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20m "ringo"
I am trying to build a 20meter 1/2wl end fed vertcal antena and havent had a
lot of success. The antenna is for use at maximum legal power so I need componets in the network that will hold up. I have tried a J pole configuration that I never was able to properly tune and I have tried lump sum LC values that melted down with max power. I guess the last way is doable but not unless I want to spend really big bucks on new HV capacitors. I was thinking about the matching section on my Ringo Ranger. Why not just scale this up for 20M? The mechanics of it arent a real problem, I can fabricate most anything I would need. Seems like I've heard the mast for a Ringo needs to be at least a 1/4 wl long, is this true? |
20m "ringo"
Feed it through a 1/4 wavelength stub.
Jimmie D wrote: I am trying to build a 20meter 1/2wl end fed vertcal antena and havent had a lot of success. The antenna is for use at maximum legal power so I need componets in the network that will hold up. I have tried a J pole configuration that I never was able to properly tune and I have tried lump sum LC values that melted down with max power. I guess the last way is doable but not unless I want to spend really big bucks on new HV capacitors. I was thinking about the matching section on my Ringo Ranger. Why not just scale this up for 20M? The mechanics of it arent a real problem, I can fabricate most anything I would need. Seems like I've heard the mast for a Ringo needs to be at least a 1/4 wl long, is this true? |
20m "ringo"
Jimmie D wrote:
I have tried a J pole configuration that I never was able to properly tune ... Why did you give up before it was properly tuned? -- 73, Cecil http://www.qsl.net/w5dxp |
20m "ringo"
On Mon, 4 Sep 2006 00:45:07 -0400, "Jimmie D"
wrote: I am trying to build a 20meter 1/2wl end fed vertcal antena and havent had a lot of success. The antenna is for use at maximum legal power so I need componets in the network that will hold up. I have tried a J pole configuration that I never was able to properly tune and I have tried lump sum LC values that melted down with max power. I guess the last way is doable but not unless I want to spend really big bucks on new HV capacitors. I was thinking about the matching section on my Ringo Ranger. Why not just scale this up for 20M? The mechanics of it arent a real problem, I can fabricate most anything I would need. Seems like I've heard the mast for a Ringo needs to be at least a 1/4 wl long, is this true? You might want to consider this approach. http://k6mhe.com/files/DualBandVert.pdf Danny, K6MHE |
20m "ringo"
That is EXACTLY what I tried less the relays. Problem is I dont have good
enough caps for full power and probably will not get any. I am trying to make do with what I have. It worked fine with 100 watts. I am considering lengthening the antenna to 5/8 wl. This should give me a lot less voltage at the feedpoint and I shouldnt even need a capacitor. I did like the idea of dual band antenna . "Danny Richardson" wrote in message ... On Mon, 4 Sep 2006 00:45:07 -0400, "Jimmie D" wrote: I am trying to build a 20meter 1/2wl end fed vertcal antena and havent had a lot of success. The antenna is for use at maximum legal power so I need componets in the network that will hold up. I have tried a J pole configuration that I never was able to properly tune and I have tried lump sum LC values that melted down with max power. I guess the last way is doable but not unless I want to spend really big bucks on new HV capacitors. I was thinking about the matching section on my Ringo Ranger. Why not just scale this up for 20M? The mechanics of it arent a real problem, I can fabricate most anything I would need. Seems like I've heard the mast for a Ringo needs to be at least a 1/4 wl long, is this true? You might want to consider this approach. http://k6mhe.com/files/DualBandVert.pdf Danny, K6MHE |
20m "ringo"
"Cecil Moore" wrote in message m... Jimmie D wrote: I have tried a J pole configuration that I never was able to properly tune ... Why did you give up before it was properly tuned? -- 73, Cecil http://www.qsl.net/w5dxp Sold my antenna support, 3 story house. |
20m "ringo"
"Dave" wrote in message . .. Feed it through a 1/4 wavelength stub. That was my first thought and I invisioned 16 ft of open wire line runing out across the yard. But now that I think of it this may be a workable solution. No reason it has to be stretched out straight, circle it around the antenna. Hmm back to Ringo again. Jimmie D wrote: I am trying to build a 20meter 1/2wl end fed vertcal antena and havent had a lot of success. The antenna is for use at maximum legal power so I need componets in the network that will hold up. I have tried a J pole configuration that I never was able to properly tune and I have tried lump sum LC values that melted down with max power. I guess the last way is doable but not unless I want to spend really big bucks on new HV capacitors. I was thinking about the matching section on my Ringo Ranger. Why not just scale this up for 20M? The mechanics of it arent a real problem, I can fabricate most anything I would need. Seems like I've heard the mast for a Ringo needs to be at least a 1/4 wl long, is this true? |
20m "ringo"
Jimmie D wrote:
"Cecil Moore" wrote in message Why did you give up before it was properly tuned? Sold my antenna support, 3 story house. The matching section for your 20m 1/2WL monopole can be mounted horizontal if it is more convenient. FP is where it connects to the 1/2WL vertical section. +-----------X-----------16.5'---------------+FP | +-----------Y-----------16.5'----------------open The coax connects at X and Y where the 50 ohm feedpoint is located. #14 or larger wire will handle anything legal that you can put into it. No high voltage capacitors required. No lossy coils required. -- 73, Cecil http://www.w5dxp.com |
20m "ringo"
Jimmie D wrote: "Dave" wrote in message . .. Feed it through a 1/4 wavelength stub. That was my first thought and I invisioned 16 ft of open wire line runing out across the yard. But now that I think of it this may be a workable solution. No reason it has to be stretched out straight, circle it around the antenna. Hmm back to Ringo again. Have you tried using coax for the caps, same as the cushcraft ringos? I'm not sure how much power a cap made from say 213 would handle, but it going to be several hundred watts at the min.. I've built what you are building. It will work fine, and the height above ground is not that critical. But I eventually changed the antenna to be a 40 GP and a 5/8 GP for 17m. I used a relay to switch the loading coil for 17m in/out. The "gamma loop" for 20m is kinda large, so you need some stiff tubing to hold stable. IE: copper tube, etc.. MK |
20m "ringo"
"Cecil Moore" wrote in message m... Jimmie D wrote: "Cecil Moore" wrote in message Why did you give up before it was properly tuned? Sold my antenna support, 3 story house. The matching section for your 20m 1/2WL monopole can be mounted horizontal if it is more convenient. FP is where it connects to the 1/2WL vertical section. +-----------X-----------16.5'---------------+FP | +-----------Y-----------16.5'----------------open The coax connects at X and Y where the 50 ohm feedpoint is located. #14 or larger wire will handle anything legal that you can put into it. No high voltage capacitors required. No lossy coils required. Thanks Cecil This was my first plan but I dont have room to run the stub straight out so I kind of tabled the idea for a while. Now that I have thought about it there is no reason I couldnt wrap it around the antenna. Talking with others sure helps the thought process. I still may play with the idea of the 20M Ringo design. It would be a lot of fun telling people you have a 20M Ringo Ranger. My only real problem with using the Ringo style matching network is that I heard once upon a time that the Ringo utilizes the mast as part of the radiator. The main thing I see the Ringo type match has going for it is that it would be about half the size of a 16.5 ft stub wrapped around the antenna |
20m "ringo"
Jimmie D wrote:
Thanks Cecil This was my first plan but I dont have room to run the stub straight out so I kind of tabled the idea for a while. Now that I have thought about it there is no reason I couldnt wrap it around the antenna. There's no reason why you couldn't spiral it around the antenna like a pancake inductor. If you kept each spiral about a foot away from the next one, the area occupied would be pretty small. Good luck. -- 73, Cecil http://www.w5dxp.com |
20m "ringo"
On Mon, 4 Sep 2006 15:23:37 -0400, "Jimmie D"
wrote: I heard once upon a time that the Ringo utilizes the mast as part of the radiator. Hi Jimmie, What was meant was that the mast inappropriately became part of the radiator due to the design of the Ringo (which has had a reputation for being a dummy load). The problem with half-wave designs is they are high Z. Being high Z they are difficult to choke. Being difficult to choke, they appropriate masts, supports, feed lines, as additional radiation surfaces. When you add these lengths to the radiator (and they are co-linear) then your radiation lobes begin to climb into the sky (no one there to hear you) and the antenna becomes deaf and dumb. 73's Richard Clark, KB7QHC |
20m "ringo"
Richard Clark wrote: On Mon, 4 Sep 2006 15:23:37 -0400, "Jimmie D" wrote: I heard once upon a time that the Ringo utilizes the mast as part of the radiator. Hi Jimmie, What was meant was that the mast inappropriately became part of the radiator due to the design of the Ringo (which has had a reputation for being a dummy load). The problem with half-wave designs is they are high Z. Being high Z they are difficult to choke. Being difficult to choke, they appropriate masts, supports, feed lines, as additional radiation surfaces. When you add these lengths to the radiator (and they are co-linear) then your radiation lobes begin to climb into the sky (no one there to hear you) and the antenna becomes deaf and dumb. It's probably more critical on VHF/UHF, but on the HF bands I never had any trouble with ringos and decoupling problems overly skewing the pattern. I've used a few with no decoupling at all, and they worked fine. But I'm of the opinion that the "gamma loop" type feed helps decouple the feedline a bit better than some other methods of feeding. I tried adding a decoupling section to one I used on 10m a few years ago, and it did help, but not in a huge amount. I found the antennas pretty easy to choke by using a 1/4 WL section of coax, and then 4 radials. Much the same as used on the "ringo ranger" antennas. Anyway, I've never seen a case on HF where I thought a ringo acted like a dummy load. I imagine it's possible on VHF though, if precautions aren't taken. I've used lots of them on 10m at various heights. Always worked pretty well. And I never noticed an overly hot feedline. The only times I had horrible results with a half wave was a time years ago when I tried to make a center fed job, using peeled back coax braid as part of the antenna. The decoupling from the line was horrible on that thing. That was on VHF though where the problem shows up more. MK |
20m "ringo"
Richard Clark wrote: On Mon, 4 Sep 2006 15:23:37 -0400, "Jimmie D" wrote: I heard once upon a time that the Ringo utilizes the mast as part of the radiator. Hi Jimmie, What was meant was that the mast inappropriately became part of the radiator due to the design of the Ringo (which has had a reputation for being a dummy load). The problem with half-wave designs is they are high Z. Being high Z they are difficult to choke. Being difficult to choke, they appropriate masts, supports, feed lines, as additional radiation surfaces. When you add these lengths to the radiator (and they are co-linear) then your radiation lobes begin to climb into the sky (no one there to hear you) and the antenna becomes deaf and dumb. It's probably more critical on VHF/UHF, but on the HF bands I never had any trouble with ringos and decoupling problems overly skewing the pattern. I've used a few with no decoupling at all, and they worked fine. But I'm of the opinion that the "gamma loop" type feed helps decouple the feedline a bit better than some other methods of feeding. I tried adding a decoupling section to one I used on 10m a few years ago, and it did help, but not in a huge amount. I found the antennas pretty easy to choke by using a 1/4 WL section of coax, and then 4 radials. Much the same as used on the "ringo ranger" antennas. Anyway, I've never seen a case on HF where I thought a ringo acted like a dummy load. I imagine it's possible on VHF though, if precautions aren't taken. I've used lots of them on 10m at various heights. Always worked pretty well. And I never noticed an overly hot feedline. The only times I had horrible results with a half wave was a time years ago when I tried to make a center fed job, using peeled back coax braid as part of the antenna. The decoupling from the line was horrible on that thing. That was on VHF though where the problem shows up more. MK |
20m "ringo"
.. The only times I had horrible results with a half wave was a time years ago when I tried to make a center fed job, using peeled back coax braid as part of the antenna. The decoupling from the line was horrible on that thing. That was on VHF though where the problem shows up more. MK Ive had trouble with this type of antenna too. Turning the shield inside out over the feedline is not a good idea. The outer viynl jacket has some very poor RF characteristics not to mention it is a bear to do. Stangely enough plans for this antenna abound. Shakespeare used to build a CB antenna lie this called the big stick They latter change it to four wires inside a fibergas tube with th wires imbedded in the fiberglass connected to the shield of the feedline. Then the feedline is centered in the tube using styrofoam. I built something similar using a metal tube connecting to the shield with the coax down the middle of the tube also using little pieces of styrofam to center the cable in the tube. This seemed to work pretty good. |
20m "ringo"
"Cecil Moore" wrote in message om... Jimmie D wrote: Thanks Cecil This was my first plan but I dont have room to run the stub straight out so I kind of tabled the idea for a while. Now that I have thought about it there is no reason I couldnt wrap it around the antenna. There's no reason why you couldn't spiral it around the antenna like a pancake inductor. If you kept each spiral about a foot away from the next one, the area occupied would be pretty small. Good luck. -- 73, Cecil http://www.w5dxp.com Cecil, I got the antenna up Sunday, for now the stub is straight out from the antenna. Is it normal for the 50 ohm point to be a little hard to find? About the best VSWR I can get now is 1.7:1 This is pretty close to the point where my radio starts limiting power. I m thinking either the stub or the antenna may be a little long is there an easy way to tell or is easier just to try something and see what happens? Checking the VSWR at differerent freqs doesnt help much. Maybe a slight indication that it is too long. Jimmie |
20m "ringo"
Jimmie D wrote:
Cecil, I got the antenna up Sunday, for now the stub is straight out from the antenna. Is it normal for the 50 ohm point to be a little hard to find? About the best VSWR I can get now is 1.7:1 This is pretty close to the point where my radio starts limiting power. I m thinking either the stub or the antenna may be a little long is there an easy way to tell or is easier just to try something and see what happens? Checking the VSWR at differerent freqs doesnt help much. Maybe a slight indication that it is too long. You've discovered the problem with SWR meters. They don't read phase. If you were using an antenna analyzer, the solution would probably be obvious. With only an SWR meter, your tuning algorithm either converges or diverges but you may not know which. The easy way to tune the antenna is to use an antenna analyzer to determine where the impedance is purely resistive and then adjust the stub tap point to 50 ohms. An antenna analyzer is a good investment. -- 73, Cecil http://www.w5dxp.com |
20m "ringo"
"Cecil Moore" wrote in message ... Jimmie D wrote: Cecil, I got the antenna up Sunday, for now the stub is straight out from the antenna. Is it normal for the 50 ohm point to be a little hard to find? About the best VSWR I can get now is 1.7:1 This is pretty close to the point where my radio starts limiting power. I m thinking either the stub or the antenna may be a little long is there an easy way to tell or is easier just to try something and see what happens? Checking the VSWR at differerent freqs doesnt help much. Maybe a slight indication that it is too long. You've discovered the problem with SWR meters. They don't read phase. If you were using an antenna analyzer, the solution would probably be obvious. With only an SWR meter, your tuning algorithm either converges or diverges but you may not know which. The easy way to tune the antenna is to use an antenna analyzer to determine where the impedance is purely resistive and then adjust the stub tap point to 50 ohms. An antenna analyzer is a good investment. -- 73, Cecil http://www.w5dxp.com I think before I start cutting I will try adding a little series capacitance or inductance to the antenna and see how it reacts to that. My work week just started so it may be a week or so before I get back at it again. |
20m "ringo"
In order to guarantee the ability to obtain a 1:1 SWR, you need to be
able to adjust at least two independent or partially independent things. This can be two variable lumped components; any two of the following: stub length, position, and Z0(*); and so forth. Adjusting, say, a stub length and the value of a capacitor across the input end of the stub won't do it because they're basically adjusting the same thing and therefore aren't independent. If you've only been varying one item, you'll get a perfect match only if lucky. If you're as close as 1.7:1, it's likely as easy or easier to find the solution by trial and error rather than calculation. The reason that two adjustments are required is that 1:1 SWR requires a particular value of R and a zero value of X. If you vary only one item, it'll change only R, or only X, or, more likely, both R and X but in some fixed relationship. (*) Because you can practically adjust Z0 over only a relatively narrow range, this is a good method only for fine tuning or as a way to set the range of other adjustments. Roy Lewallen, W7EL Jimmie D wrote: "Cecil Moore" wrote in message ... Jimmie D wrote: Cecil, I got the antenna up Sunday, for now the stub is straight out from the antenna. Is it normal for the 50 ohm point to be a little hard to find? About the best VSWR I can get now is 1.7:1 This is pretty close to the point where my radio starts limiting power. I m thinking either the stub or the antenna may be a little long is there an easy way to tell or is easier just to try something and see what happens? Checking the VSWR at differerent freqs doesnt help much. Maybe a slight indication that it is too long. You've discovered the problem with SWR meters. They don't read phase. If you were using an antenna analyzer, the solution would probably be obvious. With only an SWR meter, your tuning algorithm either converges or diverges but you may not know which. The easy way to tune the antenna is to use an antenna analyzer to determine where the impedance is purely resistive and then adjust the stub tap point to 50 ohms. An antenna analyzer is a good investment. -- 73, Cecil http://www.w5dxp.com I think before I start cutting I will try adding a little series capacitance or inductance to the antenna and see how it reacts to that. My work week just started so it may be a week or so before I get back at it again. |
20m "ringo"
On Tue, 12 Sep 2006 18:20:02 -0400, "Jimmie D"
wrote: "Cecil Moore" wrote in message t... Jimmie D wrote: Cecil, I got the antenna up Sunday, for now the stub is straight out from the antenna. Is it normal for the 50 ohm point to be a little hard to find? About the best VSWR I can get now is 1.7:1 This is pretty close to .... I think before I start cutting I will try adding a little series capacitance or inductance to the antenna and see how it reacts to that. My work week just started so it may be a week or so before I get back at it again. Roy has given you some good advice. Some further thoughts. I assume that the coax is not decoupled, that will complicate achieving your outcome. Before cutting things, an observation of whether VSWR is better at a higher or lower frequency will help guide you in the reactance dimension of the problem. Find the tap point for lowest VSWR, change frequency and do it again. This will hint to you whether the antenna / stub combination is short or long. Keep in mind that there is not a correct length of the radiator independently of the stub, small reactance due to the radiator being off resonance can be compensated by suitable stub dimensions. That says cut / lengthen the elements that are most convenient. Temporary increase in length by clamping an additional conductor to top of the radiator might less final that cutting bits off. Again, the shift in point of lowest VSWR is a hint. With knowledge, you should be able do this easy enough without an antenna analyser. Owen -- |
20m "ringo"
"Owen Duffy" wrote in message ... On Tue, 12 Sep 2006 18:20:02 -0400, "Jimmie D" wrote: "Cecil Moore" wrote in message et... Jimmie D wrote: Cecil, I got the antenna up Sunday, for now the stub is straight out from the antenna. Is it normal for the 50 ohm point to be a little hard to find? About the best VSWR I can get now is 1.7:1 This is pretty close to ... I think before I start cutting I will try adding a little series capacitance or inductance to the antenna and see how it reacts to that. My work week just started so it may be a week or so before I get back at it again. Roy has given you some good advice. Some further thoughts. I assume that the coax is not decoupled, that will complicate achieving your outcome. Before cutting things, an observation of whether VSWR is better at a higher or lower frequency will help guide you in the reactance dimension of the problem. Find the tap point for lowest VSWR, change frequency and do it again. This will hint to you whether the antenna / stub combination is short or long. Keep in mind that there is not a correct length of the radiator independently of the stub, small reactance due to the radiator being off resonance can be compensated by suitable stub dimensions. That says cut / lengthen the elements that are most convenient. Temporary increase in length by clamping an additional conductor to top of the radiator might less final that cutting bits off. Again, the shift in point of lowest VSWR is a hint. With knowledge, you should be able do this easy enough without an antenna analyser. Owen -- I am thinking about building an ANTENNASCOPE, see fig 1 at http://digilander.libero.it/hamweb/r...tennascope.htm .. This one doesnt allow you to measure impedance but i thought if I replaced one of the capacitors in the bridge circuit with a variable cap of about twice the value I could at least tell if an antenna was inductive or capacitive by which way I had to adjust the cap to get a perfect null. I think I have most if not all of the parts. Jimmie |
20m "ringo"
On Wed, 13 Sep 2006 20:30:14 -0400, "Jimmie D"
wrote: With knowledge, you should be able do this easy enough without an antenna analyser. .... I am thinking about building an ANTENNASCOPE, see fig 1 at http://digilander.libero.it/hamweb/r...tennascope.htm . This one doesnt allow you to measure impedance but i thought if I replaced one of the capacitors in the bridge circuit with a variable cap of about twice the value I could at least tell if an antenna was inductive or capacitive by which way I had to adjust the cap to get a perfect null. I think I have most if not all of the parts. It looks like you are going to develop an instrument to solve the problem, when you should be able to solve it with a little ingenuity and the VSWR meter that you have. Owen -- |
20m "ringo"
"Owen Duffy" wrote in message ... On Wed, 13 Sep 2006 20:30:14 -0400, "Jimmie D" wrote: With knowledge, you should be able do this easy enough without an antenna analyser. ... I am thinking about building an ANTENNASCOPE, see fig 1 at http://digilander.libero.it/hamweb/r...tennascope.htm . This one doesnt allow you to measure impedance but i thought if I replaced one of the capacitors in the bridge circuit with a variable cap of about twice the value I could at least tell if an antenna was inductive or capacitive by which way I had to adjust the cap to get a perfect null. I think I have most if not all of the parts. It looks like you are going to develop an instrument to solve the problem, when you should be able to solve it with a little ingenuity and the VSWR meter that you have. Owen -- Oh I know I can, this just seemed like it might be fun. I figure I can cobble this together in a couple of hours and have a useful instrument when I get finished. Jimmie |
20m "ringo"
Thanks all I got the antenna finished this past Tuesday. When I got finished
the stub seemed a little short, 5'11". Does this mean the antenna is a little long?. The stub is still straight. I got the SWR down to 1.2:1, I think I am going to leave it there. I built the ANTENNASCOPE but I am unsure whether it is telling me the antenna is inductive or capacitive at this point. Oh well I will set up a little groundplane antenna on 10 or 15 that I know is too long and see how it reacts. |
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