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balun
I am trying to build a balun. I chose the one on this web site as I like the
design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? |
balun
On Mon, 9 Jan 2006 20:53:56 -0600, "DrDeath"
wrote: I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I built one like the one on the right. I used my Hustler 5BTV manual, and it said to use a 10 turn 6 inch form. That was a bitch to find a 6 in form. SO I found the website above, and used the left as a model. The 4" PVC does not quite give you 6 inches in form. But as the website states, if you butt to couplers together, that will give you a 6 inch form. The couplers are 5 inches at the outside edges. By the time the cable is wrapped around it, it's about 6 inches. I figured that was as close as I could get. As the website mentioned, I used the 4" PVC pipe as a joint to butt the couplers together, to make them hold better. So, I don't know if I used 18-21 feet, but I think I am pretty damn close. Vinnie S. |
balun
"Vinnie S." wrote in message
... On Mon, 9 Jan 2006 20:53:56 -0600, "DrDeath" wrote: I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I built one like the one on the right. I used my Hustler 5BTV manual, and it said to use a 10 turn 6 inch form. That was a bitch to find a 6 in form. SO I found the website above, and used the left as a model. The 4" PVC does not quite give you 6 inches in form. But as the website states, if you butt to couplers together, that will give you a 6 inch form. The couplers are 5 inches at the outside edges. By the time the cable is wrapped around it, it's about 6 inches. I figured that was as close as I could get. As the website mentioned, I used the 4" PVC pipe as a joint to butt the couplers together, to make them hold better. So, I don't know if I used 18-21 feet, but I think I am pretty damn close. Vinnie S. I can get 6" pvc. Start with 21 and work my way down till we get the desired effect. |
balun
The amount of inductance is determined by the number of coils
and how closely spaced together they are. There is not going to be much difference in three feet. Maybe wrapping the coil with aluminum foil would help to increase the coupling on the coil to increase the inductance. Inductors are the exact electrical opposite of capacitors. Capacitors block DC and pass AC. They have decreasing reactance to higher frequencies. Current leads the voltage by 90 degrees. Inductors block AC and pass DC. They have increasing reactance to higher frequencies. Current lags the voltage by 90 degrees. The inductance in the coil only affects the outside of the shield, the exact place you don't want current flowing. It won't affect the signals inside the coax. |
balun
"Scott in Baltimore" wrote in message
... The amount of inductance is determined by the number of coils and how closely spaced together they are. There is not going to be much difference in three feet. Maybe wrapping the coil with aluminum foil would help to increase the coupling on the coil to increase the inductance. Inductors are the exact electrical opposite of capacitors. Capacitors block DC and pass AC. They have decreasing reactance to higher frequencies. Current leads the voltage by 90 degrees. Inductors block AC and pass DC. They have increasing reactance to higher frequencies. Current lags the voltage by 90 degrees. The inductance in the coil only affects the outside of the shield, the exact place you don't want current flowing. It won't affect the signals inside the coax. This recipe states that the amount of coils is unimportant and to wrap them as close as possible without over lapping. This balun relies on the length which has a 3 foot margin. |
balun
Hello DrDeath:
Why do you want a Balun, and on what type installation are you going to use it???? Jay in the Mojave DrDeath wrote: I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? |
balun
On Mon, 9 Jan 2006 22:40:51 -0600, "DrDeath"
wrote: I built one like the one on the right. I used my Hustler 5BTV manual, and it said to use a 10 turn 6 inch form. That was a bitch to find a 6 in form. SO I found the website above, and used the left as a model. The 4" PVC does not quite give you 6 inches in form. But as the website states, if you butt to couplers together, that will give you a 6 inch form. The couplers are 5 inches at the outside edges. By the time the cable is wrapped around it, it's about 6 inches. I figured that was as close as I could get. As the website mentioned, I used the 4" PVC pipe as a joint to butt the couplers together, to make them hold better. So, I don't know if I used 18-21 feet, but I think I am pretty damn close. Vinnie S. I can get 6" pvc. Start with 21 and work my way down till we get the desired effect. I have seen 6 inch PVC. It might be too big. Vinnie S. |
balun
"DrDeath" wrote in message ... I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I built one and it does a great job of keeping feedline currents down, no more RF in the shack. Iwas having problems regardless of grounding. Here's some pics. If you want inside detail I have pics of that too. http://i6.photobucket.com/albums/y23...f/HPIM1678.jpg http://i6.photobucket.com/albums/y23...f/HPIM1676.jpg http://i6.photobucket.com/albums/y23...f/HPIM1666.jpg Chad |
balun
On Tue, 10 Jan 2006 09:08:03 -0600, "Chad Wahls" wrote:
"DrDeath" wrote in message ... I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I built one and it does a great job of keeping feedline currents down, no more RF in the shack. Iwas having problems regardless of grounding. Here's some pics. If you want inside detail I have pics of that too. http://i6.photobucket.com/albums/y23...f/HPIM1678.jpg http://i6.photobucket.com/albums/y23...f/HPIM1676.jpg http://i6.photobucket.com/albums/y23...f/HPIM1666.jpg Great pics. What kind of symptoms were you experiencing? Vinnie S. |
balun
"Vinnie S." wrote in message ... On Tue, 10 Jan 2006 09:08:03 -0600, "Chad Wahls" wrote: "DrDeath" wrote in message ... I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I built one and it does a great job of keeping feedline currents down, no more RF in the shack. Iwas having problems regardless of grounding. Here's some pics. If you want inside detail I have pics of that too. http://i6.photobucket.com/albums/y23...f/HPIM1678.jpg http://i6.photobucket.com/albums/y23...f/HPIM1676.jpg http://i6.photobucket.com/albums/y23...f/HPIM1666.jpg Great pics. What kind of symptoms were you experiencing? Vinnie S. My radio room is also an electronics repair area. The test equipment would act erratic at best during transmit, meters would peg, you could see carrier or SSB voice on the scope, etc. The power supply intended for the radio would go into current limit even though there was a lot more on tap (acopian). Before grounding extensively I got a couple RF nips, not cool. I was also having problems with the shop stereo (mainly the unbalanced link between the Phase Linear amp and Onkyo preamp) and speakers in the house attached to cheapo soundcards. I'm not running mondo power either. I modified the balun design a tad to accommodate the weird Illinois weather and facilitate removal if it did not work as expected. All the stuff was made from scrap I had laying around. ALL RF problems associated with feedline radiation went away, the test gear sees nothing. The power supply works well when needed (I run battery/solar power) and there is no nipping at all. This even works when lifting grounds as a test. The problem with the audio equipment is still there, I'm sure it is do to the antenna being lower than optimal and ****ty soundcard grounds. All things to be fixed in time. Incidentally the audio computer with pro gear attached has no problems with interference and is closer to the radiator in height and proximity. Good grounding has paid off there, there is no noise problems and there is an assload of power there on that system, both SS and tube. So a long story short: It did not solve all my problems but made a very noticeable improvement around sensitive equipment. I have noticed NO sacrifice in transmit or receive strength. If you can build one for free or next to nothing I think it's a good idea to try. Chad |
balun
"Jay in the Mojave" wrote in message
... Hello DrDeath: Why do you want a Balun, and on what type installation are you going to use it???? Jay in the Mojave DrDeath wrote: I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I'm just messing around with a home made dipole. I want the balun to cut down on the TVI. |
balun
"Chad Wahls" wrote in message
... "DrDeath" wrote in message ... I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I built one and it does a great job of keeping feedline currents down, no more RF in the shack. Iwas having problems regardless of grounding. Here's some pics. If you want inside detail I have pics of that too. http://i6.photobucket.com/albums/y23...f/HPIM1678.jpg http://i6.photobucket.com/albums/y23...f/HPIM1676.jpg http://i6.photobucket.com/albums/y23...f/HPIM1666.jpg Chad That's pretty much what I am going for. Sweet setup. The best part is I have everything I need to build it laying around the house. |
balun
"DrDeath" wrote in message ... "Jay in the Mojave" wrote in message ... Hello DrDeath: Why do you want a Balun, and on what type installation are you going to use it???? Jay in the Mojave DrDeath wrote: I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I'm just messing around with a home made dipole. I want the balun to cut down on the TVI. Just form 4 turns or so of coax in a coil perhaps a foot or so in diameter. This will form a choke which will kill the current backfeed down the outer side of the coax. You can actually build an endfed dipole out of coax. Feed the hot (center) wire into about 9 feet of wire and form a loop (4 or 5 turns of coax) about 9 feet away from the feed. The outer conductor (shield) of the coax will form the other half of the dipole with the coil (choke) stopping the rf at that point. Simply move the coil (by turning towards or away from the center feed) to adjust your SWR. No rf on the outside of the coax. Presto ;) Questions, e-mail me at and I'll see if I can take a digital photo for you. finger crossed - old digital camera which sometimes has problems with close-ups LOL 73 from Rochester, NY Jim |
balun
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balun
"Scott in Baltimore" wrote in message . .. Questions, e-mail me at and I'll see if I can take a digital photo for you. finger crossed - old digital camera which sometimes has problems with close-ups LOL Is it a Kodak? G Scott, you old son-of-a-gun .... Yep :)) 73, Jim ps - still not on Echo Link very much .... send me an e-mail. |
balun
ps - still not on Echo Link very much .... send me an e-mail.
Look in *BALT* |
balun
Hello Dr Death:
Ok good deal I saw the impressive photos that Chad had there. One thing to consider is that those fiberglass none ground plane antennas use the coax outer shield as the counter poise or other end of the antenna, so current will be seen on the coax. And in some case you will see SWR changes from different lengths of coax, because the coax is actually radiating, acting like a antenna. I have had customers add in a line coax Balun on these type of antennas. The Balun uses a Toroid Core, with the coax would around it. But the trick here is that the Toroid Core is placed at 1/4 wavelength or about 102 inches down from the antennas connector. This allows the coax to radiate for a 1/4 wavelength, possibility allowing for a low take off angle, then choking off the currents beyond the 1/4 wavelength. Or the coil wound coax Balun can be tried. My personal experience has been that the coax Baluns didn't have enough choking impedance, allowing the antennas lowest SWR frequency to be much lower that what it really was, because the coax was also radiating and acting like part of the antenna. But this was on a beam antenna, and not a fiberglass type antenna. Suggest its worth a try, to add a choke Balun at a 1/4 wavelength below the antennas connection. Jay in the Mojave DrDeath wrote: "Jay in the Mojave" wrote in message ... Hello DrDeath: Why do you want a Balun, and on what type installation are you going to use it???? Jay in the Mojave DrDeath wrote: I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I'm just messing around with a home made dipole. I want the balun to cut down on the TVI. |
balun
"Jay in the Mojave" wrote in message ... Hello Dr Death: Ok good deal I saw the impressive photos that Chad had there. One thing to consider is that those fiberglass none ground plane antennas use the coax outer shield as the counter poise or other end of the antenna, so current will be seen on the coax. And in some case you will see SWR changes from different lengths of coax, because the coax is actually radiating, acting like a antenna. I have had customers add in a line coax Balun on these type of antennas. The Balun uses a Toroid Core, with the coax would around it. But the trick here is that the Toroid Core is placed at 1/4 wavelength or about 102 inches down from the antennas connector. This allows the coax to radiate for a 1/4 wavelength, possibility allowing for a low take off angle, then choking off the currents beyond the 1/4 wavelength. Or the coil wound coax Balun can be tried. As you may have guessed the antenna is an Imax 2000. Which mounts to the mast via a metal base that is directly coupled to the mast/tower. This being said wouldn't the mast become the counterpoise at this point if the coax is not? (The outside of the PL259 is directly coupled to the mounting provisions.) The balun was made out of spare junk on the premise that I NEEDED a reason to go out to the shop, drink some beer and relax. What a better project, a free one :) I made it removable for obvious reasons and have thought about Jay's points a couple times when they were brought up after construction of said device. This spring I hope to have a new (different) tower and at this time will play with moving the balun from the feed point to right before the ground rod next to the house. This will allow the coax to act as it should and hopefully keep my feedline currents down, wadda ya think? |
balun
"Jay in the Mojave" wrote in message
... Hello Dr Death: Ok good deal I saw the impressive photos that Chad had there. One thing to consider is that those fiberglass none ground plane antennas use the coax outer shield as the counter poise or other end of the antenna, so current will be seen on the coax. And in some case you will see SWR changes from different lengths of coax, because the coax is actually radiating, acting like a antenna. I have had customers add in a line coax Balun on these type of antennas. The Balun uses a Toroid Core, with the coax would around it. But the trick here is that the Toroid Core is placed at 1/4 wavelength or about 102 inches down from the antennas connector. This allows the coax to radiate for a 1/4 wavelength, possibility allowing for a low take off angle, then choking off the currents beyond the 1/4 wavelength. Or the coil wound coax Balun can be tried. My personal experience has been that the coax Baluns didn't have enough choking impedance, allowing the antennas lowest SWR frequency to be much lower that what it really was, because the coax was also radiating and acting like part of the antenna. But this was on a beam antenna, and not a fiberglass type antenna. Suggest its worth a try, to add a choke Balun at a 1/4 wavelength below the antennas connection. Jay in the Mojave DrDeath wrote: "Jay in the Mojave" wrote in message ... Hello DrDeath: Why do you want a Balun, and on what type installation are you going to use it???? Jay in the Mojave DrDeath wrote: I am trying to build a balun. I chose the one on this web site as I like the design http://www.hamuniverse.com/balun.html It states that, and I quote "The number of turns is not critical because the inductance depends more on the length of the wire (coax) than on the number of turns, which will vary depending on the diameter of the plastic pipe that is used." But it does not give the formula. It just says 18 to 21 feet. I plan to use 4 inch pvc and I want to cover as much of the upper 11 meters as I can. Am I better off at 18 or 21 feet? I'm just messing around with a home made dipole. I want the balun to cut down on the TVI. I don't have a toroid large enough laying around, and the goal of this project is that I end up with a working antenna without spending any money. I like Chad's idea, I have lots of PVC in different sizes. If this doesn't pan out, I will try yours or Jim's idea. |
balun
As I have said before TVI is TV INTERFERENCE due to HARMONICS. You
need a low pass filter for that or a good tuning. If you are having flat out AM rectification audio problems, it ain't gonna work. RF out is RF out. I had feedline problems in the immediate vicinity of the gear in question. RF rectification problems stayed there, kinda as expected. I even brought a spectrum analyzer in to sort it out. My RF was clean as a whistle. Cleaner than a "stock CB". Regardless of power there is a blanketing area for broadcast applications. Cleaning up the RF audio is a good step too. Audio distortion is allowed to become funky modulation (audio crossover distortion is ugly at an RF level), unlike pro broadcast where clipper limiting is used. Granted "CB" limiters suck but limiting of some sort should be used. I had an old Invonics in front of my now declared POS Galaxy (FCC accepted) Radio. With the limiter "clipped" and it was nice. I DID NOT MODULATE OFVER 100%, but I kept it there :) Could you elaborate more on the issues you are having? Maybe you have a "working antenna" but the stuff interfered with is working too well as a receive antenna. it can and does happen at all levels of radio, even the best pros. You may be clean, the other stuff may not. Chad |
balun
Hello Chad:
Wow good point here you have made. Yes I agree with you here, the mast would become the counter poise, if currents are choked at the coax. This is why these none ground plane antennas will still work when a coax Balun is placed right at the antennas connector, a Great point made here. In the 1980's I had a terrible time installing a Sigma 4 antenna. As the mast was pushed up the SWR changed. So I figured some how the mast and maybe the coax, was apart of the antenna, and dropped the mast down a foot at a time to get a decent SWR. I wish I had a Balun then. Placing the balun down the coax at a 1/4 wavelength might work well on a fiberglass boat and such. One of the things while adding such things and testing them, is to keep an eye on the field strength of the antenna. If something is done and the field strength increases or decreases you want to see this. In some cases antenna ranges will monitor the antennas swr as compared to its field strength. Jay in the Mojave Chad Wahls wrote: "Jay in the Mojave" wrote in message ... Hello Dr Death: Ok good deal I saw the impressive photos that Chad had there. One thing to consider is that those fiberglass none ground plane antennas use the coax outer shield as the counter poise or other end of the antenna, so current will be seen on the coax. And in some case you will see SWR changes from different lengths of coax, because the coax is actually radiating, acting like a antenna. I have had customers add in a line coax Balun on these type of antennas. The Balun uses a Toroid Core, with the coax would around it. But the trick here is that the Toroid Core is placed at 1/4 wavelength or about 102 inches down from the antennas connector. This allows the coax to radiate for a 1/4 wavelength, possibility allowing for a low take off angle, then choking off the currents beyond the 1/4 wavelength. Or the coil wound coax Balun can be tried. As you may have guessed the antenna is an Imax 2000. Which mounts to the mast via a metal base that is directly coupled to the mast/tower. This being said wouldn't the mast become the counterpoise at this point if the coax is not? (The outside of the PL259 is directly coupled to the mounting provisions.) The balun was made out of spare junk on the premise that I NEEDED a reason to go out to the shop, drink some beer and relax. What a better project, a free one :) I made it removable for obvious reasons and have thought about Jay's points a couple times when they were brought up after construction of said device. This spring I hope to have a new (different) tower and at this time will play with moving the balun from the feed point to right before the ground rod next to the house. This will allow the coax to act as it should and hopefully keep my feedline currents down, wadda ya think? |
balun
This could also be one reason of the "36 Foot" myth It is said that best
results are obtained when the A99 or Imax is at 36' to the feed point. Maybe it's not the relationship to ground as much as the length of the mast acting as the counterpoise. If you want to go more than 36' then a ground plane kit is recommended to lower the take off angle. Many have noticed good results with the GPK above 36' but found it a waste below 36', HMMMM. I'm only at 20' now on a push up with a tower coming in spring to get me to 36' I don't want to go much taller A. because the wife would freak, and B. it would become a lightning magnet in my one-horse-town. Another thing to ponder is that the addition of the Balun may help the ERP because you are eliminating one of the 2 counterpoises (mast and coax) which would certainly have 2 different velocity factors. This could possibly act as a phasor in certain instances and cause an omni antenna to be "not so omni" There is a possibility that my ERP may have gone up after the balun installation. Although problems associated with feedline radiation in the shack decreased, the audio problems with the stereo in there shack increased slightly. Maybe there is a tad more coming out of the stick and not being wasted elsewhere? Once again just pondering, I may be WAY off :) Chad "Jay in the Mojave" wrote in message ... Hello Chad: Wow good point here you have made. Yes I agree with you here, the mast would become the counter poise, if currents are choked at the coax. This is why these none ground plane antennas will still work when a coax Balun is placed right at the antennas connector, a Great point made here. In the 1980's I had a terrible time installing a Sigma 4 antenna. As the mast was pushed up the SWR changed. So I figured some how the mast and maybe the coax, was apart of the antenna, and dropped the mast down a foot at a time to get a decent SWR. I wish I had a Balun then. Placing the balun down the coax at a 1/4 wavelength might work well on a fiberglass boat and such. One of the things while adding such things and testing them, is to keep an eye on the field strength of the antenna. If something is done and the field strength increases or decreases you want to see this. In some cases antenna ranges will monitor the antennas swr as compared to its field strength. Jay in the Mojave Chad Wahls wrote: "Jay in the Mojave" wrote in message ... Hello Dr Death: Ok good deal I saw the impressive photos that Chad had there. One thing to consider is that those fiberglass none ground plane antennas use the coax outer shield as the counter poise or other end of the antenna, so current will be seen on the coax. And in some case you will see SWR changes from different lengths of coax, because the coax is actually radiating, acting like a antenna. I have had customers add in a line coax Balun on these type of antennas. The Balun uses a Toroid Core, with the coax would around it. But the trick here is that the Toroid Core is placed at 1/4 wavelength or about 102 inches down from the antennas connector. This allows the coax to radiate for a 1/4 wavelength, possibility allowing for a low take off angle, then choking off the currents beyond the 1/4 wavelength. Or the coil wound coax Balun can be tried. As you may have guessed the antenna is an Imax 2000. Which mounts to the mast via a metal base that is directly coupled to the mast/tower. This being said wouldn't the mast become the counterpoise at this point if the coax is not? (The outside of the PL259 is directly coupled to the mounting provisions.) The balun was made out of spare junk on the premise that I NEEDED a reason to go out to the shop, drink some beer and relax. What a better project, a free one :) I made it removable for obvious reasons and have thought about Jay's points a couple times when they were brought up after construction of said device. This spring I hope to have a new (different) tower and at this time will play with moving the balun from the feed point to right before the ground rod next to the house. This will allow the coax to act as it should and hopefully keep my feedline currents down, wadda ya think? |
balun
On Tue, 10 Jan 2006 01:31:51 -0500, Scott in Baltimore
wrote: +The amount of inductance is determined by the number of coils +and how closely spaced together they are. There is not going +to be much difference in three feet. Maybe wrapping the coil +with aluminum foil would help to increase the coupling on +the coil to increase the inductance. + If you want to increase the inductance wrapping aluminum foil on the outside is not going to produce adequate results. Instead, place ferrite material within the form so that it sits inside the windings. If you want to decrease the inductance use aluminum inside the windings. This is how tunable inductors work. +The inductance in the coil only affects the outside of the shield, +the exact place you don't want current flowing. It won't affect +the signals inside the coax. **** Coiling coax up to form a choke balun places an impedance inline with the outer conductor of the coax. It is this impedance that limits or "blocks" unwanted current from flowing down the outer shield of the coax. Coiled baluns should be located as close to the feed as possible. james |
balun
Hello Chad:
Chad Wahls wrote: This could also be one reason of the "36 Foot" myth It is said that best results are obtained when the A99 or Imax is at 36' to the feed point. I have watched received and transmitted field strength signals, from a antenna being cranked up on a crank up tower. All I ever see is the higher the antenna the stronger the signals. I never see a sweet spot or anything that is magic at 36 feet. Maybe it's not the relationship to ground as much as the length of the mast acting as the counterpoise. If you want to go more than 36' then a ground plane kit is recommended to lower the take off angle. Many have noticed good results with the GPK above 36' but found it a waste below 36', HMMMM. I'm only at 20' now on a push up with a tower coming in spring to get me to 36' I don't want to go much taller A. because the wife would freak, and B. it would become a lightning magnet in my one-horse-town. The ground plane kits I have seen do not impress me. I see shorter than a 1/4 wavelength, and tilted down. I don't think this is worth the effort. I have always wanted to add on 4 each 96 or 102 inch long fiberglass whip antennas, mounted at the base of the antenna, and flat and level. But you need to compare the field strength with the before and after ground plane installation. And at different heights. The difference will only be a dB or so (I haven't measured it either) maybe even less than a dB or more! Let those with field strength measurements tell all. Another consideration is, how much is a dB or 2 dB worth in antenna performance, as compared to distance in quiet skip times. Quit a bit! Another thing to ponder is that the addition of the Balun may help the ERP because you are eliminating one of the 2 counterpoises (mast and coax) which would certainly have 2 different velocity factors. This could possibly act as a phasor in certain instances and cause an omni antenna to be "not so omni" This is all good stuff here Chad! This all may be true, again field strength measurements will tell who's lying and who ain't. There is a possibility that my ERP may have gone up after the balun installation. Although problems associated with feedline radiation in the shack decreased, the audio problems with the stereo in there shack increased slightly. Maybe there is a tad more coming out of the stick and not being wasted elsewhere? This would be a place to add on the level 1/4 wavelength ground plane radials and test the audio interference again. It may be significantly attenuated. Once again just pondering, I may be WAY off :) Chad When it comes to antennas, no one can see where the RF Energy is going, so field strength testing will set us free. I think your on the right track. Jay in the Mojave |
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"james" wrote in message ... Coiling coax up to form a choke balun places an impedance inline with the outer conductor of the coax. It is this impedance that limits or "blocks" unwanted current from flowing down the outer shield of the coax. Coiled baluns should be located as close to the feed as possible. james When you say as close to the feed as possible. Do you mean the radio or the dipole? I'm assuming the dipole. |
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"Chad Wahls" wrote in message
oups.com... As I have said before TVI is TV INTERFERENCE due to HARMONICS. You need a low pass filter for that or a good tuning. If you are having flat out AM rectification audio problems, it ain't gonna work. RF out is RF out. I had feedline problems in the immediate vicinity of the gear in question. RF rectification problems stayed there, kinda as expected. I even brought a spectrum analyzer in to sort it out. My RF was clean as a whistle. Cleaner than a "stock CB". Regardless of power there is a blanketing area for broadcast applications. Cleaning up the RF audio is a good step too. Audio distortion is allowed to become funky modulation (audio crossover distortion is ugly at an RF level), unlike pro broadcast where clipper limiting is used. Granted "CB" limiters suck but limiting of some sort should be used. I had an old Invonics in front of my now declared POS Galaxy (FCC accepted) Radio. With the limiter "clipped" and it was nice. I DID NOT MODULATE OFVER 100%, but I kept it there :) Could you elaborate more on the issues you are having? Maybe you have a "working antenna" but the stuff interfered with is working too well as a receive antenna. it can and does happen at all levels of radio, even the best pros. You may be clean, the other stuff may not. Chad The audio is clean from my olds school 148. I was just trying my hand at making my own dipole since it was mentioned in an earlier post I noticed that while attempting to adjust the swr, I was getting interference on my PC monitor whenever I keyed. I have the sw at 1.5, when I tried to lower it further it started going back up. I remade the dipole (I have tons of wire) got it back to 1.5 but still radiating TVI. I figured I would try the balun to see what would happen. Might also throw a low pass filter in it to see if that will fix the problem. |
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"Jay in the Mojave" wrote in message ... Hello Chad: Greetings Jay: The ground plane kits I have seen do not impress me. I see shorter than a 1/4 wavelength, and tilted down. I don't think this is worth the effort. I have always wanted to add on 4 each 96 or 102 inch long fiberglass whip antennas, mounted at the base of the antenna, and flat and level. But you need to compare the field strength with the before and after ground plane installation. And at different heights. The difference will only be a dB or so (I haven't measured it either) maybe even less than a dB or more! Let those with field strength measurements tell all. Another consideration is, how much is a dB or 2 dB worth in antenna performance, as compared to distance in quiet skip times. Quit a bit! I agree with your assessment on Ground plane kits. I don't have one because it works now! Why change it? On another forum they are big on flattening them out a tad to change the take off angle, those who have done this have experienced coverage improvement. I don't know the exact angle but I can get it for you if you want. This is all good stuff here Chad! This all may be true, again field strength measurements will tell who's lying and who ain't. Yeah I know I worked in broadcast and have access to a field strength meter from friends. They would be more than happy to drink my beer and play with it :) That's who I borrowed the Spectrum analyzer from to make sure I was clean on the output. This would be a place to add on the level 1/4 wavelength ground plane radials and test the audio interference again. It may be significantly attenuated. Or better yet it's time to fix the problems with the audio systems :) The one with the most power (well over 1KW RMS) and proper wiring does not have any noise AT ALL! It's just the stuff that has been known to have problems in all installs be it amateur or not. When it comes to antennas, no one can see where the RF Energy is going, so field strength testing will set us free. I think your on the right track. I agree, Thanks for you input and interest. I am no pro by any means. When I worked in broadcast I was an audio guy, after it hit a composite signal I was done with it :) I learned any RF from shutting up and listening, I would then go home and ponder to come back the next day with questions. It's nice to have someone with your experience around to share thoughts with. I really appreciate it! Have a great weekend, Chad |
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echolink is a good place for you, scottiekins. lots of idiots there,
you will feel at home. |
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idiot, too stupid to build a balun without help. The drugs are showing
now. |
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"DrDeath" wrote in message ... "Chad Wahls" wrote in message oups.com... As I have said before TVI is TV INTERFERENCE due to HARMONICS. You need a low pass filter for that or a good tuning. If you are having flat out AM rectification audio problems, it ain't gonna work. RF out is RF out. I had feedline problems in the immediate vicinity of the gear in question. RF rectification problems stayed there, kinda as expected. I even brought a spectrum analyzer in to sort it out. My RF was clean as a whistle. Cleaner than a "stock CB". Regardless of power there is a blanketing area for broadcast applications. Cleaning up the RF audio is a good step too. Audio distortion is allowed to become funky modulation (audio crossover distortion is ugly at an RF level), unlike pro broadcast where clipper limiting is used. Granted "CB" limiters suck but limiting of some sort should be used. I had an old Invonics in front of my now declared POS Galaxy (FCC accepted) Radio. With the limiter "clipped" and it was nice. I DID NOT MODULATE OFVER 100%, but I kept it there :) Could you elaborate more on the issues you are having? Maybe you have a "working antenna" but the stuff interfered with is working too well as a receive antenna. it can and does happen at all levels of radio, even the best pros. You may be clean, the other stuff may not. Chad The audio is clean from my olds school 148. I was just trying my hand at making my own dipole since it was mentioned in an earlier post I noticed that while attempting to adjust the swr, I was getting interference on my PC monitor whenever I keyed. I have the sw at 1.5, when I tried to lower it further it started going back up. I remade the dipole (I have tons of wire) got it back to 1.5 but still radiating TVI. I figured I would try the balun to see what would happen. Might also throw a low pass filter in it to see if that will fix the problem. That's just RF man. The balun may help you though because it will reduce feedline radiation. That's kinda the same problem I was having. I say go for it, give it a try, what do you have to loose? :) Chad |
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"moparholic at hotmail dot com is a sissy" wrote in message ups.com... idiot, too stupid to build a balun without help. The drugs are showing now. I personally think that the topic is being covered well and all are learning. Chad |
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"DrDeath" wrote in message ... "james" wrote in message ... Coiling coax up to form a choke balun places an impedance inline with the outer conductor of the coax. It is this impedance that limits or "blocks" unwanted current from flowing down the outer shield of the coax. Coiled baluns should be located as close to the feed as possible. james When you say as close to the feed as possible. Do you mean the radio or the dipole? I'm assuming the dipole. The dipole, you are correct. Chad |
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doggie is a sissy wrote:
echolink is a good place for you, scottiekins. lots of idiots there, you will feel at home. I _DARE_ you to join the group and say hello. Sissy. |
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"Scott in Baltimore" wrote in message ... doggie is a sissy wrote: echolink is a good place for you, scottiekins. lots of idiots there, you will feel at home. I _DARE_ you to join the group and say hello. Sissy. I'm afraid you guys will make fun of me and Crisco Kathy again. |
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"moparholic at hotmail dot com is a sissy" wrote in message oups.com... echolink is a good place for you, scottiekins. lots of idiots there, you will feel at home. Have you seen how I installed my antenna? |
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"Scott in Baltimore" wrote in message ... I'm afraid you guys will make fun of me and Crisco Kathy again. If you're so scared, then go away. We won't dog you. We'd be glad to show you the door! I'm afraid of doors too have you seen that picture of me standing in the doorway trembling? |
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I'm afraid you guys will make fun of me and Crisco Kathy again.
If you're so scared, then go away. We won't dog you. We'd be glad to show you the door! |
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Scott in Baltimore wrote:
I'm afraid you guys will make fun of me and Crisco Kathy again. If you're so scared, then go away. We won't dog you. We'd be glad to show you the door! He's afraid of his own shadow once he leaves his section eight slum. |
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"Doug Adair" wrote:
"moparholic at hotmail dot com is a sissy" wrote in message oups.com... echolink is a good place for you, scottiekins. lots of idiots there, you will feel at home. Have you seen how I installed my antenna? I've seen it up close and personal like...too funny to put in words so here's a pic: http://img388.imageshack.us/img388/5247/dogie041hn.jpg Nice job, fugly hunch-back. lol |
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"Chad Wahls" wrote:
"moparholic at hotmail dot com is a sissy" wrote in message ups.com... idiot, too stupid to build a balun without help. The drugs are showing now. I personally think that the topic is being covered well and all are learning. Chad It's an interesting thread no doubt, Chad. |
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