Re: Topband: W8ji ATR-10 design 160M?
What is the real or best guess what value this inductor has? This is what I am using. Edge wound coil is 1/2 inch wide, 1/32 inch thick stock, coil is 2 1/2 inches long,15 turns, 4.5” ID, 5.5” OD transmit tap is at 9 turns, 6 turns remain going to antenna. Inductance calculations were found here http://www.66pacific.com/calculators/coil_calc.aspx%22http://www.66pacific.com/calculators/coil Total inductance is 29.6uH, 9 turns = 12.7uH, 6 turns = 6.7 uH, 6 turns = 7.9 feet. If you wound a coil with 1/8 inch or 1/4 inch copper tubing , is there any online calculator that can give you a good answer on its value? -- Jim K9TF _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
These transmatches these days T matches just do not have the balls for 160M running power. They do if the tuner's complex load Z is reasonable. I melted down a MFJ 998RT arced plates on an MFJ 989B melted down a 25uH Millen coil, arced wire burned up insulation all with 500 watts :-) I tried different configurations. Short 99 foot inverted L does give me a challenge. 0.175 plate spacing arcs over. 0.25 spacing on caps is needed or vacuums variables which are not in my budget.Give us the complex Z seen at the tuner's terminals on 160m and we can offer up a reason for the behavior. Without knowing the complex Z, it's one big guessing game. In the last five years, complex impedance analzers and vector network analizers have become affordable for most of us and offer superb accuracy when compared to commercial lab-grade instruments. This is definately not directed at you or anyone elase in particular but it's interesting how the general ham population will spring $600-$800 for a wattmeter that offers accuracy they don't need yet won't spend that amount on a complex Z analyzer or used oscilloscope. A fancy wattmeter should be at the tail end of an accessory priority list. Who makes a tuner that can take this abuse?Tuners that can take a lot of abuse into unreasonable terminating Z are almost all homebrew types using vacuum caps/switches and well-constructed high Q inductors. Paul, W9AC _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Not sure what happened to the text formatting but let's try this again... These transmatches these days T matches just do not have the balls for 160M running power. They do if the tuner's complex load Z is reasonable. I melted down a MFJ 998RT arced plates on an MFJ 989B melted down a 25uH Millen coil, arced wire burned up insulation all with 500 watts :-) I tried different configurations. Short 99 foot inverted L does give me a challenge. 0.175 plate spacing arcs over. 0.25 spacing on caps is needed or vacuums variables which are not in my budget. Give us the complex Z seen at the tuner's terminals on 160m and we can offer up a reason for the behavior. Without knowing the complex Z, it's one big guessing game. In the last five years, complex impedance analyzers and vector network analyzers have become affordable for most of us and offer superb accuracy when compared to commercial lab-grade instruments. This is definitely not directed at you or anyone else in particular but it's interesting how the general ham population will spring $600-$800 for a wattmeter that offers accuracy they don't need yet won't spend that amount on a complex Z analyzer or used oscilloscope. A fancy wattmeter should be at the tail end of an accessory priority list. Who makes a tuner that can take this abuse? Tuners that can take a lot of abuse into unreasonable terminating Z are almost all homebrew types using vacuum caps/switches and well-constructed high Q inductors. Paul, W9AC - Original Message - From: Paul Christensen w...@arrl.net To: topband topband@contesting.com Sent: Saturday, October 19, 2013 11:44 AM Subject: Re: Topband: W8ji ATR-10 design 160M? These transmatches these days T matches just do not have the balls for 160M running power. They do if the tuner's complex load Z is reasonable. I melted down a MFJ 998RT arced plates on an MFJ 989B melted down a 25uH Millen coil, arced wire burned up insulation all with 500 watts :-) I tried different configurations. Short 99 foot inverted L does give me a challenge. 0.175 plate spacing arcs over. 0.25 spacing on caps is needed or vacuums variables which are not in my budget.Give us the complex Z seen at the tuner's terminals on 160m and we can offer up a reason for the behavior. Without knowing the complex Z, it's one big guessing game. In the last five years, complex impedance analzers and vector network analizers have become affordable for most of us and offer superb accuracy when compared to commercial lab-grade instruments. This is definately not directed at you or anyone elase in particular but it's interesting how the general ham population will spring $600-$800 for a wattmeter that offers accuracy they don't need yet won't spend that amount on a complex Z analyzer or used oscilloscope. A fancy wattmeter should be at the tail end of an accessory priority list. Who makes a tuner that can take this abuse?Tuners that can take a lot of abuse into unreasonable terminating Z are almost all homebrew types using vacuum caps/switches and well-constructed high Q inductors. Paul, W9AC _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Jim-- It sounds like you are just shooting in the dark and hoping for a hit. Are you measuring anything? Remind me-- what is your antenna? Bill--W4BSG -Original Message- From: Jim GM Sent: Saturday, October 19, 2013 10:23 AM To: topband Subject: Re: Topband: W8ji ATR-10 design 160M? I understand least amount of inductance. I can email a Power Point file of what I have. if any one is interested. Just ignore my notes. They just remind me what I have done so I do not do over again. I am not getting multiple minimum SWR points. If I move the external capacitance in between the 2 external inductors I can run 500 watts with out an arc over. Keeping the 100 pF external cap there and add another 100pF cap back at the antenna going to ground the cap in the MFJ-989 B starts arcing around 300 watts again. I am at a bit of a loss. My MFJ-998RT auto tuner will be back from repairs soon. If I do not do something with this situation I will FRY the thing again. -- Jim K9TF _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
I am not getting multiple minimum SWR points.` That doesn't mean anything. If I move the external capacitance in between the 2 external inductors I can run 500 watts with out an arc over. The antenna you have is ~99 feet long, although folding it back some unknown angle electrically shortens it. The network you hqave, and the value of components, is far out of range of any tuner. The SWR with the components you have in the circuit you have is probably 50:1 or more. It gets worse if you decrease either inductor from maximum. Assuming you have a 45 degree angle at the flat top, a 45 uH in series from the coax to the antenna, with a 50 uH to ground at the antenna, gives about 50 ohms j0 You have a 6.7 uH in series, and a 12.7 uH to ground at the transmitter side. The values are not only too small, they are in the system backwards. With your antenna length, the shunt coil has to go on the antenna side. Keeping the 100 pF external cap there and add another 100pF cap back at the antenna going to ground the cap in the MFJ-989 B starts arcing around 300 watts again. I'd arc too, feeding a 50:1 SWR. :) I am at a bit of a loss. My MFJ-998RT auto tuner will be back from repairs soon. If I do not do something with this situation I will FRY the thing again. I bet you will. :) Fix the antenna, and you will not need a tuner except when you move off the resonant frequency. You really need to get the antenna SWR and impedance down to some reasonable value. 50:1 SWR means you could have a little as 1 ohm at the tuner, or as high as 2500 ohms, and anything between if it is significantly reactive. You are working on the wrong problem, and forget everything you heard about hairpins made out of inductors and Q. What you really have is an L network, and you have it backwards for the antenna impedance you have. You have no choice of operating Q, it will be what it is when the antenna is matched. With an L network, like you actually have, there is no choice in operating Q. Your antenna is probably around 14 -j 270. You are not going to match that with a 140 ohm inductor and an 80 ohm inductor. The numbers are not there no matter how you wire it. Even if you put both inductors in series as a loading coil, it isn't enough to handle the -j270. It certainly isn't even close when you try to bump the 14 ohms up to 50. 73 Tom _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
That tuner is capable of all those combinations? http://www.freepatentsonline.com/4763087.pdf That is just a work of art. You can switch this to any combination or add caps or inductance. Looks to me the fixed capacitance is when your in a High voltage situation gives you the isolation you need when the variable cap starts arcing over. Then you run into the cols heating up. I moved my 100pF cap, that goes to ground, on the antenna side of the series inductor, to the same input point at connection point of the tuner and external network. So the output of the MFJ 989B has a cap going to ground. Arcing at 500 watts on 160M has stopped. I beefed up the coil and installed an edge wound coil from a 1929 TBK transmitter. If my solder joints do not hold up I will have to switch out the #12 copper connecting wire to copper tubing. Wish I had all those parts from the TBK, sold it all. Alternating phase of feed line, isn't thats what they use to do on TV antennas but they twisted it for the same reason? Hard to do with home brew feed line. Must break up resonate lengths so not to be resonate on any one frequency. A, the things we forget about that still work. -- Jim K9TF _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
That tuner is capable of all those combinations? http://www.freepatentsonline.com/4763087.pdf No. It only has the T network configuration. Nothing else. The T network is reversable, which it has to be if one leg of the T is a fixed cap and you want any range. Arcing at 500 watts on 160M has stopped. I beefed up the coil and installed an edge wound coil from a 1929 TBK transmitter. If my solder joints do not hold up I will have to switch out the #12 copper connecting wire to copper tubing. Exactly what is the entire antenna and feed system are you trying to feed How are you tuning the tuner? Are you starting with maximum possible capacitance, and going from that point first by changing only the inductor? Tom _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Besides all of the focus on loss, one has to consider component values, expense, dissipation at different inductance values, connection losses, and matching range of the tuner. The L in this example needs over 5000 pF of capacitance, and all of the heat in any of the high capacitance systems would be concentrated in few turns of an inductor. So while we can have less total loss and heat, the heat is more concentrated. A power rating curve or impedance range curve is far more complex than paper efficiency or inductor Q. Not only that, we have significant wiring and connection losses that do not show up in the paper tuner. The advice I would give anyone is pretty simple. Don't design or use an antenna that has extremely low or reactive feed impedances, unless you have no other choice. If you must use one, plan on low efficiency and other problems. It really would require a book of text and drawings to cover this properly, just like it would with many one page or one line always do this or it works this way answers. - Original Message - From: Paul Christensen w...@arrl.net To: topband@contesting.com Sent: Thursday, October 17, 2013 8:31 AM Subject: Topband: W8ji ATR-10 design 160M? *L network tuners (like the Ten-Tec, Nye Viking, etc) handle more* *power into impedances near 50 ohms, but often do a poor job * *matching reactive or very low impedance loads on low frequencies. That's a true statement only if we severely limit the C value in an L tuner. But if we use a very high value of C in an L type -- or high C values in a T, losses are significantly minimized when either tuner is terminated into low Z loads on 160m. I just computed tuner losses between a high-pass L, low-pass L,and high-pass T. For the comparison, I kept coil Q at 200 although a roller inductor's Q is greatly affected by its mechanical design. See this link that shows typical Q variance in a common roller inductor: http://www.karinya.net/g3txq/temp/rollercoaster_q.png I also assumed a resistive 5-ohm load at the output terminals of the tuner models. Q for the C values was held at 1000. Frequency is 1810 kHz. Example #1 - High Pass L L =1.47 uH C = 5800 pF Loss = 0.08 dB (1.8%) Example #2 - Low Pass L L = 1.33 uH C = 5200 pF Loss = 0.08 dB (1.8%) Example #3 - High Pass T (500 pF Output C) L= 11.4 uH Cin = 180 pF Loss = 1.09 dB (22%) Example #4 - High Pass T (1000 pF Output C) L = 5.8 uH Cin = 343 pF Loss = 0.57 dB (12%) Example #5 = High Pass T (5000 pF Output C) L = 1.44 uH Cin = 3100 pF Loss = 0.11 dB (2.4%) See a pattern here? To get minimum loss in a high-pass T with low-Z terminations, it takes C values approaching the high values required in either L type. This should be of no surprise. There's no clear winner here except the T does offer an attribute not yet mentioned: We can easily control the phase shift through the T for use in various phasing projects like directional antenna systems. We can't easily do that with just an L tuner. In that case, controlled phase shift needs to be attained by another method, like changing line length. With adequate C size and reasonable coil Q we can get low loss on low bands -- and don't need the XMatch to get it . However, based on my limited knowledge of that device, it employs a lot of switched C on the output and should work very well into low Z loads. So even with the high-pass T, we need a ton of output C (and nearly commensurate input C) to get low loss into low Z terminations -- way more than what you get when you buy a T tuner off the shelf. For the examples, I used a very low load Z value of 5 ohms. Apart from a mobile installation, these are not antennas I want to use. Even on 160m. If the input end of a line is anywhere near that value, most antenna systems will be very short. Thanks, but no thanks. I will do just about anything to ensure an antenna length that's long enough such that the Z seen at the input end of the line, no matter the line length and without any other external components -- is at least 50 ohms and don't care if it rises well into the K-ohm area. Almost any simple T or L tuner will perform the matching function in this case. When using multiband wire antennas where the lowest operating frequency is a half-wave radiator length -- or base-fed verticals that are not unreasonably short, then no matter the line length, the Z at the input end stays well into the double-digits and tuner loss is reasonably low. On my QRZ.com page, you will see a motorized balanced L tuner that uses Eimac vacuum relays to switch a Jennings vacuum variable cap either in front of, or behind the balanced coil pair. If I was to build the tuner today, I would eliminate that expensive piece. That part of the circuit was designed when the input end of the line is less than about 50 ohms. Again, unless it's a mobile installation, I really don't want to operate with short
Re: Topband: W8ji ATR-10 design 160M?
The advice I would give anyone is pretty simple. Don't design or use an antenna that has extremely low or reactive feed impedances, unless you have no other choice. If you must use one, plan on low efficiency and other problems. My conclusion as well but adding more switched C will certainly help in most common situtaions. The coil Q problem is more difficult to manage with tapped L and roller type L. Coil Q can be managed very easily with just a plug-in air coil, but then we've just lost much of our tuning flexibility across multiple bands. Further, it may be tempting to look at changes in line length to manage the problem with say...a 1/4 wave section to raise the low feed Z to a higher value at the input end of the line, but then that's fraught with matched and unmatched line loss. For example, I just ran a calculation with a 5+j0 antenna feed Z and a 1/4 wave section of RG-213 (90 feet owing to velocity factor) at 1.8 MHz. The total line loss is over 1 dB and is in the same league as my T tuner example with a 500 pF output C. So, after modeling with the 1/4 wave section, there was little to gain from total loss (tuner + line) although the tuner's components will be less stressed with the added line length and tuner loss would be reduced as the line approaches an electrical 1/4 wave in length. With the use of the line, heat dissipation due to loss is also spread across 90 feet of line instead of being concentrated in the tuner's components. It really would require a book of text and drawings to cover this properly, just like it would with many one page or one line always do this or it works this way answers. A lot of examples are needed that independently move a lot of variables. There's just no way of adequately explaining these concepts without the aid of some visual and graphical help. The same is true when trying to explain transmission line mechanics. You can end up expressing a point in a thousand words that can be accomplished with a few visual charts. Paul, W9AC _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
So what different bout your tuner, is it like the ATR-10 design? Nothing special. It's just a symmetrical balanced tuner with a pair of synchronized roller inductors and a large vacuum variable cap (with a very small minimum C and large max C) that's switched with a pair of vacuum relays. A 1:1 coaxial choke is used on the input since the circuit is symmetrical. In fact, it's really just a variation of the AG6K tuner described in QST some twenty years ago. I went with this design since I'm presently restricted to wire antennas. And due to the presence of switch-mode appliance noise, the goal was to keep the open feeders as far away from the house as possible. Balanced open lines are capable of a high degree of balance but on receive, their ability to cancel noise is dependent on the orientation of the line to the direction of the noise source. If you look at early literature from the 1930s, open feeders often used transposition blocks. I own several different types made by E.F. Johsnon as display pieces. Nice concept -- I'm not sure how satisfied I would be with using them. Anyway, to better deal with the household noise issues, the tuner is located outside of the house, in a weatherproof enclosure. LMR400 is then used between the tuner and shack. Paul, W9AC _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Very interesting! I remember seeing transposition blocks at hamfests when I was a kid but I didn't know what they were at the time. Looking up some old patents, e.g. http://www.google.com/patents/US2305688 and http://www.google.com/patents/US2135344 show something very similar to what I saw as a kid. The advice I was always given about parallel lines, is to have some twist in them, not just to help with balance, but to help prevent them from turning into sails in high wind. Where possible I try to put my tuner where the wire enters the shack. I thought I was pretty clever the way I set up my link-coupled tuner, wall-mounted L network, plugboard to select L and C based on band, etc., then I open an old issue of QST and there's a picture of a kid who had the EXACT same setup on the wall of his shack 60 years ago. I mean, exact. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Paul Christensen Sent: Thursday, October 17, 2013 11:18 AM To: topband Subject: Re: Topband: W8ji ATR-10 design 160M? So what different bout your tuner, is it like the ATR-10 design? Nothing special. It's just a symmetrical balanced tuner with a pair of synchronized roller inductors and a large vacuum variable cap (with a very small minimum C and large max C) that's switched with a pair of vacuum relays. A 1:1 coaxial choke is used on the input since the circuit is symmetrical. In fact, it's really just a variation of the AG6K tuner described in QST some twenty years ago. I went with this design since I'm presently restricted to wire antennas. And due to the presence of switch-mode appliance noise, the goal was to keep the open feeders as far away from the house as possible. Balanced open lines are capable of a high degree of balance but on receive, their ability to cancel noise is dependent on the orientation of the line to the direction of the noise source. If you look at early literature from the 1930s, open feeders often used transposition blocks. I own several different types made by E.F. Johsnon as display pieces. Nice concept -- I'm not sure how satisfied I would be with using them. Anyway, to better deal with the household noise issues, the tuner is located outside of the house, in a weatherproof enclosure. LMR400 is then used between the tuner and shack. Paul, W9AC _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
On Thu, Oct 17, 2013 at 10:04 AM, Jim GM jim.gmfo...@gmail.com wrote: snip These transmatches these days T matches just do not have the balls for 160M running power. I melted down a MFJ 998RT arced plates on an MFJ 989B melted down a 25uH Millen coil, arced wire burned up insulation all with 500 watts :-) I tried different configurations. Short 99 foot inverted L does give me a challenge. 0.175 plate spacing arcs over. 0.25 spacing on caps is needed or vacuums variables which are not in my budget. Capacitor L match ARC over. Vacuums variables or open air variable caps with 0.25 inch spacing is needed for 300 watts or better. Inductive L match has heat and at times enough heat to melt spacers on a Millen coil. Who makes a tuner that can take this abuse? -- Jim K9TF The PalStar AT5K has withstood all the abuse that I've been able to muster on 160 mx. 73, -- Ken - K4XL BoatAnchor Manual Archive BAMA - http://bama.edebris.com Show me a politician who is poor, and I'll show you a poor politician. - Carlos Hank González _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Hi Tim, This is the patent for the classic Edgar F. Johnson (E.F. Johnson) transposition insulator: http://reference.insulators.info/patents/patents/pdf/4/us002043754-001.pdf http://www.google.com/patents/US2043754 I've seen these a few times at hamfests, without exception the sellers are clueless about what they are. 73 Frank W3LPL - Original Message - From: Tim Shoppa tsho...@wmata.com To: Paul Christensen w...@arrl.net, topband topband@contesting.com Sent: Thursday, October 17, 2013 4:37:09 PM Subject: Re: Topband: W8ji ATR-10 design 160M? Very interesting! I remember seeing transposition blocks at hamfests when I was a kid but I didn't know what they were at the time. Looking up some old patents, e.g. http://www.google.com/patents/US2305688 and http://www.google.com/patents/US2135344 show something very similar to what I saw as a kid. The advice I was always given about parallel lines, is to have some twist in them, not just to help with balance, but to help prevent them from turning into sails in high wind. Where possible I try to put my tuner where the wire enters the shack. I thought I was pretty clever the way I set up my link-coupled tuner, wall-mounted L network, plugboard to select L and C based on band, etc., then I open an old issue of QST and there's a picture of a kid who had the EXACT same setup on the wall of his shack 60 years ago. I mean, exact. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Paul Christensen Sent: Thursday, October 17, 2013 11:18 AM To: topband Subject: Re: Topband: W8ji ATR-10 design 160M? So what different bout your tuner, is it like the ATR-10 design? Nothing special. It's just a symmetrical balanced tuner with a pair of synchronized roller inductors and a large vacuum variable cap (with a very small minimum C and large max C) that's switched with a pair of vacuum relays. A 1:1 coaxial choke is used on the input since the circuit is symmetrical. In fact, it's really just a variation of the AG6K tuner described in QST some twenty years ago. I went with this design since I'm presently restricted to wire antennas. And due to the presence of switch-mode appliance noise, the goal was to keep the open feeders as far away from the house as possible. Balanced open lines are capable of a high degree of balance but on receive, their ability to cancel noise is dependent on the orientation of the line to the direction of the noise source. If you look at early literature from the 1930s, open feeders often used transposition blocks. I own several different types made by E.F. Johsnon as display pieces. Nice concept -- I'm not sure how satisfied I would be with using them. Anyway, to better deal with the household noise issues, the tuner is located outside of the house, in a weatherproof enclosure. LMR400 is then used between the tuner and shack. Paul, W9AC _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
See http://n4xm.myiglou.com--click on the blue ribbon for sure. I am a licensed professional electrical engineer and have a US Patent for my unique tuner. I have been an active ham for decades. Belive what and who you want, or seek the truth. I don't debate on the internet. 73 Paul N4XM At 11:42 AM 10/16/2013 -0600, you wrote: As Tom notes, the widest possible matching range for a T-Network is with two adjustable capacitors (and, presumably, a variable inductor, typically a roller inductor). Constraining any one of these parameters reduces the available matching range. Further, Tom correctly observes that many hams damage their tuners by unwisely choosing a combination of C and L that dissipates much of their transmitted RF in the tuner itself. Several years ago, I wrote a three-part series of articles for QST about a high-power homebrew T-match autotuner. Part I of the series (QST, April 2002, p.40) shows two graphs (Figures 2 and 3) that give the range of adjustment values for Cin, Cout, and L for a T-match network, using the 160m band as an illustration. The first graph (Fig.2) shows the values of Cin and Cout (for different values of L) required to match resistive loads from 3-800 ohms. The second graph (Fig.3) is the more interesting one for this discussion, however, because it shows the percentage power loss in the T-network for different values of L. Here is the key point: With a T-network, the lowest power dissipation occurs with the smallest value of L that will give a match. To illustrate the importance of this rule of thumb, suppose one is matching a 6.25 ohm feedline (8:1 VSWR) at 1.8 MHz. According to the graph, the largest practical nductance that can match this load is about 25 uH, while the smallest practical inductance is about 2 uH. Although each inductance will give a satisfactory 1:1 match (assuming Cin and Cout are properly chosen), the 25 uH choice dissipates nearly 40% of the transmit power in the tuner, which is about 600W at the legal limit. Goodbye tuner! On the other hand, the 2 uH choice dissipates only about 45W. (Note that these values are only for resistive loads, but they illustrate the general principle.) There is a tradeoff, unfortunately, in using the smallest possible value of inductance to match a given feedline, and that is that large values of Cin and Cout are required. For this example, using a 2 uH inductance requires Cin and Cout to be greater than 1000 pF. With a 25 uH inductance, Cin and Cout only need to be about 100 pF. The problem is that designers of commercial and homebrew T-network tuners sometimes skimp on the capacitance range available, instead opting for larger (and cheaper) inductors. Buyers are initially pleased at the low cost and wide matching range of their spiffy new tuner, only to discover later that the tuner destroys itself when they turn on their amplifier. And, as Tom notes, the problem is compounded if they tune their T-networks incorrectly by following the wrong rule of thumb! 73, Jim W8ZR -Original Message- Subject: Re: Topband: W8ji ATR-10 design 160M? Respectfully, the X match is nothing but a common T-match with a fixed capacitor in one leg. In a normal T-match, operating Q can be varied over a wide range by adjusting L/C ratios. By restricting range of one leg, operating Q range is limited. So it actually **is** a T match, it just has two adjustable branches instead of the more common three adjustable branches, restricting the operating Q range and matching range. The ATR10 is more like the common old Johnson matchbox, with the exceptions instead of a link it has a tap and it is single ended. The tap sets the operating Q, just as the link ratio sets the operating Q in a Matchbox. This restricts the matching range and operating Q range. Tuners that fix the operating Q at a certain value, or limit the operating Q range, will always restrict matching range. The operating Q restriction limits peak voltages or currents by preventing grossly improper adjustments, but the very same thing that limits voltages or current by definition also limits matching range. An L network limits matching range the most of any network for a give range of component values, but also limits operating Q the most. It has only one operating Q available at any given impedance ratio. The Q varies with load impedance. You cannot have too much Q, or it won't match. This is, unfortunately, the way the world works. Everything is a tradeoff of matching range, cost, complexity, and power rating. No single network, just like no single balun, is all things to all cases. The widest matching range for a given cost is a T network with two adjustable capacitors and one shunt inductor. Unfortunately, people think (and articles repeat) the silly idea that the proper way to tune is to start with capacitors at half and tune for maximum receive. Most of any improvement centers around preventing people from doing
Re: Topband: W8ji ATR-10 design 160M?
Thanks for sharing the patent info, Frank! Really interesting! 73, Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of donov...@starpower.net Sent: Thursday, October 17, 2013 12:15 PM To: topband Cc: Tim Shoppa Subject: Re: Topband: W8ji ATR-10 design 160M? Hi Tim, This is the patent for the classic Edgar F. Johnson (E.F. Johnson) transposition insulator: http://reference.insulators.info/patents/patents/pdf/4/us002043754-001.pdf http://www.google.com/patents/US2043754 I've seen these a few times at hamfests, without exception the sellers are clueless about what they are. 73 Frank W3LPL - Original Message - From: Tim Shoppa tsho...@wmata.com To: Paul Christensen w...@arrl.net, topband topband@contesting.com Sent: Thursday, October 17, 2013 4:37:09 PM Subject: Re: Topband: W8ji ATR-10 design 160M? Very interesting! I remember seeing transposition blocks at hamfests when I was a kid but I didn't know what they were at the time. Looking up some old patents, e.g. http://www.google.com/patents/US2305688 and http://www.google.com/patents/US2135344 show something very similar to what I saw as a kid. The advice I was always given about parallel lines, is to have some twist in them, not just to help with balance, but to help prevent them from turning into sails in high wind. Where possible I try to put my tuner where the wire enters the shack. I thought I was pretty clever the way I set up my link-coupled tuner, wall-mounted L network, plugboard to select L and C based on band, etc., then I open an old issue of QST and there's a picture of a kid who had the EXACT same setup on the wall of his shack 60 years ago. I mean, exact. Tim N3QE -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Paul Christensen Sent: Thursday, October 17, 2013 11:18 AM To: topband Subject: Re: Topband: W8ji ATR-10 design 160M? So what different bout your tuner, is it like the ATR-10 design? Nothing special. It's just a symmetrical balanced tuner with a pair of synchronized roller inductors and a large vacuum variable cap (with a very small minimum C and large max C) that's switched with a pair of vacuum relays. A 1:1 coaxial choke is used on the input since the circuit is symmetrical. In fact, it's really just a variation of the AG6K tuner described in QST some twenty years ago. I went with this design since I'm presently restricted to wire antennas. And due to the presence of switch-mode appliance noise, the goal was to keep the open feeders as far away from the house as possible. Balanced open lines are capable of a high degree of balance but on receive, their ability to cancel noise is dependent on the orientation of the line to the direction of the noise source. If you look at early literature from the 1930s, open feeders often used transposition blocks. I own several different types made by E.F. Johsnon as display pieces. Nice concept -- I'm not sure how satisfied I would be with using them. Anyway, to better deal with the household noise issues, the tuner is located outside of the house, in a weatherproof enclosure. LMR400 is then used between the tuner and shack. Paul, W9AC _ Topband Reflector _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Paul, there are many people on this list who have comparable professional and ham credentials to yours. Nobody means any offense or wants to start an argument, but rather just want to understand how your invention differs from an ordinary T – network with a fixed capacitor. I – and I'm sure many others – would merely like you to explain how your innovative circuit works and how it differs from T– network. Thanks, Jim w8zr Sent from my iPad On Oct 17, 2013, at 10:21, N4XM Paul D. Schrader n...@iglou.com wrote: See http://n4xm.myiglou.com--click on the blue ribbon for sure. I am a licensed professional electrical engineer and have a US Patent for my unique tuner. I have been an active ham for decades. Belive what and who you want, or seek the truth. I don't debate on the internet.glou 73o kbu Paul N4XM At 11:42 AM 10/16/2013 -0600, you wrote: As Tom notes, the widest possible matching range for a T-Network is with two adjustable capacitors (and, presumably, a variable inductor, typically a roller inductor). Constraining any one of these parameters reduces the available matching range. Further, Tom correctly observes that many hams damage their tuners by unwisely choosing a combination of C and L that dissipates much of their transmitted RF in the tuner itself. Several years ago, I wrote a three-part series of articles for QST about a high-power homebrew T-match autotuner. Part I of the series (QST, April 2002, p.40) shows two graphs (Figures 2 and 3) that give the range of adjustment values for Cin, Cout, and L for a T-match network, using the 160m band as an illustration. The first graph (Fig.2) shows the values of Cin and Cout (for different values of L) required to match resistive loads from 3-800 ohms. The second graph (Fig.3) is the more interesting one for this discussion, however, because it shows the percentage power loss in the T-network for different values of L. Here is the key point: With a T-network, the lowest power dissipation occurs with the smallest value of L that will give a match. To illustrate the importance of this rule of thumb, suppose one is matching a 6.25 ohm feedline (8:1 VSWR) at 1.8 MHz. According to the graph, the largest practical nductance that can match this load is about 25 uH, while the smallest practical inductance is about 2 uH. Although each inductance will give a satisfactory 1:1 match (assuming Cin and Cout are properly chosen), the 25 uH choice dissipates nearly 40% of the transmit power in the tuner, which is about 600W at the legal limit. Goodbye tuner! On the other hand, the 2 uH choice dissipates only about 45W. (Note that these values are only for resistive loads, but they illustrate the general principle.) There is a tradeoff, unfortunately, in using the smallest possible value of inductance to match a given feedline, and that is that large values of Cin and Cout are required. For this example, using a 2 uH inductance requires Cin and Cout to be greater than 1000 pF. With a 25 uH inductance, Cin and Cout only need to be about 100 pF. The problem is that designers of commercial and homebrew T-network tuners sometimes skimp on the capacitance range available, instead opting for larger (and cheaper) inductors. Buyers are initially pleased at the low cost and wide matching range of their spiffy new tuner, only to discover later that the tuner destroys itself when they turn on their amplifier. And, as Tom notes, the problem is compounded if they tune their T-networks incorrectly by following the wrong rule of thumb! 73, Jim W8ZR -Original Message- Subject: Re: Topband: W8ji ATR-10 design 160M? Respectfully, the X match is nothing but a common T-match with a fixed capacitor in one leg. In a normal T-match, operating Q can be varied over a wide range by adjusting L/C ratios. By restricting range of one leg, operating Q range is limited. So it actually **is** a T match, it just has two adjustable branches instead of the more common three adjustable branches, restricting the operating Q range and matching range. The ATR10 is more like the common old Johnson matchbox, with the exceptions instead of a link it has a tap and it is single ended. The tap sets the operating Q, just as the link ratio sets the operating Q in a Matchbox. This restricts the matching range and operating Q range. Tuners that fix the operating Q at a certain value, or limit the operating Q range, will always restrict matching range. The operating Q restriction limits peak voltages or currents by preventing grossly improper adjustments, but the very same thing that limits voltages or current by definition also limits matching range. An L network limits matching range the most of any network for a give range of component values, but also limits operating Q the most. It has only one operating Q available at any given impedance ratio. The Q varies with load impedance. You cannot have too much Q
Re: Topband: W8ji ATR-10 design 160M?
wants to start an argument, but rather just want to understand how your invention differs from an ordinary T – network with a fixed capacitor. I – and I'm sure many others – would merely like you to explain how your innovative circuit works and how it differs from T– network It is all explained here, complete with drawings: http://www.freepatentsonline.com/4763087.pdf You can decide what the network configuration is. _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
On Thu, Oct 17, 2013 at 10:34:47AM -0600, MU 4CX250B wrote: wants to start an argument, but rather just want to understand how your invention differs from an ordinary T – network with a fixed capacitor. I – and I'm sure many others – would merely like you to explain how your innovative circuit works and how it differs from T– network. Thanks, Jim w8zr http://www.google.com/patents/US4763087 -- George Fremin III - K5TR geo...@kkn.net http://www.kkn.net/~k5tr _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
I expect that needs to be a good quality and seriously heavy duty switch that's used to vary the configuration of the matching network - at least at full power! Thanks, Tom! Charlie, K4OTV -Original Message- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Thursday, October 17, 2013 1:45 PM To: MU 4CX250B Cc: topband Subject: Re: Topband: W8ji ATR-10 design 160M? wants to start an argument, but rather just want to understand how your invention differs from an ordinary T - network with a fixed capacitor. I - and I'm sure many others - would merely like you to explain how your innovative circuit works and how it differs from T- network It is all explained here, complete with drawings: http://www.freepatentsonline.com/4763087.pdf You can decide what the network configuration is. _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
I find that this simulator demonstrates what several of you are saying in a very comprehensive way. http://fermi.la.asu.edu/w9cf/tuner/tuner.html 73, Barry _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
On Thu, Oct 17, 2013, K9TF wrote: Hi Paul http://lists.contesting.com/_topband/1997-01/msg00037.html You posted the comment from W8JI on a reply sorry about that. . No biggie. What the patent number? I would like to read more about it. The relevant patent appears to be 4,763,087 dated August 9, 1988. You can find the full patent text and images at www.uspto.gov and search for the patent number. I think patents expire 17 years from the issue date, so this one appears to have expired. 73, Doug K1DG _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Jim, I did not make the comments you said I made below. And the XMATCH Antenna Tuner is NOT a T match. It is a patented circuit. This unique circuit is a United States Patent. And see http://n4xm.myiglou.com Paul N4XM At 12:56 PM 10/8/2013 -0500, you wrote: Tom W8JI made some measurements back in 1997 on the ATR-15 when it first came out. Not sure how this will print out. * * *The ATR-15 measures as follows for load R and loss on 1.8 MHz: 12.5 ohms 21.8%(27.8%) 25 ohms 16.5% (22.9) 50 ohms 10.6% (11.0) 100 ohms 8.9% (10.7) 200 ohms 8.1% (10.4) 400 ohms 7.4% (10.1) 800 ohms 6.9% (8.8%)* Doubling the value of C cuts low impedance losses in half. I put 500 pF air variable caps in the ATR-15 and the 12.5 ohm loss was 13.1 percent. I don't even come close to the MFJ-989 results they published. I measured the values (they are the ones in brackets above) for the 989 using both an HP 4191A analyzer and a Harris RF voltmeter, as well as confirmed on meters. My question is where in the tee match was the extra capacitance installed? was it going to ground? N4XM commented in 1997 on the MFJ 989 review. *T network tuners (like the 989, Xmatch, Vectronics, Tucker, * *Murch, etc) handle the least power on 160 and with capacitive* *reactance low resistance loads. T network tuners handle MORE * *power into higher resistance loads or loads with some amount * *of inductive reactance. * w8JI comments *L network tuners (like the Ten-Tec, Nye Viking, etc) handle more* *power into impedances near 50 ohms, but often do a poor job * *matching reactive or very low impedance loads on low frequencies. (Sometimes* *these tuners are called Pi-networks, even though* *they do not really function as a pi except perhaps on 15 or ten* *meters) * ** *In a T network tuner, maximum efficiency and power handling * *generally occurs when maximum and equal amounts of * *capacitance are used in the capacitors, and the least amount of* *inductance is used. This is true even though many other settings* *will produce a low SWR.* I later read more archives. What came up was the ATR-30 How beefy it was. What the plate spacing on this tuners capacitors? I would think on a short antenna like mine it is not enough. So back to the ATR-10. The W8JI design with variable taps seams to handle high power with nor arcing problems. I just do not know why this is working for me. Can some one please explain this to me I am confused? All this reading requires a younger mind. Jim K9TF On Sat, Oct 5, 2013 at 1:54 PM, Jim GM jim.gmfo...@gmail.com wrote: My antenna is a 99 foot inverted L for 160M with 95 short radials 2000 feet of wire. What I am trying now is W8JI suggested modification design to improve the ATR-10 design by taps on the coil for adjustment. Works well. http://www.w8ji.com/antenna_tuners.htm Had my MFJ-989B at the feed point, I had to add a capacitor to ground 250pf so it could work. Inductance was at max farthest away from ground. Voltage was so high at 300 watts in, the 0.125 meshed plate spacing arced over, it has a T network and I had expected this to happen. http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf I run 500 watts. What I was looking at is removing the coil and the input would be at the top of C1. I made a test with QRP using 2 small spaced caps taken out of an MFJ-901A. Works well. Because of the high voltage situation would there be an issue with this and I need to go to a 0.25 inch spacing between plates? Vacuum variables are out of my price range. ATR-10 with W8JI modifications is a high pass tuner or is it? Removal of the coil would make this a low pass circuit. Besides that on 160M which one would be more efficient, and off the top of your head what would be the percentages? If you had my make do with what I have setup, what tuning network would you use? Does any one have an email address for MFJ Service department? I have the wrong one. I sent my MFJ 998RT to their Service department, the High voltage that was developed with 300 watts pretty much done it in. The ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing with out the inductor. -- Jim K9TF -- Jim K9TF _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
And for more info, send him $3. 73, Pete N4ZR Check out the Reverse Beacon Network at http://reversebeacon.net, blog at reversebeacon.blogspot.com. For spots, please go to your favorite ARC V6 or VE7CC DX cluster node. On 10/16/2013 11:01 AM, N4XM Paul D. Schrader wrote: Jim, I did not make the comments you said I made below. And the XMATCH Antenna Tuner is NOT a T match. It is a patented circuit. This unique circuit is a United States Patent. And see http://n4xm.myiglou.com Paul N4XM At 12:56 PM 10/8/2013 -0500, you wrote: Tom W8JI made some measurements back in 1997 on the ATR-15 when it first came out. Not sure how this will print out. * * *The ATR-15 measures as follows for load R and loss on 1.8 MHz: 12.5 ohms 21.8%(27.8%) 25 ohms 16.5% (22.9) 50 ohms 10.6% (11.0) 100 ohms 8.9% (10.7) 200 ohms 8.1% (10.4) 400 ohms 7.4% (10.1) 800 ohms 6.9% (8.8%)* Doubling the value of C cuts low impedance losses in half. I put 500 pF air variable caps in the ATR-15 and the 12.5 ohm loss was 13.1 percent. I don't even come close to the MFJ-989 results they published. I measured the values (they are the ones in brackets above) for the 989 using both an HP 4191A analyzer and a Harris RF voltmeter, as well as confirmed on meters. My question is where in the tee match was the extra capacitance installed? was it going to ground? N4XM commented in 1997 on the MFJ 989 review. *T network tuners (like the 989, Xmatch, Vectronics, Tucker, * *Murch, etc) handle the least power on 160 and with capacitive* *reactance low resistance loads. T network tuners handle MORE * *power into higher resistance loads or loads with some amount * *of inductive reactance. * w8JI comments *L network tuners (like the Ten-Tec, Nye Viking, etc) handle more* *power into impedances near 50 ohms, but often do a poor job * *matching reactive or very low impedance loads on low frequencies. (Sometimes* *these tuners are called Pi-networks, even though* *they do not really function as a pi except perhaps on 15 or ten* *meters) * ** *In a T network tuner, maximum efficiency and power handling * *generally occurs when maximum and equal amounts of * *capacitance are used in the capacitors, and the least amount of* *inductance is used. This is true even though many other settings* *will produce a low SWR.* I later read more archives. What came up was the ATR-30 How beefy it was. What the plate spacing on this tuners capacitors? I would think on a short antenna like mine it is not enough. So back to the ATR-10. The W8JI design with variable taps seams to handle high power with nor arcing problems. I just do not know why this is working for me. Can some one please explain this to me I am confused? All this reading requires a younger mind. Jim K9TF On Sat, Oct 5, 2013 at 1:54 PM, Jim GM jim.gmfo...@gmail.com wrote: My antenna is a 99 foot inverted L for 160M with 95 short radials 2000 feet of wire. What I am trying now is W8JI suggested modification design to improve the ATR-10 design by taps on the coil for adjustment. Works well. http://www.w8ji.com/antenna_tuners.htm Had my MFJ-989B at the feed point, I had to add a capacitor to ground 250pf so it could work. Inductance was at max farthest away from ground. Voltage was so high at 300 watts in, the 0.125 meshed plate spacing arced over, it has a T network and I had expected this to happen. http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf I run 500 watts. What I was looking at is removing the coil and the input would be at the top of C1. I made a test with QRP using 2 small spaced caps taken out of an MFJ-901A. Works well. Because of the high voltage situation would there be an issue with this and I need to go to a 0.25 inch spacing between plates? Vacuum variables are out of my price range. ATR-10 with W8JI modifications is a high pass tuner or is it? Removal of the coil would make this a low pass circuit. Besides that on 160M which one would be more efficient, and off the top of your head what would be the percentages? If you had my make do with what I have setup, what tuning network would you use? Does any one have an email address for MFJ Service department? I have the wrong one. I sent my MFJ 998RT to their Service department, the High voltage that was developed with 300 watts pretty much done it in. The ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing with out the inductor. -- Jim K9TF -- Jim K9TF _ Topband Reflector _ Topband Reflector _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Respectfully, the X match is nothing but a common T-match with a fixed capacitor in one leg. In a normal T-match, operating Q can be varied over a wide range by adjusting L/C ratios. By restricting range of one leg, operating Q range is limited. So it actually **is** a T match, it just has two adjustable branches instead of the more common three adjustable branches, restricting the operating Q range and matching range. The ATR10 is more like the common old Johnson matchbox, with the exceptions instead of a link it has a tap and it is single ended. The tap sets the operating Q, just as the link ratio sets the operating Q in a Matchbox. This restricts the matching range and operating Q range. Tuners that fix the operating Q at a certain value, or limit the operating Q range, will always restrict matching range. The operating Q restriction limits peak voltages or currents by preventing grossly improper adjustments, but the very same thing that limits voltages or current by definition also limits matching range. An L network limits matching range the most of any network for a give range of component values, but also limits operating Q the most. It has only one operating Q available at any given impedance ratio. The Q varies with load impedance. You cannot have too much Q, or it won't match. This is, unfortunately, the way the world works. Everything is a tradeoff of matching range, cost, complexity, and power rating. No single network, just like no single balun, is all things to all cases. The widest matching range for a given cost is a T network with two adjustable capacitors and one shunt inductor. Unfortunately, people think (and articles repeat) the silly idea that the proper way to tune is to start with capacitors at half and tune for maximum receive. Most of any improvement centers around preventing people from doing something silly, by limiting what they can do. There isn't any magic circuit. Tom - Original Message - From: N4XM Paul D. Schrader n...@iglou.com To: Jim GM jim.gmfo...@gmail.com Cc: topband topband@contesting.com Sent: Wednesday, October 16, 2013 11:01 AM Subject: Re: Topband: W8ji ATR-10 design 160M? Jim, I did not make the comments you said I made below. And the XMATCH Antenna Tuner is NOT a T match. It is a patented circuit. This unique circuit is a United States Patent. And see http://n4xm.myiglou.com Paul N4XM _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
As Tom notes, the widest possible matching range for a T-Network is with two adjustable capacitors (and, presumably, a variable inductor, typically a roller inductor). Constraining any one of these parameters reduces the available matching range. Further, Tom correctly observes that many hams damage their tuners by unwisely choosing a combination of C and L that dissipates much of their transmitted RF in the tuner itself. As early as 1983, when I reworked the ATR8 that Prime inherited from Amp Supply's engineering, I re-wrote the manual. Prior to that virtually every antenna tuner manual or how-to guide suggested setting the capacitors at half scale, and peaking the inductance for maximum noise. When I designed the ATR15, I used fixed inductor settings that limited Q and tuning range. This eliminated the issue of picking too much inductance. Later, I rewrote MFJ manuals, eliminating the suggestion to set the capacitor at half value. There are three problems caused by using too much inductance, or too little capacitance. 1.) Voltage is too high. This causes arcing of capacitors, and can result in an instantaneous failure problem. 2.) Voltage across the inductor is too high. This can cause too much circulating current, and damage the inductor. This is a **time heating issue** related to average power. 3.) The network has to be retuned more frequently with frequency changes. All of this is far more complex than a simple dissipation issue, because the self-Q of an inductor varies wildly with inductance tap. Not does unloaded Q vary, the ability of a roller to dissipate heat also varies. If most current is concentrated in a few turns, the inductor will be able to dissipate much less power. Optimum power rating is often not where inductance is lowest, even if that is lowest inductor loss. It almost takes a book just to describe the actions inside an inductor as the system is changed. The result of this, just like with baluns and MOV surge suppression, is that virtually any article, discussion, test, opinion, or web page will give an incomplete view. The system is too complex to give ten line answers, let alone three page answers. This is why Jim Garland had to write a three section article, and even doing that, it remains a narrow slice of everything. Also, despite claims by the ARRL and others that more capacitance increases power ratings, adding more capacitance does not always increase power rating. This is because an inductor's ability to dissipate heat, and even unloaded or self-Q, can increase faster with more inductance than electrical stress on the component decreases. Simple answers are good for sales, and everyone likes a this is what you need or don't need answer, but devices with complex loads or complex system interactions cannot be represented by a simple model, simple analysis, or one line answers. The world of tuners is like a big hobo soup kettle. T network tuners are not called T network tuners, and Pi network tuners are often not really operating as Pi's. Many things are called something just to help marketing, even if they aren't really working as what they are called. An optimum design depends not only on the load and band, an optimum design depends on the physical construction of the box all the way down to the construction and behavior of components inside the box. The only accurate, simple, answer is it depends. 73 Tom _ Topband Reflector
Re: Topband: W8ji ATR-10 design 160M?
Tom W8JI made some measurements back in 1997 on the ATR-15 when it first came out. Not sure how this will print out. * * *The ATR-15 measures as follows for load R and loss on 1.8 MHz: 12.5 ohms 21.8%(27.8%) 25 ohms 16.5% (22.9) 50 ohms 10.6% (11.0) 100 ohms 8.9% (10.7) 200 ohms 8.1% (10.4) 400 ohms 7.4% (10.1) 800 ohms 6.9% (8.8%)* Doubling the value of C cuts low impedance losses in half. I put 500 pF air variable caps in the ATR-15 and the 12.5 ohm loss was 13.1 percent. I don't even come close to the MFJ-989 results they published. I measured the values (they are the ones in brackets above) for the 989 using both an HP 4191A analyzer and a Harris RF voltmeter, as well as confirmed on meters. My question is where in the tee match was the extra capacitance installed? was it going to ground? N4XM commented in 1997 on the MFJ 989 review. *T network tuners (like the 989, Xmatch, Vectronics, Tucker, * *Murch, etc) handle the least power on 160 and with capacitive* *reactance low resistance loads. T network tuners handle MORE * *power into higher resistance loads or loads with some amount * *of inductive reactance. * w8JI comments *L network tuners (like the Ten-Tec, Nye Viking, etc) handle more* *power into impedances near 50 ohms, but often do a poor job * *matching reactive or very low impedance loads on low frequencies. (Sometimes* *these tuners are called Pi-networks, even though* *they do not really function as a pi except perhaps on 15 or ten* *meters) * ** *In a T network tuner, maximum efficiency and power handling * *generally occurs when maximum and equal amounts of * *capacitance are used in the capacitors, and the least amount of* *inductance is used. This is true even though many other settings* *will produce a low SWR.* I later read more archives. What came up was the ATR-30 How beefy it was. What the plate spacing on this tuners capacitors? I would think on a short antenna like mine it is not enough. So back to the ATR-10. The W8JI design with variable taps seams to handle high power with nor arcing problems. I just do not know why this is working for me. Can some one please explain this to me I am confused? All this reading requires a younger mind. Jim K9TF On Sat, Oct 5, 2013 at 1:54 PM, Jim GM jim.gmfo...@gmail.com wrote: My antenna is a 99 foot inverted L for 160M with 95 short radials 2000 feet of wire. What I am trying now is W8JI suggested modification design to improve the ATR-10 design by taps on the coil for adjustment. Works well. http://www.w8ji.com/antenna_tuners.htm Had my MFJ-989B at the feed point, I had to add a capacitor to ground 250pf so it could work. Inductance was at max farthest away from ground. Voltage was so high at 300 watts in, the 0.125 meshed plate spacing arced over, it has a T network and I had expected this to happen. http://www.mfjenterprises.com/support/MFJ-989B/MFJ-989B.pdf I run 500 watts. What I was looking at is removing the coil and the input would be at the top of C1. I made a test with QRP using 2 small spaced caps taken out of an MFJ-901A. Works well. Because of the high voltage situation would there be an issue with this and I need to go to a 0.25 inch spacing between plates? Vacuum variables are out of my price range. ATR-10 with W8JI modifications is a high pass tuner or is it? Removal of the coil would make this a low pass circuit. Besides that on 160M which one would be more efficient, and off the top of your head what would be the percentages? If you had my make do with what I have setup, what tuning network would you use? Does any one have an email address for MFJ Service department? I have the wrong one. I sent my MFJ 998RT to their Service department, the High voltage that was developed with 300 watts pretty much done it in. The ATR-10 W8JI redesign has greatly reduce the High voltage that I was seeing with out the inductor. -- Jim K9TF -- Jim K9TF _ Topband Reflector
