Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
On Thursday 03 May 2007 21:29:00 Lyle Johnson wrote: In the olden days, analog radios would use two IF filters and slide them back and forth against each other to form variable bandwidth filters. Yes indeed. My Eddystone EA12 receiver that I bought from Tom Roberts, G3YTO (SK 1985) is a dual conversion with a tunable first IF from 1.1 Mc/s to 1.7 Mc/s and crystal controlled converters changing the bands to the tunable IF. The second IF is 100 kc/s with a slot filter and continuously variable selectivity: this is accomplished by varying, mechanically the coupling between the coils - it's like flying by the seat .. rather than by wire. At the narrow end of the filter, a 100 kc/s crystal kicks in and I can feel the switch that does it. With up to volts input to the linear ECC189 to the ECH81 first mixer, I think modern radios are building ever more complex sandcastles rather than pyramids. ( Mc/s and kc/s as in the EA12 manual) Ian, G4ICV, PP-ASEL, AB2GR, K2 #4962 -- ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
With respect Larry I must disagree about the term roofing filter being misleading. I completely agree that a narrow filter at the first IF is desireable if not essential, and it could be identified as a roofing filter in some instances - see below. This approach has been the norm in the design of certain classes of high performance receiver for some time, and obviously this filter's bandwidth must be compatible with the receiver's operating mode. I think that the confusion in understanding the meaning of the term roofing filter started in the amateur community sometime after commercial double conversion receivers began to appear on the amateur market, and appears to be increasing. Because these receivers used very wide roofing filters, and many still do, the myth arose that roofing filters were always wide and were only used in double conversion receivers. In turn this gave birth to other myths about the poor performance of double conversion receivers vs single conversion receivers, which often can be traced back to poor design and poor electro-mechanical construction. The term roofing filter was intended, and has since when correctly used, to identify the first narrow bandwidth IF filter appearing in a receiver's signal path after the first signal mixer, but *only* in those cases where additional IF filtering was introduced further down the IF chain for the purpose of establishing the overall RF / IF selectivity - as found in many amateur double conversion receivers and early single conversion ISB receivers for example. In the ISB receivers with which I was involved in the 1950s, the typical bandwidth of the roofing filter was slightly greater than twice the required traffic bandwidth of each of the following USB and LSB filters i.e.roughly speaking 7 kHz for a basic two channel at baseband receiver, not tens of kHz. In later years a variety of roofing filters, some wide some very narrow have crossed my path. The term does *not* and was *not* intended to imply that that the receiver's architecture is double conversion nor that the bandwidth of the roofing filter is by default wide, and is not used to identify any filter outside of the IF cascade. Although it is tempting to identify the roofing filter as the 1st IF filter, this could imply that there were other IFs used elsewhere in the receiver in question e,g dual conversion or triple conversion, and is usually avoided. In the case of a straightforward single conversion receiver using a single set of filters (or variable bandwidth in the case of the K2) the IF filter should not be identified as a roofing filter.The small filter prior to a product detector to attenuate unwanted sideband IF generated noise does not count as a second filter, because according to the rules the same result can be achieved by using an image reject mixer as a product detector On the other hand if for some strange reason a single conversion comms receiver did employ a widish bandwidth IF filter close after the mixer and narrow bandwidth IF filters further down the IF chain, at the risk of questionable IMD performance if the cascade between the filters is weak, it would be correct to identify the first filter as a roofing filter. In my opinion if a filter is performing the role of a roofing filter its identity should not be changed from roofing filter, which is a well established term both inside and outside of the amateur community. 73, Geoff GM4ESD On Friday, May 04, 2007, at 2:11 AM, Larry Phipps wrote: I think the term roofing filter is misleading. A narrow filter at the first IF protects a receiver even better than a roofing filter, so there is nothing inherently distortion reducing in using a wider filter at the first IF and then a narrower one later. The ideal situation for IMD would be a pair of matched narrow filters at both IFs. The real reason for a roofing filter it seems to me, is to allow passband or slope tuning. This compromises IMD and AGC performance for the sake of a feature... which may or may not be valuable to the user. Therefore, the roofing filter should be termed the passband tuning enabling filter, or PBTE filter ;-) Thankfully, I think Elecraft has done a brilliant job of giving us the options we want without compromises. By tying the DSP bandwidths and PBT functions to the roofing filters, we have the ability to have the combination of 1st and 2nd IF BW we want,,, and with the variable roofing filters, I think we will be able to almost set the relative BWs between the two... allowing a window for PBT or not as we choose. This is an exciting development, and will be copied by many companies over the next year. Kudos to the design team on this. 73, Larry N8LP ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.):
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Hi Geoff. My post was somewhat tongue-in-cheek, and it's mostly semantics, but I would say that the K3 filter would be a roofing filter or not depending on your settings. I guess my opinion is that if it's set for the same BW as the 2nd IF, then its not a roofing filter, and if it's set wider then it is. At any rate, it's a roofing filter since that what they decided to call it, and would usually be used that way. The beauty of the design is that it doesn't have to be. One other bit of semantics... if the DSP filter is set wider than the roofing filter (if the firmware even allows this), then the term roofing filter would definitely not be correct, and the DSP filter would then be an image reject filter or something similar ;-) I think I will coin another term for Elecraft... FDR, for Firmware Defined Radio ;-) 73, Larry N8LP Geoffrey Mackenzie-Kennedy wrote: With respect Larry I must disagree about the term roofing filter being misleading. I completely agree that a narrow filter at the first IF is desireable if not essential, and it could be identified as a roofing filter in some instances - see below. This approach has been the norm in the design of certain classes of high performance receiver for some time, and obviously this filter's bandwidth must be compatible with the receiver's operating mode. I think that the confusion in understanding the meaning of the term roofing filter started in the amateur community sometime after commercial double conversion receivers began to appear on the amateur market, and appears to be increasing. Because these receivers used very wide roofing filters, and many still do, the myth arose that roofing filters were always wide and were only used in double conversion receivers. In turn this gave birth to other myths about the poor performance of double conversion receivers vs single conversion receivers, which often can be traced back to poor design and poor electro-mechanical construction. The term roofing filter was intended, and has since when correctly used, to identify the first narrow bandwidth IF filter appearing in a receiver's signal path after the first signal mixer, but *only* in those cases where additional IF filtering was introduced further down the IF chain for the purpose of establishing the overall RF / IF selectivity - as found in many amateur double conversion receivers and early single conversion ISB receivers for example. In the ISB receivers with which I was involved in the 1950s, the typical bandwidth of the roofing filter was slightly greater than twice the required traffic bandwidth of each of the following USB and LSB filters i.e.roughly speaking 7 kHz for a basic two channel at baseband receiver, not tens of kHz. In later years a variety of roofing filters, some wide some very narrow have crossed my path. The term does *not* and was *not* intended to imply that that the receiver's architecture is double conversion nor that the bandwidth of the roofing filter is by default wide, and is not used to identify any filter outside of the IF cascade. Although it is tempting to identify the roofing filter as the 1st IF filter, this could imply that there were other IFs used elsewhere in the receiver in question e,g dual conversion or triple conversion, and is usually avoided. In the case of a straightforward single conversion receiver using a single set of filters (or variable bandwidth in the case of the K2) the IF filter should not be identified as a roofing filter.The small filter prior to a product detector to attenuate unwanted sideband IF generated noise does not count as a second filter, because according to the rules the same result can be achieved by using an image reject mixer as a product detector On the other hand if for some strange reason a single conversion comms receiver did employ a widish bandwidth IF filter close after the mixer and narrow bandwidth IF filters further down the IF chain, at the risk of questionable IMD performance if the cascade between the filters is weak, it would be correct to identify the first filter as a roofing filter. In my opinion if a filter is performing the role of a roofing filter its identity should not be changed from roofing filter, which is a well established term both inside and outside of the amateur community. 73, Geoff GM4ESD On Friday, May 04, 2007, at 2:11 AM, Larry Phipps wrote: I think the term roofing filter is misleading. A narrow filter at the first IF protects a receiver even better than a roofing filter, so there is nothing inherently distortion reducing in using a wider filter at the first IF and then a narrower one later. The ideal situation for IMD would be a pair of matched narrow filters at both IFs. The real reason for a roofing filter it seems to me, is to allow passband or slope tuning. This compromises IMD and AGC performance for the sake of a feature... which may or may not be valuable to the
[Elecraft] 8 pole vs 5 pole..I knew this would happen
Hi all: The notation below (previously posted) is referring to the final passband filter and NOT a roofing filter. You are trying to compare apples and oranges. I think you would be hard pressed to discern (in real use) a difference between the 200 and 250 hz ROOFING filter, except in LOSS (which will be compensated for later). Pesonally, for cw work, I think both of those will be too narrow for my liking, especially if I want to tune around the band and not have signals suddenly POP into the final passband (which I like to keep fairly wide). I want to hear what's coming! de Doug KR2Q I had 2 CW filters in my TenTec OmniV and did a lot of A/B comparing with them. One was an 8 pole Inrad 400 Hz filter and the other was a 6 pole TenTec 500 Hz filter. I had them both in the rig at the same time specifically to decide which one to keep. I was able to detect the steeper skirts of the 8 pole filter as well as the narrower passband, but the factor that eventually tipped the scales was ultimate rejection. The TT filter, had better ultimate rejection. Once I tuned past a signal, it went away and didn't come back. With the Inrad filter, the signal would drop quicker, hit bottom and then come back up. I could hear strong signals 6-8 KHz away. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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] 8 pole vs 5 pole..I knew this would happen
I think, still, someone needs to define what a ROOFING FILTER is. Say for sake of argument - I have a passive or active or crystal filter - and it is to be used as a ROOFING FILTER. Why is it called this? Why is the filter itself, called a ROOFING FILTER? And where does the adjective, ROOFING, come into play? .. I'm sure I'm dumb on this one - but would like to learn. Not until the K3 came on the Elecraft scene - did anyone mention or get concerned about the need for ROOFING FILTERS. Now they're all the rage? Fred, N3CSY __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
The term roofing filter has been around a long time, at least 20 years. Usually used in the context of up-converting receivers, where the first IF is 40.455 MHz, or 45.000 MHz or even higher. The term means the first selective filter in the receiver. If the first IF is 30 MHz, the roofing filter is generally wider than one normally needs for SSB or even AM, and the receiver's ultimate selectivity is provided in a later IF stage. As to why it is called a roofing filter, I imagine it derives from the fact that it puts a roof over the receiver's selectivity. Jack K8ZOA Fred (FL) wrote: I think, still, someone needs to define what a ROOFING FILTER is. Say for sake of argument - I have a passive or active or crystal filter - and it is to be used as a ROOFING FILTER. Why is it called this? Why is the filter itself, called a ROOFING FILTER? And where does the adjective, ROOFING, come into play? .. I'm sure I'm dumb on this one - but would like to learn. Not until the K3 came on the Elecraft scene - did anyone mention or get concerned about the need for ROOFING FILTERS. Now they're all the rage? Fred, N3CSY __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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
RE: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Roofing filters - I think the term has more to do with marketing than engineering. Other companies have made a big deal over having them and people have come to think of them as something special. They are little more than filters placed early in the RX signal path to limit bandwidth ASAP. They were added to correct issues / problems that have crept into modern synth-based mulit-mode radios and they really do make the receivers work better. I have no idea where the term Roofing comes and I certainly don't try to make sense of it. It is just a term applied to a filter that is very worth having in a rig. What is sweet about the K2 is that the filters in the K2 are positioned early in the signal path so they in effect operate similar to the roofing filters that other manufactures put in their rigs. Check out the K2's RX performance and you'll see it is great. Early filtering is partly why. - Keith N1AS - - K2 5411.ssb.100 - -Original Message- I think, still, someone needs to define what a ROOFING FILTER is. Say for sake of argument - I have a passive or active or crystal filter - and it is to be used as a ROOFING FILTER. Why is it called this? Why is the filter itself, called a ROOFING FILTER? And where does the adjective, ROOFING, come into play? .. I'm sure I'm dumb on this one - but would like to learn. Not until the K3 came on the Elecraft scene - did anyone mention or get concerned about the need for ROOFING FILTERS. Now they're all the rage? Fred, N3CSY ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
A lack of understanding is also shown in the FT-2000 Yahoo! group. A fine document which explains traditional roofing filters is here: http://www.qth.com/inrad/roofing-filters.pdf . The FT-2000 is an up-conversion receiver (unless I've lost the plot again). Elecraft's design is more subtle and has been explained several times in this list. Simon Brown, HB9DRV - Original Message - From: Darwin, Keith [EMAIL PROTECTED] Roofing filters - I think the term has more to do with marketing than engineering. Other companies have made a big deal over having them and people have come to think of them as something special. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Just cannot resist saying this Jack, the term roofing filter has certainly been around for a long time - close to 50 years I believe, possibly longer. I think that I first ran across the term being used to identify the first IF filter in an Independent Sideband Receiver which the company for whom I worked manufactured for HF Point-to-Point applications in the very late 1950's, along with companion high power ISB transmitters. Perhaps some other term might be less confusing and prevent any misuse of the term , but don't let us change from roofing filter now!! 73, Geoff GM4ESD Jack Smith wrote: The term roofing filter has been around a long time, at least 20 years. Usually used in the context of up-converting receivers, where the first IF is 40.455 MHz, or 45.000 MHz or even higher. The term means the first selective filter in the receiver. If the first IF is 30 MHz, the roofing filter is generally wider than one normally needs for SSB or even AM, and the receiver's ultimate selectivity is provided in a later IF stage. As to why it is called a roofing filter, I imagine it derives from the fact that it puts a roof over the receiver's selectivity. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
One more data point on the term roofing filter. I have a copy of the June 1981 RSGB Radio Communications magazine that reviewed Drake's TR7. It describes the design as follows: A low-noise, wide-dynamic range amplifier is used at 48.05 MHz to precede the 10-KHz wide roofing filter. Leaving aside the RSGB's odd use of hyphens, it describes the filter as a roofing filter although Drake does not use the term in its technical manual. Is it the case that roofing filter is UK terminology that has made its way to the US side of the pond only recently? Jack Geoffrey Mackenzie-Kennedy wrote: Just cannot resist saying this Jack, the term roofing filter has certainly been around for a long time - close to 50 years I believe, possibly longer. I think that I first ran across the term being used to identify the first IF filter in an Independent Sideband Receiver which the company for whom I worked manufactured for HF Point-to-Point applications in the very late 1950's, along with companion high power ISB transmitters. Perhaps some other term might be less confusing and prevent any misuse of the term , but don't let us change from roofing filter now!! 73, Geoff GM4ESD Jack Smith wrote: The term roofing filter has been around a long time, at least 20 years. Usually used in the context of up-converting receivers, where the first IF is 40.455 MHz, or 45.000 MHz or even higher. The term means the first selective filter in the receiver. If the first IF is 30 MHz, the roofing filter is generally wider than one normally needs for SSB or even AM, and the receiver's ultimate selectivity is provided in a later IF stage. As to why it is called a roofing filter, I imagine it derives from the fact that it puts a roof over the receiver's selectivity. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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
RE: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Marketing term, I tell ya, pushed extra hard by the sales folks at YaeComWood. :-) -Original Message- ... it describes the filter as a roofing filter although Drake does not use the term in its technical manual. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Oh, and no I don't think I did an apples to oranges comparison. The filters, whether placed early or late in the signal chain, have the same effect on bandwidth and out-of-band signal rejection. What I compared was 8 vs. 6 pole and that showed me some things that are applicable to the 5 vs. 8 pole choice we have with the K3. While the filters were not in the same place as they would be in a roofing application, the info gathered was certainly applicable. - Keith N1AS - - K2 5411.ssb.100 - -Original Message- The notation below (previously posted) is referring to the final passband filter and NOT a roofing filter. You are trying to compare apples and oranges. === I had 2 CW filters in my TenTec OmniV and did a lot of A/B comparing with them. One was an 8 pole Inrad 400 Hz filter and the other was a 6 pole TenTec 500 Hz filter. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Irrespective of the original source of the term roofing filter, it seems clear enough that whoever made it up wanted to imply the idea of protection, which is the word used in the RSGB document. A ROOF is a first line of protection against having nearby high-energy stuff from the outside world (rain, hail, falling rocks and trees) hit you in the head. :-) A ROOFING FILTER is likewise a first line of protection for the stage that follows it against nearby high-energy signals hitting it in the head. (Er, the base, or the gate, or whatever.) Whether it was first used in some marketing brochure or in an engineering paper, the term nonetheless is aptly descriptive. Since the concept involved really has to be understood in order for the term to make sense, however, I tend to lean toward the idea that it was made up by an engineer. Most marketing guys aren't that smart. Uh, no offense intended. :-) Bill / W5WVO Darwin, Keith wrote: Marketing term, I tell ya, pushed extra hard by the sales folks at YaeComWood. :-) -Original Message- ... it describes the filter as a roofing filter although Drake does not use the term in its technical manual. ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
I do not know where or when the term roofing filter first appeared, when I first came across it in the late 1950s I was working in Canada. I suspect that the term originated in N.America, most probably in connection with the type of equipment which I mentioned, most of which was purchased by Common Carriers for use on long haul international circuits. 73, Geoff GM4ESD Jack Smith wrote: One more data point on the term roofing filter. I have a copy of the June 1981 RSGB Radio Communications magazine that reviewed Drake's TR7. It describes the design as follows: A low-noise, wide-dynamic range amplifier is used at 48.05 MHz to precede the 10-KHz wide roofing filter. Leaving aside the RSGB's odd use of hyphens, it describes the filter as a roofing filter although Drake does not use the term in its technical manual. Is it the case that roofing filter is UK terminology that has made its way to the US side of the pond only recently? Jack ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
FW: [Elecraft] 8 pole vs 5 pole..I knew this would happen
-Original Message- From: Brett gazdzinski [mailto:[EMAIL PROTECTED] Sent: Thursday, May 03, 2007 2:02 PM To: 'Fred (FL)' Subject: RE: [Elecraft] 8 pole vs 5 pole..I knew this would happen I think, in the past, it was the first filter, before all the conversions. When they started with the general coverage receivers, plus all mode, the first filter had to be wide enough for the maximum signal you would want to listen to, or transmit, say 6Khz for AM, 15Khz for FM. So, they saved money by just installing a 15 or 20 Khz roofing filter, everything was under the one roof. You had smaller rooms under the roof (regular filters)... I am not sure, but its possible some early rigs did not HAVE a roofing filter at all.. Depending on the first IF frequency, its possible they could not make a decent filter even if they wanted to. Maybe in the 3rd IF you would have the 'real' filters and/or dsp. In the beginning, maybe the 3rd IF was at 455 Khz, or 262Khz, or 50 Khz. I think drake used 50Khz in some of their stuff. The lower you go in frequency, the easier to make and better the filter is, at least in the past it was. 262Khz IF transformers could be made much narrower than 455Khz ones, hence some companies using 50Khz. So you had multi conversion rigs, with general coverage, which meant they would go someplace beyond the highest frequency you were going to tune for the first IF to eliminate images, then they had to use a filter that would pass FM... Now that computers have invaded radios, you can do all sorts of things with the logic, but only Elecraft seems to use it to actually improve the results. I think the K2 shows that with its low parts count, single conversion, yet great results. Until very recently, most ham gear seemed to be quite poor despite all they hype and gizmos, jack of all trades, master of none. I think 'roofing filter' is a bad and silly name, but there it is. Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Fred (FL) Sent: Thursday, May 03, 2007 12:55 PM To: elecraft@mailman.qth.net Subject: [Elecraft] 8 pole vs 5 pole..I knew this would happen I think, still, someone needs to define what a ROOFING FILTER is. Say for sake of argument - I have a passive or active or crystal filter - and it is to be used as a ROOFING FILTER. Why is it called this? Why is the filter itself, called a ROOFING FILTER? And where does the adjective, ROOFING, come into play? .. I'm sure I'm dumb on this one - but would like to learn. Not until the K3 came on the Elecraft scene - did anyone mention or get concerned about the need for ROOFING FILTERS. Now they're all the rage? Fred, N3CSY __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Yes, that is exactly the point I was trying to make! You can have it as you like it (I am speculating a bit about the control options in the firmware, of course). Some people like a wider width at the first IF to hear signals approaching, even if it opens the window for AGC blocking or desense. Others would want the two passbands to be exactly aligned and as narrow as possible, which would provide the best IMD and AGC performance, but then the signals will drop off the cliff as you tune. What you appear to have done is allow nuance in these adjustments, which I think is quite clever and well thought out. I can't wait to play with it. I didn't mention the audio passband shaping, but that makes it just that much better. Well done. Look forward to seeing you at FDIM. 73, Larry N8LP Lyle Johnson wrote: Hello Larry! ...Therefore, the roofing filter should be termed the passband tuning enabling filter, or PBTE filter ;-) Thankfully, I think Elecraft has done a brilliant job of giving us the options we want without compromises. By tying the DSP bandwidths and PBT functions to the roofing filters, we have the ability to have the combination of 1st and 2nd IF BW we want,,, and with the variable roofing filters, I think we will be able to almost set the relative BWs between the two... allowing a window for PBT or not as we choose. In the olden days, analog radios would use two IF filters and slide them back and forth against each other to form variable bandwidth filters. This may be some of the PBT you were referring to. In the K3, you can set the IF selectivity almost anywhere you like. The conversion oscillator and the DSP's internal software BFO will be moved around to ensure that the narrowest available 8.215 MHz IF filter is selected. The edges of the DSP IF filters and the crystal filter aren't worked against each other. In general, we try to keep the passband of interest centered in the IF filters. The variable-width crystal filters will make this matchup fairly precise :-) Thus we can offer passband tuning without opening up the crystal filter bandwidth wider than required for the ultimate passband chosen by the operator of the radio. Oh, and did I mention we also shape the audio passband according to the filter selection? And that is overlaid with the 8-band Rx EQ? 73, Lyle KK7P ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
RE: [Elecraft] 8 pole vs 5 pole..I knew this would happen
I thought some rigs also passed the transmit signal out past the filter, and to save money just fit say an FM sized filter there. FM and AM are 'features' also I guess... The K3 is going to relay switch filters in for FM, AM, SSB, and CW. Since they are working at a lower frequency, they will really work well, and that is the main trick going on in the K3. Then you get all those DSP extra goodies... Brett N2DTS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Larry Phipps Sent: Thursday, May 03, 2007 9:12 PM To: Jack Smith Cc: Elecraft Discussion List Subject: Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen I think the term roofing filter is misleading. A narrow filter at the first IF protects a receiver even better than a roofing filter, so there is nothing inherently distortion reducing in using a wider filter at the first IF and then a narrower one later. The ideal situation for IMD would be a pair of matched narrow filters at both IFs. The real reason for a roofing filter it seems to me, is to allow passband or slope tuning. This compromises IMD and AGC performance for the sake of a feature... which may or may not be valuable to the user. Therefore, the roofing filter should be termed the passband tuning enabling filter, or PBTE filter ;-) Thankfully, I think Elecraft has done a brilliant job of giving us the options we want without compromises. By tying the DSP bandwidths and PBT functions to the roofing filters, we have the ability to have the combination of 1st and 2nd IF BW we want,,, and with the variable roofing filters, I think we will be able to almost set the relative BWs between the two... allowing a window for PBT or not as we choose. This is an exciting development, and will be copied by many companies over the next year. Kudos to the design team on this. 73, Larry N8LP ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
What is the first thing rain hits when coming down from the sky ? What is the first thing a signal hits after the first mixer coming down from the sky ? What is a leaky roofing filter ? It's what is in the K-3 G since it lets the signal from SOMEBODY through to your ears! Walt K8CV Royal Oak, MI. - Original Message - From: Fred (FL) [EMAIL PROTECTED] To: elecraft@mailman.qth.net Sent: Thursday, May 03, 2007 12:55 PM Subject: [Elecraft] 8 pole vs 5 pole..I knew this would happen I think, still, someone needs to define what a ROOFING FILTER is. Say for sake of argument - I have a passive or active or crystal filter - and it is to be used as a ROOFING FILTER. Why is it called this? Why is the filter itself, called a ROOFING FILTER? And where does the adjective, ROOFING, come into play? .. I'm sure I'm dumb on this one - but would like to learn. Not until the K3 came on the Elecraft scene - did anyone mention or get concerned about the need for ROOFING FILTERS. Now they're all the rage? Fred, N3CSY __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
On Thu, 3 May 2007, Lyle Johnson wrote: In the olden days, analog radios would use two IF filters and slide them back and forth against each other to form variable bandwidth filters. This may be some of the PBT you were referring to. Being as technically adroit as your average cow pie, all of this is over my head. I have a TR7 sitting here that has something called PassBand tuning. I recall that I used it, with one of those ancient, non-digital, I didn't build it Autek filters. I have memories of twisting many knobs to get rid of the crud, and either notching out noise or peaking the signals that were down in the mud, even lower than the bottom dwellers and scum suckers. Given that I hardly ever, but maybe now and then operate SSB, and would like to try other digital modes, what would suggest as a reasonable approach to filters? Thanks Thom, who finds ordering from a Chineese Menu easier than this filter stuff...and only has first hand knowledge of leaky roofs, which he doesn't believe is an official option for a K3. Thom www.baltimorehon.com/Home of the Baltimore Lexicon www.tlchost.net/hosting/ Web Hosting as low as 3.49/month ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Yes, that is exactly the point I was trying to make! You can have it as you like it (I am speculating a bit about the control options in the firmware, of course). Some people like a wider width at the first IF to hear signals approaching, even if it opens the window for AGC blocking or desense. Others would want the two passbands to be exactly aligned and as narrow as possible, which would provide the best IMD and AGC performance, but then the signals will drop off the cliff as you tune. What you appear to have done is allow nuance in these adjustments, which I think is quite clever and well thought out. I can't wait to play with it. One other feature you're sure to like, then, is the CW context or PB2 filter. Set this one as wide as you like -the crystal filter selection will be driven by this. Then set a suppression level maybe down 10 or 20 or 30 dB. Overlay this with the narrow filter you want and presto! You can hear the context from nearby stations, but at reduced amplitude, while the signals in the narrow filter you are working (or trying to work :-) are emphasized and drive the AGC level. 73, Lyle KK7P ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
Given that I hardly ever, but maybe now and then operate SSB, and would like to try other digital modes, what would suggest as a reasonable approach to filters? I'd start with the default 2.7 kHz filter. It'll handle the new, wider digital modes like Olivia, and handle SSTV and digital voice, for example. If you operate mostly CW or mostly narrow digital modes, I'd add the 400 Hz or 500 Hz filter. Then operate the radio for a while and see what else you'd like/want/need. 73, Lyle KK7P ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
