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Tapering open wire feedlines?
Just curious if this has ever been done? I'm thinking about
putting up a 90 foot dipole feed with homemade open wire line. I'd like to bring it into the shack using paralled runs of LMR-400 cable, since the final 25 feet is via 3" electrical conduit that also has rotor and other cables. I believe the parallel cables with give me a 100 ohm impedance. The open wire will be using #10 with homemade spreaders, I'm going to try for 600 ohms at the feedpoint. I was wondering if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? Pete k1zjh |
Tapering open wire feedlines?
"Pete Bertini" wrote in message ... Just curious if this has ever been done? I'm thinking about putting up a 90 foot dipole feed with homemade open wire line. I'd like to bring it into the shack using paralled runs of LMR-400 cable, since the final 25 feet is via 3" electrical conduit that also has rotor and other cables. I believe the parallel cables with give me a 100 ohm impedance. The open wire will be using #10 with homemade spreaders, I'm going to try for 600 ohms at the feedpoint. I was wondering if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? Pete k1zjh You have just reinvented the Delta Match. http://www.g4nsj.co.uk/delta.shtml Is one place to look. |
Tapering open wire feedlines?
On Jun 20, 10:04*am, "Pete Bertini" wrote:
I was wondering if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? My "ARRL Antenna Book", 20th edition, has a section on "Tapered Lines". They say it should be at lease one wavelength on the lowest frequency of operation. They give an "air insulated" formula for such a design. -- 73, Cecil, w5dxp.com |
Tapering open wire feedlines?
Just curious if this has ever been done? I'm thinking about
putting up a 90 foot dipole feed with homemade open wire line. I'd like to bring it into the shack using paralled runs of LMR-400 cable, since the final 25 feet is via 3" electrical conduit that also has rotor and other cables. I believe the parallel cables with give me a 100 ohm impedance. The open wire will be using #10 with homemade spreaders, I'm going to try for 600 ohms at the feedpoint. I was wondering if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? Yes, it has been done. Jasik's "Antenna Engineering Handbook" discusses tapered lines in section 31.4. You can also find a discussion of tapered-line matching in Laport's "Radio Antenna Engineering" in section 4.4.8 (this book is available as a free PDF download). In your application, though, I'm not sure why you would want to bother. Traditionally, tapered lines are used as part of a matching network, making a transition between two known resistive impedances (e.g. transmitter and antenna). That's not really the situation you seem to be setting up. You are (I presume) setting up a single doublet, to be used at multiple frequencies, with wildly varying impedances at the antenna feedpoint. You're then coming back to the shack with a high-impedance feedline (which has relatively low losses even at the high SWRs it'll be operating at), and then matching the impedance in the shack with a good transmatch-and-balun. In a setup like this, the characteristic impedance of the open-wire line isn't particularly critical.. because it'll almost never be a close match to what the antenna is presenting at any given frequency. 600 ohms is a common feedline impedance... but no matter what impedance you choose here, it's unlikely to be a close match to the antenna under actual operating conditions. As a result, the impedance you actually "see" looking up into the lower end of the open-wire line won't be 600 ohms (if untapered) or 100 ohms (if tapered down close together). Rather, it'll be the feedpoint impedance of the antenna at the frequency in question, transformed by the feedline (tapered or not). You could calculate it, knowing the antenna's feedpoint impedance (e.g. from modeling it in NEC2) and the length and Z of the feedline... but it isn't likely to be close to a convenient pure resistance except by lucky chance! Hence, there's no real need to "match" the lower Z of the parallel- coax segment (100 ohms nominal) to Z of the open-wire line, since the latter value isn't actually what you'd have to match to! Now, if you're planning to operate at a specific single frequency, you could perhaps utilize a tapered open-wire line as part of a tuned matching setup... in effect, designing the taper for that one antenna and frequency, in order to present a more convenient impedance to your transmitter's matching network (e.g. your external wide-range transmatch). However, optimizing the system in this way, for one specific frequency, might well make the antenna-and-feedline a *harder* load for you to match in the shack at other frequencies. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Tapering open wire feedlines?
"Pete Bertini" wrote in news:76qTn.8899
: Just curious if this has ever been done? I'm thinking about putting up a 90 foot dipole feed with homemade open wire line. I'd like to bring it into the shack using paralled runs of LMR-400 cable, since the final 25 feet is via 3" electrical conduit that also has rotor and other cables. I believe the parallel cables with give me a 100 ohm impedance. Yes, but will the configuration have the benefits you think? See http://www.vk1od.net/transmissionline/stcm/index.htm for more info. The open wire will be using #10 with homemade spreaders, I'm going to try for 600 ohms at the feedpoint. I was wondering What is 600 ohms, the feed line or the antenna. If the feed line operates at high VSWR, it doesn't matter a lot what Zo is. Further, that using tapered lines as a broadband impedance match requires that the taper section is quite long wrt wavelength. if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? I cannot reconcile the 90' dipole and 600 ohms from the little information you have given. Your post is very short on information, so it is entirely a guessing game. Owen |
Tapering open wire feedlines?
On Jun 20, 8:04*am, "Pete Bertini" wrote:
Just curious if this has ever been done? *I'm thinking about putting up a 90 foot dipole feed with homemade open wire line. *I'd like to bring it into the shack using paralled runs of LMR-400 cable, since the final 25 feet is via 3" electrical conduit that also has rotor and other cables. I believe the parallel cables with give me a 100 ohm impedance. The open wire will be using #10 with homemade spreaders, I'm going to try for 600 ohms at the feedpoint. I was wondering if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? Pete k1zjh Based on my personal experience trying to replace the inside shack portion of 600 ohm open feed line with two parallel pieces of RG-213 about 8 ft. long. The coax sections will effectively kill the use of your dipole on any of the higher frequencies. As I remember, the antenna was usable up through 10 meters , but after putting in the coax, I couldn't tune the system above 20 meters. My antenna is a full sized 160 meter horizontal loop in the form of a trapazoid, almost a square, up at 35 ft. Fed in one corner with 600 ohm open wire,125 ft. long. The feedline comes into the house (mfg home with aluminum siding) using two Birnbach feed through insulators. Then to a DPDT antenna switch to ground the system during thunder storms, and finally about 6 ft of 600 ohm feed line to the balun in the Dentron MT-3000 tuner. I think the problem with using the double coax is the very large capacitance it adds to the feed line, effectively becoming a low pass filter. Could be mistaken about the cause, but not the symptoms. I have actually used the system to make some local 6 meter contacts. Try it anyway, but be prepared to go all the way to the shack with your 600 ohm feed line. Paul, KD7HB |
Tapering open wire feedlines?
"Owen Duffy" wrote in message ... " wrote in news:6d1a078a-e5f4- : ... I think the problem with using the double coax is the very large capacitance it adds to the feed line, effectively becoming a low pass filter. Could be mistaken about the cause, but not the symptoms. I have actually used the system to make some local 6 meter contacts. The coax is, and always is a transmission line, and at the length you described cannot be approximated well as a shunt capacitance. What you have is a cascade of two line sections, one of say 600 ohms, then one of 100 ohms, and each is probably operating with standing waves, so there is impedance transformation. To illustrate, lets say your feedpoint at 3.6MHz with a certain loop antenna was 100+j0, and you had say 30m (100') of 600 ohm open wire, the impedance looking into that would be around 240-j675. If you feed that with say 6m (20') of LMR400 twin, then input Z would be around 60+j260 and loss would be about 40%. The synthesised shielded pair is relatively lossy, and low Zo. Most people use this configuration thinking that the shielding prevents external fields from common mode current, but they are quite wrong. See http://www.vk1od.net/transmissionline/stcm/index.htm . Though the traditional approach has been to use a 4:1 voltage balun at the rig to feed these things, there is good argument to use a 1:1 Guanella balun (current balun), and it can be located outside the shack and inboard shield effectively grounded to deal with common mode current. You still need to minimise the length of coax operated at high VSWR, and it would not be necessarily absurd to think about low loss coax. Approximating coax as a shunt capacitance might be reasonably accurate for some applications at audio frequencies, but it is probably not for most RF applications. Owen Owen, my thinking was to make a transmission line with a characteristic impedance that gradually changed from 600 ohms down to as close to 200 ohms as practical, just to avoid the impedance bump at the junction of the open wire and shielded balance line. I've found a few references that state the taper should follow a log response; and also if the line needs to be a wavelength or longer pretty much dashes that idea. It would be a lot easier to construct a line with charateristic impedance of 400 to 600 ohms, and deal with narrow spacing issue for only a relatively short portion of the entire span. I didn't expect the shielded cable to be immune to common reradiation problems, but that issue could be dealt with separately if it was a problem. Pete |
Tapering open wire feedlines?
"Owen Duffy" wrote in message ... " wrote in news:6d1a078a-e5f4- : ... Though the traditional approach has been to use a 4:1 voltage balun at the rig to feed these things, there is good argument to use a 1:1 Guanella balun (current balun), and it can be located outside the shack and inboard shield effectively grounded to deal with common mode current. You still need to minimise the length of coax operated at high VSWR, and it would not be necessarily absurd to think about low loss coax. Owen Okay, then it might make sense to do this: Plan II instead of using the balun is in the tuner, there is no reason why I couldn't mount another 4:1 balun outdoors, and use a short run of low loss coax back through the conduit into the operating room. That would be about 15 feet of LMR-400 cable. I could go to 1/2 heliax but would there be any benefit?? So, I would have balanced open-wire feedline from the dipole to the 4:1 balun followed by a 1:1 common-mode RF choke with the requiste RF ground for decoupling, followed by the short run of low loss coax going back to a unbalanced ant. port on the tuner. I'd still have coax in the mix, but the 4:1 balun should hopefully tame the high impedance excursions across the antenna operating range to reduce the coax's losses at those points? Otherwise it is going to be hard to get balanced line into the shack, unless I pull it through the PVC conduit with the other coax cables. Pete |
Tapering open wire feedlines?
"Pete Bertini" wrote in news:DiwTn.64499
: So, I would have balanced open-wire feedline from the dipole to the 4:1 balun followed by a 1:1 common-mode RF choke with See my article entitled "Is a 4:1 balun a good choice for use with an ATU on HF?" at http://vk1od.net/blog/?p=987 . It is difficult to answer the question about the LDF without knowing the impedances involved. I used TLLC ( http://www.vk1od.net/calc/tl/tllc.php ) to work the examples I gave, you could do the same if you know the feedpoint impedance etc. If you want to solve the cases for an arbitrary two wire line, try http://www.vk1od.net/calc/tl/twllc.htm . Owen |
Tapering open wire feedlines?
On Jun 20, 1:33*pm, Owen Duffy wrote:
" wrote in news:6d1a078a-e5f4- : ... I think the problem with using the double coax is the very large capacitance it adds to the feed line, effectively becoming a low pass filter. Could be mistaken about the cause, but not the symptoms. I have actually used the system to make some local 6 meter contacts. The coax is, and always is a transmission line, and at the length you described cannot be approximated well as a shunt capacitance. What you have is a cascade of two line sections, one of say 600 ohms, then one of 100 ohms, and each is probably operating with standing waves, so there is impedance transformation. To illustrate, lets say your feedpoint at 3.6MHz with a certain loop antenna was 100+j0, and you had say 30m (100') of 600 ohm open wire, the impedance looking into that would be around 240-j675. If you feed that with say 6m (20') of LMR400 twin, then input Z would be around 60+j260 and loss would be about 40%. The synthesised shielded pair is relatively lossy, and low Zo. Most people use this configuration thinking that the shielding prevents external fields from common mode current, but they are quite wrong. Seehttp://www.vk1od.net/transmissionline/stcm/index.htm. Though the traditional approach has been to use a 4:1 voltage balun at the rig to feed these things, there is good argument to use a 1:1 Guanella balun (current balun), and it can be located outside the shack and inboard shield effectively grounded to deal with common mode current. You still need to minimise the length of coax operated at high VSWR, and it would not be necessarily absurd to think about low loss coax. Approximating coax as a shunt capacitance might be reasonably accurate for some applications at audio frequencies, but it is probably not for most RF applications. Owen Thanks, Owen. I made up my test after reading the june 2008 QST story. Paul, KD7HB |
Tapering open wire feedlines?
Looks like most of the information I needed was already written up on the DX Engineering webpages. I'll have to go do a bit more reading before committing to anything. Thanks for all the comments so far.... Pete |
Tapering open wire feedlines?
"Pete Bertini" wrote in
: .... So, I would have balanced open-wire feedline from the dipole to the 4:1 balun followed by a 1:1 common-mode RF choke with I should have mentioned that 4:1 baluns integrated into ATUs are most often voltage baluns. When operated near a voltage maximum with high standing waves, they can be very lossy. Sometimes it is claimed that they 'tame' difficult antennas better than current baluns, which is often due to their internal loss. The problem as such is not the balun, it is the extreme load presented by a very poor antenna, and the lossy balun is a poor (grossly inefficient) circumvention. So, when a 4:1 voltage balun allows a match where a 1:1 current balun doesn't, the problem is probably the antenna, not the balun. Owen |
Tapering open wire feedlines?
That's pretty much what I've been reading on various websites.
At least some of the mystery is being cleared up :) A fan dipole is starting to look better; at least I can control the feedpoint impedance to within reason and keep a decent pattern on the bands. Pete "Owen Duffy" wrote in message ... "Pete Bertini" wrote in : ... So, I would have balanced open-wire feedline from the dipole to the 4:1 balun followed by a 1:1 common-mode RF choke with I should have mentioned that 4:1 baluns integrated into ATUs are most often voltage baluns. When operated near a voltage maximum with high standing waves, they can be very lossy. Sometimes it is claimed that they 'tame' difficult antennas better than current baluns, which is often due to their internal loss. The problem as such is not the balun, it is the extreme load presented by a very poor antenna, and the lossy balun is a poor (grossly inefficient) circumvention. So, when a 4:1 voltage balun allows a match where a 1:1 current balun doesn't, the problem is probably the antenna, not the balun. Owen |
Tapering open wire feedlines?
Pete Bertini wrote:
Just curious if this has ever been done? I'm thinking about putting up a 90 foot dipole feed with homemade open wire line. I'd like to bring it into the shack using paralled runs of LMR-400 cable, since the final 25 feet is via 3" electrical conduit that also has rotor and other cables. I believe the parallel cables with give me a 100 ohm impedance. The open wire will be using #10 with homemade spreaders, I'm going to try for 600 ohms at the feedpoint. I was wondering if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? Yes.. Tapered transmission lines have been around for decades, and work just like you'd expect. For the ultimate in performance, you actually want to use an exponential taper (spacing increases by the same percentage per unit distance), but a linear taper (spacing increases by the same distance per unit distance) works pretty much the same, especially if the taper is "long" (10x) relative to the spacing. that is, going from 1" to 3" spacing over a foot or two.. Pete k1zjh |
Tapering open wire feedlines?
As an academic exercise, for example using a tapered
line to match an OCD with a known FP impedance of 200 ohms down to a 1:1 balun at the 50 ohm coax line transition point. What is the recommended minimum length of cable needed to perform a four to one characteristic impedance change in the open wire for relating to the wavelength? Pete "Jim Lux" wrote in message ... Pete Bertini wrote: Just curious if this has ever been done? I'm thinking about putting up a 90 foot dipole feed with homemade open wire line. I'd like to bring it into the shack using paralled runs of LMR-400 cable, since the final 25 feet is via 3" electrical conduit that also has rotor and other cables. I believe the parallel cables with give me a 100 ohm impedance. The open wire will be using #10 with homemade spreaders, I'm going to try for 600 ohms at the feedpoint. I was wondering if tapering the spacing on the feedline would give me a smoother impedance where the open wire, arrestor, and twin coax arrange- meet? Yes.. Tapered transmission lines have been around for decades, and work just like you'd expect. For the ultimate in performance, you actually want to use an exponential taper (spacing increases by the same percentage per unit distance), but a linear taper (spacing increases by the same distance per unit distance) works pretty much the same, especially if the taper is "long" (10x) relative to the spacing. that is, going from 1" to 3" spacing over a foot or two.. Pete k1zjh |
Tapering open wire feedlines?
Pete Bertini wrote:
As an academic exercise, for example using a tapered line to match an OCD with a known FP impedance of 200 ohms down to a 1:1 balun at the 50 ohm coax line transition point. What is the recommended minimum length of cable needed to perform a four to one characteristic impedance change in the open wire for relating to the wavelength? What's the VSWR and frequency spec? 50 ohm balanced pair might be hard to come by.. the usual 276*log10(D/d) equation is only valid when Dd. (D = spacing, d = diameter) and just ballparking 50 ohms means that the spacing between the wires is about 10% more than the diameter (D/d 1.1). 200 ohms is more like D/d = 3 |
Tapering open wire feedlines?
"Pete Bertini" wrote in
: As an academic exercise, for example using a tapered line to match an OCD with a known FP impedance of 200 ohms Pete, You really don't disclose very much, certainly not in a clear way. But, some of your hints (eg OCD with open wire feed) leave me asking why? I am not going to waste time writing a lot of words based on a hint though. Owen |
Tapering open wire feedlines?
Pete Bertini wrote:
As an academic exercise, for example using a tapered line to match an OCD with a known FP impedance of 200 ohms down to a 1:1 balun at the 50 ohm coax line transition point. What is the recommended minimum length of cable needed to perform a four to one characteristic impedance change in the open wire for relating to the wavelength? Pete It's not practical to make a 50 ohm open wire line. The wires would have to be extremely close together. But as to "recommended" minimum length, it depends on who does the recommending and what your criteria are. The length of line necessary to transition from one impedance to another depends on at least three things: the amount of transformation required, the type of taper (e.g., linear, exponential, Klopfenstein), and how close the impedance match has to be (usually specified as input reflection coefficient). There's a brief treatment in Johnson, _Antenna Engineering Handbook_. In Brown, Sharpe, Hughes, and Post, _Lines, Waves, and Antennas_, it's stated that the tapered section must be at least a quarter wavelength long, and that if less than that, "it will fail in its matching function". In Skilling, _Electric Transmission Lines_, ". . . a 2 to 1 change of characteristic impedance many be accomplished by using a tapered section that is 1 wavelength long. A good impedance match results at this frequency and at all higher frequencies. Results are fairly good if the tapered section is as little as 1/2 wavelength long, particularly if the impedance ratio required is less than 2 to 1. It is not worth while to use a tapered section much shorter than 1/2 wavelength, for a taper that is 1/4 wavelength or shorter will give nearly as much reflection as will the abrupt change of impedance at a mismatch. Those frequencies for which the length of the taper is a multiple of a half-wavelength are transmitted with the least reflection. This may be a guide in choosing the length of the taper." The author goes on to state that linear and exponential tapers give practically the same results, and summarizes with a recommendation that a tapered section be between 1/2 and 1 wavelength long at the lowest frequency of use. Roy Lewallen, W7EL |
Tapering open wire feedlines?
"Roy Lewallen" wrote in message ... Pete Bertini wrote: As an academic exercise, for example using a tapered line to match an OCD with a known FP impedance of 200 ohms down to a 1:1 balun at the 50 ohm coax line transition point. What is the recommended minimum length of cable needed to perform a four to one characteristic impedance change in the open wire for relating to the wavelength? Pete It's not practical to make a 50 ohm open wire line. The wires would have to be extremely close together. But as to "recommended" minimum length, it depends on who does the recommending and what your criteria are. The length of line necessary to transition from one impedance to another depends on at least three things: the amount of transformation required, the type of taper (e.g., linear, exponential, Klopfenstein), and how close the impedance match has to be (usually specified as input reflection coefficient). There's a brief treatment in Johnson, _Antenna Engineering Handbook_. In Brown, Sharpe, Hughes, and Post, _Lines, Waves, and Antennas_, it's stated that the tapered section must be at least a quarter wavelength long, and that if less than that, "it will fail in its matching function". In Skilling, _Electric Transmission Lines_, ". . . a 2 to 1 change of characteristic impedance many be accomplished by using a tapered section that is 1 wavelength long. A good impedance match results at this frequency and at all higher frequencies. Results are fairly good if the tapered section is as little as 1/2 wavelength long, particularly if the impedance ratio required is less than 2 to 1. It is not worth while to use a tapered section much shorter than 1/2 wavelength, for a taper that is 1/4 wavelength or shorter will give nearly as much reflection as will the abrupt change of impedance at a mismatch. Those frequencies for which the length of the taper is a multiple of a half-wavelength are transmitted with the least reflection. This may be a guide in choosing the length of the taper." The author goes on to state that linear and exponential tapers give practically the same results, and summarizes with a recommendation that a tapered section be between 1/2 and 1 wavelength long at the lowest frequency of use. Roy Lewallen, W7EL Roy Thank you Roy for taking the time to post. That's exactly what I was looking for, and answers my questions completely. My curiousity is satisfied. Pete |
Tapering open wire feedlines?
Roy Lewallen wrote:
Pete Bertini wrote: As an academic exercise, for example using a tapered line to match an OCD with a known FP impedance of 200 ohms down to a 1:1 balun at the 50 ohm coax line transition point. What is the recommended minimum length of cable needed to perform a four to one characteristic impedance change in the open wire for relating to the wavelength? Pete It's not practical to make a 50 ohm open wire line. The wires would have to be extremely close together. But as to "recommended" minimum length, it depends on who does the recommending and what your criteria are. The length of line necessary to transition from one impedance to another depends on at least three things: the amount of transformation required, the type of taper (e.g., linear, exponential, Klopfenstein), and how close the impedance match has to be (usually specified as input reflection coefficient). There's a brief treatment in Johnson, _Antenna Engineering Handbook_. In Brown, Sharpe, Hughes, and Post, _Lines, Waves, and Antennas_, it's stated that the tapered section must be at least a quarter wavelength long, and that if less than that, "it will fail in its matching function". In Skilling, _Electric Transmission Lines_, ". . . a 2 to 1 change of characteristic impedance many be accomplished by using a tapered section that is 1 wavelength long. A good impedance match results at this frequency and at all higher frequencies. Results are fairly good if the tapered section is as little as 1/2 wavelength long, particularly if the impedance ratio required is less than 2 to 1. It is not worth while to use a tapered section much shorter than 1/2 wavelength, for a taper that is 1/4 wavelength or shorter will give nearly as much reflection as will the abrupt change of impedance at a mismatch. Those frequencies for which the length of the taper is a multiple of a half-wavelength are transmitted with the least reflection. This may be a guide in choosing the length of the taper." The author goes on to state that linear and exponential tapers give practically the same results, and summarizes with a recommendation that a tapered section be between 1/2 and 1 wavelength long at the lowest frequency of use. Roy Lewallen, W7EL I've seen essentially the same ... bigger than 1/2 (or 5/8) wavelength works well. BUT... that's for a "good match".. if you're willing to tolerate a "not so good match" I think you can get much shorter. There's a lot of antenna designs that use this sort of scheme to match, say the 100 ohm impedance of a helix to 50 ohms, over a distance on the order of 1/4 or 1/5 wavelength. Whether it's truly a tapered transmission line or a semi-distributed lumped L and C is probably a good question. Certainly, one could use a string of lumped L/C networks to make a synthetic transmission line that has mechanical length much shorter than 1/2 wavelength. So, when does a series of lumped LCs become a transmission line? You also see tapered transitions in microstripline all the time, and they're often shorter than 1/2 wavelength. But maybe that's more in the nature of a "distributed matching network" rather than a pure transmission line. There's a goodly amount of empiricism in both antennas and stripline design. Especially if you're talking about an balanced pair with separation smaller than the diameter/width of the conductor, it's probably not a "simple" transmission line. |
Tapering open wire feedlines?
I saw hints that the application of the tapered line matching section was
to a HF off centre fed dipole, and an assumption that as a multiband antenna, it had a feedpoint impedance of close to 200+j0. Most users of OCF dipole systems are expecting to be able to use the antenna on many bands without an ATU, and accept significant tradeoffs in peformance for that objective. It is unlikely that the feedpoint impedance of the dipole itself is sufficiently tight to worry too much about the broaband peformance of a tapered line matching section, much less the practicality of constructing low loss tapered two wire lines with Zo approaching 50 ohms. It is only when a system perspective is taken, that some of the component level discussion seems to be an interesting issue, but poor application. Owen |
Tapering open wire feedlines?
On Jun 22, 1:57*pm, Owen Duffy wrote:
It is only when a system perspective is taken, that some of the component level discussion seems to be an interesting issue, but poor application. In a multi-band system with high SWRs, are there any configurations where a tapered line would be a good application? -- 73, Cecil, w5dxp.com |
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