RTTY Filter for K3
Locked
 
|
Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH _________________________________________________________________ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-us&source=wlmailtagline_______________________________________________ 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 |
|
|
Axel:
I am watching RTTY right now and using the 200 Hz 5 pole filter. The 170 HZ shift fits perfectly within the passband. Steve Ellington [hidden email] ----- Original Message ----- From: "Axel Kaiser" <[hidden email]> To: "Elecraft Reflector" <[hidden email]> Sent: Thursday, May 15, 2008 3:52 PM Subject: [Elecraft] RTTY Filter for K3 Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH _________________________________________________________________ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-us&source=wlmailtagline_______________________________________________ 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: 269.23.16/1434 - Release Date: 5/15/2008 7:24 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 |
|
|
In reply to this post by Axel Kaiser-2
Hi Axel, DL3ZH,
In my opinion, either one would be fine. I have the 400 Hz 8-pole in my K3, but, don't forget it is a roofing filter. In my RTTY setup, using the AFSK A digital mode, and I turn on the dual bandpass. The actual bandpass is then set by the DSP to two 50 Hz filters. It works great! 73, John, W2GW ----- Original Message ----- From: "Axel Kaiser" <[hidden email]> To: "Elecraft Reflector" <[hidden email]> Sent: Thursday, May 15, 2008 3:52 PM Subject: [Elecraft] RTTY Filter for K3 Hi K3-folks, What would be the best RTTY roofing filter for the K3? Is the 400Hz 8-pole filter too small and the 500Hz 5-pole filter the better choice? Thanks in advance for your answers. 73 de Axel, DL3ZH _________________________________________________________________ Connect to the next generation of MSN Messenger http://imagine-msn.com/messenger/launch80/default.aspx?locale=en-us&source=wlmailtagline_______________________________________________ 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 |
|
|
In reply to this post by N4LQ-2
> I am watching RTTY right now and using the 200 Hz 5 pole > filter. The 170 HZ shift fits perfectly within the passband. After making extensive tests and plotting the selectivity curves of the 200 Hz filter in my K3, I'm convinced that it is too narrow for reliable weak signal RTTY operation, particularly in conjunction with the dual-tone filter. The measured -6dB bandwidth of the 200 Hz crystal filter was 209 Hz and the composite bandwidth of the 200 Hz crystal filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two 50 Hz filters with center frequencies separated by 170 Hz). After extended discussion with a well know RTTY op and K3 beta tester, I believe the combination of a 300 Hz 5-pole crystal filter, 300 Hz DSP and the dual tone filter will have a composite -6 dB bandwidth of about 250 Hz - about optimum for narrow RTTY. The currently available, "250," "400" or 500 Hz filters in combination with a 300 Hz DPS bandwidth and dual tone filter are very close to optimum. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of n4lq > Sent: Thursday, May 15, 2008 5:29 PM > To: Axel Kaiser; Elecraft Reflector > Subject: Re: [Elecraft] RTTY Filter for K3 > > > Axel: > I am watching RTTY right now and using the 200 Hz 5 pole > filter. The 170 HZ > shift fits perfectly within the passband. > > Steve Ellington > [hidden email] > ----- Original Message ----- > From: "Axel Kaiser" <[hidden email]> > To: "Elecraft Reflector" <[hidden email]> > Sent: Thursday, May 15, 2008 3:52 PM > Subject: [Elecraft] RTTY Filter for K3 > > > > Hi K3-folks, > > What would be the best RTTY roofing filter for the K3? Is the > 400Hz 8-pole > filter too small and the 500Hz 5-pole filter the better choice? > > Thanks in advance for your answers. > > 73 de > > Axel, DL3ZH > > _________________________________________________________________ > Connect to the next generation of MSN Messenger > http://imagine-msn.com/messenger/launch80/default.aspx?locale= > en-us&source=wlmailtagline____________________________________ > ___________ > 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: 269.23.16/1434 - Release > Date: 5/15/2008 > 7:24 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 > Checked by AVG. > Version: 8.0.100 / Virus Database: 269.23.16/1434 - Release > Date: 5/15/2008 7:24 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 |
|
|
Hi Axel,
full ack with Joe. I use the 400 Hz 8 Pole with a DSP of about 300-350 in dual tone. Perfect! 73! Frank, DD7ZT Joe Subich, W4TV schrieb: > After making extensive tests and plotting the selectivity curves > of the 200 Hz filter in my K3, I'm convinced that it is too > narrow for reliable weak signal RTTY operation, particularly in > conjunction with the dual-tone filter. > > The measured -6dB bandwidth of the 200 Hz crystal filter was > 209 Hz and the composite bandwidth of the 200 Hz crystal filter, > 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard > 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz > (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two > 50 Hz filters with center frequencies separated by 170 Hz). > > After extended discussion with a well know RTTY op and K3 beta > tester, I believe the combination of a 300 Hz 5-pole crystal filter, > 300 Hz DSP and the dual tone filter will have a composite -6 dB > bandwidth of about 250 Hz - about optimum for narrow RTTY. The > currently available, "250," "400" or 500 Hz filters in combination > with a 300 Hz DPS bandwidth and dual tone filter are very close to > optimum. > > 73, > > ... Joe, W4TV > > > >> >> Hi K3-folks, >> >> What would be the best RTTY roofing filter for the K3? Is the >> 400Hz 8-pole >> filter too small and the 500Hz 5-pole filter the better choice? >> >> Thanks in advance for your answers. >> >> 73 de >> >> Axel, DL3ZH >> _______________________________________________ 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 |
|
|
Frank Lammel wrote:
>Joe Subich, W4TV schrieb: > >> After making extensive tests and plotting the selectivity curves of >>the 200 Hz filter in my K3, I'm convinced that it is too narrow for >>reliable weak signal RTTY operation, particularly in conjunction with >>dual-tone filter. The measured -6dB bandwidth of the 200 Hz crystal >>filter was 209 Hz and the composite bandwidth of the 200 Hz crystal >>filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A >>standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz >>(170 + 3*22.7) and the dual tone filter represents a 220 Hz (two 50 >>Hz filters with center frequencies separated by 170 Hz). After >>extended discussion with a well know RTTY op and K3 beta tester, I >>believe the combination of a 300 Hz 5-pole crystal filter, >> 300 Hz DSP and the dual tone filter will have a composite -6 dB >>bandwidth of about 250 Hz - about optimum for narrow RTTY. The >>currently available, "250," "400" or 500 Hz filters in combination >>with a 300 Hz DPS bandwidth and dual tone filter are very close to >>optimum. 73, ... Joe, W4TV >> >Hi Axel, > >full ack with Joe. I use the 400 Hz 8 Pole with a DSP of about 300-350 >in dual tone. Perfect! > Many thanks to Joe for that analysis. However, that analysis applies only to weak signals in the absence of QRM. In the intense QRM conditions of RTTY contesting in Europe, I routinely use two cascaded 250Hz filters at 8215kHz and 455kHz in the 1000MP. (Unfortunately the new Inrad website doesn't include filter plots, so it isn't possible to estimate the cumulative bandwidths of these cascaded filters.) When the channel is clear, copy of weak signals is not noticeably degraded compared with cascaded 500Hz filters; but when QRM appears, the narrower filters often make a decisive difference by preventing a strong unwanted tone from capturing the AGC. A 200Hz 5-pole filter for the K3 is arriving next week, and then I'll be able to do some A/B/C testing against the K3's own 400Hz filter and the 250+250 filters in the MP. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek _______________________________________________ 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 |
|
|
Ian, > In the intense QRM conditions of RTTY contesting in Europe, I > routinely use two cascaded 250Hz filters at 8215kHz and 455kHz > in the 1000MP. (Unfortunately the new Inrad website doesn't > include filter plots, so it isn't possible to estimate the > cumulative bandwidths of these cascaded filters.) The "nasty little secret" is that all of the INRAD "250 Hz" filters in the 8 - 9 MHz range have -6 dB bandwidths around 325-375 Hz. That makes the original analysis accurate since your FT-1000MP is really using cascaded 370/300 Hz filters. The old Inrad site is still available at www.qth.com/inrad see the Yaesu "250" filters at: www.qth.com/inrad/graphs/704.gif (455 KHz) www.qth.com/inrad/graphs/708.gif (8125 KHz) 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Ian > White GM3SEK > Sent: Friday, May 16, 2008 4:30 AM > To: [hidden email] > Subject: Re: [Elecraft] RTTY Filter for K3 > > > Frank Lammel wrote: > >Joe Subich, W4TV schrieb: > > > >> After making extensive tests and plotting the selectivity > curves of > >>the 200 Hz filter in my K3, I'm convinced that it is too > narrow for > >>reliable weak signal RTTY operation, particularly in > conjunction with > >>dual-tone filter. The measured -6dB bandwidth of the 200 > Hz crystal > >>filter was 209 Hz and the composite bandwidth of the 200 > Hz crystal > >>filter, 200 Hz DSP and dual tone fitter was less than 170 Hz. A > >>standard 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz > >>(170 + 3*22.7) and the dual tone filter represents a 220 Hz > (two 50 > >>Hz filters with center frequencies separated by 170 Hz). After > >>extended discussion with a well know RTTY op and K3 beta tester, I > >>believe the combination of a 300 Hz 5-pole crystal filter, > >> 300 Hz DSP and the dual tone filter will have a composite -6 dB > >>bandwidth of about 250 Hz - about optimum for narrow RTTY. The > >>currently available, "250," "400" or 500 Hz filters in combination > >>with a 300 Hz DPS bandwidth and dual tone filter are very close to > >>optimum. 73, ... Joe, W4TV > > >> > >Hi Axel, > > > >full ack with Joe. I use the 400 Hz 8 Pole with a DSP of > about 300-350 > >in dual tone. Perfect! > > > > Many thanks to Joe for that analysis. However, that analysis applies > only to weak signals in the absence of QRM. > > In the intense QRM conditions of RTTY contesting in Europe, I > routinely > use two cascaded 250Hz filters at 8215kHz and 455kHz in the 1000MP. > (Unfortunately the new Inrad website doesn't include filter > plots, so it > isn't possible to estimate the cumulative bandwidths of these > cascaded > filters.) When the channel is clear, copy of weak signals is not > noticeably degraded compared with cascaded 500Hz filters; but > when QRM > appears, the narrower filters often make a decisive difference by > preventing a strong unwanted tone from capturing the AGC. > > A 200Hz 5-pole filter for the K3 is arriving next week, and > then I'll be > able to do some A/B/C testing against the K3's own 400Hz > filter and the > 250+250 filters in the MP. > > > -- > > 73 from Ian GM3SEK > http://www.ifwtech.co.uk/g3sek _______________________________________________ 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 |
|
|
CONTENTS DELETED
The author has deleted this message.
|
|
|
> It seems like Inrad may be using -3 dB for some of their > measurements. The corner of the bandpass is covered by the > data, but it looks very much like that 455 kHz 300 Hz filter > is 300 Hz wide at the -3 dB points. Collins specified their mechanical filters at -3 dB. However, crystal filters in amateur literature have been specified at -6 dB for at least 30 years. "Shape factor" has been the ratio of -6 to -60 dB bandwidth for at least as long. 73, ... Joe, W4TV > -----Original Message----- > From: [hidden email] > [mailto:[hidden email]] On Behalf Of Ron > D'Eau Claire > Sent: Friday, May 16, 2008 7:40 PM > To: [hidden email] > Subject: RE: [Elecraft] RTTY Filter for K3 > > > One thing I don't see mentioned much - something that makes > ALL the difference in the world - is exactly *where* the > bandwidth is measured on the response curve. > > Years ago I saw a lot of bandwidth measured at the -10 dB > points (that was probably before many K3 owners were born - I > haven't seen it for a long time but it was pretty common at > one time). > > Then a *lot* of bandwidths were specified at the -3 dB or > "half power" points. > > Now -6 dB seems popular. > > It seems like Inrad may be using -3 dB for some of their > measurements. The corner of the bandpass is covered by the > data, but it looks very much like that 455 kHz 300 Hz filter > is 300 Hz wide at the -3 dB points. > > Ron AC7AC > > > > -----Original Message----- > > Ian, > > > In the intense QRM conditions of RTTY contesting in Europe, I > > routinely use two cascaded 250Hz filters at 8215kHz and > 455kHz in the > > 1000MP. (Unfortunately the new Inrad website doesn't > include filter > > plots, so it isn't possible to estimate the cumulative > bandwidths of > > these cascaded filters.) > > The "nasty little secret" is that all of the INRAD "250 Hz" > filters in the 8 - 9 MHz range have -6 dB bandwidths around > 325-375 Hz. That makes the original analysis accurate since > your FT-1000MP is really using cascaded 370/300 Hz filters. > > The old Inrad site is still available at www.qth.com/inrad > see the Yaesu "250" filters at: > www.qth.com/inrad/graphs/704.gif (455 KHz) > www.qth.com/inrad/graphs/708.gif (8125 KHz) > > 73, > > ... Joe, W4TV > _______________________________________________ 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 |
|
|
In reply to this post by Joe Subich, W4TV-3
I agree with Joe's summary. Note that the "250" Hz 8-pole filter is really
about 370 Hz at the -6 dB point. Any of the current "500", "400" or "250" Hz crystal filters will be fine for RTTY. With any of them, the DSP can be narrowed to 300 Hz without rolling off the outside edges of the two tones. Note that the Dual-Tone Filter for RTTY is cascaded with the crystal and normal DSP filters and if either of the latter two filters are 250 Hz (at -6 dB) the three-filter-cascade will have significant roll-off on the outside skirts. This has the undesired effect of moving the two filter peaks much closer together than the 170 Hz split. That said, I have been running the 370 Hz crystal filter (aka "250 Hz 8-pole") with 200 Hz DSP and the DTF for several months now in RTTY contests. While the resultant passband was indeed rolled off as described, this was overall a net benefit in heavy pileup conditions because it filtered out the pileup better, producing a clear callsign quicker, despite the rolled-off passband. In other than heavy pileup conditions, it is best to keep the DSP at 300 Hz or higher, especially for copy of weaker signals. In the future, there will probably be a 200-400 (or 200-500) Hz variable 5-pole crystal filter that will be ideal to track with the DSP for high performance RTTY reception, ranging from weak signal to heavy pileup conditions. 73, Ed - W0YK > -----Original Message----- > From: [hidden email] [mailto:elecraft- > [hidden email]] On Behalf Of Joe Subich, W4TV > Sent: Friday, May 16, 2008 12:28 AM > To: 'n4lq'; [hidden email] > Subject: RE: [Elecraft] RTTY Filter for K3 > > > > I am watching RTTY right now and using the 200 Hz 5 pole > > filter. The 170 HZ shift fits perfectly within the passband. > > After making extensive tests and plotting the selectivity curves > of the 200 Hz filter in my K3, I'm convinced that it is too > narrow for reliable weak signal RTTY operation, particularly in > conjunction with the dual-tone filter. > > The measured -6dB bandwidth of the 200 Hz crystal filter was > 209 Hz and the composite bandwidth of the 200 Hz crystal filter, > 200 Hz DSP and dual tone fitter was less than 170 Hz. A standard > 170 Hz shift 45.45 baud RTTY signal needs at least 235 Hz > (170 + 3*22.7) and the dual tone filter represents a 220 Hz (two > 50 Hz filters with center frequencies separated by 170 Hz). > > After extended discussion with a well know RTTY op and K3 beta > tester, I believe the combination of a 300 Hz 5-pole crystal filter, > 300 Hz DSP and the dual tone filter will have a composite -6 dB > bandwidth of about 250 Hz - about optimum for narrow RTTY. The > currently available, "250," "400" or 500 Hz filters in combination > with a 300 Hz DPS bandwidth and dual tone filter are very close to > optimum. > > 73, > > ... Joe, W4TV > > > > > > -----Original Message----- > > From: [hidden email] > > [mailto:[hidden email]] On Behalf Of n4lq > > Sent: Thursday, May 15, 2008 5:29 PM > > To: Axel Kaiser; Elecraft Reflector > > Subject: Re: [Elecraft] RTTY Filter for K3 > > > > > > Axel: > > I am watching RTTY right now and using the 200 Hz 5 pole > > filter. The 170 HZ > > shift fits perfectly within the passband. > > > > Steve Ellington > > [hidden email] > > ----- Original Message ----- > > From: "Axel Kaiser" <[hidden email]> > > To: "Elecraft Reflector" <[hidden email]> > > Sent: Thursday, May 15, 2008 3:52 PM > > Subject: [Elecraft] RTTY Filter for K3 > > > > > > > > Hi K3-folks, > > > > What would be the best RTTY roofing filter for the K3? Is the > > 400Hz 8-pole > > filter too small and the 500Hz 5-pole filter the better choice? > > > > Thanks in advance for your answers. > > > > 73 de > > > > Axel, DL3ZH > > > > _________________________________________________________________ > > Connect to the next generation of MSN Messenger > > http://imagine-msn.com/messenger/launch80/default.aspx?locale= > > en-us&source=wlmailtagline____________________________________ > > ___________ > > 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: 269.23.16/1434 - Release > > Date: 5/15/2008 > > 7:24 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 > > Checked by AVG. > > Version: 8.0.100 / Virus Database: 269.23.16/1434 - Release > > Date: 5/15/2008 7:24 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 _______________________________________________ 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 |
|
|
J. Edward (Ed) Muns wrote:
>I agree with Joe's summary. Note that the "250" Hz 8-pole filter is >really about 370 Hz at the -6 dB point. Any of the current "500", >"400" or "250" Hz crystal filters will be fine for RTTY. With any of >them, the DSP can be narrowed to 300 Hz without rolling off the outside >edges of the two tones. > >Note that the Dual-Tone Filter for RTTY is cascaded with the crystal >and normal DSP filters and if either of the latter two filters are 250 >Hz (at -6 dB) the three-filter-cascade will have significant roll-off >on the outside skirts. This has the undesired effect of moving the two >filter peaks much closer together than the 170 Hz split. > >That said, I have been running the 370 Hz crystal filter (aka "250 Hz >8-pole") with 200 Hz DSP and the DTF for several months now in RTTY >contests. While the resultant passband was indeed rolled off as >described, this was overall a net benefit in heavy pileup conditions >because it filtered out the pileup better, producing a clear callsign >quicker, despite the rolled-off passband. In other than heavy pileup >conditions, it is best to keep the DSP at 300 Hz or higher, especially >for copy of weaker signals. > >In the future, there will probably be a 200-400 (or 200-500) Hz >variable 5-pole crystal filter that will be ideal to track with the DSP >for high performance RTTY reception, ranging from weak signal to heavy >pileup conditions. Thanks to both Joe and Ed. I hadn't realised just how wide Inrad's so-called "250Hz" filter is. 50% wider than nominal is frankly ridiculous. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek _______________________________________________ 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 |
«
Return to Elecraft
|
1 view|%1 views
| Free forum by Nabble | Edit this page |