How to outfit a K3 for JT65HF or JT9
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How to outfit a K3 for JT65HF or JT9
 
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I'm note sure the title makes any sense.
Now I hate to admit this but I've had more contacts in the last two month than in the last ten years using JT65HF. I'm using a FT-1000D with BPF on 20 and 10 meters with a Cushcraft Vertical. I think I bought it when Cushcraft was still in NH. I'm thinking of buying a new base K3/10. I'd prefer to by used but somehow the discounts on the used equipment just aren't there. But I expect for my application all I really need is already there. Maybe a 8 pool roofing filter. Any thoughts ? Larry N2CVS |
Re: How to outfit a K3 for JT65HF or JT9
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The only real concern for using the K3 with WSJT-X (JT65 and JT9 simultaneously) is to make sure you get either the FM or AM (13 KHz or 6 KHz) roofing filter so you can widen the RX bandwidth to the full 4.2 KHz. With a 2.7 or 2.8 KHz filter you will be limited to one mode or the other and switching between the two. 73, ... Joe, W4TV On 4/21/2014 10:33 AM, Larry Lopez wrote: > I'm note sure the title makes any sense. > > Now I hate to admit this but I've had more > contacts in the last two month than in the last > ten years using JT65HF. > > I'm using a FT-1000D with BPF on 20 and 10 meters > with a Cushcraft Vertical. I think I bought it when > Cushcraft was still in NH. > > I'm thinking of buying a new base K3/10. > > I'd prefer to by used but somehow the discounts > on the used equipment just aren't there. > > But I expect for my application all I really need is already there. > > Maybe a 8 pool roofing filter. > > Any thoughts ? > Larry N2CVS > > > > > -- > View this message in context: http://elecraft.365791.n2.nabble.com/How-to-outfit-a-K3-for-JT65HF-or-JT9-tp7587584.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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I have both those filters, 2.7 and 2.8 and am able to crank the width to
4KHz. Also using WSJT-X and am able to adjust/widen the screen to 4KHz for both modes, works great! 73 Dwight NS9I On 4/21/2014 9:52 AM, Joe Subich, W4TV wrote: > > The only real concern for using the K3 with WSJT-X (JT65 and > JT9 simultaneously) is to make sure you get either the FM or > AM (13 KHz or 6 KHz) roofing filter so you can widen the RX > bandwidth to the full 4.2 KHz. With a 2.7 or 2.8 KHz filter > you will be limited to one mode or the other and switching > between the two. > > 73, > > ... Joe, W4TV > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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With a 2.4 KHz filter (not on a K3) I only got partial band coverage on
JT65/JT9).
Is there any advantage to using a CW filter to look at a eq channels at a time ? Or is it better just to use the DSP to narrow it down ? Larry DGB [via Elecraft] wrote: I have both those filters, 2.7 and 2.8 and am able to crank the width to |
Re: How to outfit a K3 for JT65HF or JT9
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On 4/21/2014 8:28 AM, Larry Lopez wrote:
> Or is it better just to use the DSP to narrow it down ? K1JT says that it is best to run the radio broadband and let the WSJT software provide the needed selectivity in its decoding algorithm. The reason is simple -- phase shift can cause decoding errors, filters in the radio create phase shift. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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There are, of course, exceptions to that rule. When there is a very strong signal in the passband that is causing the receiver to reduce gain to the point that a weak signal is not copyable, a CW filter (400 Hz) centered on the weak signal can often make the difference between copy and no copy. 73, ... Joe, W4TV On 4/21/2014 12:58 PM, Jim Brown wrote: > On 4/21/2014 8:28 AM, Larry Lopez wrote: >> Or is it better just to use the DSP to narrow it down ? > > K1JT says that it is best to run the radio broadband and let the WSJT > software provide the needed selectivity in its decoding algorithm. The > reason is simple -- phase shift can cause decoding errors, filters in > the radio create phase shift. > > 73, Jim K9YC > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > Message delivered to [hidden email] > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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On 4/21/2014 10:05 AM, Joe Subich, W4TV wrote:
> There are, of course, exceptions to that rule. When there is a > very strong signal in the passband that is causing the receiver > to reduce gain to the point that a weak signal is not copyable, > a CW filter (400 Hz) centered on the weak signal can often make > the difference between copy and no copy. Yes. But the important thing is that "less is more" -- that is, the phase shift occurs in the skirts and in the passband near the skirts -- so when reducing bandwidth, stay as wide as you can and still reduce the strength of the QRM. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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Thanks Joe and Jim:
So you need a linear phase filter. Is the DSP filter linear phase ? I'm searching for linear phase filter and ending up finding references in this group !!! Larry, N2CS |
Re: How to outfit a K3 for JT65HF or JT9
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In reply to this post by Jim Brown-10
Phase noise is an issue, however, adjacent signals in the filter passband
seem to have more of an impact on the ability to decode weak signals than the phase noise associated with narrower filters. I have been able to decode weak DX stations with 400Hz and even 250Hz filters that I could not decode at all with wider filters. 73, Bob - N7RJN On 4/21/14, 10:26, "Jim Brown" <[hidden email]> wrote: >On 4/21/2014 10:05 AM, Joe Subich, W4TV wrote: >> There are, of course, exceptions to that rule. When there is a >> very strong signal in the passband that is causing the receiver >> to reduce gain to the point that a weak signal is not copyable, >> a CW filter (400 Hz) centered on the weak signal can often make >> the difference between copy and no copy. > >Yes. But the important thing is that "less is more" -- that is, the >phase shift occurs in the skirts and in the passband near the skirts -- >so when reducing bandwidth, stay as wide as you can and still reduce the >strength of the QRM. > >73, Jim K9YC > > >______________________________________________________________ >Elecraft mailing list >Home: http://mailman.qth.net/mailman/listinfo/elecraft >Help: http://mailman.qth.net/mmfaq.htm >Post: mailto:[hidden email] > >This list hosted by: http://www.qsl.net >Please help support this email list: http://www.qsl.net/donate.html >Message delivered to [hidden email] > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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Phase noise is *not* the problem/solution being discussed.
It is the phase *shift* through the filter. That is signals (within the passband) of one frequency are not delayed by exactly the same amount of time as signals of another frequency. That is a different 'animal' than phase noise. All filters will have some phase shift. but the better filters will have minimal phase shift within the flat portion of the passband. As you get closer to the slope (edges) of the passband, the phase will shift rapidly as the frequency changes. The point is - to avoid large phase shift distortion, keep the filter width as wide as possible given consideration for reducing large signals by shifting the filter or otherwise moving the offending signal outside the passband. Yes, there is often a compromise that must be made in the real world of operating. 73, Don W3FPR On 4/21/2014 3:25 PM, N7RJN wrote: > Phase noise is an issue, however, adjacent signals in the filter passband > seem to have more of an impact on the ability to decode weak signals than > the phase noise associated with narrower filters. I have been able to > decode weak DX stations with 400Hz and even 250Hz filters that I could not > decode at all with wider filters. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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In reply to this post by 'DGB'
Are you in DATA mode when you use JT65. What mode for PSK?
-- Thanks and 73's, For equipment, and software setups and reviews see: www.nk7z.net for MixW support see; http://groups.yahoo.com/neo/groups/mixw/info for Dopplergram information see: http://groups.yahoo.com/neo/groups/dopplergram/info for MM-SSTV see: http://groups.yahoo.com/neo/groups/MM-SSTV/info On Mon, 2014-04-21 at 10:01 -0500, DGB wrote: > I have both those filters, 2.7 and 2.8 and am able to crank the width to > 4KHz. Also using WSJT-X and am able to adjust/widen the screen to 4KHz > for both modes, works great! > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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On 4/21/2014 12:49 PM, David Cole wrote:
> Are you in DATA mode when you use JT65. What mode for PSK? RTFM. :) If you're using a computer to generate the signal, use DATA A for everything but RTTY. For RTTY from the computer use AFSK. "DATA A" means that the computer generates the data modulation to be transmitted as an SSB signal. Use PSK if you want the K3 to encode the PSK, use FSK D if you want the K3 to generate RTTY modulation. Note that while you COULD set the K3 for USB or LSB and feed to/from the computer, DATA A and AFSK A are far better, both because they disable CMP, because they disable TXEQ, replacing it witha high pass filter that reduces hum picked up by the unshielded input transformers. When using AFSK, be sure the tone frequencies and baud rate in your computer program (MMTTY, etc.) are the same as in the K3. One of the things you will appreciate about using the K3 for digital modes is that they all center RX and TX in the passband of your filters, sothat if you want to narrow the IF to minimize QRM,you can simply dial down the RX bandwidth. In other words, the dial readout is your TX frequency (Mark in RTTY). Current wisdom is that 400 Hz is a good choice for RTTY. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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In reply to this post by NK7Z
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Re: How to outfit a K3 for JT65HF or JT9
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In reply to this post by Joe Subich, W4TV-4
But what about EME.
You want a narrow filter and you want constant group delay. I'll research that as a separate topic. Let's close this out. In a pinch the 5 pole filter which comes with the rig is ok. 6K AM, 12K FM are recommended making up selectivity in the DSP. Narrow filters recommended when in filter band signals are producing overload. Narrow filters may degrade digital signals. Signals near the skirts of filters may be degrade digital signals. constant group delay filters are recommended. I haven't found any. Larry |
Re: How to outfit a K3 for JT65HF or JT9
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In reply to this post by Larry Lopez
I teach DSP and filters at the University of Oslo. Of the two DSP filter types, FIR (Finite Impulse Response) and IIR (Infinite Impulse Response), only an FIR filter can be designed to have exact linear phase and constant group delay. But an FIR filter can also have a non-linear phase, but that is the exception. Therefore I assume that the K3's FIR filter is linear phase (I couldn't find this mentioned in the manual). If you really need the presumably linear phase response of the FIR filter, then that requires that the DSP filter is much narrower than the roofing filter (crystal filter) so that the DSP filter is the main contributor to the passband and transition band responses. This is however not the usual way to run JT9 and JT65, but rather that the filters in the decoder software running in the PC provide the narrow bandwidth. I believe they are FFT-based filter banks which is also a kind of FIR filter with linear phase. The K3 manual has this to say on the DSP filters and how to select: "Narrow DSP Filter Types For bandwidth settings of 100 Hz or lower, the K3’s DSP normally uses a type of filter that minimizes ringing: the Finite Impulse Response or FIR filter. If you’d like steeper filter skirts, and don’t mind a small amount of ringing, you can select Infinite Impulse Response” or IIR filters for these bandwidths. Locate CONFIG:FLx BW menu entry, then tap 7 until you see IIR ON. Both main and sub receivers will use the same setting. IIR filters take longer to change from one bandwidth to another, so you may hear audio artifacts when adjusting the DSP controls. If this is objectionable, use the default FIR filters." 73 Sverre
Sverre, LA3ZA
K2 #2198, K3 #3391, LA3ZA Blog: http://la3za.blogspot.com, LA3ZA Unofficial Guide to K2 modifications: http://la3za.blogspot.com/p/la3za-unofficial-guide-to-elecraft-k2.html |
Re: How to outfit a K3 for JT65HF or JT9
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Oh my, I finally get it.
You don't even need the K3's DSP. Thank you. |
Re: How to outfit a K3 for JT65HF or JT9
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In reply to this post by Larry Lopez
Larry,
EME is about weak signal reception, and all the signals on the band segment are weak. So there are no strong adjacent signals to worry about. The situation on HF is different. If there is a station within the passband at S-9+30, it is on the borderline for activating the Hardware AGC. That signal should be moved outside the roofing filter passband to reduce its response in the K3 first IF (and DAC input). Signals with strength less that S-9+30 can be easily handled by the DSP in the K3 and likely also by the K3 DSP of the JT65HF algorithms without overload. The situation being addressed is the case where there is a strong undesired signal that will activate the hardware AGC and cause 'pumping' in the receiver response. That is where the roofing filters come into play (and consideration for their phase shift). The narrow filters will have greater group delay and greater phase shift - that is just a 'fact of life'. If there are no S-9+30 signals in the receiver passband, the combination of the K3 DSP and application DSP can handle it quite nicely. In other words, for best JT65HF, keep your filters wide so the JT65 software can do its job. If you find an extremely strong signal inside the K3 IF passband, narrowing the filter width may help, it all depends on the filters you have installed and the frequency difference between the offending strong signal and your desired station. Bottom line - when operating JTx modes (or other digital modes) learn to recognize those conditions where the K3 Hardware AGC is being activated. If Hardware AGC is not an issue, the DSP in either the K3 or the JTx software/firmware should be able to handle it. 73, Don W3FPR On 4/21/2014 4:36 PM, Larry Lopez wrote: > But what about EME. > > You want a narrow filter and you want constant group delay. > I'll research that as a separate topic. > > Let's close this out. > > In a pinch the 5 pole filter which comes with the rig is ok. > > 6K AM, 12K FM are recommended making up selectivity > in the DSP. > > Narrow filters recommended when in filter band signals > are producing overload. > > Narrow filters may degrade digital signals. > > Signals near the skirts of filters may be degrade digital signals. > > constant group delay filters are recommended. > I haven't found any. > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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don't forget the K3's tunable Notch, I have found it works quite well to
attenuate those offending S9 +30 signals. The width is just shy of a JT65 signal, but if you make sure to cover the low end it works. You can watch it working in the waterfall. I always run with the K3's AGC off...ymmv sm On 4/21/2014 7:39 PM, Don Wilhelm wrote: > The situation on HF is different. If there is a station within the > passband at S-9+30, it is on the borderline for activating the Hardware > AGC. That signal should be moved outside the roofing filter passband to > reduce its response in the K3 first IF (and DAC input). > > Signals with strength less that S-9+30 can be easily handled by the DSP > in the K3 and likely also by the K3 DSP of the JT65HF algorithms without > overload. > > The situation being addressed is the case where there is a strong > undesired signal that will activate the hardware AGC and cause 'pumping' > in the receiver response. That is where the roofing filters come into > play (and consideration for their phase shift). The narrow filters will > have greater group delay and greater phase shift - that is just a 'fact > of life'. > > If there are no S-9+30 signals in the receiver passband, the combination > of the K3 DSP and application DSP can handle it quite nicely. > > In other words, for best JT65HF, keep your filters wide so the JT65 > software can do its job. If you find an extremely strong signal inside > the K3 IF passband, narrowing the filter width may help, it all depends > on the filters you have installed and the frequency difference between > the offending strong signal and your desired station. > > Bottom line - when operating JTx modes (or other digital modes) learn to > recognize those conditions where the K3 Hardware AGC is being > activated. If Hardware AGC is not an issue, the DSP in either the K3 or > the JTx software/firmware should be able to handle it. -- GB & 73 K5OAI Sam Morgan ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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The hardware AGC cannot be turned off - it is a protection system for
the ADC that proceeds the DSP and must be protected from overload otherwise garbage will be the result. Yes, the tunable notch will attenuate signals that are within the passband of the roofing filter, but only the roofing filter can eliminate those strong signals that activate the hardware AGC. AGC off only applies to the DSP AGC. Apples and Oranges! 73, Don W3FPR On 4/21/2014 8:51 PM, Sam Morgan wrote: > don't forget the K3's tunable Notch, I have found it works quite well > to attenuate those offending S9 +30 signals. The width is just shy of > a JT65 signal, but if you make sure to cover the low end it works. You > can watch it working in the waterfall. I always run with the K3's AGC > off...ymmv > sm > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
Re: How to outfit a K3 for JT65HF or JT9
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In reply to this post by k5oai
On 4/21/2014 8:51 PM, Sam Morgan wrote: > don't forget the K3's tunable Notch, I have found it works quite well > to attenuate those offending S9 +30 signals. The Manual notch is outside the AGC loop - it can not protect the AGC system from pumping and as such only serves to protect the sound card from overload. It does not prevent blocking of the AGC. 73, ... Joe, W4TV On 4/21/2014 8:51 PM, Sam Morgan wrote: > don't forget the K3's tunable Notch, I have found it works quite well to > attenuate those offending S9 +30 signals. The width is just shy of a > JT65 signal, but if you make sure to cover the low end it works. You can > watch it working in the waterfall. I always run with the K3's AGC > off...ymmv > sm > > On 4/21/2014 7:39 PM, Don Wilhelm wrote: >> The situation on HF is different. If there is a station within the >> passband at S-9+30, it is on the borderline for activating the Hardware >> AGC. That signal should be moved outside the roofing filter passband to >> reduce its response in the K3 first IF (and DAC input). >> >> Signals with strength less that S-9+30 can be easily handled by the DSP >> in the K3 and likely also by the K3 DSP of the JT65HF algorithms without >> overload. >> >> The situation being addressed is the case where there is a strong >> undesired signal that will activate the hardware AGC and cause 'pumping' >> in the receiver response. That is where the roofing filters come into >> play (and consideration for their phase shift). The narrow filters will >> have greater group delay and greater phase shift - that is just a 'fact >> of life'. >> >> If there are no S-9+30 signals in the receiver passband, the combination >> of the K3 DSP and application DSP can handle it quite nicely. >> >> In other words, for best JT65HF, keep your filters wide so the JT65 >> software can do its job. If you find an extremely strong signal inside >> the K3 IF passband, narrowing the filter width may help, it all depends >> on the filters you have installed and the frequency difference between >> the offending strong signal and your desired station. >> >> Bottom line - when operating JTx modes (or other digital modes) learn to >> recognize those conditions where the K3 Hardware AGC is being >> activated. If Hardware AGC is not an issue, the DSP in either the K3 or >> the JTx software/firmware should be able to handle it. > Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [hidden email] |
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