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#1
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Frank wrote:
Hi all Let me preamble this by saying I am new at this, and need your help. But I am a quick learner! I have a few specific questions and perhaps you can help. I am trying to troubleshoot a Fm static problem 1) Is the car coax cable lead one or two wires? I am quite sure it is two (one outer (the ground) and one inner wire) but I'll ask to confirm "Coax" is short for "coaxial conductor", i.e. two conductor one outer one inner. 2) Should a "in-glass" rear winshield antenna be grounded to the car's body? If so, from which end of the coax cable? (see Q 3) That depends on the antenna, but if yes it would almost certainly be the outer conductor. If the antenna has two symmetrical conductors then it should either have a balun (which would be a little gizmo, probably cubical) between the coax and the antenna. 3) Does the expression "grounding the antena" (in the case of a glass mounted antenna) be as simple as soldering a grounding wire from the outside coax lead end that plugs into the HU to a metal ground of the car? Or should it be done closer to the actual antena? SUch as at the junction of the end of the coax and where the antenna starts... "HU"? Yes, grounding in a car means to the car body. Here is more detail on my problem if this helps: inconsistent FM reception ( static) with in-glass antenna where I use to get crystal clear reception with old car. However, there is a twist to my problem: I noticed that the coax cable (inner cable) from the HU is not truly connected to the antenna even if it looks like it is. I tested it with a continuity tester and it is not. When I try to connect the inner coax wire directly to the antenna (using a wire and soldering), then I can test it and it is well connected. In other words, the inner wire of the coax makes a continuous circuit from the HU's to the end of the antenna. Yet, I still get some static on some FM station (which is not induced by the engine or the car's electrical systems). Any suggestion? It is an RSX 2004 (Acura). I changed the HU twice (two models) and the problem persists (same issue with the OEM) TIA It may just be a crappy antenna. If you were really determined you could try a mag-mount external antenna just to see. If it were a symmetrical antenna I'd build a balun for it (actually I'd probably _think_ about building a balun for it any time I drove it, but wouldn't get around to it for years). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com |
#2
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![]() "Tim Wescott" wrote in message ... Frank wrote: Hi all Let me preamble this by saying I am new at this, and need your help. But I am a quick learner! I have a few specific questions and perhaps you can help. I am trying to troubleshoot a Fm static problem 1) Is the car coax cable lead one or two wires? I am quite sure it is two (one outer (the ground) and one inner wire) but I'll ask to confirm "Coax" is short for "coaxial conductor", i.e. two conductor one outer one inner. 2) Should a "in-glass" rear winshield antenna be grounded to the car's body? If so, from which end of the coax cable? (see Q 3) That depends on the antenna, but if yes it would almost certainly be the outer conductor. If the antenna has two symmetrical conductors then it should either have a balun (which would be a little gizmo, probably cubical) between the coax and the antenna. 3) Does the expression "grounding the antena" (in the case of a glass mounted antenna) be as simple as soldering a grounding wire from the outside coax lead end that plugs into the HU to a metal ground of the car? Or should it be done closer to the actual antena? SUch as at the junction of the end of the coax and where the antenna starts... "HU"? Yes, grounding in a car means to the car body. Here is more detail on my problem if this helps: inconsistent FM reception ( static) with in-glass antenna where I use to get crystal clear reception with old car. However, there is a twist to my problem: I noticed that the coax cable (inner cable) from the HU is not truly connected to the antenna even if it looks like it is. I tested it with a continuity tester and it is not. When I try to connect the inner coax wire directly to the antenna (using a wire and soldering), then I can test it and it is well connected. In other words, the inner wire of the coax makes a continuous circuit from the HU's to the end of the antenna. Yet, I still get some static on some FM station (which is not induced by the engine or the car's electrical systems). Any suggestion? It is an RSX 2004 (Acura). I changed the HU twice (two models) and the problem persists (same issue with the OEM) TIA It may just be a crappy antenna. If you were really determined you could try a mag-mount external antenna just to see. If it were a symmetrical antenna I'd build a balun for it (actually I'd probably _think_ about building a balun for it any time I drove it, but wouldn't get around to it for years). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com You have both overlooked the fact that the antenna is also most probably the heating element of the heated (rear?) window. If this is the case then there has to be a d.c. block for the antenna and something to stop the supply cable shorting out the signal. This is usually as small (often cylindrical) device somewhere near and within a short distance of the window connections. If this is faulty it is most likely the cause. The other question - if it is the heating element then does it completely work? Elements often get minute breaks in them: if the element only partly works then the working part is all you have for an aerial and so you may be suffering from lack of signal. The most important point however is the nature of the signal/interference. Is it lack of signal - which will give fading and hiss on FM - or is it crackle being produced by the vehicle? If the latter, make sure the earth bonding is good between battery, engine, and chassis. Also make sure it has the right type of spark plugs - most vehicles these days use the type that have a resistor inside them and that is singularly the most effective way of cutting spark interference. Finally make sure the radio earth is good. If the aerial is disconnected does the radio still work? It is not uncommon for the earth in the main harness to fail and the radio to be earthed through the aerial - which means there will be impedence (i.e. signal resistance) in the supply route which will definitely cause crackle. -- Woody harrogate2 at ntlworld dot com |
#3
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Frank wrote:
2) Should a "in-glass" rear winshield antenna be grounded to the car's body? If so, from which end of the coax cable? (see Q 3) Grounding an antenna completely defeats its purpose. Is this also part of a defrosting heating element or such? 3) Does the expression "grounding the antena" (in the case of a glass mounted antenna) be as simple as soldering a grounding wire from the outside coax lead end that plugs into the HU to a metal ground of the car? Or should it be done closer to the actual antena? SUch as at the junction of the end of the coax and where the antenna starts... The expression "grounding the antenna" is nonsense in the absense of better colatteral information. If it is just an antenna (and not part of a heater or something) then "grounding the antenna" sounds stupid. What/who/why is "HU"? If this is a part of the circuit you are working on, you need to reveal the entire situation. Otherwise, you will get misleading responses based on guessing from thousands of miles away. Here is more detail on my problem if this helps: inconsistent FM reception ( static) with in-glass antenna where I use to get crystal clear reception with old car. In-glass antennas have never been noted for their good performance. They are only popular because they are easier for the auto manufacturers (and car washes). Many people add a proper antenna after-market when they are stuck with these things. However, there is a twist to my problem: I noticed that the coax cable (inner cable) from the HU is not truly connected to the antenna even if it looks like it is. I tested it with a continuity tester and it is not. If "HU" means Heating Unit or something, it seems likely that the antenna lead is connected via a capacitor. The cap would conduct RF voltage while appearing to be an open circuit at DC (which is what your meter is using.) |
#4
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HU is head unit, or radio
"Richard Crowley" wrote in message ... Frank wrote: 2) Should a "in-glass" rear winshield antenna be grounded to the car's body? If so, from which end of the coax cable? (see Q 3) Grounding an antenna completely defeats its purpose. Is this also part of a defrosting heating element or such? 3) Does the expression "grounding the antena" (in the case of a glass mounted antenna) be as simple as soldering a grounding wire from the outside coax lead end that plugs into the HU to a metal ground of the car? Or should it be done closer to the actual antena? SUch as at the junction of the end of the coax and where the antenna starts... The expression "grounding the antenna" is nonsense in the absense of better colatteral information. If it is just an antenna (and not part of a heater or something) then "grounding the antenna" sounds stupid. What/who/why is "HU"? If this is a part of the circuit you are working on, you need to reveal the entire situation. Otherwise, you will get misleading responses based on guessing from thousands of miles away. Here is more detail on my problem if this helps: inconsistent FM reception ( static) with in-glass antenna where I use to get crystal clear reception with old car. In-glass antennas have never been noted for their good performance. They are only popular because they are easier for the auto manufacturers (and car washes). Many people add a proper antenna after-market when they are stuck with these things. However, there is a twist to my problem: I noticed that the coax cable (inner cable) from the HU is not truly connected to the antenna even if it looks like it is. I tested it with a continuity tester and it is not. If "HU" means Heating Unit or something, it seems likely that the antenna lead is connected via a capacitor. The cap would conduct RF voltage while appearing to be an open circuit at DC (which is what your meter is using.) |
#5
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Thanks to all who replied
yes I should have been more precise: HU = Head unit (or radio) Sorry "Richard Crowley" wrote in message ... Frank wrote: 2) Should a "in-glass" rear winshield antenna be grounded to the car's body? If so, from which end of the coax cable? (see Q 3) Grounding an antenna completely defeats its purpose. Is this also part of a defrosting heating element or such? 3) Does the expression "grounding the antena" (in the case of a glass mounted antenna) be as simple as soldering a grounding wire from the outside coax lead end that plugs into the HU to a metal ground of the car? Or should it be done closer to the actual antena? SUch as at the junction of the end of the coax and where the antenna starts... The expression "grounding the antenna" is nonsense in the absense of better colatteral information. If it is just an antenna (and not part of a heater or something) then "grounding the antenna" sounds stupid. What/who/why is "HU"? If this is a part of the circuit you are working on, you need to reveal the entire situation. Otherwise, you will get misleading responses based on guessing from thousands of miles away. Here is more detail on my problem if this helps: inconsistent FM reception ( static) with in-glass antenna where I use to get crystal clear reception with old car. In-glass antennas have never been noted for their good performance. They are only popular because they are easier for the auto manufacturers (and car washes). Many people add a proper antenna after-market when they are stuck with these things. However, there is a twist to my problem: I noticed that the coax cable (inner cable) from the HU is not truly connected to the antenna even if it looks like it is. I tested it with a continuity tester and it is not. If "HU" means Heating Unit or something, it seems likely that the antenna lead is connected via a capacitor. The cap would conduct RF voltage while appearing to be an open circuit at DC (which is what your meter is using.) |
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