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LED Interference
Before I spend $60 to$80 to replace the masthead tri-color bulb with an LED
equivalent, I am wondering what the consensus is here about interference between LEDs and VHFs (or other electronics). Are there certain LED lights that are superior or worse in this respect? What in-use experience can anyone relay? -- Good luck and good sailing. s/v Kerry Deare of Barnegat http://home.comcast.net/~kerrydeare |
LED Interference
"Roger Long" wrote:
I've had no problems with my LED anchor light and have gone to all LED's this season except for the bow light which is only on when the engine is running and the spreader light because I want that to be really bright on the sails. It's as much for increasing visability at night if someone doesn't seem to see me or answer the radio as for deck light. The problems seem to have been with the early crude LED's that were meant to plug into the original bulb sockets. I would be very surprised if there were problems with the units such as Aqua Signal and Hella that are designed from the start as LED fixtures and have been through regulatory approval processes. Go for it and don't worry about burned out bulbs and power draw again. BTW, no one seems to make a good, compact, bright, spreader light. I put on one of an $11.00 pair of small auto fog lights with a small hole drilled in the clear lense the first year when money was tight. I replace the rusting casing every 2 - 3 years. I want to put something more permanent and nautical on this year but I can't find anything I like better. Don't know if they meet your "compact" requirement, but go to Hamilton's and look at the Jabsco floodlights. I am using 2 as "spreader" lights on Barbara and they give lots of light on the deck. Cheers Michael Porter Marine Design mporter at mp-marine dot com www.mp-marine.com -- Posted via a free Usenet account from http://www.teranews.com |
LED Interference
Roger Long wrote:
... I would be very surprised if there were problems with the units such as Aqua Signal and Hella that are designed from the start as LED fixtures and have been through regulatory approval processes ... I am hoping to replace only the bulb itself rather than the entire fixture, an Aqua Signal Series 40 Tricolor/Anchor combo. Is the LED for this known for interference? -- Good luck and good sailing. s/v Kerry Deare of Barnegat http://home.comcast.net/~kerrydeare |
LED Interference
On Mar 30, 1:44 am, "Armond Perretta"
wrote: Before I spend $60 to$80 to replace the masthead tri-color bulb with an LED equivalent, I am wondering what the consensus is here about interference between LEDs and VHFs (or other electronics). Are there certain LED lights that are superior or worse in this respect? What in-use experience can anyone relay? It will always be at least a potential problem with PWM current regulators. Shielding that works adequately in automotive lights may well not be good enough for marine service. "Practical Sailor" has received complaints as recently as this year. I'd suggest using a portable AM radio to test your unit for RF before installing. If you want to avoid the PIA of testing you could insist on lights that are not PWM regulated. An acquaintance of mine runs a shop in Fiji that makes LED lights. Obviously, he's an interested party but I think he is very, very honest. Here is his description of the problem: http://www.bebi-electronics.com/regulator.html. -- Tom. |
LED Interference
On Sun, 30 Mar 2008 16:29:05 -0400, wrote:
wind my watch, even if it was already broken. I have ,a Rolex mechanical, not electric, watch that has to be wound. Rolex invented the self winding watch in 1939, but mine doesn't. There are many that I wouldn't trust to wind it. It is actually easy to screw up, unlike with most mechanical watches. Casady |
LED Interference
On Mar 30, 10:29 am, wrote:
A potential problem is not a problem. That's like saying all gasoline powered cars have the potential to explode in a ball of flames at any moment. How many manufacturers of LED units are using pulse width modulation regulators, and of those, which ones ACTUALLY have a problem? When it comes to technical information that is trustworthy, I wouldn't let the amateurs at Practical Sailor wind my watch, even if it was already broken. Whatever. PS is perfectly capable of passing on reports of problems. You might look over http://www.ssca.org/DiscBoard/viewto...t=2687&start=0 or do a little search. -- Tom. |
LED Interference
On Mar 31, 12:34 am, wrote:
Try hehttp://ogmtechnical.blogspot.com/ Thanks for that link. Speculating between the lines and being a tad skeptical of company self-reporting it sounds like they may have unit to unit differences in RFI and hence a manufacturing/QA problem. PWM regulators are made in the gazillions for the automotive market. As I recall the gent in the PS letter was quoted as saying (more or less) "gee we've installed countless LEDs in cars and we never have had a problem with RFI there, it must be a user thing." But, boats aren't cars. Rather like gasoline engines that need to be modified for marine use with things like spark arrestors and bilge blowers because of potential problems in boats, LEDs for marine use should take particular care with RFI because of potential problems. PWM regulators are great but because of their timing circuitry are potential RFI emitters. By the way, some remarks that Roger made have reminded me that changing the bulb in your nav lights from the manufacturer's tested type to anything else will take the lamp out of compliance. I'm not lawyerly enough to know what having non-USCG approved lighting does to a skipper's liability. It is likely that many LED bulbs will not comply with Annex I section 8 despite being visible at the ranges required by rule 22... It's also likely that USCG stamped LED lamps don't meet annex I.8... -- Tom. |
LED Interference
wrote in message ... On Mar 31, 12:34 am, wrote: Try hehttp://ogmtechnical.blogspot.com/ Thanks for that link. Speculating between the lines and being a tad skeptical of company self-reporting it sounds like they may have unit to unit differences in RFI and hence a manufacturing/QA problem. PWM regulators are made in the gazillions for the automotive market. As I recall the gent in the PS letter was quoted as saying (more or less) "gee we've installed countless LEDs in cars and we never have had a problem with RFI there, it must be a user thing." It most certainly is. But, boats aren't cars. Rather like gasoline engines that need to be modified for marine use with things like spark arrestors and bilge blowers because of potential problems in boats, LEDs for marine use should take particular care with RFI because of potential problems. No, the wiring in boats should be done as carefully as in cars. If the regulator can pass FCC emissions for cars, it should be passing for boats. But in some cases they don't because the wiring in too thin and too long for the intended use. The supply feed wires, rather than being low impedance become a high impedance (inductive) and do a great job of acting as an antenna for any noise on them. For the most part boat wiring is the sloppiest crap in the world. Here are some boat wiring tips: 1. Use adequate gauge wire. The feedline resistance, depending on the current it carries, should be 1/2 ohm or less. 2. Use twisted pair type wiring to reduce emissions and susceptibility. 3. Don't dump all you ground currents into the same wire. Use a single ground wire for each fixture. Don't daisy chain grounds. Keep the ground impedances low. 4. Solder, don't crimp! 5. Put ferrite chokes at the electronics box to reduce conducted EMI. Shunt the supply lines with filters caps were practical. Increase the common mode rejection on supply lines. 6. Don't loop wires into coils, keep paths as short as possible. PWM regulators are great but because of their timing circuitry are potential RFI emitters. It's not the regulator that is emitting, it is the wiring feeding into it. |
LED Interference
wrote in message ... On Mon, 31 Mar 2008 12:19:50 -0700 (PDT), " wrote: On Mar 31, 12:34 am, wrote: Try hehttp://ogmtechnical.blogspot.com/ Thanks for that link. Speculating between the lines and being a tad skeptical of company self-reporting it sounds like they may have unit to unit differences in RFI and hence a manufacturing/QA problem. Sounds more like there are variables in how they are installed. Bingo! We have a winner! PWM regulators are made in the gazillions for the automotive market. As I recall the gent in the PS letter was quoted as saying (more or less) "gee we've installed countless LEDs in cars and we never have had a problem with RFI there, it must be a user thing." But, boats aren't cars. Rather like gasoline engines that need to be modified for marine use with things like spark arrestors and bilge blowers because of potential problems in boats, LEDs for marine use should take particular care with RFI because of potential problems. PWM regulators are great but because of their timing circuitry are potential RFI emitters. The current used to power an LED mastlight is TINY. Even if the regulator WERE a bit noisy, it would be so weak that it likely wouldn't have any effect at all unless maybe the regulator was mounted directly on the antenna whip. The regulation in my anchor light is completely surrounded by the grounded metal bayonet base. If the switching signal (PWM) is run into an inductive load in a poorly designed circuit you could have tens or even hundreds of volts as a transient signal. It's not the current but dI/dt that makes the voltage. One does not need an antenna to radiate. A plain old wire can work just fine. Since this is all so variable, it points right at the installation factors. By the way, radio amateur QRP distances show over 1,000 miles range with a single NAND gate as the output driver. Figure PWM waveform is 5V @ 5mA = 25mW-- 14 dBm into 50 ohm. VHF radio sensitivity typically 0.25 uV into 50 ohm ---1.25e-15 Watt or -120 dBm. Say the PWM operates at 100 kHz so the 1500th harmonic has to be down -134 dB to be undetectable on the VHF. The Fourier expansion of a square wave PWM shows the harmonic coefficients decreasing as 1/n, n being the harmonic number so the VHF in-band harmonic is 1/1500 of the original signal or about 33 dB down. That leaves about 100 dB of required attenuation (if all the DC input power were radiated) not to interfere with the VHF. FCC requires the harmonics to be much lower, which they are in order to comply. Automotive testing is rigorous and thorough and it takes a real screw up to get the thing to radiate and cause interference in the boat. The lesson here is if you don't understand electrical installations, hire an experienced (even licensed) technician to do the work It may save your life. By the way, some remarks that Roger made have reminded me that changing the bulb in your nav lights from the manufacturer's tested type to anything else will take the lamp out of compliance. I'm not lawyerly enough to know what having non-USCG approved lighting does to a skipper's liability. It is likely that many LED bulbs will not comply with Annex I section 8 despite being visible at the ranges required by rule 22... It's also likely that USCG stamped LED lamps don't meet annex I.8... The USCG doesn't test devices and approve them. They publish standards, and a laboratory tests your product and charges you a fee to attest that it meets the standards. If you have an unapproved device and it becomes an issue in court, you can still retroactively have the device examined and declared compliant. Good info on the retroactive part. You can't do that for FCC. A kerosene lamp is perfectly valid as an anchor light as long as it meets the standards. No actual "pre-approval" is needed to use it. You just have to have confidence that it can meet the criteria. My LED anchor light is USCG approved because I say it is. No one has asked me to prove it, but I'm sure I could hire someone to validate my claim if it was ever needed. Meanwhile, just hope that when you have to defend your unit with a stamp of approval on it from some lab, the opposition doesn't take the wind out of your sails by claiming it was partially obscured by a blob of bird **** on one side and therefore didn't meet the standards at the time of the incident. Let's put windshield wipers on all navigation lights! |
LED Interference
Good info on the retroactive part. You can't do that for FCC.
FWIW the CFR is he http://ecfr.gpoaccess.gov/cgi/t/text...6:1.0.1.3.17.2 or http://tinyurl.com/ypv4ld. A mariner can not certify a light as USCG approved at any time but a non USCG approved light may be in compliance with COLREGS. -- Tom. |
LED Interference
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LED Interference
On Tue, 1 Apr 2008 06:08:14 -0400, in message
"Roger Long" wrote: wrote The USCG doesn't test devices and approve them. They publish standards, and a laboratory tests your product and charges you a fee to attest that it meets the standards. If you have an unapproved device and it becomes an issue in court, you can still retroactively have the device examined and declared compliant. Yes, but in the US legal system, the issue is not whether you are right or wrong but whether you can afford to prove it. When that guy who Teeboned you on the port side claims it was because he couldn't see your red nav light, how much do you think it's going to cost to prove it's compliance with his lawyer obstructing, questioning, and protesting every step of the process? One morning last summer, just towards dawn, I was very puzzled by a green light that seemed to moving in the wrong direction. As it got a little lighter I could make out the hull and passed fairly close astern, giving way as a port tack boat should. I was able to read the name off the transom and radioed to ask why they were showing green on the port side... Attention to detail is important ;-) Ryk |
LED Interference
In article ,
"Roger Long" wrote: I'm thinking the Aqua Signal stern lights might actually make good spreader lights. You may want to have a look at these: http://www.hellamarine.com/ specifically deck light http://www.hellamarine.com/?a=3&t=3&...D=690&pcid=170 navigation lights http://www.hellamarine.com/default.a...tory&newsID=41 HTH Marc -- remove bye and from mercial to get valid e-mail http://www.heusser.com |
LED Interference
On Apr 1, 12:26 am, wrote:
Nowhere in that link is there anything that says I can't declare my lights to be USCG compliant. I'm not sure how constructive this is, but I'm trying to make the distinction between USCG approved (which involves a lab test and a submission to the CG and is done by OEMs or importers) and COLREGS legal which means it meets rule 22. It is easy to install a USCG approved light in a non COLREGS compliant way (I see it all the time). Too, USCG approval is not a requirement under COLREGS as such. As I said right from the start of this I don't know what the implications for any given boater might be for carrying non USCG approved lights. I suspect the most common problem might be convincing a surveyor to pass an unstamped light. In any event, since the OP was looking to change the bulb in his lamp I wanted him to be aware that doing so will invalidate the USCG approval of the lamp. I presume he is sailing on an uninspected vessel so it may well be perfectly legal for him to go with LED bulbs but he might be unhappy if his surveyor insists that he remove them in order to get insurance. --Tom. |
LED Interference
wrote in message
... On Apr 1, 12:26 am, wrote: Nowhere in that link is there anything that says I can't declare my lights to be USCG compliant. I'm not sure how constructive this is, but I'm trying to make the distinction between USCG approved (which involves a lab test and a submission to the CG and is done by OEMs or importers) and COLREGS legal which means it meets rule 22. It is easy to install a USCG approved light in a non COLREGS compliant way (I see it all the time). Too, USCG approval is not a requirement under COLREGS as such. As I said right from the start of this I don't know what the implications for any given boater might be for carrying non USCG approved lights. I suspect the most common problem might be convincing a surveyor to pass an unstamped light. In any event, since the OP was looking to change the bulb in his lamp I wanted him to be aware that doing so will invalidate the USCG approval of the lamp. I presume he is sailing on an uninspected vessel so it may well be perfectly legal for him to go with LED bulbs but he might be unhappy if his surveyor insists that he remove them in order to get insurance. --Tom. I would be kind of amazed if a surveyor did anything more than flip the lights switches on and off. No way s/he could tell if a bulb was approved or not without physically inspecting it.. certainly no way during the day. -- "j" ganz @@ www.sailnow.com |
LED Interference
On Apr 1, 8:07 am, "Capt. JG" wrote:
No way s/he could tell if a bulb was approved or not without physically inspecting it.. certainly no way during the day. A cluster of LEDs inside a normally incandescent lamp might be a clue. -- Tom. |
LED Interference
wrote in message
... On Apr 1, 8:07 am, "Capt. JG" wrote: No way s/he could tell if a bulb was approved or not without physically inspecting it.. certainly no way during the day. A cluster of LEDs inside a normally incandescent lamp might be a clue. -- Tom. Might be, might not be... at the masthead? without taking off the lens on the bowlights? And, then s/he would have to know if the particular fixture is USCG approved. Without a close inspection, that might not be so easy. -- "j" ganz @@ www.sailnow.com |
LED Interference
On Apr 1, 8:45 am, "Capt. JG" wrote:
Might be, might not be... at the masthead? without taking off the lens on the bowlights? And, then s/he would have to know if the particular fixture is USCG approved. Without a close inspection, that might not be so easy. Unless the lenses on your lights are badly fogged you can see the bulbs through them clearly in the day in the lit and unlit states. LED clusters also have distinctive bright spots when lit. I don't have a clue if any particular surveyor would refuse to pass leds in an incandescent lamp but if he doesn't even notice them he's incompetent. Since the surveyor is not going to be able to insure that the lamps are compliant with 22 by testing he could reasonably insist on a USCG approved fixture. The CFR is specific: fixtures are approved with the supplied bulb only. Putting in a different kind of bulb makes them not USCG approved (that's different from not legal as running lights under COLREGS). AFIK, the whole point of having USCG approved fixtures is so end users and interested parties can be assured that a lamp meets Annex I without testing the color, luminosity and so on. As soon as you modify the lamp all bets are off. There aren't all that many USCG approved fixtures out there. Surveyors will be familiar with the common ones and should closely inspect any they don't recognize. -- Tom. |
LED Interference
wrote in message
... On Apr 1, 8:45 am, "Capt. JG" wrote: Might be, might not be... at the masthead? without taking off the lens on the bowlights? And, then s/he would have to know if the particular fixture is USCG approved. Without a close inspection, that might not be so easy. Unless the lenses on your lights are badly fogged you can see the bulbs through them clearly in the day in the lit and unlit states. LED clusters also have distinctive bright spots when lit. I don't have a clue if any particular surveyor would refuse to pass leds in an incandescent lamp but if he doesn't even notice them he's incompetent. Since the surveyor is not going to be able to insure that the lamps are compliant with 22 by testing he could reasonably insist on a USCG approved fixture. The CFR is specific: fixtures are approved with the supplied bulb only. Putting in a different kind of bulb makes them not USCG approved (that's different from not legal as running lights under COLREGS). AFIK, the whole point of having USCG approved fixtures is so end users and interested parties can be assured that a lamp meets Annex I without testing the color, luminosity and so on. As soon as you modify the lamp all bets are off. There aren't all that many USCG approved fixtures out there. Surveyors will be familiar with the common ones and should closely inspect any they don't recognize. -- Tom. Hmm.. well, I can't tell during the day when the bowlight is unlit, as least I don't recall being able to tell. I looked at the hi-res images of the following, but next time I'm at the boat, I'll look again. Isn't the point whether or not the lights are visible from the prescribed distance? And, this would be at night of course. So, it seems to me that if you're involved in a collision at night, and you could show that no matter what you had was in fact visible, does the CG care that they're "approved?" I don't know the answer... just wondering. http://picasaweb.google.com/SailNOW....49198843692818 http://picasaweb.google.com/SailNOW....18970863861506 -- "j" ganz @@ www.sailnow.com |
LED Interference
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LED Interference
On Apr 1, 11:58 am, "Capt. JG" wrote:
Isn't the point whether or not the lights are visible from the prescribed distance? And the right colors and properly displayed &c (see 22 and annex I)... But, yeah. does the CG care that they're "approved?" I don't know the answer... just wondering. I don't think so for uninspected vessels but the OP was talking about spending $80 on some bulbs and was worried about the remote possibility of RFI so I though he might be interested in the certainty that he'd no longer have USCG approved fixtures if he installed different bulbs... I suppose he might get into insurance difficulty if the bulb started a fire or if he had a collision and couldn't prove that he had legal fixtures but those seem like pretty remote issues. A quick phone call to the surveyor that works for his insurance company would likely reveal if there would be a problem there. It may be that he doesn't care about USCG approval. That's cool, too. -- Tom. |
LED Interference
"Tony Helton" wrote in message ... If the switching signal (PWM) is run into an inductive load in a poorly designed circuit you could have tens or even hundreds of volts as a transient signal. It's not the current but dI/dt that makes the voltage. One does not need an antenna to radiate. A plain old wire can work just fine. Since this is all so variable, it points right at the installation factors. By the way, radio amateur QRP distances show over 1,000 miles range with a single NAND gate as the output driver. Figure PWM waveform is 5V @ 5mA = 25mW-- 14 dBm into 50 ohm. VHF radio sensitivity typically 0.25 uV into 50 ohm ---1.25e-15 Watt or -120 dBm. Say the PWM operates at 100 kHz so the 1500th harmonic has to be down -134 dB to be undetectable on the VHF. The Fourier expansion of a square wave PWM shows the harmonic coefficients decreasing as 1/n, n being the harmonic number so the VHF in-band harmonic is 1/1500 of the original signal or about 33 dB down. That leaves about 100 dB of required attenuation (if all the DC input power were radiated) not to interfere with the VHF. FCC requires the harmonics to be much lower, which they are in order to comply. Automotive testing is rigorous and thorough and it takes a real screw up to get the thing to radiate and cause interference in the boat. The lesson here is if you don't understand electrical installations, hire an experienced (even licensed) technician to do the work It may save your life. Hey Tony, The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not 1/n (that is for voltage). Power is proportional to voltage squared. Hence, your 1500th harmonic is down 66 dB, not 33 dB. Amen! Bob Crantz PhD |
LED Interference
Bob Crantz wrote:
The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not 1/n (that is for voltage). Power is proportional to voltage squared. Hence, your 1500th harmonic is down 66 dB, not 33 dB. Amen! Bob Crantz PhD And given that you are coupling into some Gawd awful mismatched radiator you can probably chop of at least another 30 or 40db. Cheers Marty |
LED Interference
"Capt. JG" wrote in message news:HpGdnRFII8-DLW_anZ2dnUVZ_sSlnZ2d@bayareasolutions... Hmm.. well, I can't tell during the day when the bowlight is unlit, as least I don't recall being able to tell. I looked at the hi-res images of the following, but next time I'm at the boat, I'll look again. Isn't the point whether or not the lights are visible from the prescribed distance? And, this would be at night of course. So, it seems to me that if you're involved in a collision at night, and you could show that no matter what you had was in fact visible, does the CG care that they're "approved?" I don't know the answer... just wondering. Is all this worry about the USCG somehow related to the fact that they are now part of your rather scary Department of Homeland Security? Have they unilaterally set up their own approval standards for lights? And if so, why? The internationally accepted Colregs and, in particular, their Annex No 1 'Positioning and technical detailsabout lights and shapes' clearly states how far lights should be visible at night and goes on to give highly technical details about the necessary chromacity and power to achieve that. Also it even goes on to give a warning not to have lights so bright that they interfere with the navigators night vision. That should be enough for anybody surely. If you have bought decent lights,warranted by the makers to comply with Colregs, and position them correctly is the USCG really going to stop you at sea and check the chromacity and candlepower of the bulbs in them as long as they are actually alight? |
LED Interference
"Marty" wrote in message ... Bob Crantz wrote: The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not 1/n (that is for voltage). Power is proportional to voltage squared. Hence, your 1500th harmonic is down 66 dB, not 33 dB. Amen! Bob Crantz PhD And given that you are coupling into some Gawd awful mismatched radiator you can probably chop of at least another 30 or 40db. Cheers Marty Not all wires are bad radiators at all frequencies. Your assumption is correct if you intend for the wire to radiate. My premise is correct if you don't want it to. Nature always works against man's desires or more correctly, man always works against nature. Amen! |
LED Interference
"Edgar" wrote in message
... "Capt. JG" wrote in message news:HpGdnRFII8-DLW_anZ2dnUVZ_sSlnZ2d@bayareasolutions... Hmm.. well, I can't tell during the day when the bowlight is unlit, as least I don't recall being able to tell. I looked at the hi-res images of the following, but next time I'm at the boat, I'll look again. Isn't the point whether or not the lights are visible from the prescribed distance? And, this would be at night of course. So, it seems to me that if you're involved in a collision at night, and you could show that no matter what you had was in fact visible, does the CG care that they're "approved?" I don't know the answer... just wondering. Is all this worry about the USCG somehow related to the fact that they are now part of your rather scary Department of Homeland Security? Have they unilaterally set up their own approval standards for lights? And if so, why? The internationally accepted Colregs and, in particular, their Annex No 1 'Positioning and technical detailsabout lights and shapes' clearly states how far lights should be visible at night and goes on to give highly technical details about the necessary chromacity and power to achieve that. Also it even goes on to give a warning not to have lights so bright that they interfere with the navigators night vision. That should be enough for anybody surely. If you have bought decent lights,warranted by the makers to comply with Colregs, and position them correctly is the USCG really going to stop you at sea and check the chromacity and candlepower of the bulbs in them as long as they are actually alight? These days one wonders. I just picked up my TWIC (Transportation Workers Identification Credential). Besides the $132, they sure don't make it easy, at least not in northern Cal. There are three offices. Two are in Oakland... right. Couldn't find them after 2 hours of driving around when I went to apply. They don't have a phone number... except for the 800 number, and they're no help. Finally, in desperation, I drove an hour out to Martinez. Still couldn't find the place. I stopped at the Shell refinery guard shack, which was being guarded by someone in uniform toting a friggin howitzer. He said, and I'm not making this up, "Oh, there's no way you can find it if you don't know where it is." And, he proceeded to give me directions to turn on a road without a street sign, go a certain number of 1/10s of a mile, then park and walk. Sure, there was a sign. It was about this big: xxxx (TWIC in tiny letters). After I found it, the process went really fast... fingerprints, retinal scan, all about 15 minutes soup to nuts. Then, I waited six weeks and went and picked up the card. -- "j" ganz @@ www.sailnow.com |
LED Interference
On Wed, 2 Apr 2008 08:19:02 -0600, "Bob Crantz"
wrote: "Marty" wrote in message m... Bob Crantz wrote: The Fourier coefficients for the Power Spectra decrease as 1/(n^2), not 1/n (that is for voltage). Power is proportional to voltage squared. Hence, your 1500th harmonic is down 66 dB, not 33 dB. Amen! Bob Crantz PhD And given that you are coupling into some Gawd awful mismatched radiator you can probably chop of at least another 30 or 40db. Cheers Marty Not all wires are bad radiators at all frequencies. Your assumption is correct if you intend for the wire to radiate. My premise is correct if you don't want it to. Nature always works against man's desires or more correctly, man always works against nature. Amen! There is more BS on this NG than you could shake a stick at. :-) |
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