 receiver, 2 antenna, diversity reception where the frequency of the sub needs to be matched to withing a Hz of the main, this is not necessary. 73, Eric WA6HHQ _..._ Tom Whiteside wrote: > I note in the new KRX3 manual the comment that diversity reception may be enhanced by using filters with matched offsets for the main and sub-receivers. I'm a 160M nut and this is certainly an important point to me... I have these filterson backorder: > > KFL3A-200 2 K3 200 Hz, 5 pole filter > KFL3A-500 2 K3 500 Hz, 5 pole filter > > I'm wondering if Elecraft has plans for shipping these as matched sets or if I should scramble to change my order for 8 pole filters which should not need the offset. Heads up and anyone know the answer? > > Tom N5TW > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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OK, I have to ask. WHAT is diversity? Two receivers tuned to the same
signal, what is the advantage gained? Still waiting for mine. 73, Jim KG0KP ----- Original Message ----- From: "Eric Swartz WA6HHQ - Elecraft" <[hidden email]> To: "Tom Whiteside" <[hidden email]> Cc: <[hidden email]> Sent: Friday, July 04, 2008 1:35 PM Subject: Re: [Elecraft] K3: KRX3 question > H Tom, > > We will match the 5 pole filters (to within 40 Hz) on request. If your > filters are already that close you are in good shape. We can't guarantee > a good enough yield on filter offsets to get closer than that, though > most will be closer. Fortunately 40 Hz is more than adequate as you can > set the K3 menu offsets for the two filters the same at the mean between > them and both will be within 20 Hz or less of their ideal center. > > The $30 option is per matched set (not per filter) and will be on the > web order form next week. (We're officially on national holiday today > :-) We just put it into the in-house ordering system yesterday. This > applies to either matching two of the same bandwidth filter at time of > shipment or matching a second same b/w filter to one you already have in > your radio. > > For everyone else, if you are not planning on doing 2 receiver, 2 > antenna, diversity reception where the frequency of the sub needs to be > matched to withing a Hz of the main, this is not necessary. > > 73, Eric WA6HHQ > > _..._ > > > > Tom Whiteside wrote: > > I note in the new KRX3 manual the comment that diversity reception may sub-receivers. I'm a 160M nut and this is certainly an important point to me... I have these filterson backorder: > > > > KFL3A-200 2 K3 200 Hz, 5 pole filter > > KFL3A-500 2 K3 500 Hz, 5 pole filter > > > > I'm wondering if Elecraft has plans for shipping these as matched sets or if I should scramble to change my order for 8 pole filters which should not need the offset. Heads up and anyone know the answer? > > > > Tom N5TW > > _______________________________________________ > > Elecraft mailing list > > Post to: [hidden email] > > You must be a subscriber to post to the list. > > Subscriber Info (Addr. Change, sub, unsub etc.): > > http://mailman.qth.net/mailman/listinfo/elecraft > > > > Help: http://mailman.qth.net/subscribers.htm > > Elecraft web page: http://www.elecraft.com > > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Eric Swartz - WA6HHQ
Tom (and others planning to use diversity), this means you have the following options using the current filter prices: 1. Dual 5-pole filters (matched by Elecraft). 2 X $100 plus $30 = $230 per BW. 2. Dual 8-pole filters (no match needed). 2 X $125 = $250 per BW. This tilts your decision toward 8-pole filters, however there is still an issue of bandwidth. Since the 400 8-pole is actually 435 Hz and the 250 8-pole is actually 370 Hz, I would definitely not order both. I'm faced with the same issue but will probably order one matched 500 since my order was at the original price of $80 for a 5-pole...plus I like the wider BW for contests. I was never planning to use the 200 in diversity mode (you can still use a 500 down to DSP = 250). BTW having used my 200 awhile in a few 160 contests, I would absolutely NOT be without it for huge simplex pileups. So another option for you might be two 400s for diversity, and at least one 200 for the extreme situations we sometimes have on 160. 73, Bill W4ZV |
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In reply to this post by hf4me
> OK, I have to ask. WHAT is diversity? Two receivers tuned to the same
> signal, what is the advantage gained? If each receiver is attached to a different antenna, perhaps one horizontally and one vertically polarized, you might hear better in one or the other as propagation shifts. If both are attached to the same antenna, there isn't much gain to be had :-) Lyle KK7P _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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Of course. I figured there would be a simple answer. Just hadn't thought
it through yet since I am yet waiting for my K3. AND I thought you guys were supposed to be OFF today. Thanks es 73, de Jim KG0KP ----- Original Message ----- From: "Lyle Johnson" <[hidden email]> To: "Jim Miller" <[hidden email]> Cc: <[hidden email]> Sent: Friday, July 04, 2008 2:48 PM Subject: Re: [Elecraft] K3 Diversity > > OK, I have to ask. WHAT is diversity? Two receivers tuned to the same > > signal, what is the advantage gained? > > If each receiver is attached to a different antenna, perhaps one > horizontally and one vertically polarized, you might hear better in one > or the other as propagation shifts. > > If both are attached to the same antenna, there isn't much gain to be > had :-) > > Lyle KK7P > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Tom Whiteside
Thanks Bill. I like the 5 poles for the reasons you stated recommending them way back when. I ordered the ones you spec'd based on the idea of covering the octaves... I agree that the narrow ones are for more extreme situations but figured for $30 I'd get the narrow ones matched as well.
To Jim's question - I mainly use diversity to switch listen to the transmit antenna in one ear and to a Beverage receive antenna in the other ear. Sometimes this is an experience that defies description except you find yourself copying in very tough SNR conditions that you could not otherwise do. Tom N5TW Tom (and others planning to use diversity), this means you have the following options using the current filter prices: 1. Dual 5-pole filters (matched by Elecraft). 2 X $100 plus $30 = $230 per BW. 2. Dual 8-pole filters (no match needed). 2 X $125 = $250 per BW. This tilts your decision toward 8-pole filters, however there is still an issue of bandwidth. Since the 400 8-pole is actually 435 Hz and the 250 8-pole is actually 370 Hz, I would definitely not order both. I'm faced with the same issue but will probably order one matched 500 since my order was at the original price of $80 for a 5-pole...plus I like the wider BW for contests. I was never planning to use the 200 in diversity mode (you can still use a 500 down to DSP = 250). BTW having used my 200 awhile in a few 160 contests, I would absolutely NOT be without it for huge simplex pileups. So another option for you might be two 400s for diversity, and at least one 200 for the extreme situations we sometimes have on 160. 73, Bill W4ZV _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by hf4me
> AND I thought you guys were supposed to be OFF today.
So did I :-( Lyle _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Eric Swartz - WA6HHQ
So am I to assume that the 8-pole filters are not going to need to worry
about this as they are all at 0 anyway? What is the advantage of getting two matched pairs of 5-pole filters when you can get two 8-poles for only 10 bucks a filter more? I'm assuming that its 100 + 100 + 30 for matched 5-pole filters or 125 + 125 for the 8-pole filters. I can see there being a great advantage if you already have a 5-pole and want to match it in your sub RX. But if you're just getting 2 at the same time it seems like the 8-pole makes for a good option too.. At least I hope so cause diversity receive was the main reason I figured I'd go for the 8-poles... :) ~Brett(KC7OTG) _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Eric Swartz - WA6HHQ
Thanks, Eric, for the update. This is exactly the kind of info I was
hoping for from Elecraft on the diversity filter issue. Now I can complete the process of finalizing my RX3 and filter order to complement my existing 5 pole filters. The $30 fee for matching to the offsets I already have is reasonable enough. ... Craig AC0DS _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Brett Howard
You're correct that 8-poles have no offsets and avoid this problem. When I ordered my 5-poles there was a $40 per filter discount to 8-poles and nobody (including Elecraft) understood that the Sub RX filters needed to matched if using 5-poles. EI6IZ on the Field Test team discovered this in December when he saw slight frequency offsets as the WIDTH control toggled different filters. But the real reason I ordered my 500 and 200 combination is purely bandwidth. Here are Elecraft's measurements: Filter BW(-6dB) Shape Factor 200 224 4.0 250 370 2.1 400 435 2.1 500 565 3.1 For weak CW signals or in contests I prefer a wider bandwidth. For weak signals the additional bandwidth gives my ears a better context in which to apply my ear/brain's internal 50 Hz filter. In contests, I also want to be able to hear stations calling me off-frequency as well as hear what's going on around my run frequency (so I can chase off those folks who send "?" once and then start CQ-ing 250 Hz above me). I would actually prefer 8-pole filters for rejection reasons, but the bandwidth choices above are simply wrong for my use. The 400 is too narrow and the 250 is too wide (and only 65 Hz between the two!). When I need a narrow filter, I want a *truly* narrow filter. The main use I have for the 200 is in nearly simplex pileups with lots of S9+++ signals (think 160m DX pileups). Another reason one might want 8-poles is when using N8LP's LP-PAN and SDR software for a panadaptor/waterfall display. The 5-pole offsets can cause a similar problem here as you rotate WIDTH through different filters. However, with the recent addition of Elecraft's programming commands to read the internal filter offsets, N8LP says WU2X can correct for the offsets in his PowerSDR-IF software. The bottom line to me is that I choose filters primarily for their bandwidth and I prefer the 500/200 combination even with their offset warts. If Elecraft offered different BW choices in the 8-poles, I might prefer them. Quite frankly, given the current $25 price differential, I don't see why Elecraft doesn't go to all 8-pole filters and make some better bandwidth choices (e.g. at least octave differences at the low end...say 600 and a *true* 250...not the one above which is actually 370). I wouldn't be surprised to see Inrad eventually do this even if Elecraft doesn't. 73, Bill |
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Hi Bill,
If you worked RTTY you would find out that the "250Hz" filter is ideal for recovering weak ones and for 20M during RTTY contests. The dual passband filter fits very nicely within it. I don't care what bandwidth you call it. Don't eliminate it as a choice. I was astounded the difference it made during yesterdays DL RTTY contest. Fine tuning + the selectivitiy made the 20 KHz RTTY band seem like 100KHz wide while doing search and pounce. A/B comparisons between it and the 400Hz filter did indeed show significant benefit. Spectrogram spectra, with a band loaded with signals, strengthen this A/B comparions conclusion. Some offending signals simply fell off the edge of the 250 Hz filter slope. Part of this benefit is undoubtedly due to the capture effect of FM like modes. Strongest wins. 73 de Brian/K3KO Bill W4ZV wrote: >Brett Howard wrote: > > >>So am I to assume that the 8-pole filters are not going to need to worry >>about this as they are all at 0 anyway? What is the advantage of >>getting two matched pairs of 5-pole filters when you can get two 8-poles >>for only 10 bucks a filter more? >> >>I'm assuming that its 100 + 100 + 30 for matched 5-pole filters or 125 + >>125 for the 8-pole filters. I can see there being a great advantage if >>you already have a 5-pole and want to match it in your sub RX. But if >>you're just getting 2 at the same time it seems like the 8-pole makes >>for a good option too.. At least I hope so cause diversity receive was >>the main reason I figured I'd go for the 8-poles... :) >> >> >> > >You're correct that 8-poles have no offsets and avoid this problem. When I >ordered my 5-poles there was a $40 per filter discount to 8-poles and nobody >(including Elecraft) understood that the Sub RX filters needed to matched if >using 5-poles. EI6IZ on the Field Test team discovered this in December >when he saw slight frequency offsets as the WIDTH control toggled different >filters. > >But the real reason I ordered my 500 and 200 combination is purely >bandwidth. Here are Elecraft's measurements: > >Filter BW(-6dB) Shape Factor > > 200 224 4.0 > 250 370 2.1 > 400 435 2.1 > 500 565 3.1 > >For weak CW signals or in contests I prefer a wider bandwidth. For weak >signals the additional bandwidth gives my ears a better context in which to >apply my ear/brain's internal 50 Hz filter. In contests, I also want to be >able to hear stations calling me off-frequency as well as hear what's going >on around my run frequency (so I can chase off those folks who send "?" once >and then start CQ-ing 250 Hz above me). > >I would actually prefer 8-pole filters for rejection reasons, but the >bandwidth choices above are simply wrong for my use. The 400 is too narrow >and the 250 is too wide (and only 65 Hz between the two!). When I need a >narrow filter, I want a *truly* narrow filter. The main use I have for the >200 is in nearly simplex pileups with lots of S9+++ signals (think 160m DX >pileups). > >Another reason one might want 8-poles is when using N8LP's LP-PAN and SDR >software for a panadaptor/waterfall display. The 5-pole offsets can cause a >similar problem here as you rotate WIDTH through different filters. >However, with the recent addition of Elecraft's programming commands to read >the internal filter offsets, N8LP says WU2X can correct for the offsets in >his PowerSDR-IF software. > >The bottom line to me is that I choose filters primarily for their bandwidth >and I prefer the 500/200 combination even with their offset warts. If >Elecraft offered different BW choices in the 8-poles, I might prefer them. >Quite frankly, given the current $25 price differential, I don't see why >Elecraft doesn't go to all 8-pole filters and make some better bandwidth >choices (e.g. at least octave differences at the low end...say 600 and a >*true* 250...not the one above which is actually 370). I wouldn't be >surprised to see Inrad eventually do this even if Elecraft doesn't. > >73, Bill > > _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Bill W4ZV
I think I must be missing something.
As I understand it, the additional crystal filters are only really necessary when operating with very strong adjacent signals in the passband. So, if you don't have a need for rejection of such strong signals, let's say >40 over S9 (somebody correct this figure please) then you don't need these extra filters, the DSP will cope with these large signals. The filters are only there to prevent overload of the DSP. Therefore, to perform the very best diversity reception in <40 over S9 conditions, turn off those extra filters in configuration menu. Having turned off the filters, I can engage the attenuator to avoid DSP overload if needed. Yes, I know it also reduces the signal I'm trying to hear, but that sacrifice may be what is needed. For diversity reception using low gain loop, pennant, flag, Beverage, loaded whip antennas, the signal input is very much lower than from the tx antenna, so, crystal filters are probably not be needed at all. Or do I have it all completely wrong? David G3UNA _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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David,
In most instances, you are correct. My K3 has only the stock 2.7 filter, but then I am not into heavy contesting nor intense DX chasing - I do some contesting and work DX for fun only. When it gets to the point where I really need narrow roofing filters, it is time for me to go listen to some relaxing music, so you will not find me using diversity reception to pull out some obscure weak signal. One related point - the Hardware AGC should prevent overload of the DSP, so the K3 will handle those strong signals nicely. The problem is that the AGC action when a strong unwanted signal is within the roofing filter passband, the AGC will reduce the sensitivity of the entire receiver, so your wanted signal gets weaker too - and you may not even know the offending signal is there if you have the DSP bandwidth at a narrow width - it will behave as though there is QSB on the signal you are listening to. Of course using diversity reception with one antenna having lower gain, that QSB effect may be minimized. 73, Don W3FPR David Cutter wrote: > I think I must be missing something. > > As I understand it, the additional crystal filters are only really > necessary when operating with very strong adjacent signals in the > passband. So, if you don't have a need for rejection of such strong > signals, let's say >40 over S9 (somebody correct this figure please) > then you don't need these extra filters, the DSP will cope with these > large signals. The filters are only there to prevent overload of the > DSP. > > Therefore, to perform the very best diversity reception in <40 over S9 > conditions, turn off those extra filters in configuration menu. > > Having turned off the filters, I can engage the attenuator to avoid > DSP overload if needed. Yes, I know it also reduces the signal I'm > trying to hear, but that sacrifice may be what is needed. > > For diversity reception using low gain loop, pennant, flag, Beverage, > loaded whip antennas, the signal input is very much lower than from > the tx antenna, so, crystal filters are probably not be needed at all. > > Or do I have it all completely wrong? > Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by alsopb
> If you worked RTTY you would find out that the "250Hz" filter
> is ideal for recovering weak ones and for 20M during RTTY > contests. The dual > passband filter fits very nicely within it. I don't care what > bandwidth you call it. Don't eliminate it as a choice. > > I was astounded the difference it made during yesterdays DL > RTTY contest. Fine tuning + the selectivitiy made the 20 KHz > RTTY band seem like 100KHz wide while doing search and > pounce. A/B comparisons between it and the 400Hz filter did > indeed show significant benefit. > Spectrogram spectra, with a band loaded with signals, > strengthen this A/B comparions conclusion. > Some offending signals simply fell off the edge of the 250 Hz > filter slope. Part of this benefit is undoubtedly due to the > capture effect of FM like modes. Strongest wins. What DSP bandwidths were you using and where did you have your crystal filters engaging? There is only a 65 Hz bandwidth difference between the "400" and "250" crystal filters and both are wider than the what is needed for 170 Hz shift RTTY. The crystal filter function is to protect the DSP from strong nearby signals and a 65 Hz delta is irrelevant at 400 Hz. So there will NOT be any discernible benefit on RTTY or any other mode if you do the A/B comparison with the same DSP bandwidth (with or without the DTF). For example, if your 400 Hz filter engages at DSP bandwidth of 400 Hz and your 250 Hz filter engages at 250 Hz, then you are really A/B comparing DSP bandwidths of 400 and 250 Hz, not the crystal filter differences. What can make a difference in large RTTY pileups is running the DSP down as low as 200 Hz which rolls off the outer edges of the tones, but eliminates enough of the pileup to sometimes be a net advantage. In general, running the DSP at 300 Hz with the DTF engaged is ideal for 170 Hz shift RTTY because there is little roll off of the desired passband. Of course, the 250 Hz DSP bandwidth is a step between these two settings and also a viable alternative in some situations. The "250 Hz" crystal filter at an actual -6 dB bandwidth of 370 Hz is a good roofer for these three DSP bandwidths, but the "400 Hz" crystal filter at an actual BW of 435 Hz is essentially the same as far as protecting the DSP from nearby strong signals. 73, Ed - W0YK _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by David Cutter
I find that the narrower filters take out a lot of the noise before it
hits the DSP and it can even make just rag chew conditions nicer in my very electrically noisy area. Actually I'm quite excited that once I get my K3 back that I can set the 250Hz filter to be able to use it up at 350. I even am adding the 1Khz filter as the step in the noise when switching from my 250Hz to my 1.8Khz was pretty large. Honestly I'm not so sure that the 1.8 is really all that much of a help over the 2.7 but the 250 is a big help over the 2.7 and the 1.8. Plus I just like having the radio do all the intelligent rock switching. Makes it a very nice combination and mixing of the old way of doing things and the new way of doing things. On Sun, 2008-07-06 at 13:56 +0100, David Cutter wrote: > I think I must be missing something. > > As I understand it, the additional crystal filters are only really necessary > when operating with very strong adjacent signals in the passband. So, if > you don't have a need for rejection of such strong signals, let's say >40 > over S9 (somebody correct this figure please) then you don't need these > extra filters, the DSP will cope with these large signals. The filters are > only there to prevent overload of the DSP. > > Therefore, to perform the very best diversity reception in <40 over S9 > conditions, turn off those extra filters in configuration menu. > > Having turned off the filters, I can engage the attenuator to avoid DSP > overload if needed. Yes, I know it also reduces the signal I'm trying to > hear, but that sacrifice may be what is needed. > > For diversity reception using low gain loop, pennant, flag, Beverage, loaded > whip antennas, the signal input is very much lower than from the tx antenna, > so, crystal filters are probably not be needed at all. > > Or do I have it all completely wrong? > > David > G3UNA > > _______________________________________________ > Elecraft mailing list > Post to: [hidden email] > You must be a subscriber to post to the list. > Subscriber Info (Addr. Change, sub, unsub etc.): > http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/subscribers.htm > Elecraft web page: http://www.elecraft.com _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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In reply to this post by Ed Muns, W0YK
Ed Muns wrote:
> What DSP bandwidths were you using and where did you have your crystal > filters engaging? There is only a 65 Hz bandwidth difference between the > "400" and "250" crystal filters and both are wider than the what is needed > for 170 Hz shift RTTY. The crystal filter function is to protect the DSP For clarity, 170Hz is less than the minimum required bandwidth for RTTY. That needs to be extended by some multiple (> 1.0) of the baud rate, to avoid excessive truncation of significant sidebands. I would suggest that a filter that was significantly down at 250 Hz would be introducing significant distortion. -- David Woolley "The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> _______________________________________________ Elecraft mailing list Post to: [hidden email] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com |
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David you may be suggesting that "in theory" but I would pay *close attention* to what W0YK says. Ed wins many RTTY contests including several current world records from P49X, and results sometimes speak louder to me than theory (and I'm an engineer if that means anything). http://www.radio-sport.net/wpxrtty08_post1.htm FYI, the DSP filter in the K3 follows the following formula for shape factor according to Lyle KK7P: Shape Factor = (6 dB BW) / (6 dB BW + 300 Hz) At 200 Hz BW, the DSP shape factor computes to 2.5. The 200 Hz crystal filter was measured by Elecraft to be 224 Hz wide with a shape factor of 4.0, so whether you use a 400, 250, or 200 Hz roofing filter, that has little bearing on the final BW when WIDTH is set to 200 as Ed suggested (since all XFILs are wider than the DSP's BW). Many folks seem to have problems confusing the role of roofing filters for determining the final bandwidth in the K3. That is simply not the case. The purpose of the roofing filter is mainly to reduce strong (approximately S9+30) signals from over-driving the ADC in the DSP. If they do that, then the DSP determines the final selectivity over its ~100 dB dynamic range. 73, Bill |
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FYI, the DSP filter in the K3 follows the following formula for shape factor according to Lyle KK7P:
Shape Factor = (6 dB BW) / (6 dB BW + 300 Hz) Oops...no coffee yet. Make that Shape Factor = (6 dB BW + 300 Hz) / (6 dB BW) 73, Bill |
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