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Does coax length affect swr

Does coax length affect swr. Use 49 feet of coax from the antenna to your meter, and 6 feet from your meter to your radio. #19. Been doing it for almost 35 years on frequencies from 1. . Many authors have stated that an antenna tuner tunes coax #1, but has no effect on coax #2 or the antenna. > instances, the coax will act as a portion of the antenna itself. Return loss is the measure of how small the “return” or reflection/echo is. specific length of cable duplicates the feedpoint impedance of. 7 GHz and haven't seen it happen yet. Usually, SWR is defined as the ratio of the maximum radio-frequency ( RF ) voltage to the minimum RF voltage along the line. Nov 18, 1998 · 1/2 wavelength of coax and tune your antenna with that. Posted March 10, 2022. You cannot use them with your CB radio. You would need likely a 4:1 balun from your coax to the ladder line feeding the dipole. The reason for using 300 ohm balanced line is that it is a good match for certain types of antennas, and has lower loss than a typical coaxial Note that the very first dip is where the cable is less than 1/4 wavelength. For example, I bet a 2m whip on the corner of But change the load to some value that does not match its characteristic impedance, then the coax behaves like an impedance transformer. Nov 26, 2014 · Nov 26, 2014. Sorry to say, this is Apr 12, 2016 · The only disadvantage is the extra loss in the coax from the extra length. edu/w9cf/tr For this you will need your meter and a short jumper of coax with the correct connectors on it (usually PL-259s). You SHOULD NOT transmit with your CB at SWR levels above 3. “100-foot cable might result in a 33% loss of the original signal. 5:1 or lower, which corresponds to a reflection loss of less than 4%. Test the beam again for shorts and opens. There are two special cases that are very useful. When your reading changes significantly after changing coax length, that means you are fooling the meter into seeing a better match. 4) Are CB Amplifiers Illegal? Yes, CB amplifiers are illegal. Aug 22, 2013 · Also the way to make coaxial cable works as impedance transformer & proper SWR measurement technique. As does air, trees, buildings, antennas, hills and other medium that reside between two radios that are trying to communicate. If caught, you will be prosecuted. If you add/subtract coax it changes that total 'mix' to change the SWR. Shorten the Antenna. using a electrical half wavelength of coax can help meters read vswr more accurately . > nature of the matching mechanism between the antenna and the feedline. Follow this guide to test your CB coax for problems. In this video Jan 4, 2014 · The 18' general length is no where near the proper length for my purposes. Remember that, while the SWR remains constant along a length of feedline (ignoring losses), the impedance varies when the line is not perfectly matched. Feb 2, 2011 · Again, coiling coax does NOT add inductance and will NOT affect SWR. This is probably the number one way coax is ruined. SWR will be higher when the beam is near the ground but you should be able to see a dip as you make tests across each band. But as I wrote, SWR doesn't create a lot of losses and in most cases doesn't affect performance to a degree that you have to worry about it. 5:1 (or something like that, I just made up the numbers)-- it isn't a coupling improvement to the antenna you are Jun 11, 2011 · Jun 11, 2011. it also does not change the vswr . It will affect the reading. But there are cases where you CAN change the SWR at the shack end of the line by changing the coax length. Try folding and twisting the wire back on itself before cutting it, though. 5:1 SWR. How does having multiple coax jumpers affect the antenna SWR? Say you have a radio, amp, power meter, switch between antenna and dummy load, freq injector for alignments, etc. Sep 6, 2005 · If you have a ground plane problem or a slight mismatch, then the length of your coax will affect the reading you get on your meter. #3. Coax Part of Antenna = coax affect SWR reading. If the SWR is too high, not only is the performance of your CB seriously hindered, but you run a very high Oct 23, 2021 · Yes, the length of cable does have an effect on both transmission and reception equally. Impedance mismatches result in standing waves along the transmission line, and SWR is defined as the ratio of the partial standing wave 's Oct 18, 2011 · Using a 1/2 wave length and using a 25 or 100 ohm load will show 2:1 the same as a 150 ohm load will show 3:1. The SWR is the ratio standing wave voltage at two different points on the line (the points with maximum and minimum voltage). “50-foot cable might result in 20% loss of the original signal. 3: If your SWR "changes" with different lengths of coax, you have a problem at the FEEDPOINT of the Mar 26, 2018 · A helpful guide on how to determine the right length of coaxial cable for your antenna. However, I do not believe 100-120ft results in such a significant drop. 0. If later on you decide you want to add another device Use 49 feet of coax from the antenna to your meter, and 6 feet from your meter to your radio. RF engineers often measure return loss on a “dB It's just that it is conventional for amateur radio equipment to be designed with 50 ohms characteristic impedance, so if you substitute 75 ohm coax without doing anything else you will have mismatches. In some. The second graph demonstrates 2:1 SWR. Aug 26, 2021 · For example, for a center frequency of 14. It is not true that any specified length lowers SWR. Return Loss. that 's a lot of 1-3 foot jumpers. > instance, length will effect SWR. If you have a perfect match at both ends then the coax length doesn't matter at all. the result which is very near the actual lenght of the Coaxial cable, 100 mm (rubber gommet to base) + 10 mm (rubber gommet to connector) = 110 mm. Proper Use and Storage of Coax: Verify that your coax is not crimped, bent, or crushed. Voltage Standing Wave Ratio (VSWR) and Structural Return Loss (SRL) are basically the same - only different. You can use the metal parts of your structure as part of the antenna, if that makes things easier. 37 : 1, but the impedance the analyzer sees is now 25 + j19 ohms, just due to the effect of the short coax jumper cable. Aug 14, 2011 · The bottom line shows 1. And one final thought. ”. The transformation ratio will depend on coax's characteristic impedance, the load's complex impedance, and length of coax. Dec 1, 2021 · In both cases you use a specific length of a coax to get rid of the SWR. Smaller return loss is bad, and means less energy is going into our antenna. We want a small return, so a large loss on the return “echo” is good. It's true that you cannot "tune" an antenna by changing the coax length. Depending on the specified type of coax cable used, it does suffer from what's called attenuation, which is signal loss over distance. or the input tuning of a amp . Went back and sprayed the insulator at the ground radials,( just enough to saturate that area) and the swr went up to nearly a 2 to 1 swr. Then, add about 6 inches to that length on each side and raise the antenna to its permanent location. Apr 21, 2022 · Optimum frequency is around 150MHz, SWR close to 1. Here is my situation. 11 X 6 = 66. Reducing the antenna’s length is one of the most common solutions to minimize high SWR on 1 and 40. The third graph demonstrates 3:1 SWR. When I want to tune an antenna, the e1/2ƛ jumper serves to permit me to read the condition of the antenna without transforming the the impedance through some other length, as would be the case with an actual 18'. VSWR is essentially the ratio of the Input Impedance to the average Characteristic Impedance as a result of Mar 21, 2024 · An SWR of 1:1 represents a perfect match, where all the power is transmitted to the load and no power is reflected. A typical 11-meter signal has a basic wavelength of 36 feet/wave. Coax Radiating = coax acts as part of antenna. Therefore, there is no “maximum length coax cable before signal loss”. Your connector reflects power, and pretty strongly so! An SWR or 4:1, more or less, on 40m isn't unexpected from the G5RV JR. That is only apparent SWR (what the radio "see's") and thats when condition of noise, hot mic etc appear. Another nuance with this Dec 5, 2023 · If your coax cable has an open - that is, the wire is broken and current can't flow through it - you'll get off-the-chart SWR readings. But they didn't affect it for the other radiator. In fact because SWR is a measurement of reflected power and if you measure at the transmitter output your SWR can look better because there's more cable loss than if it were shorter. But that's only really gonna happen if the antenna isn't presenting a 50 ohms, non-reactive load, meaning it is really tuned incorrectly. Nov 2, 2011 · Using old coax like Mike5511 was saying works just fine, but usually what I do is strip off the outer jacket of the coax, then pull the center conductor wire out, then flatten the braid and put a little solder on the ends, then attach that using self tapping screwsBut either way would work. Most SWR meters do not actually measure the voltage Feb 26, 2017 · No issues now, steady signal and 1. Because radio waves are tuned wavelengths of energy, we have to take into account the coax cable length. Feb 7, 2017. Hence it is essential to check your coax cable thoroughly before purchasing. One note I forgot to mention is that if cable gets kinked, that can hurt the signal/SWR. Couplers can have an affect but again, it's usually very minimal. If you’d like to calculate the loss of your aerial signal, there’s a simple formula: K1 x F + K2 x F + CLF x F = CL. A more realistic target for system designers is an SWR of 1. The length of coax to used to "repeat" the SWR of a non-resonant antenna (other than 50 ohm match to your system) at the other end would be 1/2 wave multiple length coax. Online program address: http://fermi. Jan 19, 2015 · For the antenna to be really in the clear, two wavelengths is a good rule of thumb. Yes, its really that simple. In radio engineering and telecommunications, standing wave ratio ( SWR) is a measure of impedance matching of loads to the characteristic impedance of a transmission line or waveguide. Attach the antenna analyzer to the end of the coax run and find the lowest SWR. The only reason SWR changes with coax length is due to loss going to the antenna and then loss coming back (as SWR is a ratio). 1:1 is equivalent to 26dB RL. We recommend 18 feet of coax even if you don't need that much. This. A perfect match between the radio and the antenna results in an SWR of SWR of 2:1 is equivalent to 9. but it doesn't change the actual vswr of the antenna . Is this telling me that the coax cable is detuning the system down to 130MHz or am I using the VNA incorrectly? Oct 8, 2005 · 1: SWR is a measurement between the FEEDLINE and the antenna at the FEEDPOINT of the antenna (not the radio, not the SWR meter, etc!) 2: If your antenna is 44' from your radio, at 27MHz your coax should be 44' long. Search titles only By: Search Advanced search… Jan 17, 2024 · LMR®400 is a flexible communications coax with an impedance of 50 Ohm. 2:1 (RL =21dB) is pretty good. Store any additional coax in a figure 8 style, about a foot in length, and loosely bound in the center with a zip tie. You can probably get as close as a quarter wavelength and still make things work with some adjustments to the tuning. Coax was designed to be roughted next to metal, for Naval Ships. 96 feet (468/14. The video from YG1CCR also shows you how to make coaxial cable work as an impedance transformer and how to make proper SWR measurements. A modern GMRS mobile radio will be OK with an SWR of 2:1, where a tuned up CB radio really needs a low (1:1-1. Just like potential coax problems, if the wire in your antenna is broken you'll experience high SWR. These losses affect SWR in only one direction, they lower it. Dec 7, 2021 · How to Calculate Signal Loss. 5:1 (RL=14dB) is acceptable and an SWR better than 1. This is the case if the line is lossy. Plugging this into the equation we calculate the cable length Impedance and resistance are also entirely separate, related terms. the coax lenght will only make you see incorect swr readings if your antenna is not tuned and your not using a 1/2 wave multiple of coax. Coax is a critical component. A coax can get twisted, shorted, or pinched while routing through the vehicle. Not much loss, but it adds some. 5cm using a bolt cutter. In effect, power is lost/consumed as it travels through any medium. It adds loss. Coax Length. Some tuners operate manually; you twist the knobs until the SWR meter shows a 1:1 SWR, or something reasonably close to it. 6:1 SWR can be equal to either 80 Ω or 31 Ω resistive? (1. The gain over a dipole is now a few db at some really low angles, so it can be better than a dipole. Lower the beam and remove the coax cable. they say use around 18 feet cause that is a 1/2 wave multiple on 11 meters. voltage values along the transmission line measured with hf probe , but again SWR would remain constant along the line length. A perfect (but unachievable) 1:1 SWR is equivalent to a Return Loss of infinity. Mar 2, 2016 · For instance; If you have, say, an SWR of 2:1 with a short length of cable on Frequency-X, the coax having say 0. In the real world an SWR better than 1. If the coax is not properly connected an any end, you will see such a change in SWR, when it is moved around. LMR®400 was designed to replace the RG-8 cables. #9 - Test Your Antenna for Defects / Opens. Properly store any excess coax in a figure 8, about one foot in length, and bound in the middle- it should look like a long, skinny 8. Nov 6, 2005 · The coax only needs to be as long as it takes to connect the radio to the antenna. Jan 31, 2012 · Unless a remote SWR meter head is incorporated, we usually use the standard SWR meter located at the radio. Yes, cable can effect SWR. Antenna systems work on a balance between capacitive and resistive. Suggest you check the coax connections at the radio and antenna. Jul 22, 2004 · When a length of coax is slightly made longer or shortened, and diffferent SWR is measured, this indiactes that the coax is now radiating energy from the outside of the shield. 2 MHz, the length comes out to 32. However Jan 27, 2003 · COAX LENGTH DOES NOT MATTER. If you have a correctly tuned antenna resonant and matched to the frequency in use and the correct impedance coaxial cable to the transmitter then the length of the cable makes no difference whatsoever. Put your ugly balun in place before you do this, BTW. Apr 14, 2002 · On a theoretical "perfect" coax that has no loss, length does not affect SWR. K. And the choke doesn't affect minimum SWR on its own, but choke AND cable affect minimum SWR. now 18 feet is only getting close or around a 1/2 Nov 5, 2023 · It 100% does depend on that mismatch or it would not be useful for measuring the mismatch. Mar 23, 2022 · For years the online "experts" have been telling us that if we coil up our unused coax cable it will damage the radio by creating a high-SWR . Suppose you put up an HF antenna, trim it to resonance, and the feedpoint impedance turns out to be about 110 ohms, resistive. 5:1) Or you have some common mode issues, then coax length make a huge difference. 3. Learn How to calculate 1/2 wave multiples for use in special setups. Nov 5, 2023 · If you're just measuring the voltage amplitude, it doesn't make sense to talk about the SWR at a particular point on the line --- what you're measuring is the SWR of the load mismatch, by measuring multiple points on the line. If your antenna is anything other than 50 ohms (ie swr greater than 1. Feb 11, 2022 · Whilst you’ll see vague claims across the internet such as…. The drawback is that resistance and slight impedance mismatch of the coax affects the overall SWR reading. if your anp has crappy input/output tuning getting the amp fixed is the only Oct 29, 2013 · ladder used to get to the bottom of the antenna, I started spraying water at the black base and coax connector,( moved the ladder every time) and rechecked the swr with no change (1. If a mismatch exisits, > then the swr will can vary with length, depending on the type of antenna and. It might come damaged when buying from the market. I was able to get a short jumper at flying j if that helps. Aug 4, 2020 · yep, it's a terrible non-constant complex impedance seen from the perspective of the VNA that's everything but 50 Ω. . asu. This description sounds very similar to the MFJ-1777 doublet, which uses a tuner for matching on the 80-10m bands. Another issue with running the coax inside of the pipe is the rough edges on both the top and bottom of the pipe could easily scrape the coax and cause water penetration (and associated failures) as the coax moves around either due to the wind or pipe swaying around. standing-wave ratio (SWR, VWSR, IWSR): Standing-wave ratio (SWR) is a mathematical expression of the non-uniformity of an electromagnetic field ( EM field ) on a transmission line such as coaxial cable . Feb 19, 2022 · Does coax length affect SWR? The ONLY issue coax length has in a basic system is the longer it is the more loss you have . I’m relatively new to antenna tuning and am wondering about coax quality effects on SWR. Jul 11, 2017 · Experiment with a good choking balun on your coax and a purposeful counterpoise of various lengths in various orientations. K1 marks the resistive loss, and K2 is the dielectric constant. They are both good in the original configuration and I get good range to a HT. Or so goes the story I have. Taking the antenna tuner approach is not a good idea when you are using coaxial cable under high (greater than 3:1) SWR conditions. swr down as low as possible by either measuring the swr right at. Other tuners are automatic and do all the adjustments for you. Short answer is NO, coax doesn't change the SWR only the antenna can. Mar 10, 2022 · 5. 6 = 80/50 or 50/31) From the Smith Chart, where the SWR circle crosses the hori- Jul 26, 2022 · Mount the antenna in its final location as the SWR and resonant frequency will change a bit depending on the environment. The fourth graph was meant to demonstrate a 5:1 SWR, however they did not have a resistor of the correct size so I chose the closest one Dec 19, 2023 · SWR, or Standing Wave Ratio, is a critical measurement in the world of ham radio. </p>. Use a 50-ohm coax for single antennas and a 75-ohm coax for dual antennas. 3:1) SWR. It is considered a major factor in the performance of your entire system. You could have an antenna with a 100' coax cable length with a perfect 1. This is why when adding coax the SWR appears to drop. 0:1 SWR but an improperly tuned antenna with a 10' coax cable length may have a bad 2:1 SWR. When I connect a length of coax cable (<1m) between the VNA and antenna everything shifts down to ~130MHz. For most cases when using a single antenna system with a 50 ohm coax feed ANY coaxial length will work Jun 20, 2014 · Step four. It's used for jumper assemblies in wireless communications systems and antenna feeder runs. Both terms are used to characterize the uniformity of a cable’s impedance along its length as it relates to reflected energy. 6:1 terminating SWR, as you move along the trans-mission line away from the load, you move along the constant SWR circle on the chart. Selecting Co-axial for mobile radios has become Jun 24, 2020 · It depends a lot on the length of the coax and if it is a 1/4 or 3/4 wavelength resonant length or a 1/2, full, etc, wavelength length or something in betweeen. Run the coax in a large figure 8 or purposely run the coax in a longer path to the radio. Loss in a coaxial cable, when measured in dB, is proportional to the length of the cable . So if you use 100 feet of RG-58A/U and see 1. With ladder line, there's not too much loss, so more of the signal will get radiated even when SWR is high. In this case, antenna performance is preferable to a small increase in SWR. 2:1 SWR. One is a 1/4 wavelength line. 9. 2 to 1). It is a "mirror. It doesn't. Jay in the Mojave. The coax length shouldn't matter but the length of the parallel line, which is a matching section, does matter. However, in practical systems, achieving a perfect match is rare. Let's summarize it High SWR = coax radiates signal. 2 Db loss, and you increase the same type of coax to a longer run, now with a loss of 5 Db's and see the SWR drop to 1. Even when wanting to use coax as a transformer for Some tuners operate manually; you twist the knobs until the SWR meter shows a 1:1 SWR, or something reasonably close to it. Connect the SWR analyzer with a short piece of good cable to the beam and test the SWR. image" of what the antenna's swr really is. Feb 7, 2017 · NEW MEXICO. There in lies the myth of "cutting the coax till it reads 1:1". If you can borrow an antenna analyze, that would help a lot since you could use it to measure swr outside of the Ham bands, figure out exactly where your antenna is tuned, then make and measure your adjustments. SWR is expressed as a ratio, typically written as a fraction or a decimal. This is also Mar 22, 2021 · CB Coax Cable is to do two things: To take received a signal from antenna towards radio, and to transfer the signal from radio towards the antenna. A 1:1 current balun between the parallel line and the coax is good. With a sectional pipe, this issue is not only at the top of Feb 27, 2017 · Here's one "radio wive's tale" put to rest. #12. 5 to 1. 5) Are CB Radios still Used in 2021? Yes, they are still popular especially among truckers who have been using them for a couple of decades now. 0+: Performance will be severely affected, and you're likely to damage your radio with extended transmission use. From then on the dips occur when the cable is an odd number of quarterwaves, or the distance between each dip is caused by an additional half-wave. So even if it isn't that big a deal to operate with the higher A damaged coaxial cable is a big reason behind high SWR readings. So in this case there will be a length of coax that will trick or indicate the SWR meter into showing a lower SWR. Mar 18, 2013 · A slightly shorter cable can insignificantly affect signal strength but the coax cable length has no effect on the antenna's SWR. In that. not the actual swr level. If changes in mast length or feed line length or grounding affect the antenna pattern or SWR, it is an antenna design problem. That is not a good explanation. 5dB RL and an SWR of 1. Return the antenna to its base, secure it in its original position, and check the SWR. A balun is a good start to solving your problem. Apr 22, 2011 · The total reactances of the feed line and the antenna are what make up SWR when measured at the transmitter end of the feed line. However, "lossless" coax does not exist in what many people call the "real world". It is a measure of how efficiently radio frequency power is transmitted from the radio to the antenna and vice versa. If you find that 49 feet is too short from the antenna, then add 11 feet to the coax from the antenna to the meters, making your total length, with jumper cable, 66 feet. If your coax cable has a 1. …the truth is that this depends very much on the factors at play. A 9 foot cable will be 108 inches long, which is 1/4 of a wavelength at 27 MHz. The only thing I can thing of would be coupling together two coax cables CB'ers for example often talk about grounding coax or changing coax length to match an antenna. May 1, 2016 · OK, Here Is something I have been curious about when I see benches full of meters,testers, etc and only one coax connection to a radio. 4 to 1. To troubleshoot, you'll likely need to move the mounting location and/or use a more suitable antenna. 2:1 SWR what you are actually getting is 1. Put the antenna in a stable position and secure it in a vise. No. Cut the antenna by . The antenna's coax now connects to the "Antenna" socket on the meter. This makes the antenna appear to be resonant, and coax #2 becomes the correct electrical length for re-reflections to happen. If you don't have a counterpoise and choke in the system, you may be able to adjust the length of the EF wire to get closer to the SWR dips that you previously had. The more losses you have, the lower the SWR appears to be. An 18 foot cable is 1/2 of a wavelength at 27 MHz. This bounce back reflection is called “return”. Connect one end of the jumper to the back of your radio. SWR 3. LMR®600. COAX cable plays an important part in radio communication system. I should have answered your question better, Different coax sizes and types do not affect SWR as long as they are all 50 ohm coax cables. Start by adjusting the length of the shortest section for the highest frequency band. la. Too high of an SWR reduces performance (range) and can potentially damage your radio, though the latter is more of an issue the lower you go in frequencies or higher you go in power. Jan 29, 2024 · A low SWR means that your antenna is transmitting a satisfactory amount of RF (radio frequency) power instead of sending it back into your transmitter. Yes, the SWR can change along the transmission line. This is exactly how antenna tuner coils work. Feb 21, 2021 · 3) Does Coax Length Affect SWR? No, it does not. I can go close to 12 meters and close to 10 meters before there is any significant changes. The distance between the first two dips (deltaF) is 99 MHz. A "good" cable starts at a return loss of -20 dB, but typically, general-purpose pre-configured coax cabling has more like -30 dB to -50 dB of loss. Multiband antennas are a bit more complex to adjust. 2 Mhz) or about 16. The antenna height matters too. The SWR is constant along the transmission line if the line is, or may be considered, lossless. 5 feet per side of the half wave dipole. Look at what I said. The only difference that the length of cable can make is that if the cable is so long that it attenuates the transmitted Standing wave ratio. 5 mm. For example, if your 60 feet of cable has 6 dB of loss as used, then you will have 2 dB if you cut it down or replace it with 20 feet of the same cable. 2 swr's with the box on or off. The coiling adds inductance myth is due to a misunderstanding of what common mode currents are and how they can be choked off using a coil of coax at the antenna feedpoint. A 1/4 or 3/4 resonant length will present a low impedance at the feedpoint inviting current to flow on the coax just like it does on the grounded side of the dipole. If you were to look in the ARRL Antenna Book, you would find nothing that says that coax length has anything to do with SWR. If your coax is part of the radiating antenna, inserting an SWR bridge or antennalyzer will actually change the tuning of the antenna slightly. If changing your coax length seems to change your SWR, then you have a problem with the antenna. 49 + 6 = 55. Why does my coax length affect the SWR of my antenna? How many of you change the length of your coax to tune your antenna? One of my good friends said to me, “I think changing the length of the coax is the same as moving the gamma rod adjustment on my Moonraker 4”. If you need a cable that requires periodic or repeated flexing, choose this one. 8 MHz up to 1. F stands for frequency in Hz, and the CLF is the connector loss factor. My setup: I picked up a Midland MXT 500 along with a Midland MXTA26 antenna. Adding coax does change the phase of RF, so you can actually tune 2:1 SWR systems to 1:1x by adding or removing coax line. You should be able to get s half wave dipole down to around 1. Reply. So if you have any problems with swr's, picket fencing (signal wobble) or trouble getting your carrier right, try changing the coax length before and after the amp. Remember from the article text that a 1. If you use a length that is shorter or longer, you might risk having trouble achieving good SWR readings. 125 meter = 125 mm. If your antenna is a 50 Ohm load no special coax lengths needed. Apr 29, 2022 · A basic 1/4-wave vertical antenna with a good set of radials, fed by 50-Ohm coax, will have an SWR of approximately 1. the antenna at the radio's end of the coax. "Tuning" the coax for the exact full wavelength tends to throw off the SWR meter by not allowing any standing waves to return to the meter. Because cutting is permanent, I recommend first extending the wire by 5% of its length, perhaps with a bit of aluminium foil and tape, or for lower frequencies and larger antennas, a crocodile clip lead. Aug 28, 2016 · Use 49 feet of coax from the antenna to your meter, and 6 feet from your meter to your radio. Jan 31, 2024 · WRONG. signal travel slower by 10% in the copper wire, so if you multiply 125 mm x 90% = 112. If once you get the. Aug 11, 2011 · using a certain length of coax does not compensate for a amp that does not have a 50 ohm input/output . Now connect the other end to the "Transmitter" socket on the SWR meter. The basic idea behind tuning a CB antenna is to get the SWR to a suitably low reading. Apr 26, 2011 · so the wavelength = 300,000,000 meter / 2,400,000,000 Hz = 0. 6 = 80/50 or 50/31) From the Smith Chart, where the SWR circle crosses the hori- Jun 4, 2005 · FL Native said: the guy that blew up his amp had nothing to do with coax length. For the latest Amateur/Ham Radio news and information, please visit these websites: May 29, 2021 · Equally, one can measure the forward voltage and return voltage at the same location, or their sum and their difference to determine SWR. So the cable from radio to choke doesn't affect minimum SWR on its own (though it does change the frequency where the minimum SWR happens). If you make a change to the feedline, that will affect the characteristics of the antenna system. May 1, 2013 · Feb 11, 2017. The SWR still reads 2. With end feds, it is primarily a cut and try process. lv mv cb zf uq qy ps wu rf go