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Antenna Tuner
Hi
Does anyone know of a manufacturer of an ATU that places a 1:1 balun on the input side, like the Palstar AT4K does? I like that tuner, but it is a bit pricey. Just wondering who the competitors are, if any. Thanks |
On 9 Dec 2004 10:25:13 -0800, "
wrote: Hi Does anyone know of a manufacturer of an ATU that places a 1:1 balun on the input side, like the Palstar AT4K does? I like that tuner, but it is a bit pricey. Just wondering who the competitors are, if any. Thanks You could make your own 1:1 balun for a few bucks, and place it on either side of the tuner. See W2DU's article: http://home.iag.net/~w2du/Reflection...nProblem. pdf bob k5qwg |
"Bob Miller" wrote in message
... On 9 Dec 2004 10:25:13 -0800, " wrote: Hi Does anyone know of a manufacturer of an ATU that places a 1:1 balun on the input side, like the Palstar AT4K does? I like that tuner, but it is a bit pricey. Just wondering who the competitors are, if any. Thanks You could make your own 1:1 balun for a few bucks, and place it on either side of the tuner. See W2DU's article: http://home.iag.net/~w2du/Reflection...nProblem. pdf bob k5qwg Nice article. I guess QST used have technical articles, eh? :) Paul AB0SI |
Yes, thank you..I have been thinking about modifying an existing tuner
with the balun on the output. The problem is that ALL components must be isolated from ground. I suppose I could pull that off, but it is not as simple as you might think, especially with a tuner that uses a tapped inductor in a T match. I t would probably be easier to float a roller inductor than a tapped inductor because of the switch. The caps are usually above ground already in a T match, so thats not a problem. I'm thinking about it, but it would be nice if there was a good affordable balanced tuner out there. Jim |
As a ham of over 25 years experience and most of those using a ladder line
fed 80 meter doublet, I would highly recommend procuring an old Johnson Matchbox. These units were made back in the '50s, very well made and will match on all bands, except 30 meters, from 80 thru 10 meters. They are a link coupled transmatch, made excusively for use with ladder line or twin lead. There are a lot of them advertised on eBay. wrote in message ups.com... Yes, thank you..I have been thinking about modifying an existing tuner with the balun on the output. The problem is that ALL components must be isolated from ground. I suppose I could pull that off, but it is not as simple as you might think, especially with a tuner that uses a tapped inductor in a T match. I t would probably be easier to float a roller inductor than a tapped inductor because of the switch. The caps are usually above ground already in a T match, so thats not a problem. I'm thinking about it, but it would be nice if there was a good affordable balanced tuner out there. Jim |
MFJ has at least a couple of "balanced" devices that place a choke type
balun on the transmitter side of the device. As I recall, MFJ uses a piece of coax with Teflon dielectric that is surrounded with unknown material. 73 Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: wrote in message ups.com... Hi Does anyone know of a manufacturer of an ATU that places a 1:1 balun on the input side, like the Palstar AT4K does? I like that tuner, but it is a bit pricey. Just wondering who the competitors are, if any. Thanks |
Jim
MFJ have a balanced line tuner out, my friend has one and says it's great. I have built several Z-Match tuners and swear my them, they are easy to make if you can get the parts. It depends what sort of power you intend to run. Linear Amp UK make a high power balanced line tuner, you can find thier website he http://www.lauk.karoo.net/ Jon G2FHF wrote: Hi Does anyone know of a manufacturer of an ATU that places a 1:1 balun on the input side, like the Palstar AT4K does? I like that tuner, but it is a bit pricey. Just wondering who the competitors are, if any. Thanks |
Hello
Thank you for that link..I was not aware of those products!..Maybe I should subscribe to the RSGB magazine, Hi . I don't like MFJ products and the Palstars are very expensive. I will seriously look at the Linear Amp products. Do you have any experience with them, or know where I can get a product review? Thanks! |
Hello
Yes I am aware of the Matchbox, having been licensed since 1964. In those days the Matchbox was still "new", Hi . They have a limited matching range. They can work great on some antennas and bands, and not at all on others. Jimn |
On 13 Dec 2004 04:11:07 -0800, "
wrote: Hello Thank you for that link..I was not aware of those products!..Maybe I should subscribe to the RSGB magazine, Hi . I don't like MFJ products and the Palstars are very expensive. I will seriously look at the Linear Amp products. Do you have any experience with them, or know where I can get a product review? Thanks! I think you're going to have to make a choice between mfj products with "okay" components and reasonable prices, versus much higher prices for a Palstar (or Linear Amp) tuner with deluxe components like they used in the old days. There's not much in between. FWIW, my "wretched" mfj 989c T-type tuner easily gives a 1:1 match on an 80 meter-w/ladderline dipole on all bands between 80 & 10 meters. Mfj also makes a couple of balanced-line tuners, one in the $200 range, and the other in the $500 range. THe only alternative I know, Ten Tec sells their variable caps and variable inductors that they use in their tuner as open stock items. You could breadboard your own tuner with one of the easily obtainable circuits on the internet for a balanced design. (Do a Google on Richard Measures.) Surplus Sales of Nebraska also has a plethora of variable caps & inductors... bob k5qwg |
wrote Yes, thank you..I have been thinking about modifying an existing tuner with the balun on the output. The problem is that ALL components must be isolated from ground. I suppose I could pull that off, but it is not as simple as you might think, especially with a tuner that uses a tapped inductor in a T match. I t would probably be easier to float a roller inductor than a tapped inductor because of the switch. The caps are usually above ground already in a T match, so thats not a problem. I'm thinking about it, but it would be nice if there was a good affordable balanced tuner out there. Jim Jim, your original query and subsequent comments leave a couple of questions: 1. Is an ATU desired? 2. Will it operate a balanced line? (other antennas as well?) 3. Why is isolation from ground so important to you? Radio Works puts out some good products, one of them is the Line Isolator for just the situation you are possibly describing: http://www.radioworks.com/PDFLineIsolator.htm However it should be noted that this is offered by Radio Works (in my opinion) mainly because they promote the Carolina Windom style antennas, which are designed to radiate vertical components of feedline. Most antenna types, especially anything using a Balun at the feedpoint would have no such radiation on the feedline or shield. Antennas requiring good RF ground or radials would do so, those that don't still require bonding and grounding for lightning protection, at least in any area that can have lightning. So the multiple use of line isolators, and/or your insistence on having all components isolated from ground may correct RF problems that should be addressed at their cause, and at the expense of maintaining safe bonding and grounding of the station equipment for lightning protection. As Bob Miller also added (fwiw): I use two MFJ tuners, the 962D 1.5kw air-core inductor and the 994 600w ATU "Intellituner". Both perform very well for me on end fed wires and dipoles. Isolating anything in my station from ground is out of the question, as it should be for anyone who remains connected to either or both power and antennas during thunderstorms. 73, Jack Painter Virginia Beach VA |
THe only alternative I know, Ten Tec sells their variable caps and
variable inductors that they use in their tuner as open stock items. MFJ will sell the roller inductor they use in their tuners. I bought one at the MFJ exhibit at a hamfest. They indicated that they will sell pretty much any part of their products if you call and let them know what you want. I built my tuner out of the MFJ inductor and Ten Tec capacitors. It's my MFJ Tec tuner. Parts cost around $150, works well and has handled the legal limit. 73 Gary N4AST |
Hello Jack
Yes, the tuner is required, because I use a balanced line to feed a multiband doublet. The issue is placeing a 1:1 balun at the input of the tuner, rather than the output. In order to do that with an existing T match type tuner, all components must be isolated from ground. This is uncommon, because a typical T match grounds one side of the inductor. I have read that a 1:1 balun at the input of a T match is desireable over a 4:1 at the output. Thanks |
Interesting..what did you use for a cabinet? I have been looking
around for one that might fit the bill. |
wrote Hello Jack Yes, the tuner is required, because I use a balanced line to feed a multiband doublet. The issue is placeing a 1:1 balun at the input of the tuner, rather than the output. In order to do that with an existing T match type tuner, all components must be isolated from ground. This is uncommon, because a typical T match grounds one side of the inductor. I have read that a 1:1 balun at the input of a T match is desireable over a 4:1 at the output. Thanks Hi Jim, I can't imagine what's possibly gained by 1:1 in front of the tuner v. 4:1 (when applicable, some antennas recommend this, including for twin-lead) after it. Can you recall the writing you saw the recommendation to isolate from ground before the tuner? I just don't see what it will do for you, but as I said there is at least one good reason not to do so. Ungrounded and especially unbonded equipment should be disconnected from antennas and power supplies before the chance of a thunderstorm. An exception could be if you totally isolate the antennas from ground, and no balun can safely do that. But a similar principle called a high voltage isolation transformer could, and so could a fiber optic isolation transformer. Both are pretty expensive alternatives to staying with generally accepted lightning protection plans for the shack. Even if you intend to toss the feed out the window before a storm, I'm still curious what is gained by a 1:1 between transceiver and transmatch. 73, Jack |
Here is a quote from one site:
Of interest is the 1:1 balun mounted at the input of the tuner (rather than the output where it would be exposed to highly reactive loads). The various components are floated above chassis ground. When properly adjusted, the balun sees a 50 ohm load both at the input from the transmitter and at the output. Its not a perfect replacement for the link coupled circuits of yesteryear, but in my experience so far, it perfoms significantly better than competing tuners employing 4:1 baluns. I've tried a few of these matching networks and not one of them provided an output to tuned feeders even close to being balanced. The AT4K-BAL is a leg up on this account. There are dozens of other sites, but it is all the same info..including several ARRL articles. The issue is not lightning protection, as you suggested. Thanks |
Hi
I tried to reply to your post, but it does not seem to have made it..so here is another try: This is a quote taken from one site: Of interest is the 1:1 balun mounted at the input of the tuner (rather than the output where it would be exposed to highly reactive loads). The various components are floated above chassis ground. When properly adjusted, the balun sees a 50 ohm load both at the imput from the transmitter and at the output. Its not a perfect replacement for the link coupled circuits of yesteryear, but in my experience so far, it perfoms significantly better than competing tuners employing 4:1 baluns. I've tried a few of these matching networks and not one of them provided an output to tuned feeders even close to being balanced. The AT4K-BAL is a leg up on this account. I have seen dozens of other sites with the same info, including several ARRL articles. Thanks |
wrote Hi I tried to reply to your post, but it does not seem to have made it..so here is another try: This is a quote taken from one site: Of interest is the 1:1 balun mounted at the input of the tuner (rather than the output where it would be exposed to highly reactive loads). The various components are floated above chassis ground. When properly adjusted, the balun sees a 50 ohm load both at the imput from the transmitter and at the output. Its not a perfect replacement for the link coupled circuits of yesteryear, but in my experience so far, it perfoms significantly better than competing tuners employing 4:1 baluns. I've tried a few of these matching networks and not one of them provided an output to tuned feeders even close to being balanced. The AT4K-BAL is a leg up on this account. I have seen dozens of other sites with the same info, including several ARRL articles. Thanks Your first post did make it, and I also found that reference that shed no light, but further: http://fermi.la.asu.edu/w9cf/articles/balun/ (quoted below) 4 Baluns on the input and output of unbalanced tuners: Roy, W7EL, worked out the math for moving a current balun from output to input of an unbalanced tuner using his model of a choke balun and found that essentially nothing changed. ....the most sensible place to put a balun is on an unbalanced tuner's output, like it is on nearly all commercial tuners, and not on its input -- Interesting theory presented there, but does not support the wives tale either. And yes you can stand-by-for-fireworks if you think lightning protection isn't an issue. Anyone that thinks "floating equipment chassis" (isolated from ground) is a good plan, lives in a place where lighting is something they watch only on the Discovery Channel. 73, Jack |
On 14 Dec 2004 02:31:11 -0800, "
wrote: Here is a quote from one site: Of interest is the 1:1 balun mounted at the input of the tuner (rather than the output where it would be exposed to highly reactive loads). The various components are floated above chassis ground. When properly adjusted, the balun sees a 50 ohm load both at the input from the transmitter and at the output. Its not a perfect replacement for the link coupled circuits of yesteryear, but in my experience so far, it perfoms significantly better than competing tuners employing 4:1 baluns. I've tried a few of these matching networks and not one of them provided an output to tuned feeders even close to being balanced. The AT4K-BAL is a leg up on this account. There are dozens of other sites, but it is all the same info..including several ARRL articles. The issue is not lightning protection, as you suggested. Thanks The few balanced tuners that are being manufactured nowadays all seem to employ the balun on the input side. To use the words from MFJ's ad copy for their balanced tuners: "A 1:1 current balun is placed on the low impedance 50 input side to convert the balanced T-Network to unbalanced operation. The balun is made of 50 ferrite beads on RG-303 Teflon™ coax to give exceptional and efficient isolation. It stays cool even at maximum power." Basically, the balun hooks the balanced tuner to the unbalanced output of the transceiver. In years past, there have been heated discussions in this group as to whether the balun belongs on the input or output -- you could do a Google search if you're interested. Bob k5qwg |
And yes you can stand-by-for-fireworks if you think lightning
protection isn't an issue. Anyone that thinks "floating equipment chassis" (isolated from ground) is a good plan, lives in a place where lighting is something they watch only on the Discovery Channel. 73, Jack Jack Let me assure you, my station is well grounded, Hi! I even have an abnormal passion regarding grounds. My remark was in regarding to a "floating" balanced antenna tuner, which is not grounded anymore than is a balanced line fed doublet. Certainly everything before the tuner is well grounded. I even have a spark gap type lightning protector on the balanced feeds. As far as the debate regarding baluns at the input or output, I would be delighted to be convinced that it either does not matter, or is better at the output..because it makes my life a lot simpler. Right now I am using about 5 feet or so of LMR400 from my unbalanced tuner to a Radio Works remote balun, terminated with 300 ohm transmitting twinlead, feeding a 40 meter doublet. Works like gangbusters. Jim |
And yes you can stand-by-for-fireworks if you think lightning
protection isn't an issue. Anyone that thinks "floating equipment chassis" (isolated from ground) is a good plan, lives in a place where lighting is something they watch only on the Discovery Channel. 73, Jack Jack Let me assure you, my station is well grounded, Hi! I even have an abnormal passion regarding grounds. My remark was in regarding to a "floating" balanced antenna tuner, which is not grounded anymore than is a balanced line fed doublet. Certainly everything before the tuner is well grounded. I even have a spark gap type lightning protector on the balanced feeds. As far as the debate regarding baluns at the input or output, I would be delighted to be convinced that it either does not matter, or is better at the output..because it makes my life a lot simpler. Right now I am using about 5 feet or so of LMR400 from my unbalanced tuner to a Radio Works remote balun, terminated with 300 ohm transmitting twinlead, feeding a 40 meter doublet. Works like gangbusters. Jim |
In article E6tvd.6659$7p.4476@lakeread02,
Jack Painter wrote: I can't imagine what's possibly gained by 1:1 in front of the tuner v. 4:1 (when applicable, some antennas recommend this, including for twin-lead) after it. The reason I've seen stated, is that many 4:1 balun designs only work "as advertised" if they're working into something fairly close to their design impedances. For example, a 4:1 balun intended to match 200 ohms to 50 ohms, will only provide a 4:1 ratio and good current balance and efficiency when matching impedances fairly close to those. If you put such a balun at the output of a wide-range transmatch, and try to match up a difficult load, then the balun might "see" something like 750-j250 or 25+10j on its "200-ohm" side. The result might be poor current balance on the "balanced" side, or excessively high current flows which would require de-rating the balun's power handling capability. "Voltage" baluns seem to be most vulnerable to this sort of problem. Putting a 1:1 balun on the input side of the tuner, and using a fully-balanced or pseudo-balanced tuner is one way around this, since the balun "sees" only the impedance load for which it was designed. Another approach, often suggested, is to use a 1:1 transmission-line current balun on the output. Using a link-coupled tuner (a classic Matchbox, or a Z-match) is yet another option. -- Dave Platt AE6EO Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
"chuck" wrote Jack, I do think there's some confusion here. In cases where the balun is a part of the tuner input, the tuner chassis is usually connected directly to the transmitter chassis through the normal coax. You can ground the tuner chassis to an external earth ground if you so wish. Internally, the balanced output of the balun is connected to the "T" components at the input side. The coil, of course is not at chassis rf ground potential, but that is not relevant. It is, however, at DC ground potential (via the balun winding). I don't see any additional lightning issues associated with placing the balun at the tuner input. 73, Chuck Hi Chuck (and Jim), I was unclear on what the benefits would be, hence my questions to Jim (and the Group). But the file I referenced earlier also questioned the benefits, and explained the need for floating the tuner when a Balun i used in front of it, which would be a very bad move if lightning protection was an issue. There would be no ground connection to the tuner, leaving it as a sacrifice gear but inside the shack!. That's not all that uncommon to sacrifice a tuner by the way, but usually seen where the tuner is up in the air at the feedpoint. Marine applications often use this configuration. I don't! Hi! -- 6. Conclusions As noted by Roy Lewallen, W7EL,[2] putting a choke balun on the input of an unbalanced tuner to drive a balanced line is useless. It introduces a ``hot'' tuner case which must be isolated with no benefit over putting the balun on the output. -- I agree that a 4:1 after the tuner (or after coax from tuner to feedpoint where laddr-line begins) is a compromise at best, offering beneficial performance at some frequencies and degradation at others. All a matter of choices I guess, make the decision that's safe (first) and best for your needs after that. As always, I find this group shakes out great comments and explanations. If Roy L wants to add something to this I'm sure we would all be interested. 73, Jack wrote: And yes you can stand-by-for-fireworks if you think lightning protection isn't an issue. Anyone that thinks "floating equipment chassis" (isolated from ground) is a good plan, lives in a place where lighting is something they watch only on the Discovery Channel. 73, Jack Jack Let me assure you, my station is well grounded, Hi! I even have an abnormal passion regarding grounds. My remark was in regarding to a "floating" balanced antenna tuner, which is not grounded anymore than is a balanced line fed doublet. Certainly everything before the tuner is well grounded. I even have a spark gap type lightning protector on the balanced feeds. As far as the debate regarding baluns at the input or output, I would be delighted to be convinced that it either does not matter, or is better at the output..because it makes my life a lot simpler. Right now I am using about 5 feet or so of LMR400 from my unbalanced tuner to a Radio Works remote balun, terminated with 300 ohm transmitting twinlead, feeding a 40 meter doublet. Works like gangbusters. Jim |
Jack Painter wrote:
As always, I find this group shakes out great comments and explanations. If Roy L wants to add something to this I'm sure we would all be interested. I think you gentlemen have pretty well covered the basics. I'll just encourage everyone to read Kevin's (W9CF) excellent treatment at the URL posted by Jack a short while ago. Roy Lewallen, W7EL |
Yes, moving a current balun to a position before the tuner is a
"useless" exercise but it doesn't render the balun "useless" -- it's equally effective at the input as at the output (provided that the tuner case is floated if the balun is at the input). To answer your question about why not use one at the input and output, I recommend against using one at the input because the case of the tuner has to be floated for one at the tuner input to be effective. This has some potential safety implications. If you want to use two baluns in order to increase the common mode impedance, I suggest putting them both at the output. And for maximum effectiveness, space them about a quarter wavelength apart at the most troublesome band. Roy Lewallen, W7EL Cecil Moore wrote: Jack Painter wrote: 6. Conclusions As noted by Roy Lewallen, W7EL,[2] putting a choke balun on the input of an unbalanced tuner to drive a balanced line is useless. The choke on the input is *still* in series with the common-mode current and is still performing the choking function. Moving the balun to the input doesn't relieve the stress on the choke but it also does NOT render the choke non-functional as the word "useless" implies. -- 73, Cecil http://www.qsl.net/w5dxp -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =----- |
Roy Lewallen wrote:
To answer your question about why not use one at the input and output, I recommend against using one at the input because the case of the tuner has to be floated for one at the tuner input to be effective. Sorry, that's NOT true for remote autotuners. When I was remote autotuning my elevated-radial vertical, the autotuner was 20 feet from the antenna and 65 feet from the shack. Field strength improved the most with chokes on the input AND output. -- 73, Cecil http://www.qsl.net/w5dxp -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =----- |
Hm, that's interesting. Was the tuner case floating? Did you try putting
both baluns at the input or both at the output for comparison? And how much did the field strength improve and how did you measure it? Roy Lewallen, W7EL Cecil Moore wrote: Roy Lewallen wrote: To answer your question about why not use one at the input and output, I recommend against using one at the input because the case of the tuner has to be floated for one at the tuner input to be effective. Sorry, that's NOT true for remote autotuners. When I was remote autotuning my elevated-radial vertical, the autotuner was 20 feet from the antenna and 65 feet from the shack. Field strength improved the most with chokes on the input AND output. -- 73, Cecil http://www.qsl.net/w5dxp -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =----- |
Roy Lewallen wrote:
Hm, that's interesting. Was the tuner case floating? Did you try putting both baluns at the input or both at the output for comparison? And how much did the field strength improve and how did you measure it? The tuner case was tied to a ground rod at the base of the antenna support. In the last version, the radials were up at 20 ft. I didn't try it without a choke on the input but adding a choke to the output improved the ground level field strength at ~200 yards by a little over one dB on 40m, if memory serves me right. I can't locate my notebook at the moment. The field strength was measured using a Palomar FS-1 and ferrite rod pickup antenna. The choke on the output appeared to slightly reduce the received noise which is the problem I was chasing at the time. I never could get the received noise down to an acceptable level compared to my horizontal dipole so the vertical is gone. -- 73, Cecil http://www.qsl.net/w5dxp -----------== Posted via Newsfeed.Com - Uncensored Usenet News ==---------- http://www.newsfeed.com The #1 Newsgroup Service in the World! -----= Over 100,000 Newsgroups - Unlimited Fast Downloads - 19 Servers =----- |
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