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zip cord feeding a g5rv antenna
someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ?
(european meaning double the Volts compared to USA, thus half amps for the same lamp wattage) Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. sorry if this has been up too many times, search didŽnt give a clue! Tnx for info, 73 Per / sm7aha malmo, sweden |
On Tue, 12 Jul 2005 20:44:33 GMT, "pegge"
wrote: someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ? Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. Hi Per, Hard to apply the name g5rv to this, but that makes no difference anyway. Simply call it a dipole driven with close spaced twin lead. That twin lead will be 50 to 70 Ohms characteristic impedance. It will also have a suspect dielectric loss. This does not make it a bad antenna. There will be the usual high loss with high SWR - depending upon the gauge of the wire. In short, no worse than an ordinary antenna used outside of its natural resonance. 73's Richard Clark, KB7QHC |
"pegge" wrote in message
... someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ? (european meaning double the Volts compared to USA, thus half amps for the same lamp wattage) Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. sorry if this has been up too many times, search didŽnt give a clue! Tnx for info, 73 Per / sm7aha malmo, sweden Check out the following analysis: http://www.vk1od.net/G5RV/index.htm Frank |
I had thought about it because I had a 500 ft roll on hand at the time - but
changed my mind because research showed zip cord to be high-loss "pegge" wrote in message ... someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ? (european meaning double the Volts compared to USA, thus half amps for the same lamp wattage) Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. sorry if this has been up too many times, search didŽnt give a clue! Tnx for info, 73 Per / sm7aha malmo, sweden |
Hal Rosser wrote:
I had thought about it because I had a 500 ft roll on hand at the time - but changed my mind because research showed zip cord to be high-loss "pegge" wrote in message ... someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ? (european meaning double the Volts compared to USA, thus half amps for the same lamp wattage) Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. sorry if this has been up too many times, search didŽnt give a clue! Tnx for info, 73 Per / sm7aha malmo, sweden Go for it. I've seen a dipole fed by electric blasting wire. Worked fine. Dave N WD9BDZ |
I have a 40meter band xmit/recv antenna up with good swr and works great.
Cost me nothing but my time, and a plastic center insulator to strain releive the zip cord (rather than tie a knot in the cord at the center. Just rip down 33 ft of zip cord, tie a knot or use the insulator, and cut the feedlinne section to a integral half wave long (20, 40, 60etc meters long). If cut to a half wave (use a dip meter) the swr of the dipole will be translated unaltered to the radio end of your feedline and 70 ohms is OK for a swr of 1.4 and the xcvr will not care usually. Great emergency antenna. "pegge" wrote in message ... someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ? (european meaning double the Volts compared to USA, thus half amps for the same lamp wattage) Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. sorry if this has been up too many times, search didŽnt give a clue! Tnx for info, 73 Per / sm7aha malmo, sweden |
"tjs" wrote in message ... I have a 40meter band xmit/recv antenna up with good swr and works great. Cost me nothing but my time, and a plastic center insulator to strain releive the zip cord (rather than tie a knot in the cord at the center. Just rip down 33 ft of zip cord, tie a knot or use the insulator, and cut the feedlinne section to a integral half wave long (20, 40, 60etc meters long). If cut to a half wave (use a dip meter) the swr of the dipole will be translated unaltered to the radio end of your feedline and 70 ohms is OK for a swr of 1.4 and the xcvr will not care usually. Great emergency antenna. Why do you think the SWR of the dipole will be unaltered at the radio end of the feedline? You are apparently ignoring the loss in the line that makes the SWR at the radio end less than that at the dipole terminals. If the zip cord had zero loss the SWR would be the same everywhere along the line, only the terminal impedance at the radio end would be the same as at the dipole. Without knowing the vf (velocity factor) of the zip cord how do you determine that the length is a half wave? And last, why would you want the length to be a half wave? Walt, W2DU -------------------------------------------------------------------------------- |
On Wed, 13 Jul 2005 13:50:03 -0400, "Walter Maxwell"
wrote: This is a multi-part message in MIME format. Why? Because you are using that POS Outlook Express again! :-( Why do you think the SWR of the dipole will be unaltered at the radio = end of the feedline? You are apparently ignoring the loss in the line = that makes the SWR at the radio end less than that at the dipole = terminals. If the zip cord had zero loss the SWR would be the same everywhere = along the line, only the terminal impedance at the radio end would be = the same as at the dipole. Without knowing the vf (velocity factor) of the zip cord how do you = determine that the length is a half wave? And last, why would you want the length to be a half wave?=20 Walt, W2DU And your posting mentions nothing in it that suggests why there is a GIF attachment which may be infected. Walt, This is like running full power deliberately into a 10:1 mismatch: 15 lines of content does not warrant a 156 line posting. 73's Richard Clark, KB7QHC |
Walter Maxwell wrote:
Richard, I can't imagine why you'd see a 156 line posting. I deleted everything except 12 lines above my posting. And 12 are all that come up when I review my post. Something musta happened that I'm not aware of. However, I will confess that I overlooked a GIF attachment. I have never claimed that I could go through an entire day without screwing something up. Walt Walt Both this post and your previous one look fine on Mozilla; no huge number of lines. A file called p.gif is coming along with it, though. tom K0TAR |
"Walter Maxwell" wrote in message ... "tjs" wrote in message ... I have a 40meter band xmit/recv antenna up with good swr and works great. Cost me nothing but my time, and a plastic center insulator to strain releive the zip cord (rather than tie a knot in the cord at the center. Just rip down 33 ft of zip cord, tie a knot or use the insulator, and cut the feedlinne section to a integral half wave long (20, 40, 60etc meters long). If cut to a half wave (use a dip meter) the swr of the dipole will be translated unaltered to the radio end of your feedline and 70 ohms is OK for a swr of 1.4 and the xcvr will not care usually. Great emergency antenna. Why do you think the SWR of the dipole will be unaltered at the radio end of the feedline? You are apparently ignoring the loss in the line that makes the SWR at the radio end less than that at the dipole terminals. If the zip cord had zero loss the SWR would be the same everywhere along the line, only the terminal impedance at the radio end would be the same as at the dipole. Without knowing the vf (velocity factor) of the zip cord how do you determine that the length is a half wave? And last, why would you want the length to be a half wave? Walt, W2DU I think he was correct about the half-wave length of feedline: according to the ARRL Antenna Book - 17th edition copyright 1994 - page 24-12 in chapter 24, under the Heading "Special Cases" and under the sub-heading "The Half-WaveLength Line", it pretty clearly states that regardless of z, it will be the same on both ends of a half-wave line. and sections having such length can be added or removed without changing the load Z. (as long as loss is negligible) Also - You don't need to know the VF if you use a dip meter (or MFJ 259) - And he would want the length to be half-wave so as to be able to ignore the characteristic impedence of the zip line and deal directly with the impedence of the dipole directly. |
On second thought -
If you feed it like that, then it will cease to be a G5RV. "pegge" wrote in message ... someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ? (european meaning double the Volts compared to USA, thus half amps for the same lamp wattage) Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. sorry if this has been up too many times, search didŽnt give a clue! Tnx for info, 73 Per / sm7aha malmo, sweden |
On Wed, 13 Jul 2005 17:40:02 -0400, "Hal Rosser"
wrote: I think he was correct about the half-wave length of feedline: according to the ARRL Antenna Book - 17th edition copyright 1994 - page 24-12 in chapter 24, under the Heading "Special Cases" and under the sub-heading "The Half-WaveLength Line", it pretty clearly states that regardless of z, it will be the same on both ends of a half-wave line. and sections having such length can be added or removed without changing the load Z. (as long as loss is negligible) Also - You don't need to know the VF if you use a dip meter (or MFJ 259) - And he would want the length to be half-wave so as to be able to ignore the characteristic impedence of the zip line and deal directly with the impedence of the dipole directly. This analysis seems to imply use of the antenna on only one one band. Ill conceived alternative feed arrangments are the most common reason why so-called G5RVs performs even poorer than the "genuine" article. The original question about how well "Euro zip line" will perform will depend on the characteristics of the line. I hazard a guess that it will be unlikely to have a characteristic impedance as low as 75 ohms as suggested by some, more likely 100 ohms or more. It is likely to be PVC insulated, and lines of that type perform much poorer than a high z line made of the same conductor, not just because of the dielectric issue, but because the RF resistance of the conductor increases as the spacing is reduced for very close spacings (proximity effect). As to whether it "works" for you, you need to define your criteria for "works". If "works" means you make some QSOs, then I am sure it "works", but if "works" meand you want to deliver 80% plus of the transmitter power to the "G5RV variant" antenna feedpoint on several bands, then it is unlikely to "work". For arguments sake, if the feedpoint Z of a 30.5m centre fed dipole (G5RV length) on 3.6MHz is 10-j340, using the characteristics of US Zip cord measured by K8ZOA, the loss in 25m of such feeder would be 13dB with a Zin of 563-61, so there would be some small (insignificant) additional tuner loss. Is this what you mean by "works"? Owen -- |
"Hal Rosser" wrote in message ... I think he was correct about the half-wave length of feedline: according to the ARRL Antenna Book - 17th edition copyright 1994 - page 24-12 in chapter 24, under the Heading "Special Cases" and under the sub-heading "The Half-WaveLength Line", it pretty clearly states that regardless of z, it will be the same on both ends of a half-wave line. and sections having such length can be added or removed without changing the load Z. (as long as loss is negligible) Also - You don't need to know the VF if you use a dip meter (or MFJ 259) - And he would want the length to be half-wave so as to be able to ignore the characteristic impedence of the zip line and deal directly with the impedence of the dipole directly. Exactly I also have a W6RCA type antenna up...80m dipole in the trees 25-50 feet, fed by 98 feet of homemade 4" spaced ladder line, and ending outside the shack wall with a way to add-in lengths of the feed line by 1 foot, 2 foot, 4 feet or 8 feet. This allows tuning the feedline onto any ham band almost via harmonic relationship of the bands . You endup with a multiple halfwave feedline and whatever swr the antenna runs shows up at the feedpoint (50 ferrite coax to ladder balun 1:1). Best antenna I have. Always better to tune the feedline, and translate the antenna characteristic from the remote locale to the shack wall. There is some loss I guess, but I cant detect it or measure it, and I dont care because the antenna radiates and receives and I get 59 reports. Tim |
Any body dealing with antennas in this group, what I read was pretty off
color and off subject. Want to know what a CCD antenna is really supposed to do compared to say a delta loop...Just put one up and it seems too good to be true compared to my well known hot signal 40 meter delta...what is your opinion and please reply all so I will get a person response. dont think Ill be reading this group everyday...who cares about the british pound? EH? thanks Murray K5MDM Richard Clark wrote: On Tue, 12 Jul 2005 20:44:33 GMT, "pegge" wrote: someone tried to feed a type g5rv antenna with ŽeuropeanŽ zip-cord ? Would yield a simple ant, peel the first say abt 15- 17 meters, splitting them up to the dipole part and the the rest X meter to a balanced tuner etc. Hi Per, Hard to apply the name g5rv to this, but that makes no difference anyway. Simply call it a dipole driven with close spaced twin lead. That twin lead will be 50 to 70 Ohms characteristic impedance. It will also have a suspect dielectric loss. This does not make it a bad antenna. There will be the usual high loss with high SWR - depending upon the gauge of the wire. In short, no worse than an ordinary antenna used outside of its natural resonance. 73's Richard Clark, KB7QHC |
On Thu, 14 Jul 2005 19:19:28 -0500, Murray wrote:
This is a multi-part message in MIME format. This is still pretty obnoxious. --------------010006030806060308030708 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Any body dealing with antennas in this group, what I read was pretty off color and off subject. Hi Murray, It is called the price of admission, and is the exercise of American rights to unrestrained speech. Want to know what a CCD antenna is really supposed to do compared to say a delta loop...Just put one up and it seems too good to be true compared to my well known hot signal 40 meter delta...what is your opinion and please reply all so I will get a person response. The CCD is one of those arm-chair designs that is a gift to mankind in the form of gain from a dipole. To being with, the theory behind it is that this antenna is frequency specific, and that it is much larger than the standard dipole it replaces. If this is news to you, then there's trouble ahead. Continuing, the theory behind it maintains that each section is tuned and presents a current maxima that aids with each of its neighbors to thus increase gain. The standard current distribution along the standard dipole is cosine shaped by and large. For the CCD it is presumably linear - until you get to the ends of course where it plummets to 0 in the last section. Myself, I respond to this description of an antenna by parts as being much like a fresnel lens in its conception. However, modeling, such as I have done, fails to substantiate the claims even if through contortions and exasperation I do manage to attains some semblance of the linear current model. Further, physical models bear out no particular boon to mankind that has been extolled. dont think Ill be reading this group everyday...who cares about the british pound? EH? This falls into the category of off topic response, something you presumably eschew and simultaneously indulge in. This, too, is a commonplace activity. I am happy to respond to all topics that interest me. There are other endlessly boring discussion of antennas - notably those that have survived hurricanes as evidenced by photo doctoring - that remain on topic, and off interest. I don't complain about it though, except to recite as a parable. 73's Richard Clark, KB7QHC |
Want to know what a CCD antenna is really
supposed to do compared to say a delta loop...Just put one up and it seems too good to be true compared to my well known hot signal 40 meter delta...what is your opinion and please reply all so I will get a person response. We already quickly talked about this a year or two ago, but I'm not that great a fan of them. Or at least, I see no real advantage to any other type of antenna. I've worked and check signals on scads of those over the years, and to tell you the truth, as far as performance compared to just a dipole, they are often inferior in the real world. Or to put it another way....Many of the CCD users often had inferior signals compared to the dipole users, when you take an average reading over a period of days or weeks.. I never saw any that were better... Why does it seem to good to be true? All a CDD does is supposably maintain a more constant current distribution across the antenna. In some cases, IE: a steep inv vee, this could be a *disadvantage*. Or seems to me...I would prefer the current concentrated at the apex, which is the high point of the antenna. If you spread current more towards lower sections of the wire, this could actually decrease perfomance. Myself, I see no advantage, and will stick to my dipoles, etc...MK |
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