Roofing Filter Usage
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I purchased a K3 with the standard 2.7 Khz SSB filter plus the 1.8 Khz SSB filter. I did not purchase a cw filter because I operate very little cw. But that may change. The 2.7 is in slot #1 and the 1.8 is in slot #2. I know that if I push the FILT button that I can switch filters. But I was experimenting around listening to a weak station that was rather close to a real strong station and when I activated the 1.8 Khz filter I was still getting some carryover from the strong station on the weak station. Are there other controls that I need to use that would enable me to knock out the real strong station so that I could clearly hear the weak station? I'm sure there is help in the manual but I certainly can't find it. Any help would be much appreciated. Oh and by the way, I love the radio. It's like a breath of fresh air compared to my Kenwood TS0480s. Mark KB3Z ______________________________________________________________ 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 |
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Hi Mark
Try reducing the bandwidth further using the width control, then the DSP filtering will be responsible for narrowing the bandwidth. You could also try adjusting the shift control to slide the passband one way or the other. Although I have all my filter slots filled, I never use the xfil button to change width, just the width control. The effect is the same. Yes, it's a lovely radio, and I came from a TS480 too, via a K2 that is :-) 73 Stephen G4SJP On 28/10/2010 11:41, "[hidden email]" <[hidden email]> wrote: > > > I purchased a K3 with the standard 2.7 Khz SSB filter plus the 1.8 Khz SSB > filter. I did not purchase a cw filter because I operate very little cw. But > that may change. The 2.7 is in slot #1 and the 1.8 is in slot #2. I know > that if I push the FILT button that I can switch filters. But I was > experimenting around listening to a weak station that was rather close to a > real strong station and when I activated the 1.8 Khz filter I was still > getting some carryover from the strong station on the weak station. Are there > other controls that I need to use that would enable me to knock out the real > strong station so that I could clearly hear the weak station? I'm sure there > is help in the manual but I certainly can't find it. Any help would be much > appreciated. Oh and by the way, I love the radio. It's like a breath of fresh > air compared to my Kenwood TS0480s. Mark KB3Z > ______________________________________________________________ > 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 > ______________________________________________________________ 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 |
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Hi,
I agree with forgetting about the XFIL button and use the passband controls exclusively. But using SHIFT/WIDTH on SSB is very awkward as you constantly have to touch up both controls. Use HiCut/LoCut instead. Leave LoCut at 300Hz and use HiCut as the QRM fighting tool. If you have the 1.8kHz filter you will see it kick in automatically when HiCut is at or blow 2.1kHz. If your cut frequencies are on 350, 450 etc boundaries, pop back to SHIFT/WIDTH mode and adjust the SHIFT one click, then go back to HiCut/Locut and they should be on even 100Hz boundaries (unless of course you prefer it the other way). AB2TC - Knut
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In reply to this post by pastormg
Go back to filter settings and set the bandwidth of the 1.8 filter a bit
wider, say 2.1. Then use the hi/lo adjustments during operation. Typically I keep the low full and gradually lower the hi settings. When you get the filter narrow enough the K3 will automatically switch from the 2.7 to the 1.8 filter. Several experienced users recommended this to me and it works well. -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of [hidden email] Sent: Thursday, October 28, 2010 3:41 AM To: [hidden email] Subject: [Elecraft] Roofing Filter Usage I purchased a K3 with the standard 2.7 Khz SSB filter plus the 1.8 Khz SSB filter. I did not purchase a cw filter because I operate very little cw. But that may change. The 2.7 is in slot #1 and the 1.8 is in slot #2. I know that if I push the FILT button that I can switch filters. But I was experimenting around listening to a weak station that was rather close to a real strong station and when I activated the 1.8 Khz filter I was still getting some carryover from the strong station on the weak station. Are there other controls that I need to use that would enable me to knock out the real strong station so that I could clearly hear the weak station? I'm sure there is help in the manual but I certainly can't find it. Any help would be much appreciated. Oh and by the way, I love the radio. It's like a breath of fresh air compared to my Kenwood TS0480s. Mark KB3Z ______________________________________________________________ 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 ______________________________________________________________ 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 |
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In reply to this post by pastormg
The purpose of the roofing filter is to reduce receiver generated
distortion products, not to provide selectivity. Are you sure that that: 1) the strong signals are completely out of band; 2) the only distortion products are those generated by the K3 itself, and not the transmitter. [hidden email] wrote: > I purchased a K3 with the standard 2.7 Khz SSB filter plus the 1.8 + I was experimenting around listening to a weak station that was rather + close to a real strong station and when I activated the 1.8 Khz filter I + was still getting some carryover from the strong station on the weak + station. Are there other controls that I need to use that would enable + me to knock out the real strong station so that I could clearly hear the + weak station? I'm sure there is help in the manual but I certainly can't > -- David Woolley "we do not overly restrict the subject matter on the list, and we encourage postings on a wide range of amateur radio related topics" List Guidelines <http://www.elecraft.com/elecraft_list_guidelines.htm> ______________________________________________________________ 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 |
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Unfortunately, they do. Personally I dislike the term.
For example: A "A narrow roofing filter -- compatible with the communications bandwidth required -- will protect "downstream" stages. The K3's shift/width/hicut/locut controls automatically select and properly position the optimal roofing filter. You'll see the FL1-FL5 icons selected as you rotate these controls." http://elecraft.365791.n2.nabble.com/Re-roofing-filters-when-to-use-them-td446665.html#a446666 --- On Thu, 10/28/10, Ron D'Eau Claire <[hidden email]> wrote: That's why the Elecraft doesn't call the first I.F. crystal filters "roofing filters". Unlike some receivers, the first I.F. crystal filters in the K3 are there for selectivity to isolate the desired signal. That is further enhanced in the second conversion with the variable DSP filter, but the crystal first I.F. filters are a key part of the selectivity equation. ______________________________________________________________ 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 |
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In reply to this post by n7ws
Yes, they do. Elecraft presents it's position on the term "Roofing Filter" here:
http://www.elecraft.com/K3/Roofing_Filters.htm where the "protective" function is emphasized. Bob NW8L On Thu, Oct 28, 2010 at 5:37 PM, Wes Stewart <[hidden email]> wrote: > Unfortunately, they do. Personally I dislike the term. > ______________________________________________________________ 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 |
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Re: Roofing Filter Usage
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With respect Ron, as far as I know the term "Roofing Filter" was in use many
years before up-conversion superhet receivers with a fist IF at VHF started to appear in the market. It was at least fifty years ago when I first ran across the term, which was used to describe the first IF filter used in a voice/data multichannel Independent Sideband down conversion superhet receiver manufactured by our company at the time. In this particular case the bandwidth of this Roofing Filter was wide enough to allow both the upper and lower sidebands of the incoming signal to pass, and further downstream in the IF two filters described as USB and LSB IF filters were used to separate the signal's sidebands for further processing. It could be argued that the input bandpass filters of a receiver act as Roofing Filters, and that all filters which follow should be described as IF filters, Audio filters or whatever. However the applicable "rules" of terminology as I have understood them since those ancient times restricts the use of the term Roofing Filter to the first IF Filter, but the term should only be used if a second and narrower *IF* filter follows the first ( which would include DSP filters, but only if working at IF not audio). The use of relatively wide bandwidth Roofing Filters at VHF in up-conversion receivers is actually not such a problem that it might appear to be, because the use of a very narrow filter behind the mixer can be counter productive in terms of close in dynamic range, especially if the filter is followed by a well designed decent IF. The same is true of down-conversion. LO phase noise is a problem when up-converting to VHF. 73, Geoff GM4ESD On Friday, October 29, 2010, at 03:04 +0100, Ron D'Eau Claire wrote: > The term "roofing filter" came into use when receiver designers started > up-converting to a first I.F. in the VHF range. There are no practical > narrow filters at those frequencies but it was necessary to filter out > mixing products far from the desired frequency, so very wide (several kHz > wide) filters were used to define the general range to be further > processed. ______________________________________________________________ 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 |
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Correct Geoff. The first up-conversion ham rigs were introduced in the early 1980s (TS-930S I believe). The Japanese manufacturers got the idea that everyone wanted general coverage in their receivers, which then required up-conversion and an IF at VHF. Rob Sherwood had been marketing his 600 Hz "roofing filter" mod for the down-conversion Drake R4C several years before that, and as you said the term had already been in use many years prior. 73, Bill |
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Bill and group - Can't say it was first, but has to be the first US
designed and produced ham rigs to use up conversion. The DRAKE TR-7 has no RF Amplifier and uses a diode ring "up converter" to 43 mhz as the first IF. The design was in the late 60s, early 70s. Bob Drake and his company have always been know for innovative design. In those days the term "Roofing Filter" hadn't be coined by the marketing types and the TR-7 has only one fixed filter at the high IF. BTW - The TR-7 second IF with the switchable mode filters is at 8.2 MHz. 73 Bob W7AVK On 10/29/2010 4:45 AM, Bill W4ZV wrote: > > Geoffrey Mackenzie-Kennedy wrote: >> With respect Ron, as far as I know the term "Roofing Filter" was in use >> many >> years before up-conversion superhet receivers with a fist IF at VHF >> started >> to appear in the market. >> > Correct Geoff. The first up-conversion ham rigs were introduced in the > early 1980s (TS-930S I believe). The Japanese manufacturers got the idea > that everyone wanted general coverage in their receivers, which then > required up-conversion and an IF at VHF. Rob Sherwood had been marketing > his 600 Hz "roofing filter" mod for the down-conversion Drake R4C several > years before that, and as you said the term had already been in use many > years prior. > > 73, Bill > ______________________________________________________________ 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 |
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Racal's RA-17 was an up-converting receiver, with a first IF at 40 MHz.
However, the 40 MHz IF filter was wideband, with the real selectivity applied at 1.6 MHz and 100 KHz. With the Wadley Loop tuning system, it was an extremely advanced design for 1955, all done with vacuum tubes, of course. Jack K8ZOA On 10/29/2010 8:57 AM, Bob W7AVK wrote: > Bill and group - Can't say it was first, but has to be the first US > designed and produced ham rigs to use up conversion. The DRAKE TR-7 > has no RF Amplifier and uses a diode ring "up converter" to 43 mhz as > the first IF. The design was in the late 60s, early 70s. Bob Drake and > his company have always been know for innovative design. In those days > the term "Roofing Filter" hadn't be coined by the marketing types and > the TR-7 has only one fixed filter at the high IF. BTW - The TR-7 > second IF with the switchable mode filters is at 8.2 MHz. > > 73 Bob W7AVK > > > > > On 10/29/2010 4:45 AM, Bill W4ZV wrote: >> Geoffrey Mackenzie-Kennedy wrote: >>> With respect Ron, as far as I know the term "Roofing Filter" was in use >>> many >>> years before up-conversion superhet receivers with a fist IF at VHF >>> started >>> to appear in the market. >>> >> Correct Geoff. The first up-conversion ham rigs were introduced in the >> early 1980s (TS-930S I believe). The Japanese manufacturers got the idea >> that everyone wanted general coverage in their receivers, which then >> required up-conversion and an IF at VHF. Rob Sherwood had been marketing >> his 600 Hz "roofing filter" mod for the down-conversion Drake R4C several >> years before that, and as you said the term had already been in use many >> years prior. >> >> 73, Bill >> > ______________________________________________________________ > 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 > 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 |
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