Re: [Elecraft] New K3 SN#207 built but question on AM Filter
David Woolley (Elecraft) wrote: Oops. I calculated this with one sideband equal in amplitude to the carrier, well that may well be true if you are trying squeeze the last Hz out of the receiver filter, the corrected values are: If you do that with standard AM (envelope) detection, you will get up to about 20% (even) harmonic distortion. You will probably get better 22% (need to double check this, but no time now.) audio treating it as SSB, in spite of frequency and phase errors. (For Scroggie fans, consider the phasor diagram for 100% modulation at the point where the sideband is at 90 degrees to the carrier. That gives an amplitude of sqrt(2) when you should just have the nominal sqrt (1.5) carrier amplitude of 1. At 0 and 180 degrees, you get the expected Half the nominal carrier amplitude. amplitudes of 1.5 and 0.5) -- David Woolley Emails are not formal business letters, whatever businesses may want. RFC1855 says there should be an address here, but, in a world of spam, that is no longer good advice, as archive address hiding may not work. ___ 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] New K3 SN#207 built but question on AM Filter
This is admittedly topic skew, but for non-critical occasional am listening, it would be nice to have a much lower cost option than the $120 filters. A cheap ceramic or 2-xtal filter, about 15Khz bw would have been a nice addition to the K3, maybe even as a st'd component. 73, Barry N1EU Joe Subich, W4TV-3 wrote: Even with the 10 kHz channel spacing used in the USA, AM broadcast stations do not have 5 kHz audio bandwidth. The FCC requires a guard band between stations. As I recall, rgulations require that the audio start to drop off at about 4 kHz so that it can be down 20 dB or so by 6 kHz (the passband edge of the adjacent station). I don't think that's right ... or wasn't the last time I was around an AM station (I spent most of my career in TV). I remember the AM guys doing proof to 10 KHz. Admittedly, many of the directional stations could not maintain 10 KHz through the phasors and the high end got trashed at night but the old allocation systems generally kept first adjacent situations far enough apart that 10 KHz could be obtained on groundwave during the daytime. In the day most receivers would start to roll off somewhere around 6 KHz and the better ones had a 10 KHz notch for nighttime conditions. Given the DSP demodulation in the K3, it's a shame that there isn't an offset option to do vestigial sideband demodulation (offset the AM filter to the upper sideband or lower sideband) and demodulate carrier and one sideband for better fidelity. This would work quite well if the carrier were placed at the -6dB point on the composite filter passband since it would keep the proper ratio between carrier and sideband. Alternatively, the carrier could be moved to 1 KHz from the -6 dB point and the DSP could equalize out the 6 dB boost in audio below 1 KHz from the opposite sideband. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alan Bloom Sent: Sunday, January 13, 2008 10:48 PM To: David Woolley Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] New K3 SN#207 built but question on AM Filter On Sun, 2008-01-13 at 02:49, David Woolley wrote: Paul Webb wrote: ... The basic reason has already been explained, however, there are very few cases were exceeding 3kHz audio bandwidth is useful. HF broadcast stations use 5kHz channelling, which would only allow them 2.5kHz with brick wall filtering at both transmit and receive ends, although they probably do expect to suffer significant adjacent channel interference. MF broadcast stations use 9kHz channelling in Europe and 10kHz in the USA, but I suspect that adjacent channel interference is less acceptable. As they were designed to be received with LC IF filters, with poor shape factors, I suspect they don't even make use of the full channel, and if they did, they would probably be required to have filters which put the adjacent channel into the filter stop band. Even with the 10 kHz channel spacing used in the USA, AM broadcast stations do not have 5 kHz audio bandwidth. The FCC requires a guard band between stations. As I recall, rgulations require that the audio start to drop off at about 4 kHz so that it can be down 20 dB or so by 6 kHz (the passband edge of the adjacent station). So there's not much point in the receiver audio being wider than 4 kHz. Al N1AL ___ 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 -- View this message in context: http://www.nabble.com/New-K3-SN-207-built-but-question-on-AM-Filter-tp14780362p14800931.html Sent from the Elecraft mailing list archive at Nabble.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] New K3 SN#207 built but question on AM Filter
I am hoping that Elecraft will have a different option for AM listening by the time that my K3 arrives (in April). A simple, lower-cost ceramic filter would be nice. Or, perhaps the roofing filter can be bypassed for AM listening. There are several receivers out there that have DSP-only selectivity for AM or SW listening. Or, at least, the audio BW will be opened up to 6kHz for AM listening. I ordered the 6kHz filter thinking that I can use the entire 6kHz for AM listening. The process of amplitude modulation produces 2 sidebands and a carrier. Each sideband has the same information (one is a mirror-image of the other). If the highest modulating frequency is 5kHz, then the BW of each sideband will be 5kHz, and the total AM signal will have a BW of 10kHz. At the receiver, one of the sidebands is discarded, and the other is demodulated. So, a 6kHz filter should produce a nice sounding AM signal since a 5kHz-wide signal is passing through it. (I have heard some SW stations that must be using a wider bandwidth, based on how nice they sound on an old Hallicrafters radio. Radio China International comes to mind). Not to be able to have a 6kHz BW with a 6KHz filter is a surprising limitation (IMHO). 72, John W2XS -- View this message in context: http://www.nabble.com/New-K3-SN-207-built-but-question-on-AM-Filter-tp14780362p14804472.html Sent from the Elecraft mailing list archive at Nabble.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] New K3 SN#207 built but question on AM Filter
I am hoping that Elecraft will have a different option for AM listening by the time that my K3 arrives (in April). Perhaps the roofing filter can be bypassed for AM listening. There are several radios out there that have DSP-only selectivity for AM reception: RX-320, Jupiter, etc. (Which also applies to transmitting on those radios). I purchased the 6kHz AM filter, but now I realize that the 15kHz FM filter is better suited for full-fidelity AM listening. The 6kHz filter may not see much use, even if I were to transmit on AM. According to the ARRL web site, 9 kHz is the ARRL's recommendation for double-sideband AM. A typical AM Broadcast signal's BW is 10kHz. Passing these signals through a 6kHz filter will result in a restricted-audio sounding signal. This is good for AM ham reception on the crowded 75m band but it is not full-fidelity sounding on AM BCB or SW. (I have heard some SW stations that must be using a wider bandwidth than 10kHz, based on how nice they sound on an old Hallicrafters radio - the kind with just the IF transformers for selectivity. Radio China International comes to mind). 73, John W2XS -- View this message in context: http://www.nabble.com/New-K3-SN-207-built-but-question-on-AM-Filter-tp14780362p14805922.html Sent from the Elecraft mailing list archive at Nabble.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] New K3 SN#207 built but question on AM Filter
On Sun, 13 Jan 2008, Dave Martin wrote: adjacent channels. But the wide IF sure brightens up the music when listening to your local honky-tonk station, We don't have any AM honky-tonk local stations...that's why a top-knotch receiver would be great to listen to the Grand Ole Opry. But then who (other than yours truly) would be using a K3 to listen to the local BC when he could be working CW while enjoying 100 Hz selectivity? Can I join you if the BC is kinda, sorta, stretching it from Baltimore to Nashville kinda local? Back in the old days, one of the first things hams did that migrated up here to work in the airplane and radio plants from their country backgrounds was to insure that their receivers could tune-in down home stations. 73 k3hrn Thom,EIEIO Email, Internet, Electronic Information Officer 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] New K3 SN#207 built but question on AM Filter
David Woolley wrote: HF broadcast stations use 5kHz channelling, which would only allow them 2.5kHz with brick wall filtering at both transmit and receive ends, although they probably do expect to suffer significant adjacent channel interference. Absolutely, and there is a lot of it -- which is why it's so cool to listen to SWBC in SSB mode, one sideband or the other. Since in AM mode it is one station's lower sideband interfering with another station's upper sideband (or vice-versa), choosing the sideband being interfered with the least is a terrific aid to listening. Bill W5WVO SWL since 1957 (age 10) ___ 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] New K3 SN#207 built but question on AM Filter
John W2XS wrote: the other). If the highest modulating frequency is 5kHz, then the BW of each sideband will be 5kHz, and the total AM signal will have a BW of 10kHz. At the receiver, one of the sidebands is discarded, and the other is demodulated. So, a 6kHz filter should produce a nice sounding AM signal since a 5kHz-wide signal is passing through it. If you do that with standard AM (envelope) detection, you will get up to about 20% (even) harmonic distortion. You will probably get better audio treating it as SSB, in spite of frequency and phase errors. To reproduce single sideband full and reduced carrier signals accurately, you need synchronous detection. (It should also be quieter for double sideband full carrier.) (For Scroggie fans, consider the phasor diagram for 100% modulation at the point where the sideband is at 90 degrees to the carrier. That gives an amplitude of sqrt(2) when you should just have the nominal carrier amplitude of 1. At 0 and 180 degrees, you get the expected amplitudes of 2 and 0.) -- David Woolley The Elecraft list is a forum for the discussion of topics related to Elecraft products and more general topics related ham radio List Guidelines http://www.elecraft.com/elecraft_list_guidelines.htm ___ 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] New K3 SN#207 built but question on AM Filter
Paul Webb wrote: now when i select SSB and tune to a AM signal i can alter the ] bandwidth to anything up to 6KHz, when i switch to AM i can only adjust ] the bandwidth up to 3KHz , the audio sounds like it is a 3KHz filter ] too, what am i doing wrong since i cant set the 6KHz bandwidth in AM. any ideas??? The basic reason has already been explained, however, there are very few cases were exceeding 3kHz audio bandwidth is useful. HF broadcast stations use 5kHz channelling, which would only allow them 2.5kHz with brick wall filtering at both transmit and receive ends, although they probably do expect to suffer significant adjacent channel interference. MF broadcast stations use 9kHz channelling in Europe and 10kHz in the USA, but I suspect that adjacent channel interference is less acceptable. As they were designed to be received with LC IF filters, with poor shape factors, I suspect they don't even make use of the full channel, and if they did, they would probably be required to have filters which put the adjacent channel into the filter stop band. [ Note: excessively long lines re-wrapped. See RFC 1855. (Probably using yahoo.) ] -- David Woolley Emails are not formal business letters, whatever businesses may want. RFC1855 says there should be an address here, but, in a world of spam, that is no longer good advice, as archive address hiding may not work. ___ 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] New K3 SN#207 built but question on AM Filter
I would. :=) I'm not a hardcore ham operator, and one of the big selling points for the K3 for me was getting excellent broadcast radio receive capability (say, on par with a Drake R8B or AOR7030). (I currently run a K2-100 with which I'm very satisfied.) - Paul, N6LQ --- Dave Martin [EMAIL PROTECTED] wrote: I've seen a number of old U.S. broadcast receivers with a 10 KHz notch filter in the audio to get rid of the high pitched hetrodynes from the adjacent channels. But the wide IF sure brightens up the music when listening to your local honky-tonk station, and nobody gave a rip how wide their IF was if their music sounded good. That's why I was hoping for the option of going as wide as I see fit when conditions allow. But then who (other than yours truly) would be using a K3 to listen to the local BC when he could be working CW while enjoying 100 Hz selectivity? Dave W5DHM The basic reason has already been explained, however, there are very few cases were exceeding 3kHz audio bandwidth is useful. HF broadcast stations use 5kHz channelling, which would only allow them 2.5kHz with brick wall filtering at both transmit and receive ends, although they probably do expect to suffer significant adjacent channel interference. MF broadcast stations use 9kHz channelling in Europe and 10kHz in the USA, but I suspect that adjacent channel interference is less acceptable. As they were designed to be received with LC IF filters, with poor shape factors, I suspect they don't even make use of the full channel, and if they did, they would probably be required to have filters which put the adjacent channel into the filter stop band. ... David Woolley ___ 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 Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ ___ 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] New K3 SN#207 built but question on AM Filter
On Sun, 2008-01-13 at 02:49, David Woolley wrote: Paul Webb wrote: ... The basic reason has already been explained, however, there are very few cases were exceeding 3kHz audio bandwidth is useful. HF broadcast stations use 5kHz channelling, which would only allow them 2.5kHz with brick wall filtering at both transmit and receive ends, although they probably do expect to suffer significant adjacent channel interference. MF broadcast stations use 9kHz channelling in Europe and 10kHz in the USA, but I suspect that adjacent channel interference is less acceptable. As they were designed to be received with LC IF filters, with poor shape factors, I suspect they don't even make use of the full channel, and if they did, they would probably be required to have filters which put the adjacent channel into the filter stop band. Even with the 10 kHz channel spacing used in the USA, AM broadcast stations do not have 5 kHz audio bandwidth. The FCC requires a guard band between stations. As I recall, rgulations require that the audio start to drop off at about 4 kHz so that it can be down 20 dB or so by 6 kHz (the passband edge of the adjacent station). So there's not much point in the receiver audio being wider than 4 kHz. Al N1AL ___ 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] New K3 SN#207 built but question on AM Filter
Even with the 10 kHz channel spacing used in the USA, AM broadcast stations do not have 5 kHz audio bandwidth. The FCC requires a guard band between stations. As I recall, rgulations require that the audio start to drop off at about 4 kHz so that it can be down 20 dB or so by 6 kHz (the passband edge of the adjacent station). I don't think that's right ... or wasn't the last time I was around an AM station (I spent most of my career in TV). I remember the AM guys doing proof to 10 KHz. Admittedly, many of the directional stations could not maintain 10 KHz through the phasors and the high end got trashed at night but the old allocation systems generally kept first adjacent situations far enough apart that 10 KHz could be obtained on groundwave during the daytime. In the day most receivers would start to roll off somewhere around 6 KHz and the better ones had a 10 KHz notch for nighttime conditions. Given the DSP demodulation in the K3, it's a shame that there isn't an offset option to do vestigial sideband demodulation (offset the AM filter to the upper sideband or lower sideband) and demodulate carrier and one sideband for better fidelity. This would work quite well if the carrier were placed at the -6dB point on the composite filter passband since it would keep the proper ratio between carrier and sideband. Alternatively, the carrier could be moved to 1 KHz from the -6 dB point and the DSP could equalize out the 6 dB boost in audio below 1 KHz from the opposite sideband. 73, ... Joe, W4TV -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Alan Bloom Sent: Sunday, January 13, 2008 10:48 PM To: David Woolley Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] New K3 SN#207 built but question on AM Filter On Sun, 2008-01-13 at 02:49, David Woolley wrote: Paul Webb wrote: ... The basic reason has already been explained, however, there are very few cases were exceeding 3kHz audio bandwidth is useful. HF broadcast stations use 5kHz channelling, which would only allow them 2.5kHz with brick wall filtering at both transmit and receive ends, although they probably do expect to suffer significant adjacent channel interference. MF broadcast stations use 9kHz channelling in Europe and 10kHz in the USA, but I suspect that adjacent channel interference is less acceptable. As they were designed to be received with LC IF filters, with poor shape factors, I suspect they don't even make use of the full channel, and if they did, they would probably be required to have filters which put the adjacent channel into the filter stop band. Even with the 10 kHz channel spacing used in the USA, AM broadcast stations do not have 5 kHz audio bandwidth. The FCC requires a guard band between stations. As I recall, rgulations require that the audio start to drop off at about 4 kHz so that it can be down 20 dB or so by 6 kHz (the passband edge of the adjacent station). So there's not much point in the receiver audio being wider than 4 kHz. Al N1AL ___ 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
[Elecraft] New K3 SN#207 built but question on AM Filter
Hi All just built my K3 up to the 10 watt level (still to fit the 100w pa) have been giving it a quick test and have a question, i have fitted the AM filter in FL2 (The FM will go in FL1) and the stock filter in FL3 (2.7KHz), i have set the filters for all modes and set FL2 (6KHz) for AM mode and also selectable in SSB Modes. now when i select SSB and tune to a AM signal i can alter the bandwidth to anything up to 6KHz, when i switch to AM i can only adjust the bandwidth up to 3KHz , the audio sounds like it is a 3KHz filter too, what am i doing wrong since i cant set the 6KHz bandwidth in AM. any ideas??? regards Paul M0BMN K3 S/N 207 __ Sent from Yahoo! Mail - a smarter inbox http://uk.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] New K3 SN#207 built but question on AM Filter
In a message dated 1/12/2008 3:40:37 P.M. Pacific Standard Time, [EMAIL PROTECTED] writes: Hi All just built my K3 up to the 10 watt level (still to fit the 100w pa) have been giving it a quick test and have a question, i have fitted the AM filter in FL2 (The FM will go in FL1) and the stock filter in FL3 (2.7KHz), i have set the filters for all modes and set FL2 (6KHz) for AM mode and also selectable in SSB Modes. now when i select SSB and tune to a AM signal i can alter the bandwidth to anything up to 6KHz, when i switch to AM i can only adjust the bandwidth up to 3KHz , the audio sounds like it is a 3KHz filter too, what am i doing wrong since i cant set the 6KHz bandwidth in AM. any ideas??? regards Paul M0BMN K3 S/N 207 It's working OK. AM bandwidth includes both sidebands. Also, if you tune in an AM station using AM mode and then switch to a SSB mode, you will note a change in the fidelity (audio band response). There was much discussion on the list a while ago on the subject. I'm looking toward the release of the fm filter that should be in excess of 12 Khz, thus improving the fidelity. The advantage of the 6 KHz filter in AM is primarily for transmitting, to maintain a legal bandwidth, and to eliminate the heterodynes to some degree. Al WA6VNN **Start the year off right. Easy ways to stay in shape. http://body.aol.com/fitness/winter-exercise?NCID=aolcmp0030002489 ___ 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
