Coax balun turns
To Balun or Not to Balun, this is the question? Like Ford vs Holden, Canon vs Nikon or Yaesu vs Icom; the world is divided into two camps on how best to connect a resonate wire antenna to a bit of coax. It is not a balun, and I agree, if you have no CMC's, it is pointless to add one to your antenna system. Also, baluns can be designed to work over a wide range of frequencies, all of HF for eg. 99% that give generic instructions for making a balun (e. - operates over a somewhat limited bandwidth (100 to 1) current - uses transmission lines wound on a core The coax is single-layer close-wound on the plastic pipe. Something as simple as 10 turns of coaxial cable coiled up on a diameter about the size of a dinner plate makes an effective choke balun for frequencies from about 10 MHz to beyond 30 MHz.
From what I have read there seem to be two common types of choke baluns employed at 146 MHz, the coiled coax balun and the W2DU type with ferrite beads over the coax. This “coil” of coax concentrates the inductance like any coil of wire and provides the same high impedance to out of balance currents. I decided to make the video to show how straightfoward I am interested in building my own RG8X coax balun to install at the transition point of a G5RV where it goes from Balanced to coax line. e. 9.
How does this work and why is it needed. If a coax sleeve balun is chosen, the power requirements are solely dependent on the coax size (will it handle the RF current/voltage). I thought that possibly the W2AU balun did not have enough inductance on 160 meters and that this could affect the resonance on 160 meters. Get the best deal for Radio Communication Baluns & Chokes from the largest online selection at eBay. One factor in the high-frequency limit of the balun is determined by how close to 50-ohm is that transmission-line’s characteristic-impedance; parasitic generally are absorbed but can be another factor.
The first and last turns of the coax are secured to the plastic pipe with nylon cable ties passed through small holes drilled in the plastic pipe. Some purists will say to space the turns, for example, by the diameter of the coax. com (Ed Gilbert) Date: Mon, 12 Aug 1996 08:40:24 -0400 When the balun is built using transformer-like windings, it can also provide resistive source-to-load impedance matching by selection of appropriate primary/secondary turns ratio, using the well-known formula: This allows a single component to serve two roles, thus reducing cost, footprint, and BOM. Instead of making the balun of a single, tapped length of coax, two sepa rate pieces were used, making in effect, two adjacent coils, each with eight turns of coax. ” Baluns and RF Chokes: Ham Radio Q & A Episode 3.
The distributed-capacitance of the balun is increased and the RF-lossy vinyl jacket of the coax is subjected to a high RF-voltage. This 4-BAND COLA ANTENNA (20-17-15-10m) – G8ODE (Concentric Open Loop Antenna Fed Off-Centre) G8ODE Design Published 28 May 2014 issue 1. the RF current depending on the choking impedance). I thought that the antenna was working perfectly well, until I replaced the 10 turns of coax balun with two ring cores. It simply stops (or helps reduce) common mode currents flowing on the coax as a result of the miss-match at the feedpoint.
was substituted. He measured various coax baluns and compared results. I put this on the test jig to examine the following: Differential mode S21 of the coax from one end to the next, Air-cored coax chokes are narrow band devices, so you need to get the number of turns and the diameter right. 25" former is about optimum; that should give you >1kOhm impedance on both bands. The coax size is chosen to handle the RF current/voltage and the ferrite sleeve choke is chosen to physically fit the coax snugly or with appropriate shims.
The problem with scramble-winding is that the first and last turns of the coax may touch each other. Armed with this happy find, I wound another #43 toroid with 12 turns of RG316 coax spending extra time on dressing the turns evenly. a wide range of ratios is possible. This can be accomplished with five RCT-2, five RCT-2T, five RND-5, or It deals with the problems of the coax becoming part of the antenna when that is unwanted. My 75 to 450 ohm Beverage transformers, for example, only require two-turn primary and 5-turn secondary windings.
If you own an antenna fed with coax, you need RF chokes on the feedline! Using a choke/balun with adequate RF choking impedance will improve the performance of your antenna, prevent pattern distortion, and prevent RF coming down the feedline, which can cause RFI. One advantage of the bead balun installed over coax is that the impedance of the line is not changed. The novel thing was that I only built it the day before and it uses a Coghlan camping washing line spool with the string taken off and about 21m of wire wound onto it. This reduced the noise level on 80m from S6 to S0 and on 160m from S8 to S0. It's Creating a Choke Balun.
greater than 6:1 where a balun is used or the transmitter is directly connected to the coax (no tuner). If the antenna is perfectly tuned and is mounted in a location where it isn’t couple with any nearby structures, then the choke isn’t necessary. 1:1 current Balun Ham Radio VK3BQ Sota. When feeding this antenna with an unbalanced line (such as coaxial cable), it is a good idea to use a 1:1 choke BALUN at the coax to feedpoint connection. For an HF transformer and a powdered iron core, about nine or ten turns per winding is a good place to start.
I am wondering which size PVC pipe would be best and how many turns of RG8X to use. I wanted to The balun consists of an FT114 -43 ferrite core wrapped with 10-turns of RG-174 coax as shown in Figure 1. You’ve heard a lot of people recommend putting a few loops of coax near the feed point of your antenna to keep the RF energy out. Bunched turns starts to be a no-no above 7 mhz, though acceptable on 160/75M. A good starting point is 10 turns of small coax like RG-58 through an FT240-43 core or maybe a few less turns through an FT240-61 or other material.
No need to worry about toroids etc. This balun will convert 200 ohms into 50 ohms, and you can actually test this with an antenna analyzer and a 200 ohm resistor. Mix 31 is currently the best for the HF bands. Wikipedia bug tracking comparison essay This article is a comparison of issue tracking systems that are notable, including bug tracking systems, help desk and service desk issue tracking systems, as well as. for as “Bill” mentioned in the Baluns are devices to balance unbalanced systems.
Want your ham radio question answered? How to Make a Balun or Unun: I needed a simple portable HF antenna. Wind them as a single layer on a form. Baluns are important because many types of antennas (dipoles, yagis, loops) are balanced loads, which are fed with an unbalanced transmission line (coax). Transmission line transformers are formed by winding bifilar turns, multi-filar turns, coaxial cable, or stripline cable (two strips of the flat conductor with a dielectric material between the strips) on a core having high permeability. njd.
A crossover winding gets the input and output ends of the coax on opposite sides of the ferrite core, which is necessary to fit the balun, an input RCA-style coax balun on PVC form? From: eyg@hpnjlc. These are sometimes known as a Magnetic Longwire Balun. A Balun is special type of transformer that performs two functions i. Current baluns typically consist of ferrite beads on a section of 2-conductor transmission line such as a coax, or conversely, coax wound multiple times through a ferrite ring, or tight-wound coil of coax turns (air core). Its purpose is to provide high impedance to common-mode current on the transmission line: it "chokes" that current.
Now that we know that a coax cable behaves more like 3 conductors, not 2, let's look at how that works with a coaxial balun. For this reason it is often said that a balun is a type of transformer, but it is more accurate to say that a transformer can sometimes be used to implement a balun. The balun consists of 16 turns, split at the center, wound on a PVC form 31/2 inches in diameter and about 6 inches long. An ugly balun is also fairly narrow band where ferrite versions can be effective 80 through 10m. It shows that some of the conventional wisdom is incorrect, especially when using these techniques above 7mhz.
An Inexpensive, High-Performance, Ugly 50ohm-Balun. Sometimes these are called 1:1 baluns, choke balun, but technically a balun is an impedance transformer while these coils are chokes. The bead balun amounts to one turn on the core. So the idea of an ugly balun in part is to stop the RF on the coax before it reaches the mast. Instead of neatly winding 10 turns of coax in a single layer, 6” diameter, as suggested by the manufacturer, I had just haphazardly coiled up a half-dozen turns and taped them to a nearby pole.
To cover 40m and 17m, 8 turns of RG213 on a 7" diameter former or 16 turns on a 4. When using a coax connector at the bottom and screws at the top, there is a trick that enables you to keep all of the coil’s windings in the same direction, for instance “clockwise. This reduces the mutual coupling and helps keep symmetry in case you are using this as a balun. If you own an antenna fed with coax, you need RF chokes on the feedline! Using a balun with adequate RF choking impedance will improve the performance of your antenna, prevent pattern distortion, and prevent RF coming down the feedline, which can cause RFI. And it thus deals with things like the mast & other close by conductive materials causeing RFI as a result of the coax radiating RF.
The impedance of that inductor is what matters, and the diameter, number of turns, height, coax size, and spacing between turns are all factors, and the required parameters depend on the frequency in play. Shack Plumbing: You may not be able to bring balanced feeder into the Shack so have to rely on a small length of coax through the wall; After some reading of Steve G3TXQ’s page on tuner balun ratios, I decided to wind myself a “proper” 4:1 Current Balun to see how it compared against my existing 8-turns of RG58 on a single FT240-31 ferrite. I've also read that this antenna doesn't need a balun as long as you have a good tuner, but I'd like to try my hand at building a balun next - never Save coax choke to get e-mail alerts and updates on your eBay Feed. I built this simple air cored balun in next to no time. You could get the Al by wrapping a fixed number of turns of wire around one then measuring the inductance.
10. This will also result in an imbalance in the radiation of the pattern too AND reduce performance. These are such simpl. A balun made from this cable will have an insertion loss of about . Requiring a choking balun to isolate the potential RF pick up on the coax cable as it runs past equipment such as computer within the radio room at lower HF and MF frequencies a simple method of winding RG58 coax onto a Powdered Iron Toroid Core was constructed.
So you need 5uHy minimum for a choke balun at 14 MHz and above. It works from 3 to 30 mhz and handles 200 watts easy. com. Snazzy Balun Lets Ham Use Off-The-Shelf Coax. True, these clip-on ferrites are typically seen on computer equipment to prevent interference.
A plastic cap from a food jar is used as at the top of the BALUN. If the balun doesn't heat, from inadequate common mode impedance or being largely reactive, the system will often just go out of balance. 4 inch type 43 ferrite toroids stacked together. is it better to have more turns on a small diameter coil form, or to have less turns on a larger diameter coil form? (i realize it is a small consideration, but i am still curious which one is preferable) Requiring a balun to feed a balanced feed line with an un-balanced T-Match network a 4:1 Ruthroff voltage balun design using a T200-2 Toroid core was selected. This balun would be great, even at high power, for 80 through 15 meters.
Pictured is a Spiderbeam 1:1 Guanella balun, 7 turns per side. In all of the following, I will assume that the balun is a 1:1 choke or current type. antenna. Two turns is about ¼ around the core and 3 turns is close to halfway. 8.
Examples are the ferrite bead balun described by Walter Maxwell, W2DU[1], coiled up coax, and coax or a bi lar winding through a toroidal core. After this transfromer you then need a bifilar current balancing balan which then drives the antenna and counterpoise. Connect the output of an antenna tuner to one of the balanced feedline conductors. 1:1 Balun Recommendations I believe that you should have at least 400 ohms of impedance on the coax shields in order to have a good 1:1 choke balun. Ferrite beads over coax also make an effective 1:1 current balun by preventing the flow of RF currents along the outside of the coax shield.
, a dipole or driven element) to an UNbalanced line such as coax which is not balanced, thus the name, Balun. The plots above show with a DX Engineering 4:1 balun and reasonably good coaxial cable, you can operate a loop over most of 80 and all of 40 meters. B) IMPROVED COAX CHOKE: Wrap coax onto a PVC pipe, using nylon rope to space the turns. "wrap the coax 5 turns", "wrap some wire around a ferrite core", etc) Per recommendations I've seen on numerous sites, I coiled up 3 turns of coax about 1 foot in diameter right after the feed point which is supposed to help keep RF from coming back in to the shack. Using heliax is a little impractical because it doesn't bend so easily but something like Benelec LMR400 is ideal.
5" core should yield suppression in the -30 dB range over a 50-Ohm path and will handle up to a kW (2" core for higher). Vertical or Horizontal Loop: The best balun for operation moderately far from resonance or on harmonics is a 4:1 ratio current Tuner Ferrite beads are used for RF decoupling and parasitic suppression. C) FERRITE BEADS OVER COAX: Slide a number of beads over the outside of the coax, and cover with heat-shrink tubing. The name of this simple but effective device is a choke-balun. So.
Baluns, coax, open wire line, and other items used by Amateurs to construct antennas are hard to come by locally. Since there are so many types, exact figures can't be quoted here. g. Coiled-Coax Balun. Note: although called a choke balun, this DOES NOT match the unbalanced feedline to the balanced antenna.
Build an All Band HF Air Core 1:1 Choke Balun THE "UGLY BALUN" A balun's purpose is to allow connecting a BALanced load (e. A You'll notice most of the transformers I use have only one or two turns for every 100 ohms of impedance. + Items in search results RF CHOKE BALUN 80 - 6 METERS COMMON MODE CURRENT COAX ISOLATOR- AMPHENOL PL-259s If you want the best radiation you want to use a choke balun (beads along the coax) into a balun / issolating / link / transformer to bring the antenna resistive component into the correct match (reactive match in ATU). In most cases, the lowest-impedance part of the circuit is the 50ohm coax input to the antenna-tuner. This is a common problem for off-center fed antennas.
Works with a 4:1 UNUN. Again, about a 5:1 frequency range. Using more turns than necessary degrades the choke's performance. The number of turns will depend on the core material. Remove any extra tape ties on wire at the ends.
Five microhenries will give about 400 ohms impedance at 14MHz. Anywhere on the net that has a chart or something that states turns per band - or length of coax per band - on a coax balun UHF to HF? When coiling coax around some form to make a balun, you are making an inductor. That makes the balun-building task much easier. See the picture. These problems were particularly evident when the transformer was installed at the base of a short vertical, in order to facilitate the use of a remote, coax fed tuner.
A long wire and some insulators is pretty easy to carry. Strip insulation off the wire back to within about ½ in of he core. 8m out. 5" tube, and the first measured resonance was about 24 MHz. Coaxial Toroid Choke Balun Test.
While the 4:1 ratio is often referred to for the interface between T-Match network and a balanced antenna system it will often not be the ideal choice when very low impedances are However, I decided to use a 4:1 balun at the feedpoint. Balun/Unun Construction – 50Ω Coax RG303, RG142 2 X 8 bifilar turns #14 on single 2. 8” mini-plastic box as shown in Figures 2. Air Wound Balun Construction 1:1 Choke Balun. Optimum Coax Coiled Turns Choke Baluns for Antennas (1/1) K1JJ: Here's an interesting piece written by WA2SQR.
Rod or toroidal cores may be used. The coil inductance and self-capacitance resonate as a parallel trap whose high impedance inhibits unwanted shield current. Watch this episode for more information on common mode currents, baluns, and RF chokes. Aside from the reasons mentioned last time there are a few more where balun and unun devices are concerned. Wind two cores this way: One for a choke balun and one for the If the 1:1 current-balun is used in a 50-ohm system, then the transmission-line’s characteristic-impedance used in the balun is 50-ohm.
It's up to the designer to select the best design for the job at hand and to utilize that design in the most efficient way. You can make a simple current balun by coiling coaxial feedline in a particular way. . The choke balun, which can be as simple as six turns of coax or ferrite chokes near the feedpoint of the antenna will stop the excess RF energy from returning down the feedline. If there's a matching network involved at the feedpoint, install the balun on the feedline side of it.
0 This article is dedicated to my friend Bill Stevenson - G4KKI (SK), a fellow RSARS member, who shared my 90% of sites say "you should use a balun to balance the antenna" or equivalent statements 9% of sites try to sell an antenna with a balun as part of a kit 0. Many HAM Commercial antennas require an RF choke like Cushcraft A3/A4/AW3S. – For 40 or 30 meters, use 12 turns of RG-213 on 4 inch PVC sewer pipe. Building a no-grief 1. hp.
A low "turns count" is a good indicator the correct core size and core material is being used. 8MHz to 30MHz 50ohm-balun is easy. Im hooking up a 2m/440 J pole - 3 turns of coax on 6 inch form about right? I also need amount of turns on 17M. 8-30 MHz Double Guanella Balun - Hi-res pictures of a double 4:1 guanella balun by PA1HR Sorbie Balun and Bottle Choke - Homebrew a 1:1 balun consistsing of 4+4 turns of mini coaxial cable o Broad band 1:1 current balun - A 1:1 current balun that offeres a almost flat swr homebrew 1 to 1 balun is a curation of 21 resources about , A Cost Effective Current-mode 1:1 Balun, Ferrite Balun for HF, Broad band 1:1 current balun , A 1:1 Coaxial Balun, UnUn with Amidon T200. 4” OD core (cover each wire with teflon tubing) #GeorgeChristofi #GeorgesWorkbench I was asked by a friend to get some information on baluns as he needs one for an antenna he is building.
– Don’t bunch the turns together. I decided to isolate the whole balun further from ground by wrapping 18 turns of RG8x on two 2. Space the turns such that the coil is 4 inches long. So building a 4:1 balun was the best option I had. This decoupling Build your own HF balun A balun is a MUST for dipoles or similar antennas when they are feed with coaxial cables.
To connect it to the radio I needed a Balun. Baluns can be designed so they can transform impedance, a coax choke cannot. This system is generally good on 80, 40, 20, 15 and 12 meters. 05db. At one end of the coax coil connect the braid to the antenna The Ruthroff balun uses a minimal amount of turns to achieve a 4:1 impedance match.
The circuit below shows a 4:1 transmission line current balun in operation feeding a balanced load. You may have seen/used an “ugly balun” which is simply many turns of coax about 4-6″ diameter – See the “Bottle Choke” section near the bottom of this page for details (and a note of caution). turns evenly around the core. Its really an impedance transformer (9:1) to feed a high impedance, end fed (unbalanced) random wire which is likely to be a few hundred ohms, and transform it into something closer to a 50Ω (unbalanced) coaxial input, hence UnUn. Picture of How to Make a Balun or Unun See more Something as simple as 10 turns of coaxial cable coiled up on a diameter about the size of a dinner plate makes an effective choke balun for frequencies from about 10 MHz to beyond 30 MHz.
– A 1:1 coaxial balun with excellent choking reactance for 10 through 20 meters can be made by winding 6 turns of RG-213 on inexpensive 4 inch PVC sewer pipe. Baluns used for high-power operation should be tested by checking for temperature rise before use. But they don't usually offer enough attenuation to use them on an antenna - that either takes several turns of coax on the ferrite (as in the 1:1 balun photograph shown in the article), or a very large stack of ferrites. The "ugly balun" or coax choke is just a way to reduce CMC's. If you use thicker wire it will handle a cool 1KW.
This creates two complications. Resources listed under Antenna Balun category belongs to Antennas main collection, and get reviewed and rated by amateur radio operators. The G5RV is a balanced antenna fed with a balanced 450 ohm line. If we take a few feet of coax and wrap it around a ferrite toroid, the fields generated by the center conductor and the inside of the coax shield are still cancelling out, nothing much has changed inside the coax. anyone ever use a coax balun as described below? Wind a 3.
A 9:1 Balun For Your End Fed Antenna End-Fed antennas do have their place in radio and other communications work. Transformers of all types are constructed with isolating properties between turns and between windings rated at a given voltage. Like everything else, antennas come in many forms and flavors. The wire used for winding the balun ( 14 Guage ) was scavanged from an old transformer. The balun belongs to a class of devices known as “transmission line transformers”.
Contrary to what most commercial balun vendors try to make us believe, there is no such thing as a "best" balun or "one-size-fits-all" balun. 12 Some Common Mode Chokes • A coil of coax at the antenna • A string of ferrite beads around coax (Walt Maxwell, W2DU) • Multiple turns of transmission line through a toroid (Joe Reisert, unbalanced. So, why have we been putting the balun in the wrong part of the circuit for these many years? Good question. l The W2DU “string of beads” current choke works OK but it takes a lot of beads, typically > 50 JSX UglyBalun (HF bands 1:1 coax RF choke) by N6JSX/8 06/2013 The UglyBalun is not a true transforming balun but a 1:1 coax decoupling RF Choke. impedance transformation and balanced to unbalanced transformation.
This was 9m vertically metres up a fishing pole and then about 5. Coax Choke BALUN for Coaxial Feeder Coax Choke BALUN for Twin Line Feeder The two coaxial Choke BALUNS are constructed from 40mm plastic drain pipe using 8-10 turns of Mil Spec RG58 or MIN-8 Coax (approx 2metres) The bottom end coax is held in place with a small plastic tie-wrap. Browse your favorite brands affordable prices free shipping on many items. 4:1 Transmission Line Balun with Balanced Load. When placed over a wire, cable or coaxial cable they suppresses common mode current flowing on the wire or wire bundle or the outside of the coax shield but does not affect the signal inside the coax cable or wire (differential current).
rarely the best balun approach l Stop the RF on the outside of coax with a ferrite-based current choke balun l Getting the correct ferrite material for the planed operating frequency is essential. The 1:1 choke "balun" is not actually a balun. Resources listed under 1 to 1 Balun category belongs to Baluns main collection, and get reviewed and rated by amateur radio operators. It is sometimes used on its 3rd harmonic with coax, or used multiband as a doublet with balun, ladder line and wideband tuner. The balun consists of an FT114-43 ferrite core wrapped with 10-turns of RG-174 coax as shown in Figure 1, and mounted with an input RCA-style phono jack and #6 stainless steel hardware into a 2.
what length of coax will i have to use to form the coil for the choke to work on 11 meters (cb freqs)? (i will be using LMR-240UF coax) 2. These are such simple things but yet they cost so much from some places. I started investigating balun construction as a result of various observations I made whilst building HF antennas. turns) and the other winding is then connected in series with combining phase so that the antenna is fed from 24 turns --- twice the voltage, and ½ the current, hence 4 times the impedance. Three effective and very simple baluns in wide use today are described as choke baluns because the high impedance they place on the outside of the coax keeps RF from flowing back down the outside of the cable.
To construct the balun, mark RG-6 coax with tape at two spots 27″ apart (26″ for RG-59). In addition, the center coax also drives the primary of a transformer. It is important use the best coax you can for the balun even if you use lousy coax for the feedline. As an example, I built a G5RV antenna and used 10 turns of coax on a 4 former as the 1:1 balun at the base of the open wire feeder section. feed line choke from coax Over the years coiled coax has been used to choke off RF from the outside of coax feed lines.
is a curation of 137 resources about , The Guanella Balun, Making a simple current balun, Homebrew Balun Case, Balun Information, TH6 balun replacement project. dipole, the balun you use doesn't have to perform any impedance transformation. This balun is a 4:1 ratio and feeds a balanced 200-ohm load. The coil winding must not be placed against a conductor. Since a current balun is a type of common mode choke, the more turns the better.
At low frequencies, the terms balun and transformer are often used interchangeably because low frequency baluns are almost always implemented using flux coupled transformers. Then solder the PL connector onto the end of the RF current depending on the choking impedance). The term balun is a contraction of “balanced to unbalanced transformer”. A quick and dirty choke balun can also be made by looping coax in a coil several turns. The balun windings are cross-con Radio engineer.
The center conductor of a coaxial cable directly drives one antenna lead (represented here as RL). One side will be driven harder than the other by this amount. 36” x 1. I’ve added a JSX-UB to my Hy-Gain 18AVT HF vertical getting great results. ) If fed off center, say at 30%-70% point, impedance is approximately 200 ohms and can be used on multiple bands with an antenna tuner.
That is, use a balun on the input of a balanced tuner as shown in gure 3. Which toroid size? Which Ferrite mix? Which size of wire or which type of coax? How many turns of wire or coax? Reisert cross-wind or classic wind? An in-line balun takes care of potential feedline unbalance and radiation problems. I wound 10 bifilar turns of the 14 The antenna we used was a portable multi-band end-fed half wave (EFHW) 40-10m with a 49:1 Unun. The magnetic material may be air, but it is a transmission line transformer. Ferrite Balun for HF - Diagram and sample ferrite balaun for 1.
Twelve turns of bifilar-wound #16 or #18 enameled wire on a 1. If the core overheats, add turns or use a larger or lower-loss core. See the picture of a fully wound core. What Ferrite Core? – for 1:1 baluns/chokes/isolators For a simple 100w choke, 8 turns of RG174/RG316 on an FT140-43. Coaxial Transmitting Chokes Jim Brown K9YC coax (Walt Maxwell, W2DU) •Multiple turns of transmission line –Guanella balun To connect it to the radio I needed a Balun.
5 inch diameter with 7 turns of RG-58. Current through a choke balun winding is the “antenna current” on the line; if the balun is effective, this current is small. 1. Many hams connect the center conductor of the coaxial cable to one side of the dipole, and the shield to the other. * * * A Bad Rap? balun types voltage - transformer with windings giving a balanced output - in-out impedances are determined by the turns ratio.
The secondary is connected across the I made a solenoid balun with 25 feet of RG303 teflon (RTM), about 20 turns on a 4. 38” x 0. coax balun turns
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