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#71
June 29th 04, 09:13 PM
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#72
June 29th 04, 09:48 PM
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Richard Clark beweerde :
On Tue, 29 Jun 2004 16:14:57 +0200, Gert-Jan Dam PG0G wrote: Op dinsdag 29-6-2004 krabbelde Mark1 op mijn schermpje 'zou u slechts een van de loodglanskristal en kat bakkebaard nodig hebben om uw hoofdtelefoon aan te drijven' Ja haha. Lachen zo'n vertaal programma  rofl Mark Hi OM, het van het kattenbakkebaard en loodglans kristal is de oude componenten van de tijddetector. De bakkebaard van de kat is fijne draad. Het kristal van het loodglans is semiconducting mineraal (waar de draad raakt en contact met een oxyde opneemt). De twee componenten maken een diode. 73's Richard Clark, KB7QHC Translation, : it from it cat-sideburn and leadshine cristal is the old components of the timedetector. The sideburn of the cat is fine thread. And so on. So pse remove this group from future postings. |
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#73
June 29th 04, 09:48 PM
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Richard Clark beweerde :
On Tue, 29 Jun 2004 16:14:57 +0200, Gert-Jan Dam PG0G wrote: Op dinsdag 29-6-2004 krabbelde Mark1 op mijn schermpje 'zou u slechts een van de loodglanskristal en kat bakkebaard nodig hebben om uw hoofdtelefoon aan te drijven' Ja haha. Lachen zo'n vertaal programma rofl Mark Hi OM, het van het kattenbakkebaard en loodglans kristal is de oude componenten van de tijddetector. De bakkebaard van de kat is fijne draad. Het kristal van het loodglans is semiconducting mineraal (waar de draad raakt en contact met een oxyde opneemt). De twee componenten maken een diode. 73's Richard Clark, KB7QHC Translation, : it from it cat-sideburn and leadshine cristal is the old components of the timedetector. The sideburn of the cat is fine thread. And so on. So pse remove this group from future postings. |
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#74
June 29th 04, 11:23 PM
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"Richard Clark" wrote in message ... On 29 Jun 2004 11:30:01 -0700, (RHF) wrote:............................................ .............. So why are you posting to an amateur group? Why an antenna group? You would be better served through your self-imposed limitations by staying out of the fast lane. 73's Richard Clark, KB7QHC, WPE0EPH p.s. if the WPE0EPH is unknown to you, it denotes my having been a Shortwave listener for 40 years and registered with the Popular Electronics DX club (as well as a sack full of others from around the world). Richard, Probably to a lot of people a radio or electronic hobbyist is an "amateur". Impression I get is that some CBers think so also. From looking at old literature, the search for the holy grail of a noise free antenna, seems to back to around T=0. It would help, if the manufacturers of SWL receivers would add noise blankers in sub $500 radios. I did not see any in the AES catalog below that price that claimed to have a noise blanker. I won't even delve on IF filter shape factor. ps. I can beat your 40 years by about 10. Tam/WB2TT |
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#75
June 29th 04, 11:23 PM
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"Richard Clark" wrote in message ... On 29 Jun 2004 11:30:01 -0700, (RHF) wrote:............................................ .............. So why are you posting to an amateur group? Why an antenna group? You would be better served through your self-imposed limitations by staying out of the fast lane. 73's Richard Clark, KB7QHC, WPE0EPH p.s. if the WPE0EPH is unknown to you, it denotes my having been a Shortwave listener for 40 years and registered with the Popular Electronics DX club (as well as a sack full of others from around the world). Richard, Probably to a lot of people a radio or electronic hobbyist is an "amateur". Impression I get is that some CBers think so also. From looking at old literature, the search for the holy grail of a noise free antenna, seems to back to around T=0. It would help, if the manufacturers of SWL receivers would add noise blankers in sub $500 radios. I did not see any in the AES catalog below that price that claimed to have a noise blanker. I won't even delve on IF filter shape factor. ps. I can beat your 40 years by about 10. Tam/WB2TT |
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#76
June 29th 04, 11:34 PM
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Richard Clark wrote:
Antennas have no capacity to reduce Signal to Noise ratios except by virtue of narrowing lobes to eliminate noise by placing it in a null (if that is in fact a viable option either in the sense of having a null, or having a null to a noise source that is not on the same meridian as the signal of interest). Not true. You are making the assumption that that the antenna only picks up radiated modes. Non-radiated electromagnetic modes are also troublesome, particularly common mode on the transmission line. This tends to be the way that locally generated noise from household gadgets gets into an antenna system. Consider a lamp dimmer that generates 10 mW of RFI, which rides out in common mode on the mains, finds its way to the power cord of your transceiver, rides out on the feedline to the antenna, and then couples back through differential mode to your receiver input. That's not a very efficient coupling path, so suppose it has a loss of 60 dB. You'll still get 10 nW to the receiver. This is a lot: even if it's spread over 30 MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a very serious quantity of noise. On the other hand, if your transmitter puts out 1 kW, 60 dB of loss means it only delivers 1 mW of RF to the dimmer, an amount unlikely to interfere with its operation. Reciprocity does not mean *consequences* are symmetrical. To this point, you have not offered any particularly receive dominated issue that is not already a heavily trafficked topic with transmission antennas. A deep, steerable null can be extremely useful for reception, but its not generally useful for transmission. In fact, the presumption there are unique reception antennas that are more suitable than their transmission cousins is simply the artifice of my aforementioned advantage of the RF Gain control. It has been long established (through the simple act of purchase power) that receivers have far more gain available than needed except for the worst of antenna designs (and that has to be an exceptionally vile design). Such examples of small loops used for MF are proof positive how poor an antenna can be, and the RF gain knob resurrecting its pitiful efficiency. But for MWDX reception, efficiency simply isn't an important virtue. Gain is cheap. What matters is the steerable nulls. An efficient *steerable* MW antenna is enormous and expensive. This does NOT demonstrate some illusion of superior receive antenna design; rather it is more smoke and mirrors as an argument. Inverting the argument, if you had a full sized antenna for that band, you would only need a galena crystal and cat whisker to power your hi-Z headset. For DX you would only need a $5 AF amplifier. The smaller antenna clearly needs more dollars expended to offset the debilities of the poorer efficiency. Sensitivity is the cheapest, easiest virtue to put into a receiver. Essentially all modern receivers have plenty. Indeed, the cheap ones often overload when presented with an efficient antenna: you have to spend the dollars to be able to handle the big signals! Speaking of strawmen, have you ever actually tried DXing with a crystal radio? The specious argument is tailored for the technically effete who would rather push a credit card across the display counter than build their own cheap solution. Take heart that this not simply a cheap shot, there are as many Hams who don't know which end of the soldering iron to pick up either. I love designing and building antennas: applied physics is fun. But it's good engineering to go with the strengths of your technology. For my inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of effective bandwidth, something that is perhaps of little use to hams, but is very useful to an SWL in conjunction with the frequency agility of a modern receiver. 4 dB of efficiency loss is of negligible consequence at HF and below if your receiver has a decent noise figure. I've never seen mention of this efficiency/bandwidth tradeoff in the ham literature, but it's not hard to find in the professional literature. For details of a specific calculation, see: http://anarc.org/naswa/badx/antennas/SWL_longwire.html -jpd |
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#77
June 29th 04, 11:34 PM
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Richard Clark wrote:
Antennas have no capacity to reduce Signal to Noise ratios except by virtue of narrowing lobes to eliminate noise by placing it in a null (if that is in fact a viable option either in the sense of having a null, or having a null to a noise source that is not on the same meridian as the signal of interest). Not true. You are making the assumption that that the antenna only picks up radiated modes. Non-radiated electromagnetic modes are also troublesome, particularly common mode on the transmission line. This tends to be the way that locally generated noise from household gadgets gets into an antenna system. Consider a lamp dimmer that generates 10 mW of RFI, which rides out in common mode on the mains, finds its way to the power cord of your transceiver, rides out on the feedline to the antenna, and then couples back through differential mode to your receiver input. That's not a very efficient coupling path, so suppose it has a loss of 60 dB. You'll still get 10 nW to the receiver. This is a lot: even if it's spread over 30 MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a very serious quantity of noise. On the other hand, if your transmitter puts out 1 kW, 60 dB of loss means it only delivers 1 mW of RF to the dimmer, an amount unlikely to interfere with its operation. Reciprocity does not mean *consequences* are symmetrical. To this point, you have not offered any particularly receive dominated issue that is not already a heavily trafficked topic with transmission antennas. A deep, steerable null can be extremely useful for reception, but its not generally useful for transmission. In fact, the presumption there are unique reception antennas that are more suitable than their transmission cousins is simply the artifice of my aforementioned advantage of the RF Gain control. It has been long established (through the simple act of purchase power) that receivers have far more gain available than needed except for the worst of antenna designs (and that has to be an exceptionally vile design). Such examples of small loops used for MF are proof positive how poor an antenna can be, and the RF gain knob resurrecting its pitiful efficiency. But for MWDX reception, efficiency simply isn't an important virtue. Gain is cheap. What matters is the steerable nulls. An efficient *steerable* MW antenna is enormous and expensive. This does NOT demonstrate some illusion of superior receive antenna design; rather it is more smoke and mirrors as an argument. Inverting the argument, if you had a full sized antenna for that band, you would only need a galena crystal and cat whisker to power your hi-Z headset. For DX you would only need a $5 AF amplifier. The smaller antenna clearly needs more dollars expended to offset the debilities of the poorer efficiency. Sensitivity is the cheapest, easiest virtue to put into a receiver. Essentially all modern receivers have plenty. Indeed, the cheap ones often overload when presented with an efficient antenna: you have to spend the dollars to be able to handle the big signals! Speaking of strawmen, have you ever actually tried DXing with a crystal radio? The specious argument is tailored for the technically effete who would rather push a credit card across the display counter than build their own cheap solution. Take heart that this not simply a cheap shot, there are as many Hams who don't know which end of the soldering iron to pick up either. I love designing and building antennas: applied physics is fun. But it's good engineering to go with the strengths of your technology. For my inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of effective bandwidth, something that is perhaps of little use to hams, but is very useful to an SWL in conjunction with the frequency agility of a modern receiver. 4 dB of efficiency loss is of negligible consequence at HF and below if your receiver has a decent noise figure. I've never seen mention of this efficiency/bandwidth tradeoff in the ham literature, but it's not hard to find in the professional literature. For details of a specific calculation, see: http://anarc.org/naswa/badx/antennas/SWL_longwire.html -jpd |
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#78
June 29th 04, 11:44 PM
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pse remove the nl newsgroup from this discussion.
John Doty schreef op 29-6-04 : Richard Clark wrote: Antennas have no capacity to reduce Signal to Noise ratios except by virtue of narrowing lobes to eliminate noise by placing it in a null (if that is in fact a viable option either in the sense of having a null, or having a null to a noise source that is not on the same meridian as the signal of interest). Not true. You are making the assumption that that the antenna only picks up radiated modes. Non-radiated electromagnetic modes are also troublesome, particularly common mode on the transmission line. This tends to be the way that locally generated noise from household gadgets gets into an antenna system. Consider a lamp dimmer that generates 10 mW of RFI, which rides out in common mode on the mains, finds its way to the power cord of your transceiver, rides out on the feedline to the antenna, and then couples back through differential mode to your receiver input. That's not a very efficient coupling path, so suppose it has a loss of 60 dB. You'll still get 10 nW to the receiver. This is a lot: even if it's spread over 30 MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a very serious quantity of noise. On the other hand, if your transmitter puts out 1 kW, 60 dB of loss means it only delivers 1 mW of RF to the dimmer, an amount unlikely to interfere with its operation. Reciprocity does not mean *consequences* are symmetrical. To this point, you have not offered any particularly receive dominated issue that is not already a heavily trafficked topic with transmission antennas. A deep, steerable null can be extremely useful for reception, but its not generally useful for transmission. In fact, the presumption there are unique reception antennas that are more suitable than their transmission cousins is simply the artifice of my aforementioned advantage of the RF Gain control. It has been long established (through the simple act of purchase power) that receivers have far more gain available than needed except for the worst of antenna designs (and that has to be an exceptionally vile design). Such examples of small loops used for MF are proof positive how poor an antenna can be, and the RF gain knob resurrecting its pitiful efficiency. But for MWDX reception, efficiency simply isn't an important virtue. Gain is cheap. What matters is the steerable nulls. An efficient *steerable* MW antenna is enormous and expensive. This does NOT demonstrate some illusion of superior receive antenna design; rather it is more smoke and mirrors as an argument. Inverting the argument, if you had a full sized antenna for that band, you would only need a galena crystal and cat whisker to power your hi-Z headset. For DX you would only need a $5 AF amplifier. The smaller antenna clearly needs more dollars expended to offset the debilities of the poorer efficiency. Sensitivity is the cheapest, easiest virtue to put into a receiver. Essentially all modern receivers have plenty. Indeed, the cheap ones often overload when presented with an efficient antenna: you have to spend the dollars to be able to handle the big signals! Speaking of strawmen, have you ever actually tried DXing with a crystal radio? The specious argument is tailored for the technically effete who would rather push a credit card across the display counter than build their own cheap solution. Take heart that this not simply a cheap shot, there are as many Hams who don't know which end of the soldering iron to pick up either. I love designing and building antennas: applied physics is fun. But it's good engineering to go with the strengths of your technology. For my inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of effective bandwidth, something that is perhaps of little use to hams, but is very useful to an SWL in conjunction with the frequency agility of a modern receiver. 4 dB of efficiency loss is of negligible consequence at HF and below if your receiver has a decent noise figure. I've never seen mention of this efficiency/bandwidth tradeoff in the ham literature, but it's not hard to find in the professional literature. For details of a specific calculation, see: http://anarc.org/naswa/badx/antennas/SWL_longwire.html -jpd |
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#79
June 29th 04, 11:44 PM
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pse remove the nl newsgroup from this discussion.
John Doty schreef op 29-6-04 : Richard Clark wrote: Antennas have no capacity to reduce Signal to Noise ratios except by virtue of narrowing lobes to eliminate noise by placing it in a null (if that is in fact a viable option either in the sense of having a null, or having a null to a noise source that is not on the same meridian as the signal of interest). Not true. You are making the assumption that that the antenna only picks up radiated modes. Non-radiated electromagnetic modes are also troublesome, particularly common mode on the transmission line. This tends to be the way that locally generated noise from household gadgets gets into an antenna system. Consider a lamp dimmer that generates 10 mW of RFI, which rides out in common mode on the mains, finds its way to the power cord of your transceiver, rides out on the feedline to the antenna, and then couples back through differential mode to your receiver input. That's not a very efficient coupling path, so suppose it has a loss of 60 dB. You'll still get 10 nW to the receiver. This is a lot: even if it's spread over 30 MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a very serious quantity of noise. On the other hand, if your transmitter puts out 1 kW, 60 dB of loss means it only delivers 1 mW of RF to the dimmer, an amount unlikely to interfere with its operation. Reciprocity does not mean *consequences* are symmetrical. To this point, you have not offered any particularly receive dominated issue that is not already a heavily trafficked topic with transmission antennas. A deep, steerable null can be extremely useful for reception, but its not generally useful for transmission. In fact, the presumption there are unique reception antennas that are more suitable than their transmission cousins is simply the artifice of my aforementioned advantage of the RF Gain control. It has been long established (through the simple act of purchase power) that receivers have far more gain available than needed except for the worst of antenna designs (and that has to be an exceptionally vile design). Such examples of small loops used for MF are proof positive how poor an antenna can be, and the RF gain knob resurrecting its pitiful efficiency. But for MWDX reception, efficiency simply isn't an important virtue. Gain is cheap. What matters is the steerable nulls. An efficient *steerable* MW antenna is enormous and expensive. This does NOT demonstrate some illusion of superior receive antenna design; rather it is more smoke and mirrors as an argument. Inverting the argument, if you had a full sized antenna for that band, you would only need a galena crystal and cat whisker to power your hi-Z headset. For DX you would only need a $5 AF amplifier. The smaller antenna clearly needs more dollars expended to offset the debilities of the poorer efficiency. Sensitivity is the cheapest, easiest virtue to put into a receiver. Essentially all modern receivers have plenty. Indeed, the cheap ones often overload when presented with an efficient antenna: you have to spend the dollars to be able to handle the big signals! Speaking of strawmen, have you ever actually tried DXing with a crystal radio? The specious argument is tailored for the technically effete who would rather push a credit card across the display counter than build their own cheap solution. Take heart that this not simply a cheap shot, there are as many Hams who don't know which end of the soldering iron to pick up either. I love designing and building antennas: applied physics is fun. But it's good engineering to go with the strengths of your technology. For my inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of effective bandwidth, something that is perhaps of little use to hams, but is very useful to an SWL in conjunction with the frequency agility of a modern receiver. 4 dB of efficiency loss is of negligible consequence at HF and below if your receiver has a decent noise figure. I've never seen mention of this efficiency/bandwidth tradeoff in the ham literature, but it's not hard to find in the professional literature. For details of a specific calculation, see: http://anarc.org/naswa/badx/antennas/SWL_longwire.html -jpd |
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#80
June 30th 04, 03:58 AM
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On Tue, 29 Jun 2004 15:34:42 -0600, John Doty
wrote: You are making the assumption that that the antenna only picks up radiated modes. I am making no such assumption and all following commentary does absolutely nothing to separate the concerns of SWLers from Ham activity. Non-radiated electromagnetic modes are also troublesome, particularly common mode on the transmission line. This tends to be the way that locally generated noise from household gadgets gets into an antenna system. Consider a lamp dimmer that generates 10 mW of RFI, which rides out in common mode on the mains, finds its way to the power cord of your transceiver, rides out on the feedline to the antenna, and then couples back through differential mode to your receiver input. That's not a very efficient coupling path, so suppose it has a loss of 60 dB. You'll still get 10 nW to the receiver. This is a lot: even if it's spread over 30 MHz, it's still 10 uV in a 6 kHz channel. That's S6 on my Drake R-8, a very serious quantity of noise. Let's work with exactly that scenario you offered. S6 (Calibrated) on my Drake TR-7 is -88dBm - so close to your 10µV to be indistinguishable. My TS-430 varies from -80dBm to -73dBm. There is no calibrated S-Meter for my DX-440, but for a $200 SW set, its sensitivity is -90dBm for a full scale meter indication (about 7dB range from top to bottom). All very well and good. Now if we regard this speculation of 10mW (it is, after all, the epitome of a wild ass guess, isn't it?); then, let's reverse engineer that 10nW product from 6kHz buckets over the range of 30MHz to find 50µW which is 23dB below the original power presumably suppressed 60dB. Well, I have either pencil-whipped you, or you me, or each other - the numbers don't add up. Hardly matters given the original specification had no basis in fact. However, if I return to the original "problem" of noise derived from household sources; then that is also something I have closely measured. Across time, frequency, antennas, and known noise sources I have found it as low as S1 for my longwire (an antenna supposedly unused by Hams) to as high as S7 (for that same longwire). My loops, dipoles and verticals hardly fell outside of this range to present any gilt-edge design. With every circuit in the house broken (operating battery power in the dark), average noise level was either S2 for a vertical, or S1 to S3 for a loop (rather upsetting the voodoo of loops being quiet and verticals being noisy). When I returned power to the house by stages, I insured every opportunity of injecting noise by setting dimmers to their worst position (about 50%). In the low bands, I suffered as much as S8 noise levels with an average of S5 when the house was full lit (also including fluorescents) and all noise sources adding to the cacophony of reception. This was for a loop antenna. On the other hand, if your transmitter puts out 1 kW, 60 dB of loss means it only delivers 1 mW of RF to the dimmer, an amount unlikely to interfere with its operation. Reciprocity does not mean *consequences* are symmetrical. This effect of reciprocity has been reported so frequently in this group so as to negate your premise. We have many queries for how to solve this problem. To this point, you have not offered any particularly receive dominated issue that is not already a heavily trafficked topic with transmission antennas. A deep, steerable null can be extremely useful for reception, but its not generally useful for transmission. This really goes off the deep edge. Barring loss introduced for the sake of jimmying the logic, transmitters AND receivers enjoy the GAIN derived from the introduction of a null not otherwise part of the characteristic. This is a commonplace of theory and practice. Where ever you can design or contribute to a null; then this must of necessity result in an increase in signal outside of its region. These are all commonplace observations discussed here that are observable for either Ham or SWL operations. There is NO differential offered in these observations that separate SWL from Ham activities. Such examples of small loops used for MF are proof positive how poor an antenna can be, and the RF gain knob resurrecting its pitiful efficiency. But for MWDX reception, efficiency simply isn't an important virtue. I believe I have said that at least 3 to 5 times already. Gain is cheap. What matters is the steerable nulls. An efficient *steerable* MW antenna is enormous and expensive. Who needs an efficient MW antenna? This does NOT demonstrate some illusion of superior receive antenna design; rather it is more smoke and mirrors as an argument. Inverting the argument, if you had a full sized antenna for that band, you would only need a galena crystal and cat whisker to power your hi-Z headset. For DX you would only need a $5 AF amplifier. The smaller antenna clearly needs more dollars expended to offset the debilities of the poorer efficiency. Sensitivity is the cheapest, easiest virtue to put into a receiver. Essentially all modern receivers have plenty. Indeed, the cheap ones often overload when presented with an efficient antenna: you have to spend the dollars to be able to handle the big signals! All of $20 if you have any technical capacity. Otherwise push the credit card across the display counter and spend as much as they can sell you. This argument is like driving your car into the shop to get the air changed in your tires every 100 miles. Again, front end overload is a very common complaint offered here by SWLers who are then advised in how to simply AND cheaply combat this problem. Speaking of strawmen, have you ever actually tried DXing with a crystal radio? Sure, what is so remarkable about that? Beyond this simple design, ever hear of a super-Regen receiver? You don't need to spend half a kilo-buck to get the same sensitivity and filtering is dirt cheap. How about Q-multipliers? All such topics barely spread the wallet as much as the illusion of more buttons make a better rig. I love designing and building antennas: applied physics is fun. But it's good engineering to go with the strengths of your technology. For my inverted-L's, I spend a little efficiency (4 dB or so) to get octaves of effective bandwidth, something that is perhaps of little use to hams, but is very useful to an SWL in conjunction with the frequency agility of a modern receiver. 4 dB of efficiency loss is of negligible consequence at HF and below if your receiver has a decent noise figure. As I pointed out to Yahoo, if you choose to cripple yourself, then slide on over to the shoulder and enjoy kicking up dust and rocks as you travel down the road. a 4dB loss for an inverted L (hardly a SW invention) is far too simple to remedy to make its suffering a boast of martyrdom. It is a strange argument to offer that you can't afford a $20 solution for your $500 set and $2 worth of wire. I've never seen mention of this efficiency/bandwidth tradeoff in the ham literature, You haven't looked. Either contrived, wholly fictional, or accurately represented, it is part of the stock in trade for selling antennas. In this group, I would wager its discussion consumes more bandwidth than bragging about how many QSL cards have been pasted to the wall. but it's not hard to find in the professional literature. For details of a specific calculation, see: http://anarc.org/naswa/badx/antennas/SWL_longwire.html -jpd It would do you well to note that this "professional" whom you rely upon, John Kraus, is one of the most notable Ham Radio Operators frequently acknowledged and referred to here. Do you or others have any actual differentiable discussion, or is this simply an outlet for appoligia for why it isn't worth the strain to lift a soldering iron when you can bench press a credit card? 73's Richard Clark, KB7QHC |
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