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The following page was printed from RemoteCentral.com:
What sort of AM antenna to use?
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Topic: | What sort of AM antenna to use? This thread has 19 replies. Displaying posts 1 through 15. |
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Post 1 made on Wednesday November 10, 2004 at 10:03 |
Theaterworks Founding Member |
Joined: Posts: | April 2002 1,898 |
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I've been encountering more and more customers who ask why their AM tuning is poor. Used to be that this did not matter at all, to anyone. Now, in the last year, the worm has turned.
We've been using the loop antenna supplied with our Marantz and B&K receivers. The performance is poor at best. I'm working on the untested assumption that the tuners are OK, and at least as good as the clock radios and car radios my customers use as examples of how the signal should be there. Given that my trading area is Chicago, many of these systems are located in basements below grade. Even on the first floor, tuning can still be a problem.
Is there a way to install an AM antenna in the attic or on the roof? Is there a correct way to prewire for it? We've usually got an extra RG-6 going to the top of the house that could be used, but what might I hang on the end of it?
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Carpe diem! |
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Post 2 made on Wednesday November 10, 2004 at 10:50 |
mr2channel Select Member |
Joined: Posts: | August 2002 1,701 |
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On 11/10/04 15:03 ET, Theaterworks said...
We've been using the loop antenna supplied with our Marantz and B&K receivers. The performance is poor at best. I'm working on the untested assumption that the tuners are OK, and at least as good as the clock radios and car radios ...
I would say that not all tuners are created equal, and that car tuners would be better, since they are used more often than the one that is in most A/V components, and as far as a clock radio goes, I would also say you have a better chance of the tuner also being better, since it is most often used to wake up to. Is there a way to install an AM antenna in the attic or on the roof? Is there a correct way to prewire for it? We've usually got an extra RG-6 going to the top of the house that could be used, but what might I hang on the end of it? RG-6 is fine, but you have to remember that AM is Amplitude Modulated NOT Frequency Modulated, so since the earth is not flat you will lose your ablity to pick up the station sooner than with Frequency Modulation (FM). The "loop" antenna for AM reception is the only way I am aware of to receive AM reception, but the size and direction of the loop will affect reception, as well as the quality of the tuner. I know Terk make a specific AM antenna a while back, it seemed to be OK as far as perfomance but I would say it was not suited for use in an attic, and definantly not an outdoors unit. I would contact Weingard an antenna manufacture , as they have in my opinion made some of the best FM antennas as well as off air NTSC and ATSC antennas. Oh yeah don't forget that ground wire...
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What part of "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." do you not understand? |
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Post 3 made on Wednesday November 10, 2004 at 11:15 |
Impaqt RC Moderator |
Joined: Posts: | October 2002 6,233 |
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Get the C-Crane Justice Am Antenna. C-Crane makes the Terk loop that works prety well, but the Justice is a powered tunable AM antenna that rocks.... [Link: ccrane.com]
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Post 4 made on Wednesday November 10, 2004 at 12:14 |
avintegrator Long Time Member |
Joined: Posts: | March 2003 348 |
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I agree with the crane antenna it works great
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Post 5 made on Wednesday November 10, 2004 at 12:16 |
mr2channel Select Member |
Joined: Posts: | August 2002 1,701 |
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On 11/10/04 16:15 ET, Impaqt said...
Get the C-Crane Justice Am Antenna. C-Crane makes the Terk loop that works prety well, but the Justice is a powered tunable AM antenna that rocks.... [Link: ccrane.com]you learn something new everyday...I love this site thanks Impaqt
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What part of "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." do you not understand? |
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Post 6 made on Wednesday November 10, 2004 at 12:32 |
Ernie Bornn-Gilman Yes, That Ernie! |
Joined: Posts: | December 2001 30,104 |
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I just finished reading this. I should have just said "don't get me started." I didn't. I started out in this industry as a hobbyist listening to AM radio...used to get, in Southern California, KOA in Denver, KOB in Albuquerque, sometimes WLS in Chicago, occasionally WWL in New Orleans.... On 11/10/04 15:50 ET, mr2channel said...
I would say that not all tuners are created equal, Right. When I started in HiFi in 1970, I got the impression that once manufacturers could put high fidelity FM tuners into their products, they decided to only spend about a buck twenty on an AM tuner. After all, there is no way it can be hifi (in this modern profit-driven world)! Unless you buy one that actually pushes its AM reception, the AM section is likely to be crap. and that car tuners would be better, since they are used more often than the one that is in most A/V components, OEM car tuners are better because they are designed to be used all across the country (see the section on distance below). I recently drove from northern Arizona to Los Angeles around four in the morning, and I was clearly receiving a station in Norman, OK while in Arizona. After that I switched to a San Francisco station. Most car HiFi radios have poor AM sections, just like home HiFi. Same principle. and as far as a clock radio goes, I would also say you have a better chance of the tuner also being better, since it is most often used to wake up to. This seems like a nice wish. You can wake up to FM and it sounds better, so there is no reason for a clock radio to have a good AM section. After all, loud static will wake you up, right? Are you saying you have found this to be true, or are you theorizing? RG-6 is fine, but you have to remember that AM is Amplitude Modulated NOT Frequency Modulated, so since the earth is not flat you will lose your ablity to pick up the station sooner than with Frequency Modulation (FM). Unfortunately, pure bunk. RG-6 is fine if your AM antenna has a 75 ohm output. RG-6 will work well with amplitude modulated signals. Analog TV signals have AM picture and FM sound. It is not the type of modulation, but the frequency, that determines the possible reception distance. At AM frequencies, there is a "ground wave" that hugs the earth, so reception is possible beyond where the curvature of the earth would eliminate it. FM, at 100 mHz, is line-of -sight. Transmitters on mountains can send FM signals (100 mHz signals, that is) more than a hundred miles, but 100 mHz. transmitters at ground level are limited to around 100 miles. AM signals go along the ground, attenuating as they spread. They also are radiated up into the air, and actually bounce off the ionosphere before returning to earth. There is a distance between where the ground wave is too weak and where the ionospheric bounce returns the signal to earth; in this range you cannot receive an AM (oops, I mean 1 mHz) signal. The ionosphere is calmer when the sun is not shining on it, making a better reflecting "surface," so 1 mHz reception is much better at night. The "loop" antenna for AM reception is the only way I am aware of to receive AM reception, but the size and direction of the loop will affect reception, as well as the quality of the tuner. Yeah, the old 1948 RCA consoloe I had as a teenager had a loop. About 12" wide, 30" high, and 2" thick. You had to orient it for best reception of each station...which is a drawback to this day with any AM reception (1 mHz, really). I once had an early 1930s Philco radio (it had a tube in it with a label saying that it had been installed as a replacement in 1935). This radio took one ground wire and one wire tossed out the window, or as long as you could get it. It did not work with a loop. Lops are not the only possible antenna type for 1 mHz recetpion. I know Terk make a specific AM antenna a while back, it seemed to be OK as far as performance but I would say it was not suited for use in an attic, and definitely is not an outdoors unit. It is the best AM antenna I have seen, and that is saying a lot since I have hated Terk for looking good but performing like junk since day One. In fact, I have one. You rotate it for best orientation each time you change stations, and there is a tuning knob that can peak the signal or "unpeak" an interfering signal. It is awesome but it does not lend itself to use in a customer's home unless they want ONE AM station or they are willing to mess with it all the time. This antenna does not even need to be connected: just place it near the radio's AM antenna and its internal resonating coil/capacitor system will aid the radio. I would contact Weingard, an antenna manufacturer, as they have in my opinion made some of the best FM antennas as well as off air NTSC and ATSC antennas. Oh yeah don't forget that ground wire... I don't think Winegard has anything to offer for AM, although you are RIGHT ON about their other products. Basically,an AM antenna needs two wires, similar to an FM one, but the frequency difference makes the rest of it dissimilar. You should use the loop that comes with the reciever, remembering you have to orient it to maximize a station you are listening for or minimize an interfering station. When you use the loop, the AM section of the radio is matched to a type of circuit it wants to see. You can then augment this by connecting one terminal to GROUND. I mean the earth, planet, dirt, wet sand, wormtown, whatever, not the closest electrical ground. Amplitude Modulation is exactly the type of signal put out by motors and fluorescent fixtures, so going to ground without going to the electrical fixture ground will be quieter. Then, put up a wire connected to the other AM antenna terminal. A long one. In fact, "long wire" is a technical name for a type of AM (oops, 1 mHz) antenna (google "long wire antenna")! Basically, run it out the window, up to the chimney, out to the tree, across to the neighbor's house...the longer it is, the better. Longer means more signal pickup, which means the fluorescent noise will fade more into the background. Longer also means less directional for some reason, so you don't have to worry about reorienting your sixty to one hundred foot antenna. Oh, yeah, and don't forget to keep this NOT connected to the ground.
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OP | Post 7 made on Wednesday November 10, 2004 at 13:40 |
Theaterworks Founding Member |
Joined: Posts: | April 2002 1,898 |
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To everyone; I've tried the C. Crane, with varying results. If the antenna happens to be in the basement, or near a noise source, it still is not perfect.
To Ernie: you need to send me an invoice for that response. Wow!
So, a follow-on question. Can I use the center conductor for an RG-6 going up to the attic, and then connect that to some uninsulated wire that would be laced back & forth through the attic to add up to 100+ feet? And send another wire out of the house to ground to the earth? Sounds like, from you description, that this would be the ticket.
I've also thought about making my own dual loop, using old 5 gal paint buckets. Wrap each with a loooong length of wire, orient them 90 degrees off from one another, and locate them in the attic. Would that work? Quicker than stapling up long wire runs after the house is complete.
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Carpe diem! |
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Post 8 made on Wednesday November 10, 2004 at 13:44 |
mr2channel Select Member |
Joined: Posts: | August 2002 1,701 |
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On 11/10/04 17:32 ET, Ernie Bornn-Gilman said...
I just finished reading this. I should have just said "don't get me started." I didn't.
I started out in this industry as a hobbyist listening to AM radio...used to get, in Southern California, KOA in Denver, KOB in Albuquerque, sometimes WLS in Chicago, occasionally WWL in New Orleans....
Right. When I started in HiFi in 1970, I got the impression that once manufacturers could put high fidelity FM tuners into their products, they decided to only spend about a buck twenty on an AM tuner. After all, there is no way it can be hifi (in this modern profit-driven world)! Unless you buy one that actually pushes its AM reception, the AM section is likely to be crap.
OEM car tuners are better because they are designed to be used all across the country (see the section on distance below). I recently drove from northern Arizona to Los Angeles around four in the morning, and I was clearly receiving a station in Norman, OK while in Arizona. After that I switched to a San Francisco station.
Most car HiFi radios have poor AM sections, just like home HiFi. Same principle.
This seems like a nice wish. You can wake up to FM and it sounds better, so there is no reason for a clock radio to have a good AM section. After all, loud static will wake you up, right?
Are you saying you have found this to be true, or are you theorizing?
Unfortunately, pure bunk. RG-6 is fine if your AM antenna has a 75 ohm output. RG-6 will work well with amplitude modulated signals. Analog TV signals have AM picture and FM sound. It is not the type of modulation, but the frequency, that determines the possible reception distance. At AM frequencies, there is a "ground wave" that hugs the earth, so reception is possible beyond where the curvature of the earth would eliminate it. FM, at 100 mHz, is line-of -sight. Transmitters on mountains can send FM signals (100 mHz signals, that is) more than a hundred miles, but 100 mHz. transmitters at ground level are limited to around 100 miles.
AM signals go along the ground, attenuating as they spread. They also are radiated up into the air, and actually bounce off the ionosphere before returning to earth. There is a distance between where the ground wave is too weak and where the ionospheric bounce returns the signal to earth; in this range you cannot receive an AM (oops, I mean 1 mHz) signal. The ionosphere is calmer when the sun is not shining on it, making a better reflecting "surface," so 1 mHz reception is much better at night.
Yeah, the old 1948 RCA consoloe I had as a teenager had a loop. About 12" wide, 30" high, and 2" thick. You had to orient it for best reception of each station...which is a drawback to this day with any AM reception (1 mHz, really).
I once had an early 1930s Philco radio (it had a tube in it with a label saying that it had been installed as a replacement in 1935). This radio took one ground wire and one wire tossed out the window, or as long as you could get it. It did not work with a loop. Lops are not the only possible antenna type for 1 mHz recetpion.
It is the best AM antenna I have seen, and that is saying a lot since I have hated Terk for looking good but performing like junk since day One.
In fact, I have one. You rotate it for best orientation each time you change stations, and there is a tuning knob that can peak the signal or "unpeak" an interfering signal. It is awesome but it does not lend itself to use in a customer's home unless they want ONE AM station or they are willing to mess with it all the time.
This antenna does not even need to be connected: just place it near the radio's AM antenna and its internal resonating coil/capacitor system will aid the radio.
I don't think Winegard has anything to offer for AM, although you are RIGHT ON about their other products.
Basically,an AM antenna needs two wires, similar to an FM one, but the frequency difference makes the rest of it dissimilar. You should use the loop that comes with the reciever, remembering you have to orient it to maximize a station you are listening for or minimize an interfering station.
When you use the loop, the AM section of the radio is matched to a type of circuit it wants to see. You can then augment this by connecting one terminal to GROUND. I mean the earth, planet, dirt, wet sand, wormtown, whatever, not the closest electrical ground. Amplitude Modulation is exactly the type of signal put out by motors and fluorescent fixtures, so going to ground without going to the electrical fixture ground will be quieter.
Then, put up a wire connected to the other AM antenna terminal. A long one. In fact, "long wire" is a technical name for a type of AM (oops, 1 mHz) antenna (google "long wire antenna")! Basically, run it out the window, up to the chimney, out to the tree, across to the neighbor's house...the longer it is, the better. Longer means more signal pickup, which means the fluorescent noise will fade more into the background. Longer also means less directional for some reason, so you don't have to worry about reorienting your sixty to one hundred foot antenna.
Oh, yeah, and don't forget to keep this NOT connected to the ground. good to know I know so little...and learn a little more. One question though Ernie if the antenna is not grounded (for better performance) how can you stay up to code (NEC) since all "antenna's" are required to be grounded?
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What part of "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." do you not understand? |
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Post 9 made on Wednesday November 10, 2004 at 14:40 |
hifiguru Long Time Member |
Joined: Posts: | October 2004 148 |
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Great info on AM reception. I wish more manufacturers would supply a quality AM section for us sports and talk radio junkies.
I have used thge C Crane antennas an had very good results. Also McIntosh built a very high performance AM section in their MX130 and MX132 PrePro's. I do not know how good the current generation is. A crucial part of these processors was the amplified remote AM antenna. If you can find one (McIntosh did not sell it seperatly) this makes the best AM antenna I have ever used.
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We are the people our parents warned us about |
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Post 10 made on Wednesday November 10, 2004 at 17:02 |
Impaqt RC Moderator |
Joined: Posts: | October 2002 6,233 |
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The tuning of the C-Crane stuff is a little annoying, but I've found that most people who use AM just deal with one station...... The people who have the Crane say the ext ra 10 seconds required to tune the antenna are worth it for the reception gain......
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Post 11 made on Wednesday November 10, 2004 at 19:41 |
FreddyFreeloader Super Member |
Joined: Posts: | April 2004 3,243 |
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I know that Radio Shack sells an AM loop kit for like $20. It gets "stapled around" in the attic, getting the loop away from the A/V gear. Speaker wire for prewire cause it's not shielded. I guess coak conld wotk as long there is an unshielded loop connected to it in the attic.
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Post 12 made on Wednesday November 10, 2004 at 20:43 |
Larry Fine Loyal Member |
Joined: Posts: | August 2001 5,002 |
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The coax is a fine lead-in cable. At the receiver, connect the shield to the same terminal as the external ground, and in the attic, make sure the shield is cut away carefully.
Keep in mind that the antenna doesn't "begin" until it emerges from the shield. Solder the joint, heat-shrink it, and make the largest loop around the attic you can, closing the loop.
I've never heard of using 5-gallon cans as antenna cores, so I can't comment intelligently about the idea. I can, however, think of several unintelligent comments, but I'll refrain.
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OP | Post 13 made on Thursday November 11, 2004 at 13:02 |
Theaterworks Founding Member |
Joined: Posts: | April 2002 1,898 |
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I've never heard of using 5-gallon cans as antenna cores, so I can't comment intelligently about the idea. I can, however, think of several unintelligent comments, but I'll refrain. Please do. I have a sense of humor. :-)
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Carpe diem! |
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Post 14 made on Saturday November 13, 2004 at 03:59 |
Tom Ciaramitaro Loyal Member |
Joined: Posts: | May 2002 7,965 |
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On 11/10/04 15:50 ET, mr2channel said...
I would say that not all tuners are created equal, They are consistently mediocre in HT receivers. RG-6 is fine, but you have to remember that AM is Amplitude Modulated NOT Frequency Modulated, so since the earth is not flat you will lose your ablity to pick up the station sooner than with Frequency Modulation (FM). You have the two reversed - FM is line of sight and gets lost sooner, disappearing into space, while AM follows the curvature of the earth and can be heard at far greater distance. Make sure you expose lots of the end of that RG6 like Larry says. The whole distance on the way to the attic is shielded from receiving any AM or any outside radiation at all.
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There is no truth anymore. Only assertions. The internet world has no interest in truth, only vindication for preconceived assumptions. |
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Post 15 made on Saturday November 13, 2004 at 13:46 |
Larry Fine Loyal Member |
Joined: Posts: | August 2001 5,002 |
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On 11/13/04 08:59 ET, Tom Ciaramitaro said...
Make sure you expose lots of the end of that RG6 like Larry says. The whole distance on the way to the attic is shielded from receiving any AM or any outside radiation at all. Actually, my suggestion was to string up a long, single wire, and connect it to the end of the RG-6 inner conductor.
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