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FM antenna curiosity
"Richard Clark" wrote in message ... On Fri, 19 Mar 2010 17:42:15 -0500, "amdx" wrote: Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike Hi Mike, Normally, a too strong signal is not a problem with FM as FM literally locks onto the strongest signal and rejects the competitors. This is not a characteristic of the RF wave, but rather the modulation employed. Collapsing your antenna is the same thing as moving it. Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). A simple test is to tune into at least two of these off-frequency stations, note what frequency they should be and subtract the frequency where they appear. If you are having image issues (no, this is not a self-help hint), the two or more stations should come up with the same differences. If you come up with the same number, AND you have trouble with interference from adjacent stations (there are guard bands to prevent this), THEN you have one crappy receiver. 73's Richard Clark, KB7QHC The receiver is an undercounter mounting Sony AM/FM, radio with CD. Nothing great, but Sony ususally does a fair job. Mike |
FM antenna curiosity
I have an FM radio inside an aluminum boat. The radio worked ok with the
AC cord as the antenna but I got interference when I used my laptop. I found the circuit that ran from the power transformer to the antenna input on the FM IC. I installed a connector that is used on car radios and wired the center pin to the foil that went to the FM IC (capacitor on pcb isolated) and the shield side to dc ground near the IC. I then plugged in a telescoping car antenna and it worked great on the bench . So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. BTW, the mod did cure the computer hash. Mike |
FM antenna curiosity
amdx Inscribed thus:
I have an FM radio inside an aluminum boat. The radio worked ok with the AC cord as the antenna but I got interference when I used my laptop. I found the circuit that ran from the power transformer to the antenna input on the FM IC. I installed a connector that is used on car radios and wired the center pin to the foil that went to the FM IC (capacitor on pcb isolated) and the shield side to dc ground near the IC. I then plugged in a telescoping car antenna and it worked great on the bench . So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. BTW, the mod did cure the computer hash. Mike Sounds as if the antenna is fed with co-ax and has too much capacitance across the input. Put a trimmer capacitor in series with the centre pin and see if that improves things. Try 2-20 or 5-50pf. -- Best Regards: Baron. |
FM antenna curiosity
On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote:
So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC |
FM antenna curiosity
"Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike |
FM antenna curiosity
On Fri, 19 Mar 2010 17:42:15 -0500, "amdx" wrote:
Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike Hi Mike, Normally, a too strong signal is not a problem with FM as FM literally locks onto the strongest signal and rejects the competitors. This is not a characteristic of the RF wave, but rather the modulation employed. Collapsing your antenna is the same thing as moving it. Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). A simple test is to tune into at least two of these off-frequency stations, note what frequency they should be and subtract the frequency where they appear. If you are having image issues (no, this is not a self-help hint), the two or more stations should come up with the same differences. If you come up with the same number, AND you have trouble with interference from adjacent stations (there are guard bands to prevent this), THEN you have one crappy receiver. 73's Richard Clark, KB7QHC |
FM antenna curiosity
amdx wrote:
"Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |
FM antenna curiosity
Richard Clark wrote:
On Fri, 19 Mar 2010 17:42:15 -0500, "amdx" wrote: Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike Hi Mike, Normally, a too strong signal is not a problem with FM as FM literally locks onto the strongest signal and rejects the competitors. This is not a characteristic of the RF wave, but rather the modulation employed. Collapsing your antenna is the same thing as moving it. Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). ... One solution: Try to get an old Becker car radio. And I mean old, at least 40 year, the first transistorized ones that could still be switched to 6V. They used to be standard issue in Mercedes Benzes. [...] -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |
FM antenna curiosity
"Joerg" wrote in message ... amdx wrote: "Joerg" wrote in message ... amdx wrote: "Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg This morning I got on the boat and the signal that was improved to good by shortening the antenna is now bad. 94.5 has interference from 101.1. Oh well! You really need a better quality radio and with radios and a lot of other stuff older = better :-) I mean, considering what the boat must have cost ... Well the boat is a pontoon boat (maybe $6,000) that I run my business from, my wife or I are on the boat 70 hrs a week. The radio was fine when I used the original AC cord antenna, except when I was on my laptop, it caused hash in the audio. That's why I isolated the antenna from the AC, that did eliminate the computer hash. I have put together a car radio and wall wart that I use with a pillow speaker at night. Maybe later I'll put together another one for the boat. Mike |
FM antenna curiosity
"Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. ..... Phil |
FM antenna curiosity
On Sat, 20 Mar 2010 16:42:29 +1100, "Phil Allison"
wrote: ** Hearing the same FM station at more than one spot is still possible even in a very crappy receiver. It has already been said. Not the usual quality one expects from Sony, but Mike's testimony suggests otherwise hence we cannot discount a comb generator having been dropped into the LO chip's place. Pity that, it must have been a bad year. 73's Richard Clark, KB7QHC |
FM antenna curiosity
"Phil Allison" wrote ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxemburg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. S* |
FM antenna curiosity
The usual solution on boats: Use a decent car radio.. Well shielded,
expects outdoor antenna. Runs on 12Volts... Can be had with CD player, separate input for your Ipod etc.., good audio power to speakers etc.... And designed to work inside a metal vehicle.... |
FM antenna curiosity
"Richard Clark" "Phil Allison" ** Hearing the same FM station at more than one spot is still possible even in a very crappy receiver. ** Not by any method you alluded to - ****wit. It has already been said. ** But not in any detail - ****wit. No surprise a radio ham ****head like YOU deleted all the facts. Pure embarrassment to a know nothing turds like radio hams. ..... Phil |
FM antenna curiosity
"Joerg" wrote in message ... amdx wrote: "Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg This morning I got on the boat and the signal that was improved to good by shortening the antenna is now bad. 94.5 has interference from 101.1. Oh well! Mike |
FM antenna curiosity
amdx wrote:
"Joerg" wrote in message ... amdx wrote: "Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg This morning I got on the boat and the signal that was improved to good by shortening the antenna is now bad. 94.5 has interference from 101.1. Oh well! You really need a better quality radio and with radios and a lot of other stuff older = better :-) I mean, considering what the boat must have cost ... -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |
FM antenna curiosity
amdx wrote:
"Richard Clark" wrote in message ... On Fri, 19 Mar 2010 17:42:15 -0500, "amdx" wrote: Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike Hi Mike, Normally, a too strong signal is not a problem with FM as FM literally locks onto the strongest signal and rejects the competitors. This is not a characteristic of the RF wave, but rather the modulation employed. Collapsing your antenna is the same thing as moving it. Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). A simple test is to tune into at least two of these off-frequency stations, note what frequency they should be and subtract the frequency where they appear. If you are having image issues (no, this is not a self-help hint), the two or more stations should come up with the same differences. If you come up with the same number, AND you have trouble with interference from adjacent stations (there are guard bands to prevent this), THEN you have one crappy receiver. 73's Richard Clark, KB7QHC The receiver is an undercounter mounting Sony AM/FM, radio with CD. Nothing great, but Sony ususally does a fair job. Mike I have learned not to trust any radio that's newer than 30 years, whether name-brand or not. And that's from experience. Unless it is from companies like Icom. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |
FM antenna curiosity
TerryKing wrote:
The usual solution on boats: Use a decent car radio.. Well shielded, expects outdoor antenna. Runs on 12Volts... Can be had with CD player, separate input for your Ipod etc.., good audio power to speakers etc.... And designed to work inside a metal vehicle.... Best of all, it can be bolted down. That's really important on a boat. However, many newer car radios (newer as in "last 20-30 years") don't have very good tuners. Best to get one from the era of Ge-transistors, those radios were usually good. Better yet, get an Icom, Yeasu or whatever comms receiver. Most have a WFM setting. Ok, no stereo sound but one can easily listen to NOAA radio, ship-to-shore channels and so on. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |
FM antenna curiosity
Joerg wrote: amdx wrote: "Joerg" wrote in message ... amdx wrote: "Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg This morning I got on the boat and the signal that was improved to good by shortening the antenna is now bad. 94.5 has interference from 101.1. Oh well! You really need a better quality radio and with radios and a lot of other stuff older = better :-) I mean, considering what the boat must have cost ... Or a tuned trap to reduce the signal from that one station. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' |
FM antenna curiosity
On Mar 20, 8:26*am, Szczepan Białek wrote:
*"Phil Allison" ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). *If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. *The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. *This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** *Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - *if the signal is very strong. * The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxemburg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz *- *so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. S* all antennas are dipoles, you just can't always see the other half. and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. |
FM antenna curiosity
"Dave" all antennas are dipoles, you just can't always see the other half. and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. ** ROTFL !! Dave should be writing scripts for Mickey Mouse cartoons. Cos he has the IQ of Daffy Duck. .... Phil |
FM antenna curiosity
On Mar 21, 11:34*am, "Phil Allison" wrote:
"Dave" all antennas are dipoles, you just can't always see the other half. and Luxembourg *has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. ** ROTFL *!! Dave should be writing scripts for Mickey Mouse cartoons. Cos he has the IQ of Daffy Duck. ... * Phil just trying to put it on S.B.'s level of understanding. |
FM antenna curiosity
"Dave" wrote ... On Mar 20, 8:26 am, Szczepan Białek wrote: "Phil Allison" ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxembourg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. all antennas are dipoles, you just can't always see the other half. If I can't see the other half it is the monopole. So I repeat my question: Are now the FM stations which use the dipoles? and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. The dipoles have the directional pattern like this: http://www-antenna.ee.titech.ac.jp/~...ole/index.html It looks like the interference of the many sources (dipoles have the two). The two sources not in phase double the frequencies. S* |
FM antenna curiosity
On Mar 21, 11:42*am, Szczepan Białek wrote:
"Dave" ... On Mar 20, 8:26 am, Szczepan Bia ek wrote: "Phil Allison" ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that).. ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxembourg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. all antennas are dipoles, you just can't always see the other half. If I can't see the other half it is the monopole. So I repeat my question: Are now the FM stations which use the dipoles? and Luxembourg *has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. The dipoles have the directional pattern like this:http://www-antenna.ee.titech.ac.jp/~...ole/index.html It looks like the interference of the many sources (dipoles have the two).. The two sources not in phase double the frequencies. S* so why when i switch my transmitter from a 'monopole' where YOU can't see the other half to a dipole does the frequency stay the same? |
FM antenna curiosity
"Dave" wrote ... On Mar 21, 11:42 am, Szczepan Białek wrote: "Dave" ... On Mar 20, 8:26 am, Szczepan Bia ek wrote: "Phil Allison" ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxembourg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. all antennas are dipoles, you just can't always see the other half. If I can't see the other half it is the monopole. So I repeat my question: Are now the FM stations which use the dipoles? and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. The dipoles have the directional pattern like this:http://www-antenna.ee.titech.ac.jp/~...ole/index.html It looks like the interference of the many sources (dipoles have the two). The two sources not in phase double the frequencies. S* so why when i switch my transmitter from a 'monopole' where YOU can't see the other half to a dipole does the frequency stay the same? Your transmitter has the same but in the receiver antenna is possibility that appear the doubled frequency. Luxembourg effect was observed in 1930. Now radio people manage with eliminating it. S* |
FM antenna curiosity
On Sat, 20 Mar 2010 09:26:04 +0100, Szczepan Bia?ek
wrote: It sound like the "Luxemburg Effect". The signal was from the dipole antenna. The Luxemburg effect is usually contributed to the suspected Radio Luxemburg intermodulation products caused by the _ionosphere_ nonlinearities. Similar intermodulation effects can be obtained by the nonlinearities caused by rusty bolts in a transmitter tower. |
FM antenna curiosity
On Mar 21, 12:11*pm, Szczepan Białek wrote:
*"Dave" ... On Mar 21, 11:42 am, Szczepan Bia ek wrote: "Dave" ... On Mar 20, 8:26 am, Szczepan Bia ek wrote: "Phil Allison" ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxembourg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver.. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. all antennas are dipoles, you just can't always see the other half. If I can't see the other half it is the monopole. So I repeat my question: Are now the FM stations which use the dipoles? and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. The dipoles have the directional pattern like this:http://www-antenna.ee.titech.ac.jp/~...le/index..html It looks like the interference of the many sources (dipoles have the two). The two sources not in phase double the frequencies. S* so why when i switch my transmitter from a 'monopole' where YOU can't see the other half to a dipole does the frequency stay the same? Your transmitter has the same but in the receiver antenna is possibility that appear the doubled frequency. Luxembourg effect was observed in 1930. Now radio people manage with eliminating it. S* nope, the receiver still hears the proper transmitted frequency. |
FM antenna curiosity
Szczepan Białek wrote:
"Dave" wrote ... On Mar 20, 8:26 am, Szczepan Białek wrote: "Phil Allison" ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxembourg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. all antennas are dipoles, you just can't always see the other half. If I can't see the other half it is the monopole. So I repeat my question: Are now the FM stations which use the dipoles? You significant lack of understanding of dipoles is causing you to ask silly questions that are meaningless. and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. The dipoles have the directional pattern like this: http://www-antenna.ee.titech.ac.jp/~...ole/index.html This shows effects over a 48:1 frequency range. The FM band represents a 1.23:1 range. The image has no bearing on the topic at hand. It looks like the interference of the many sources (dipoles have the two). The two sources not in phase double the frequencies. This is completely wrong. In a _linear_ systems adding two signals cannot create new frequencies, including doubling. In the frequency domain this is clear. If you look in the time domain and look at zero crossings you may be confused. Do the math for the addition of two sine waves of different phase. Stop relying on internet images you don't understand and may not have any relevance to the discussion. You can do the math in the time domain, or frequency domain. Either should tell you there is no doubling of frequencies. In order to generate new frequencies you need to have a non-linear effect. Addition is NOT a non-linear operation. S* |
FM antenna curiosity
Szczepan Białek wrote:
"Dave" wrote ... On Mar 21, 11:42 am, Szczepan Białek wrote: "Dave" ... On Mar 20, 8:26 am, Szczepan Bia ek wrote: "Phil Allison" ... "Richard Clark" Now, as to your experience of receiving signals on the wrong frequency, that is a classic situation of image rejection being poor due to the lack of a tuned front-end (something that dissappeared with the dinosaurs). If I were to guess on the basis of 40 year old experience fixing these suckers, your off-frequency signals are probably shifted by twice the IF frequency of your receiver. The classical FM IF frequency of 10.7 MHz might apply, but time has marched on and designers may select their own. This old standard would argue that you shouldn't experience images except where they would be out-of-band (the 88-107 band with this IF would force that). ** Hearing the same FM station at more than one spot is still possible even with a 10.7 MHz IF frequency - if the signal is very strong. The reason is harmonics of the incoming carrier generated in the RF stage interacting with harmonics of the local oscillator in the mixer. It sound like the "Luxembourg Effect". The signal was from the dipole antenna. Are now the FM stations which use the dipoles? Eg: A 100MHz FM carrier generates a harmonic at 200MHz in the receiver. When the local oscillator is adjusted to 94.65 MHz, its second harmonic is 189.3 MHz. The difference frequency is then 10.7 MHz - so goes through to the FM detector. In this situation, the FM deviation is doubled so the recovered audio will be distorted on loud passages. all antennas are dipoles, you just can't always see the other half. If I can't see the other half it is the monopole. So I repeat my question: Are now the FM stations which use the dipoles? and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. The dipoles have the directional pattern like this:http://www-antenna.ee.titech.ac.jp/~...ole/index.html It looks like the interference of the many sources (dipoles have the two). The two sources not in phase double the frequencies. S* so why when i switch my transmitter from a 'monopole' where YOU can't see the other half to a dipole does the frequency stay the same? Your transmitter has the same but in the receiver antenna is possibility that appear the doubled frequency. Luxembourg effect was observed in 1930. Now radio people manage with eliminating it. I doubt that ionization in the atmosphere has anything to do with what is being observed. However, overloading or cross modulation in the receiver is much more likely. S* |
FM antenna curiosity
Michael A. Terrell wrote:
Joerg wrote: amdx wrote: "Joerg" wrote in message ... amdx wrote: "Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg This morning I got on the boat and the signal that was improved to good by shortening the antenna is now bad. 94.5 has interference from 101.1. Oh well! You really need a better quality radio and with radios and a lot of other stuff older = better :-) I mean, considering what the boat must have cost ... Or a tuned trap to reduce the signal from that one station. Well, that's what I suggested above, notch = trap :-) But it's tough and can be impossible if there are useful weaker stations near the one you want to muffle. In Europe they had a pager service right at the lower end of the FM band. Whichever committee signed off on that one should be dunked into a moat for gross incompetence, until they either learn or quit their career. Anyhow, the inevitable happened, and despite being a school kid I predicted that: A barrage of complaints by FM listeners. In Germany they pay a radio tax so that makes them sort of constituents with rights. Long story short the governement had to furnish rather expensive notch filters to anyone who complained. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |
FM antenna curiosity
"joe" wrote ... Szczepan Białek wrote: So I repeat my question: Are now the FM stations which use the dipoles? You significant lack of understanding of dipoles is causing you to ask silly questions that are meaningless. and Luxembourg has nothing to do with it, your silly frequency doubling notions should be packaged up in art's box and never see the light of day. The dipoles have the directional pattern like this: http://www-antenna.ee.titech.ac.jp/~...ole/index.html This shows effects over a 48:1 frequency range. The FM band represents a 1.23:1 range. The image has no bearing on the topic at hand. It looks like the interference of the many sources (dipoles have the two). The two sources not in phase double the frequencies. This is completely wrong. In a _linear_ systems adding two signals cannot create new frequencies, including doubling. In the frequency domain this is clear. If you look in the time domain and look at zero crossings you may be confused. Do the math for the addition of two sine waves of different phase. In reality no sine waves. In the ends of a dipole the voltage is doubled (VSWR) and the strong picks are radiated. Stop relying on internet images you don't understand and may not have any relevance to the discussion. Discussion is on the harmonics. The dipoles can produce the frequency doubling. You can do the math in the time domain, or frequency domain. Either should tell you there is no doubling of frequencies. In the school math the water waves are transversal. Look as they are like: http://en.wikipedia.org/wiki/Stokes_drift In order to generate new frequencies you need to have a non-linear effect. Addition is NOT a non-linear operation. The two picks from the ends of the dipole are not linear. S* S* |
FM antenna curiosity
"Paul Keinanen" wrote ... On Sat, 20 Mar 2010 09:26:04 +0100, Szczepan Bia?ek wrote: It sound like the "Luxemburg Effect". The signal was from the dipole antenna. The Luxemburg effect is usually contributed to the suspected Radio Luxemburg intermodulation products caused by the _ionosphere_ nonlinearities. Are such products the hours independent? Is ionosphere all time the same. The dipole on the tip top of the mountain (the both end of the dipole were :seen") produced the doubled frequency. Similar intermodulation effects can be obtained by the nonlinearities caused by rusty bolts in a transmitter tower. The same was obtained in Warsaw tower (collapsed years ago). Now Warsaw use monopole. S* |
FM antenna curiosity
Joerg wrote: Michael A. Terrell wrote: Joerg wrote: amdx wrote: "Joerg" wrote in message ... amdx wrote: "Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg This morning I got on the boat and the signal that was improved to good by shortening the antenna is now bad. 94.5 has interference from 101.1. Oh well! You really need a better quality radio and with radios and a lot of other stuff older = better :-) I mean, considering what the boat must have cost ... Or a tuned trap to reduce the signal from that one station. Well, that's what I suggested above, notch = trap :-) But it's tough and can be impossible if there are useful weaker stations near the one you want to muffle. In Europe they had a pager service right at the lower end of the FM band. Whichever committee signed off on that one should be dunked into a moat for gross incompetence, until they either learn or quit their career. Anyhow, the inevitable happened, and despite being a school kid I predicted that: A barrage of complaints by FM listeners. In Germany they pay a radio tax so that makes them sort of constituents with rights. Long story short the governement had to furnish rather expensive notch filters to anyone who complained. So you move the trap slightly to one side. A good trap can be narrow enough to only affect one or two channels if it is built with the right components, but it isn't cheap. Glass piston capacitors and glass inductors are temperature stable and have a very high 'Q'. -- Lead free solder is Belgium's version of 'Hold my beer and watch this!' |
FM antenna curiosity
Szczepan Białek wrote:
"joe" wrote ... This is completely wrong. In a _linear_ systems adding two signals cannot create new frequencies, including doubling. In the frequency domain this is clear. If you look in the time domain and look at zero crossings you may be confused. Do the math for the addition of two sine waves of different phase. In reality no sine waves. The you had better learn what Fourier analysis is all about. In the ends of a dipole the voltage is doubled (VSWR) and the strong picks are radiated. Stop relying on internet images you don't understand and may not have any relevance to the discussion. Discussion is on the harmonics. The dipoles can produce the frequency doubling. If that were true radio communications would be much more of a mess than it currently is. You don't understand antennas and need to start learning. You can do the math in the time domain, or frequency domain. Either should tell you there is no doubling of frequencies. In the school math the water waves are transversal. Look as they are like: http://en.wikipedia.org/wiki/Stokes_drift In order to generate new frequencies you need to have a non-linear effect. Addition is NOT a non-linear operation. The two picks from the ends of the dipole are not linear. How would you go about proving that? S* S* |
FM antenna curiosity
joe wrote:
Szczepan Białek wrote: Joe, he's either a troll or an idiot. It matters little which. Reasoning with him is fruitless, and he lives in a world where he makes up his own facts, similar to Art, so facts won't work either. He's been trolling here off and on for a few months. Most of his posts run on about the same couple themes. tom K0TAR |
FM antenna curiosity
In article ,
"amdx" wrote: I have an FM radio inside an aluminum boat. The radio worked ok with the AC cord as the antenna but I got interference when I used my laptop. I found the circuit that ran from the power transformer to the antenna input on the FM IC. I installed a connector that is used on car radios and wired the center pin to the foil that went to the FM IC (capacitor on pcb isolated) and the shield side to dc ground near the IC. I then plugged in a telescoping car antenna and it worked great on the bench . So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. BTW, the mod did cure the computer hash. Mike It's probably a severe impedance mismatch between your new antenna and the old pickup coil. You might need to create a little step-up transformer between the board and jack. I looked at a few FM chip specs and they leave it up to the designer to figure out the right input transformer. You'll probably need trial and error to figure it out. -- I won't see Google Groups replies because I must filter them as spam |
FM antenna curiosity
"Dave" wrote ... On Mar 21, 12:11 pm, Szczepan Białek wrote: The dipoles have the directional pattern like this:http://www-antenna.ee.titech.ac.jp/~...ole/index.html It looks like the interference of the many sources (dipoles have the two). The two sources not in phase double the frequencies. S* so why when i switch my transmitter from a 'monopole' where YOU can't see the other half to a dipole does the frequency stay the same? Your transmitter has the same but in the receiver antenna is possibility that appear the doubled frequency. Luxembourg effect was observed in 1930. Now radio people manage with eliminating it. S* nope, the receiver still hears the proper transmitted frequency. Yes. THY receiver is tuned to the transmitted frequency. Luxembourg effect means that another receiver tuned to the doubled your frequency hears you. S* |
FM antenna curiosity
"joe" wrote ... Szczepan Białek wrote: "joe" wrote ... This is completely wrong. In a _linear_ systems adding two signals cannot create new frequencies, including doubling. In the frequency domain this is clear. If you look in the time domain and look at zero crossings you may be confused. Do the math for the addition of two sine waves of different phase. In reality no sine waves. The you had better learn what Fourier analysis is all about. Real waves are not symetrical. They are like the solitons: http://paws.kettering.edu/~drussell/.../solitons.html In the ends of a dipole the voltage is doubled (VSWR) and the strong picks are radiated. Stop relying on internet images you don't understand and may not have any relevance to the discussion. Discussion is on the harmonics. The dipoles can produce the frequency doubling. If that were true radio communications would be much more of a mess than it currently is. The mess was in 1930. Remedy was applied. You don't understand antennas and need to start learning. I started year ago. You can do the math in the time domain, or frequency domain. Either should tell you there is no doubling of frequencies. In the school math the water waves are transversal. Look as they are like: http://en.wikipedia.org/wiki/Stokes_drift In order to generate new frequencies you need to have a non-linear effect. Addition is NOT a non-linear operation. The two picks from the ends of the dipole are not linear. How would you go about proving that? I am not able to measure the shape of the picks. You all can. You can also check the "addition of two" picks (solitons). S* |
FM antenna curiosity
Luxembourg effect was observed in 1930. Now radio people manage with eliminating it. S* nope, the receiver still hears the proper transmitted frequency. Yes. THY receiver is tuned to the transmitted frequency. Luxembourg effect means that another receiver tuned to the doubled your frequency hears you. Perhaps you should read up on what the Luxembourg Effect actually was!! It had nothing to do with antennas!! It was Cross Modulation in the ionosphere between Radio Luxenbourg and other radio stations, where by the modulation of Radio Luxenbourg was heard superimposed onto the second station. Jeff |
FM antenna curiosity
Michael A. Terrell wrote:
Joerg wrote: Michael A. Terrell wrote: Joerg wrote: amdx wrote: "Joerg" wrote in message ... amdx wrote: "Richard Clark" wrote in message ... On Fri, 19 Mar 2010 15:22:42 -0500, "amdx" wrote: So I installed the antenna on the outside of the boat and the radio inside, now one station I listen to is weak, but if I unplug the antenna and let the center pin touch ground of the connector on the radio it comes in great. Just curious why it is working this way. Hi Mike, You moved the antenna. Most loss of signal as you describe comes from not being a weak signal, but the mixture of signals that combine negatively at some spot due to multiple reflections. When you replaced the line cord as antenna for this better implementation, you also found that "sour (not sweet) spot." This can occur for any frequency with the equal likelihood of reflections combining negatively. Move your antenna a quarter wave and see what happens. Your description of your having an aluminum boat almost guarantees a multitude of RF-bright reflections. At short wavelengths, this also guarantees many, many regions that will exhibit destructive (as well as constructive) combinations of those reflections. Put your antenna as far away from the superstructure or hull as possible. This will reduce the reflection path differences. BTW, the mod did cure the computer hash. Mike FM has what is called a "full quieting" effect. It would suggest that your first signal levels were just barely above the level of full quiet (and perhaps not even that good). 73's Richard Clark, KB7QHC Richard, after I read your letter I did a little better checking and found my signal is not weak it is to strong, I'm getting interference from other frequencies. Also I get stations on the wrong frequency. I went out and collapsed the antenna to minimum about 1/3 of what it was and my problem station is perfect and the other station I listen to is still good. The local NPR station isn't good though. But I can download the podcast of Science Friday :-) Thanks, Mike The usual, lousy FM tuner. They don't make'em like they used to. It's the same with television sets, one large signal and they fall off the rocker. If you have a radio with a signal strength meter you could notch out a strong station. But that only works it it's just one and far away from the NPR frequency. The only other options are to get a better radio, a directional antenna, or just live with it and use the podcast. -- Regards, Joerg This morning I got on the boat and the signal that was improved to good by shortening the antenna is now bad. 94.5 has interference from 101.1. Oh well! You really need a better quality radio and with radios and a lot of other stuff older = better :-) I mean, considering what the boat must have cost ... Or a tuned trap to reduce the signal from that one station. Well, that's what I suggested above, notch = trap :-) But it's tough and can be impossible if there are useful weaker stations near the one you want to muffle. In Europe they had a pager service right at the lower end of the FM band. Whichever committee signed off on that one should be dunked into a moat for gross incompetence, until they either learn or quit their career. Anyhow, the inevitable happened, and despite being a school kid I predicted that: A barrage of complaints by FM listeners. In Germany they pay a radio tax so that makes them sort of constituents with rights. Long story short the governement had to furnish rather expensive notch filters to anyone who complained. So you move the trap slightly to one side. A good trap can be narrow enough to only affect one or two channels if it is built with the right components, but it isn't cheap. ... ^^^^^^^^^^^^^^^^^^ Bingo! ... Glass piston capacitors and glass inductors are temperature stable and have a very high 'Q'. I just hope someone was read the riot act for making that frequency allocation. I mean, that allocation was really borderline daft ;-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM. |
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