RTTY filter for K3
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To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _________________________________________________________________ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE_______________________________________________ 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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I think it is just the difference between books and the real world. I
run AFSK, and with the K3 setup you can make full use of the filters. If I want to drill into a signal the 400hz works well. You leave a little drop off on each side. If you get it too narrow, the signal does not decode well. If you have issues beyond that, like I had when I hand two signals intermixing, then I went to the dual-pass-band filter, and that nails it down pretty hard. I have the 400hz, 1.0khz, newley received 1.8khz, and the 2.7khz, and it worked great in the volta rtty contest, and have used it some on 20m Friday evening. I am very happy with the setup. Start out with the 400hz, and put it in the second slot. If you want to add a 250 later, it takes about 15m to do it. Dave Wilburn K4DGW K2/100 - S/N 5982 K3/100 - S/N 766 "For those who fought for it, freedom has a flavor the protected will never know." Axel Kaiser wrote: > > > > To all you filter aficionados, > > first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. > One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. > So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? > > Best 73 de > > Axel, DL3ZH > > > > _________________________________________________________________ > Discover the new Windows Vista > http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE_______________________________________________ > 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 Axel Kaiser-2
The Elecraft "250 Hz 8-pole" crystal filter is 370 Hz at the -6 dB point.
You can run the DSP down as low as 300 Hz with this crystal filter and have minimal roll-off of the 170 Hz shift RTTY signal. In practice, I have run 200 Hz DSP in large RTTY pileups with great success in contests for months now. Yes, there is roll-off, but the narrower filter eliminated more of the pileup so that the net result was faster clear copy of at least one call sign, compared to even a 300 Hz DSP bandwidth. This trade-off was a net advantage. In non-pileup situations, the 300 Hz DSP bandwidth with the "250 Hz" (actually 370 Hz) crystal filter is as narrow as you should, especially for weak signal reception. Furthermore the 400 and 500 Hz crystal filters are nearly as good as the 250 (really 370) for this application as roofing filters. In few cases, if any, will you be able to tell any difference between these three roofing filters. 73, Ed - W0YK > -----Original Message----- > From: [hidden email] [mailto:elecraft- > [hidden email]] On Behalf Of Axel Kaiser > Sent: Sunday, May 18, 2008 5:15 AM > To: Elecraft Reflector > Subject: [Elecraft] RTTY filter for K3 > > > > > > To all you filter aficionados, > > first of all thank you very much for all your detailed answers to my > original question, which roofing filter ist best for RTTY operation of the > K3. Lots of very detailed and informative answers were given and even a > general discussion on this issue among several others was started. But to > tell you the truth, I am still somewhat uncertain, which filter to order > with my K3. > One of my theory books about HF technology, modulation, bandwidth and so > forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY > signal should be around 320 Hz. Now some of you guys write, that you are > using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this > 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, > which means that the actual bandwidth at about 0 db is even less. > So my understanding for a 170 Hz shift RTTY operation is, to use a filter > of at least 400 - 500 Hz (at -6dB) in order to get all the information > through the filter. This I can confirm also with my current OMNI VI+ which > does not allow me to copy RTTY signals with a 250 Hz filter . So please, > where is the point which I am missing with the K3, that you can work weak > RTTY signals with a 250 Hz roofing filter?? > > Best 73 de > > Axel, DL3ZH > > > > _________________________________________________________________ > Discover the new Windows Vista > http://search.msn.com/results.aspx?q=windows+vista&mkt=en- > US&form=QBRE_______________________________________________ > 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 Axel Kaiser-2
To try and answer this question completely, I generated a single Spectrogram plot showing:
1) A typical dual peak RTTY filter response (expect the K3 looks like this). It was from a Timewave DSP-559ZX. Receiver IF filter is about 350Hz. MTTY looks the same. 2) A RTTY signal. I haven't figured out how to post it here. Send me an E-mail and I'll send it to you. Bottom line: The DSP dual peak filter is 8-10 db down at a bandwidth of 260Hz. The actual signal fits completely within the minimally attenuated portion of the dual peak filter response. The concern about loosing information for weak signals is unfounded. The weak signal sidebands are so far in the noise that no information can be recovered. Theory about the sidebands being there is correct. It just doesn't consider this weak signal case. Thus the "250 Hz" filter is plenty wide enough for S&P and DXing. I'm not a believer in using AFC, even when running them during contests, but if you are, then perhaps a wider filter is more appropriate for that. 400Hz ought to be plenty wide enough. Guys who call you 100Hz or more off frequency don't deserve to be worked! I'll run this again when my K3 arrives. I don't expect the conclusions to change. More important is that the narrow filter response is centered within the passband. I note that available plots show 8 pole filters as much as 25 Hz from this. Five poles filters are probably even worse. Thus one needs to use the K3's ability to offset filters (of shift) for RTTY to achieve centering. Spectrogram is an easy to use, free tool to help sort things out. 73 de Brian/K3KO
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The RTTY decoder in fldigi is very good - I use this source in DM780.
Knowing how it works I am sure that a very tight 200Hz or 250Hz filter would be fine. In fact it would be interesting to compare the K3's RTTY decoding with external software, I'll do this sometime... Simon Brown, HB9DRV -------------------------------------------------- From: "K3KO" <[hidden email]> > > Thus the "250 Hz" filter is plenty wide enough for S&P and DXing. I'm > not > a believer in using AFC, even when running them during contests, but if > you > are, then perhaps a wider filter is more appropriate for that. > 400Hz ought to be plenty wide enough. Guys who call you 100Hz or more off > frequency don't deserve to be worked! > _______________________________________________ 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 Axel Kaiser-2
Axel
I was the first to respond to your question. I told you that I was listening to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the experts came on here and using many words, explained why it couldn't work because it is too narrow. Maybe they do not actually have the filter but I do. Looking at the waterfall on MixW, 200Hz filter engaged, a RTTY signal easily fits within the waterfall's passband with a little room on either side. The vertical stripes of the RTTY signal do not quiet reach the outer edge of the waterfall which tells me that the "data" is not being chopped off. Both weak and strong RTTY signals seem perfectly copyable. No I would not use this in a contest unless I had a bandscope so I could find signals. I have ordered the LP-PAN which should take care of that little detail. 73 Steve Ellington [hidden email] ----- Original Message ----- From: "Axel Kaiser" <[hidden email]> To: "Elecraft Reflector" <[hidden email]> Sent: Sunday, May 18, 2008 4:14 AM Subject: [Elecraft] RTTY filter for K3 To all you filter aficionados, first of all thank you very much for all your detailed answers to my original question, which roofing filter ist best for RTTY operation of the K3. Lots of very detailed and informative answers were given and even a general discussion on this issue among several others was started. But to tell you the truth, I am still somewhat uncertain, which filter to order with my K3. One of my theory books about HF technology, modulation, bandwidth and so forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY signal should be around 320 Hz. Now some of you guys write, that you are using a 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which means that the actual bandwidth at about 0 db is even less. So my understanding for a 170 Hz shift RTTY operation is, to use a filter of at least 400 - 500 Hz (at -6dB) in order to get all the information through the filter. This I can confirm also with my current OMNI VI+ which does not allow me to copy RTTY signals with a 250 Hz filter . So please, where is the point which I am missing with the K3, that you can work weak RTTY signals with a 250 Hz roofing filter?? Best 73 de Axel, DL3ZH _________________________________________________________________ Discover the new Windows Vista http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE_______________________________________________ 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 -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM _______________________________________________ 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 Axel Kaiser-2
Order a 400 cycle filter and be done with it. You won't miss a contact.
Ken http://www.cashcowhunter.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 N4LQ-2
Please turn on the K3 dual peak RTTY filter and tell us what you see then.
Brian/K3KO
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In reply to this post by Axel Kaiser-2
At 01:14 AM 18 05 2008, Axel Kaiser, DL3ZH wrote: >This I can confirm also with my current OMNI VI+ which does not >allow me to copy RTTY signals with a 250 Hz filter . Lieber Axel, I use the 250 Hz all the time with my Omni VI+. Great performance: good copy and little interference. Perhaps PBT needs tweaking. I use the waterfall display and adjust PBT to center passband on the two RTTY tones. 73, Hank, W6SX Mammoth Lakes, California Elevation 8083 feet in John Muir's Range of Light _______________________________________________ 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
I'm using DATA A mode. Contrary to the manual, the Dual Tone RTTY filter
will not activate in DATA A mode. When attempted, the display shows N/A. To use the DTF, I changed to AFSK A mode. This allows the DTF to work however the center frequency of the IF changes from 1500Hz to 1356Hz. I will notify Elecraft about these. As far as copying RTTY with the 200hz filter and DTF....It appears to work fine. The only difference I could detect on the waterfall with DTF turned on is the obvious "hole" between the filter peaks. Steve Ellington [hidden email] ----- Original Message ----- From: "K3KO" <[hidden email]> To: <[hidden email]> Sent: Sunday, May 18, 2008 10:12 AM Subject: Re: [Elecraft] RTTY filter for K3 > > Please turn on the K3 dual peak RTTY filter and tell us what you see then. > Brian/K3KO > > > n4lq wrote: >> >> Axel >> I was the first to respond to your question. I told you that I was >> listening >> to RTTY through the 200 Hz, 5 pole filter and it worked fine. Then the >> experts came on here and using many words, explained why it couldn't work >> because it is too narrow. Maybe they do not actually have the filter but >> I >> do. >> Looking at the waterfall on MixW, 200Hz filter engaged, a RTTY signal >> easily >> fits within the waterfall's passband with a little room on either side. >> The >> vertical stripes of the RTTY signal do not quiet reach the outer edge of >> the >> waterfall which tells me that the "data" is not being chopped off. Both >> weak >> and strong RTTY signals seem perfectly copyable. >> No I would not use this in a contest unless I had a bandscope so I could >> find signals. I have ordered the LP-PAN which should take care of that >> little detail. >> 73 >> >> Steve Ellington >> [hidden email] >> ----- Original Message ----- >> From: "Axel Kaiser" <[hidden email]> >> To: "Elecraft Reflector" <[hidden email]> >> Sent: Sunday, May 18, 2008 4:14 AM >> Subject: [Elecraft] RTTY filter for K3 >> >> >> >> >> >> >> To all you filter aficionados, >> >> first of all thank you very much for all your detailed answers to my >> original question, which roofing filter ist best for RTTY operation of >> the >> K3. Lots of very detailed and informative answers were given and even a >> general discussion on this issue among several others was started. But to >> tell you the truth, I am still somewhat uncertain, which filter to order >> with my K3. >> One of my theory books about HF technology, modulation, bandwidth and so >> forth, tells me, that the necessary bandwidth for a 170 Hz shift RTTY >> signal >> should be around 320 Hz. Now some of you guys write, that you are using a >> 250 Hz filter for RTTY operation. A 250 Hz filter though has this 250 Hz >> (ok, a few Hz more in reality) bandwidth at - 6dB attenuation, which >> means >> that the actual bandwidth at about 0 db is even less. >> So my understanding for a 170 Hz shift RTTY operation is, to use a filter >> of >> at least 400 - 500 Hz (at -6dB) in order to get all the information >> through >> the filter. This I can confirm also with my current OMNI VI+ which does >> not >> allow me to copy RTTY signals with a 250 Hz filter . So please, where is >> the >> point which I am missing with the K3, that you can work weak RTTY signals >> with a 250 Hz roofing filter?? >> >> Best 73 de >> >> Axel, DL3ZH >> >> >> >> _________________________________________________________________ >> Discover the new Windows Vista >> http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&form=QBRE_______________________________________________ >> 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 >> >> >> -------------------------------------------------------------------------------- >> >> >> >> No virus found in this incoming message. >> Checked by AVG. >> Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: >> 5/17/2008 >> 6:26 PM >> >> _______________________________________________ >> 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 >> >> > > -- > View this message in context: > http://www.nabble.com/RTTY-filter-for-K3-tp17300221p17303427.html > Sent from the Elecraft mailing list archive at Nabble.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 -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM _______________________________________________ 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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You can change the MARK freq in AFSK A mode to one of four values
ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A knob which, of course, will change the center frequency accordingly. 73, Ken K3IU ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ n4lq wrote: > To use the DTF, I changed to AFSK A mode. This allows the DTF to work > however the center frequency of the IF changes from 1500Hz to 1356Hz. > I will notify Elecraft about these. _______________________________________________ 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 but it won't change the center fq. to 1500Hz so it will be like DATA A.
I'm not sure what the purpose of changing the pitch is. Steve Ellington [hidden email] ----- Original Message ----- From: "Ken K3IU" <[hidden email]> To: "n4lq" <[hidden email]> Cc: <[hidden email]> Sent: Sunday, May 18, 2008 2:43 PM Subject: Re: [Elecraft] RTTY filter for K3 > You can change the MARK freq in AFSK A mode to one of four values > ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A > knob which, of course, will change the center frequency accordingly. > > 73, > Ken K3IU > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > n4lq wrote: >> To use the DTF, I changed to AFSK A mode. This allows the DTF to work >> however the center frequency of the IF changes from 1500Hz to 1356Hz. >> I will notify Elecraft about these. -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM _______________________________________________ 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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As far as I know, the reason for having the capability of changing the
Mark freq is for personal preference in what you like to listen to. The Dual PB filter works at whatever frequency you select. I can think of no reason why AFSK A and DATA A modes would necessarily have to be the same. I'm not sure why you want to change the center frequency to specifically 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. I prefer the lower mark frequency of 915 Hz. The software that is decoding the signal sure doesn't care and it doesn't make any difference to what you are sending. But as they say here ofter.... YMMV. 73, Ken K3IU ~~~~~~~~~~~~~~~~~~~~~ n4lq wrote: > Yes but it won't change the center fq. to 1500Hz so it will be like > DATA A. I'm not sure what the purpose of changing the pitch is. > > Steve Ellington > [hidden email] > ----- Original Message ----- From: "Ken K3IU" <[hidden email]> > To: "n4lq" <[hidden email]> > Cc: <[hidden email]> > Sent: Sunday, May 18, 2008 2:43 PM > Subject: Re: [Elecraft] RTTY filter for K3 > > >> You can change the MARK freq in AFSK A mode to one of four values >> ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A >> knob which, of course, will change the center frequency accordingly. >> >> 73, >> Ken K3IU >> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> n4lq wrote: >>> To use the DTF, I changed to AFSK A mode. This allows the DTF to work >>> however the center frequency of the IF changes from 1500Hz to 1356Hz. >>> I will notify Elecraft about these. > > > -------------------------------------------------------------------------------- > > > > > No virus found in this incoming message. > Checked by AVG. > Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: > 5/18/2008 9:31 AM > > 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 N4LQ-2
> Yes but it won't change the center fq. to 1500Hz so it will be like DATA
> A. I'm not sure what the purpose of changing the pitch is. DATA A is a general purpose mode. It is SSB with some features that could cause distortion (like the speech processor) disabled. It is data mode agnostic: you can run RTTY, PSK, Olivia, DRM, ... We also put some specialized modes under the DATA umbrella. AFSK, FSK D and PSK D are the current ones. AFSK and FSK D assume you are probably running RTTY, or at least an FSK mode with similar data rate and the same shift. The dual tone filter (DTF) is thus available for AFSK and for FSK D, but not for DATA A or PSK D. The reason for the various tone pairs is that some of you will likely want to run an external decoder and/or encoder (MTTY, or HRD+DM780, for example) and these programs often assume certain standard tone pairs will be used. We put the most popular of these as selectable pairs. 73, 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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In reply to this post by Ken Wagner K3IU
Bear with me on this Ken....It's long but hopefully I can explain.:
By the same token....I can see no reason why the center frequency of DATA A and AFSK A should be different. Most advanced digital mode programs such as MixW have something similar to an "Align" macro. You tell the macro what you filter's center frequency is then whenever you click on that macro it instantly tunes your K3 so that the desired trace on your waterfall is exactly centered in the IF passband. You can then choose your most narrow filter and that signal will still be in the IF's center. I have a macro for the filter selection too so everything is really fast and easy. Here's how it works for me. 1. K3 filter set on very wide....3+ KHZ. 2. See signal on waterfall. 3. Click on signal. 4. Begin to copy data on screen. 5. Signal is weak, QRM, need narrow filter. 6. Click on "Align" macro. Signal is now centered in passband. 7. Click on filter macro, choosing 200Hz filter. 8. QRM gone...Signal now easy to copy. Now this was all in DATA A mode. I use DATA A for PSK31, MFSK and anyother digital mode. So what if I want to operate RTTY? Well I can go ahead and do so in DATA A mode however that DUAL FIL feature will not activate. Is this a flaw? So I got to AFSK A....Now DUAL FIL works but now my ALIGN macro won't work because my IF Center is different. It should not be....1500 HZ should be the default. If I wanted to use 910 HZ and enjoy that low pitch sound, I would have to either change my Align macro or try to manually tune the RTTY signal which is terribly difficult, especially in a contest when transmissions last for only a few seconds. Steve Ellington [hidden email] ----- Original Message ----- From: "Ken K3IU" <[hidden email]> To: "n4lq" <[hidden email]> Cc: <[hidden email]> Sent: Sunday, May 18, 2008 3:37 PM Subject: Re: [Elecraft] RTTY filter for K3 > As far as I know, the reason for having the capability of changing the > Mark freq is for personal preference in what you like to listen to. The > Dual PB filter works at whatever frequency you select. I can think of no > reason why AFSK A and DATA A modes would necessarily have to be the same. > > I'm not sure why you want to change the center frequency to specifically > 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. > I prefer the lower mark frequency of 915 Hz. The software that is > decoding the signal sure doesn't care and it doesn't make any difference > to what you are sending. > > But as they say here ofter.... YMMV. > > 73, > Ken K3IU > ~~~~~~~~~~~~~~~~~~~~~ > n4lq wrote: >> Yes but it won't change the center fq. to 1500Hz so it will be like >> DATA A. I'm not sure what the purpose of changing the pitch is. >> >> Steve Ellington >> [hidden email] >> ----- Original Message ----- From: "Ken K3IU" <[hidden email]> >> To: "n4lq" <[hidden email]> >> Cc: <[hidden email]> >> Sent: Sunday, May 18, 2008 2:43 PM >> Subject: Re: [Elecraft] RTTY filter for K3 >> >> >>> You can change the MARK freq in AFSK A mode to one of four values >>> ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the VFO A >>> knob which, of course, will change the center frequency accordingly. >>> >>> 73, >>> Ken K3IU >>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>> n4lq wrote: >>>> To use the DTF, I changed to AFSK A mode. This allows the DTF to work >>>> however the center frequency of the IF changes from 1500Hz to 1356Hz. >>>> I will notify Elecraft about these. >> >> >> -------------------------------------------------------------------------------- >> >> >> >> >> No virus found in this incoming message. >> Checked by AVG. >> Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: >> 5/18/2008 9:31 AM >> >> -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM _______________________________________________ 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... thanks Steve. I am familiar with MixW... have used it for years
and I see what you are talking about. But let me suggest the following... Go to AFSK A mode and set the mark frequency to 1445. That will give you a center frequency of 1530 which would put you within 30 Hz of your align frequency of 1500 Hz. If signal is still a l'il off, then use mouse to get it on or let the AFC move it on. I just tried it on a PSK signal with my filter cranked down as narrow as it would go in Data Mode and it hardly missed a beat decoding. 73, Ken K3IU n4lq wrote: > Bear with me on this Ken....It's long but hopefully I can explain.: > > By the same token....I can see no reason why the center frequency of > DATA A and AFSK A should be different. > Most advanced digital mode programs such as MixW have something > similar to an "Align" macro. You tell the macro what you filter's > center frequency is then whenever you click on that macro it instantly > tunes your K3 so that the desired trace on your waterfall is exactly > centered in the IF passband. You can then choose your most narrow > filter and that signal will still be in the IF's center. I have a > macro for the filter selection too so everything is really fast and easy. > Here's how it works for me. > 1. K3 filter set on very wide....3+ KHZ. > 2. See signal on waterfall. > 3. Click on signal. > 4. Begin to copy data on screen. > 5. Signal is weak, QRM, need narrow filter. > 6. Click on "Align" macro. Signal is now centered in passband. > 7. Click on filter macro, choosing 200Hz filter. > 8. QRM gone...Signal now easy to copy. > > Now this was all in DATA A mode. I use DATA A for PSK31, MFSK and > anyother digital mode. > So what if I want to operate RTTY? Well I can go ahead and do so in > DATA A mode however that DUAL FIL feature will not activate. Is this a > flaw? > So I got to AFSK A....Now DUAL FIL works but now my ALIGN macro won't > work because my IF Center is different. It should not be....1500 HZ > should be the default. If I wanted to use 910 HZ and enjoy that low > pitch sound, I would have to either change my Align macro or try to > manually tune the RTTY signal which is terribly difficult, especially > in a contest when transmissions last for only a few seconds. > > > > > Steve Ellington > [hidden email] > ----- Original Message ----- From: "Ken K3IU" <[hidden email]> > To: "n4lq" <[hidden email]> > Cc: <[hidden email]> > Sent: Sunday, May 18, 2008 3:37 PM > Subject: Re: [Elecraft] RTTY filter for K3 > > >> As far as I know, the reason for having the capability of changing the >> Mark freq is for personal preference in what you like to listen to. The >> Dual PB filter works at whatever frequency you select. I can think of no >> reason why AFSK A and DATA A modes would necessarily have to be the >> same. >> >> I'm not sure why you want to change the center frequency to specifically >> 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. >> I prefer the lower mark frequency of 915 Hz. The software that is >> decoding the signal sure doesn't care and it doesn't make any difference >> to what you are sending. >> >> But as they say here ofter.... YMMV. >> >> 73, >> Ken K3IU >> ~~~~~~~~~~~~~~~~~~~~~ >> n4lq wrote: >>> Yes but it won't change the center fq. to 1500Hz so it will be like >>> DATA A. I'm not sure what the purpose of changing the pitch is. >>> >>> Steve Ellington >>> [hidden email] >>> ----- Original Message ----- From: "Ken K3IU" <[hidden email]> >>> To: "n4lq" <[hidden email]> >>> Cc: <[hidden email]> >>> Sent: Sunday, May 18, 2008 2:43 PM >>> Subject: Re: [Elecraft] RTTY filter for K3 >>> >>> >>>> You can change the MARK freq in AFSK A mode to one of four values >>>> ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the >>>> VFO A >>>> knob which, of course, will change the center frequency accordingly. >>>> >>>> 73, >>>> Ken K3IU >>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>>> n4lq wrote: >>>>> To use the DTF, I changed to AFSK A mode. This allows the DTF to work >>>>> however the center frequency of the IF changes from 1500Hz to 1356Hz. >>>>> I will notify Elecraft about these. >>> >>> >>> -------------------------------------------------------------------------------- >>> >>> >>> >>> >>> >>> No virus found in this incoming message. >>> Checked by AVG. >>> Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: >>> 5/18/2008 9:31 AM >>> >>> > > > -------------------------------------------------------------------------------- > > > > > No virus found in this incoming message. > Checked by AVG. > Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: > 5/18/2008 9:31 AM > > 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 Ken but that's with a BW of 150Hz, not too critical. Soon, I am told,
Elecraft will activate the 50Hz filter so it can be used in Data mode. I suggested to Lyle that they change the default center fq. in AFSK to 1500 so it will match Data A then let the user change as desired. Then also allow use of the Dual PB feature in Data A. That should perfect things. Then I would not even bother using AFSK A. Steve Ellington [hidden email] ----- Original Message ----- From: "Ken K3IU" <[hidden email]> To: "n4lq" <[hidden email]> Cc: "Elecraft Reflector" <[hidden email]> Sent: Sunday, May 18, 2008 5:04 PM Subject: Re: [Elecraft] RTTY filter for K3 > OK... thanks Steve. I am familiar with MixW... have used it for years > and I see what you are talking about. But let me suggest the > following... Go to AFSK A mode and set the mark frequency to 1445. That > will give you a center frequency of 1530 which would put you within 30 > Hz of your align frequency of 1500 Hz. If signal is still a l'il off, > then use mouse to get it on or let the AFC move it on. I just tried it > on a PSK signal with my filter cranked down as narrow as it would go in > Data Mode and it hardly missed a beat decoding. > > 73, > Ken K3IU > > n4lq wrote: >> Bear with me on this Ken....It's long but hopefully I can explain.: >> >> By the same token....I can see no reason why the center frequency of >> DATA A and AFSK A should be different. >> Most advanced digital mode programs such as MixW have something >> similar to an "Align" macro. You tell the macro what you filter's >> center frequency is then whenever you click on that macro it instantly >> tunes your K3 so that the desired trace on your waterfall is exactly >> centered in the IF passband. You can then choose your most narrow >> filter and that signal will still be in the IF's center. I have a >> macro for the filter selection too so everything is really fast and easy. >> Here's how it works for me. >> 1. K3 filter set on very wide....3+ KHZ. >> 2. See signal on waterfall. >> 3. Click on signal. >> 4. Begin to copy data on screen. >> 5. Signal is weak, QRM, need narrow filter. >> 6. Click on "Align" macro. Signal is now centered in passband. >> 7. Click on filter macro, choosing 200Hz filter. >> 8. QRM gone...Signal now easy to copy. >> >> Now this was all in DATA A mode. I use DATA A for PSK31, MFSK and >> anyother digital mode. >> So what if I want to operate RTTY? Well I can go ahead and do so in >> DATA A mode however that DUAL FIL feature will not activate. Is this a >> flaw? >> So I got to AFSK A....Now DUAL FIL works but now my ALIGN macro won't >> work because my IF Center is different. It should not be....1500 HZ >> should be the default. If I wanted to use 910 HZ and enjoy that low >> pitch sound, I would have to either change my Align macro or try to >> manually tune the RTTY signal which is terribly difficult, especially >> in a contest when transmissions last for only a few seconds. >> >> >> >> >> Steve Ellington >> [hidden email] >> ----- Original Message ----- From: "Ken K3IU" <[hidden email]> >> To: "n4lq" <[hidden email]> >> Cc: <[hidden email]> >> Sent: Sunday, May 18, 2008 3:37 PM >> Subject: Re: [Elecraft] RTTY filter for K3 >> >> >>> As far as I know, the reason for having the capability of changing the >>> Mark freq is for personal preference in what you like to listen to. The >>> Dual PB filter works at whatever frequency you select. I can think of no >>> reason why AFSK A and DATA A modes would necessarily have to be the >>> same. >>> >>> I'm not sure why you want to change the center frequency to specifically >>> 1500 HZ in AFSK A mode. I sure wouldn't... that's too high for my ears. >>> I prefer the lower mark frequency of 915 Hz. The software that is >>> decoding the signal sure doesn't care and it doesn't make any difference >>> to what you are sending. >>> >>> But as they say here ofter.... YMMV. >>> >>> 73, >>> Ken K3IU >>> ~~~~~~~~~~~~~~~~~~~~~ >>> n4lq wrote: >>>> Yes but it won't change the center fq. to 1500Hz so it will be like >>>> DATA A. I'm not sure what the purpose of changing the pitch is. >>>> >>>> Steve Ellington >>>> [hidden email] >>>> ----- Original Message ----- From: "Ken K3IU" <[hidden email]> >>>> To: "n4lq" <[hidden email]> >>>> Cc: <[hidden email]> >>>> Sent: Sunday, May 18, 2008 2:43 PM >>>> Subject: Re: [Elecraft] RTTY filter for K3 >>>> >>>> >>>>> You can change the MARK freq in AFSK A mode to one of four values >>>>> ranging from 915 Hz to 2125 Hz by pressing PITCH and rotating the >>>>> VFO A >>>>> knob which, of course, will change the center frequency accordingly. >>>>> >>>>> 73, >>>>> Ken K3IU >>>>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >>>>> n4lq wrote: >>>>>> To use the DTF, I changed to AFSK A mode. This allows the DTF to work >>>>>> however the center frequency of the IF changes from 1500Hz to 1356Hz. >>>>>> I will notify Elecraft about these. >>>> >>>> >>>> -------------------------------------------------------------------------------- >>>> >>>> >>>> >>>> >>>> >>>> No virus found in this incoming message. >>>> Checked by AVG. >>>> Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: >>>> 5/18/2008 9:31 AM >>>> >>>> >> >> >> -------------------------------------------------------------------------------- >> >> >> >> >> No virus found in this incoming message. >> Checked by AVG. >> Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: >> 5/18/2008 9:31 AM >> >> -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1453 - Release Date: 5/18/2008 9:31 AM _______________________________________________ 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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> ...I
> suggested to Lyle that they change the default center fq. in AFSK to > 1500 so it will match Data A then let the user change as desired. The center frequency in AFSK will be between the two tones selected for the tone pair. It really can;t be anything else. DATA A is a general purpose data mode. AFSK is targeted for RTTY operation. 73, 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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In reply to this post by N4LQ-2
> I was the first to respond to your question. I told you that > I was listening to RTTY through the 200 Hz, 5 pole filter and > it worked fine. Then the experts came on here and using many > words, explained why it couldn't work because it is too narrow. Using a excessively narrow filter on RTTY is a balancing act. If the bandwidth is too narrow the tones tend to become "smeared" - the transitions become less easy to detect (in other words, the "eye" begins to close). However, narrowing the bandwidth also reduces the amount of QRM/QRN making it through the filter and to the decoder/detector. In some cases the benefits of reduced interference are greater than the losses caused by data smearing in the "too narrow" filter. This is particularly true if the desired signal is strong enough in the absence of QRM/QRN to be decoded even with compromised bandwidth. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of n4lq > Sent: Sunday, May 18, 2008 8:42 AM > To: Axel Kaiser; Elecraft Reflector > Subject: Re: [Elecraft] RTTY filter for K3 > > > Axel > I was the first to respond to your question. I told you that > I was listening > to RTTY through the 200 Hz, 5 pole filter and it worked fine. > Then the > experts came on here and using many words, explained why it > couldn't work > because it is too narrow. Maybe they do not actually have the > filter but I > do. > Looking at the waterfall on MixW, 200Hz filter engaged, a > RTTY signal easily > fits within the waterfall's passband with a little room on > either side. The > vertical stripes of the RTTY signal do not quiet reach the > outer edge of the > waterfall which tells me that the "data" is not being chopped > off. Both weak > and strong RTTY signals seem perfectly copyable. > No I would not use this in a contest unless I had a bandscope > so I could > find signals. I have ordered the LP-PAN which should take > care of that > little detail. > 73 > > Steve Ellington > [hidden email] > ----- Original Message ----- > From: "Axel Kaiser" <[hidden email]> > To: "Elecraft Reflector" <[hidden email]> > Sent: Sunday, May 18, 2008 4:14 AM > Subject: [Elecraft] RTTY filter for K3 > > > > > > > To all you filter aficionados, > > first of all thank you very much for all your detailed answers to my > original question, which roofing filter ist best for RTTY > operation of the > K3. Lots of very detailed and informative answers were given > and even a > general discussion on this issue among several others was > started. But to > tell you the truth, I am still somewhat uncertain, which > filter to order > with my K3. > One of my theory books about HF technology, modulation, > bandwidth and so > forth, tells me, that the necessary bandwidth for a 170 Hz > shift RTTY signal > should be around 320 Hz. Now some of you guys write, that you > are using a > 250 Hz filter for RTTY operation. A 250 Hz filter though has > this 250 Hz > (ok, a few Hz more in reality) bandwidth at - 6dB > attenuation, which means > that the actual bandwidth at about 0 db is even less. > So my understanding for a 170 Hz shift RTTY operation is, to > use a filter of > at least 400 - 500 Hz (at -6dB) in order to get all the > information through > the filter. This I can confirm also with my current OMNI VI+ > which does not > allow me to copy RTTY signals with a 250 Hz filter . So > please, where is the > point which I am missing with the K3, that you can work weak > RTTY signals > with a 250 Hz roofing filter?? > > Best 73 de > > Axel, DL3ZH > > > > _________________________________________________________________ > Discover the new Windows Vista > http://search.msn.com/results.aspx?q=windows+vista&mkt=en-US&f 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 ------------------------------------------------------------------------ -------- No virus found in this incoming message. Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM _______________________________________________ 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 Checked by AVG. Version: 8.0.100 / Virus Database: 269.23.20/1452 - Release Date: 5/17/2008 6:26 PM _______________________________________________ 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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On Sun, 2008-05-18 at 19:27, Joe Subich, W4TV wrote:
... > Using a excessively narrow filter on RTTY is a balancing act. > > If the bandwidth is too narrow the tones tend to become "smeared" > - the transitions become less easy to detect (in other words, > the "eye" begins to close). However, narrowing the bandwidth > also reduces the amount of QRM/QRN making it through the filter > and to the decoder/detector. How about using a Nyquist filter? A Nyquist filter is one that results in no inter-symbol interference. That is, the filtered output is guaranteed to pass exactly through the nominal symbol location at the middle of each symbol, no matter what data may have been sent in adjacent symbols. So you get the narrowest possible bandwidth without "smearing" the signal, "closing the eye" or whatever you want to call it. For that to work, the total response must be Nyquist, including both the filter in the transmitter as well as in the receiver. Many commercial systems use "Root Nyquist" filters in both the transmitter and receiver. Since each filter's frequency response is the square root of a Nyquist filter response, the total system response is Nyquist, resulting in no inter-symbol interference. However, most RTTY transmitters do not have such a filter. Typically they just use a single-pole R-C low-pass filter to limit the transmitted bandwidth. However, if the time constant of the R-C filter were known, it would be straightforward to design a receive filter that results in a net Nyquist response. The problem is that different RTTY transmitters use different amounts of filtering. However I suspect that a "Nyquist" receive filter designed to compensate a typical/average transmit filter probably would have pretty good performance on most received signals. Does anyone know if this has ever been tried? Al N1AL _______________________________________________ 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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