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Auto tuners & verticals
I am considering purchasing a remote auto tuner for my continuing
tinkering with verticals. My current focus is on 80-160 meters with 33+ foot verticals. The auto tuners specs claim a max inductance of around 32 uh. The tuners computed with the ARRL program TLW20 require much larger values of inductance. Will the Auto tuner (SGC-237) that claims to match any wire greater than 28 feet long really do it? John Ferrell W8CCW |
Auto tuners & verticals
On Sun, 03 Dec 2006 23:13:38 -0500, John Ferrell
wrote: Will the Auto tuner (SGC-237) that claims to match any wire greater than 28 feet long really do it? I have a SGC-230 (the big one) and an approximate 35' telescoping whip on the R/rear of a 30' 5th wheel and it tunes fine on the lower bands, including 160M. I have to shorten the whip up a bit to get it to tune on 10M though. S.T.W. |
Auto tuners & verticals
John Ferrell wrote:
Will the Auto tuner (SGC-237) that claims to match any wire greater than 28 feet long really do it? I once forgot to attach my bugcatcher so my SG-230 tuned a single four foot bottom section and reported finding a match on 75m. The question is not will it find a match but will it put any power into the antenna at that "match" point - or is the tuner itself just a dummy load? -- 73, Cecil http://www.w5dxp.com |
Auto tuners & verticals
On Sun, 03 Dec 2006 23:13:38 -0500, John Ferrell
wrote: I am considering purchasing a remote auto tuner for my continuing tinkering with verticals. My current focus is on 80-160 meters with 33+ foot verticals. The auto tuners specs claim a max inductance of around 32 uh. The tuners computed with the ARRL program TLW20 require much larger values of inductance. Did you model the exact circuit of the SGC tuner? IIRC they use a l/pi-l configuration and an autotransformer. Will the Auto tuner (SGC-237) that claims to match any wire greater than 28 feet long really do it? The demands on the tuner will depend on how good a ground system you build. If you use a poor ground system, a side benefit of the poor efficiency is a subtantial amount of resistance in the feedpoint impedance, though you are probably still looking at thousands of ohms of capacitive reactance. If on the other hand you have an outstanding ground system, the very low value of feedpoint R becomes challenging for the tuner, and the efficiency you saved with the gound system might be lost in the tuner. Of course, the other option is to lengthen the vertical to raise the radiation resistance so that it is not totally swamped by ground system resistance. Back to you question, will you get a match? If the tuner lives up to its specification, you should... but you are looking at the world through your VSWR meter, and that is a very limited view! Owen -- |
Auto tuners & verticals
Cecil Moore wrote:
John Ferrell wrote: Will the Auto tuner (SGC-237) that claims to match any wire greater than 28 feet long really do it? I once forgot to attach my bugcatcher so my SG-230 tuned a single four foot bottom section and reported finding a match on 75m. The question is not will it find a match but will it put any power into the antenna at that "match" point - or is the tuner itself just a dummy load? That's precisely the point. If you wanted to match a 30ft whip on the lower bands, and didn't have a tuner, you would be thinking about large air-wound base loading coils. The small inductors inside amateur auto-tuners are nothing like that standard of construction, so the losses inside the tuner will be higher. As Cecil says, when a tuner is forced into a tough situation, its 'load' impedance may consist mostly of internal losses... and an auto-tuner is perfectly capable of matching that. One of my prized possessions is a Racal military auto-tuner that is rated to handle 1kW continuously into a 30ft whip at 2MHz. Sure enough, it contains some very large air-wound inductors, with the kind of high-Q construction that you'd expect to see at the base of a mobile whip. A really good amateur project would be to combine the smart controller of a modern auto-ATU with your own individual collection of large inductors, capacitors and relays. However, it would take some guts to buy an auto-tuner, remove all the undersized RF components, measure their inductances and capacitances, and then throw them away! -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Auto tuners & verticals
Ian White GM3SEK wrote:
A really good amateur project would be to combine the smart controller of a modern auto-ATU with your own individual collection of large inductors, capacitors and relays. However, it would take some guts to buy an auto-tuner, remove all the undersized RF components, measure their inductances and capacitances, and then throw them away! And then install a foot long hi-Q air core coil where once rested a toroidal coil. :-) -- 73, Cecil http://www.w5dxp.com |
Auto tuners & verticals
A really good amateur project would be to combine the smart controller
of a modern auto-ATU with your own individual collection of large inductors, capacitors and relays. That really would be great. I'm keeping that in mind for some day. For a non-random-wire installation and not too many bands, you can go with manual switching of networks. When I lived in an apartment, I had a magnet wire antenna that consisted of two random lengths fed in the "middle." As such, every time the antenna broke and I put it back up, I needed a new match on each band. This is the kind of a situation where an autotuner really shines; I decided to use a remote manual tuner instead: http://www.n3ox.net/projects/servo When I moved into a house, I was able to put up something a little sturdier for the lower bands. Since it's always the same radiator and always the same ground system, I'm just using switched L-networks at the base to match it. It's 40 feet tall; the 80m matching network is a 20 turn tapped coil, #10 copper wire, about 3.5 inches in diameter. The other matching networks have air variable caps and 2" self-supporting #10 coils. http://www.n3ox.net/projects/lowbandvert John, if you're thinking of using a 33 foot vertical on 160,80, and the higher bands, might I suggest an approach where you use a GIANT tapped coil matching scheme for 160m, taps switched with a big relay, and then have relays to select whether you're using the 160m/80m matching network or the autotuner. For both of these bands, an inductor with the bottom end attached to the ground system with a tap near the bottom for the feedline and a tap up further for the antenna should work fine. It's basically an L-L step-up L network. The autotuner should be fairly efficient on 40m and up, though you might want to add a few feet to the vertical to avoid the high impedance of a half wavelength on 20m, but I dunno. It's really the bands where the vertical is significantly shorter than a 1/4 wavelength where you need a high-Q matching network. Dan |
Auto tuners & verticals
Cecil Moore wrote:
Ian White GM3SEK wrote: A really good amateur project would be to combine the smart controller of a modern auto-ATU with your own individual collection of large inductors, capacitors and relays. However, it would take some guts to buy an auto-tuner, remove all the undersized RF components, measure their inductances and capacitances, and then throw them away! And then install a foot long hi-Q air core coil where once rested a toroidal coil. :-) Yes, that's the idea... well, roughly the idea... -- 73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB) http://www.ifwtech.co.uk/g3sek |
Auto tuners & verticals
John Ferrell wrote:
I am considering purchasing a remote auto tuner for my continuing tinkering with verticals. My current focus is on 80-160 meters with 33+ foot verticals. The auto tuners specs claim a max inductance of around 32 uh. The tuners computed with the ARRL program TLW20 require much larger values of inductance. Will the Auto tuner (SGC-237) that claims to match any wire greater than 28 feet long really do it? John Ferrell W8CCW As others have noted, the auto tuners will have no trouble matching a 33 foot vertical on either 80 or 160 meters, even over sea water. Using one at the antenna may reduce losses in your coax since the swr will always be low. The auto tuners will introduce their own losses, as will any antenna tuners, although with shorter antennas the losses may be greater. QST had an article in which auto tuner losses and matching ranges were measured and I think compared with conventional tuners. If I recall, the results were less unfavorable toward auto tuners than I had expected. To reduce auto tuner matching losses to insignificant levels, you might consider adding some lumped inductance at the base of your vertical (or even better, part way up as in center-loading). You can add a capacitance hat as well. If you cause the 33 foot antenna to appear resonant at either 80 or 160, you will see reduced auto tuner matching losses on both bands. Just a rough approximation to the required number of turns ought to work. You're only trying to provide enough external loading to reduce the tuner's losses. Resonance really doesn't matter much. If you do this, you should be able to enjoy the ease of QSY without a serious loss penalty and without a need to switch taps or retune manually. Of course your 33 foot vertical resonant at 80 or 160 meters may not perform well at 40 meters and above, or worse, may not provide an impedance your tuner can handle at those frequencies. Chuck, NT3G ----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- |
Auto tuners & verticals
On Mon, 4 Dec 2006 14:47:34 +0000, Ian White GM3SEK
wrote: .... When you're using an auto-tuner, your whole approach to antennas gets turned around. Just put up whatever you want, or whatever you can, and in most cases the tuner will take care of it. .... The autotuner at the feedpoint is certainly an interesting solution to convenient frequency agile operation. The risk, as some have identified, whilst a match is obtained for the transmitter, and transmission line losses are low, that antenna performance (efficiency) may be lacking. You just can't tell by looking at the VSWR meter on the radio. I put some notes together exploring models of an antenna system based on NEC models of the radiator, estimates of ground system loss, calculated loss of a practical L match, and calculated transmission line losses. There are three articles that may be of interest (John and others): http://www.vk1od.net/NaroomaEFW/NaroomaEFW.htm http://www.vk1od.net/InvertedL/InvertedL.htm http://www.vk1od.net/multibandunload...ical/index.htm Some have mentioned avoiding high impedance resonances as they will damage the tuner. Some of the articles above predict the voltage impressed on the tuner, and for longish wires, it isn't nearly as severe as using one of these tuners on 2.4m long mobile whip (as people do, and in compliance with the tuner user manual). Taking a system view, all three of the articles show that there is a lower frequency limit to efficient operation of the antenna system, and the major contibutions to loss. Ground loss is commonly the most signigicant element for minimal installations. It seems obvious that in order to reduce ground loss, one should improve the ground system. Taking that system perspective, one of the ways (and it may be the best way in most situations) to reduce ground loss is to lengthen the radiator. Owen -- |
Auto tuners & verticals
On Mon, 04 Dec 2006 19:43:55 GMT, Owen Duffy wrote:
On Mon, 4 Dec 2006 14:47:34 +0000, Ian White GM3SEK wrote: There are three articles that may be of interest (John and others): http://www.vk1od.net/NaroomaEFW/NaroomaEFW.htm http://www.vk1od.net/InvertedL/InvertedL.htm http://www.vk1od.net/multibandunload...ical/index.htm Some have mentioned avoiding high impedance resonances as they will damage the tuner. Some of the articles above predict the voltage impressed on the tuner, and for longish wires, it isn't nearly as severe as using one of these tuners on 2.4m long mobile whip (as people do, and in compliance with the tuner user manual). Taking a system view, all three of the articles show that there is a lower frequency limit to efficient operation of the antenna system, and the major contibutions to loss. Ground loss is commonly the most signigicant element for minimal installations. It seems obvious that in order to reduce ground loss, one should improve the ground system. Taking that system perspective, one of the ways (and it may be the best way in most situations) to reduce ground loss is to lengthen the radiator. Owen There is a lot to digest there... I am still at it John Ferrell W8CCW |
Auto tuners & verticals
On Mon, 04 Dec 2006 06:49:11 GMT, Owen Duffy wrote:
On Sun, 03 Dec 2006 23:13:38 -0500, John Ferrell wrote: I am considering purchasing a remote auto tuner for my continuing tinkering with verticals. My current focus is on 80-160 meters with 33+ foot verticals. The auto tuners specs claim a max inductance of around 32 uh. The tuners computed with the ARRL program TLW20 require much larger values of inductance. Did you model the exact circuit of the SGC tuner? IIRC they use a l/pi-l configuration and an autotransformer. Will the Auto tuner (SGC-237) that claims to match any wire greater than 28 feet long really do it? The demands on the tuner will depend on how good a ground system you build. If you use a poor ground system, a side benefit of the poor efficiency is a subtantial amount of resistance in the feedpoint impedance, though you are probably still looking at thousands of ohms of capacitive reactance. If on the other hand you have an outstanding ground system, the very low value of feedpoint R becomes challenging for the tuner, and the efficiency you saved with the gound system might be lost in the tuner. Of course, the other option is to lengthen the vertical to raise the radiation resistance so that it is not totally swamped by ground system resistance. Back to you question, will you get a match? If the tuner lives up to its specification, you should... but you are looking at the world through your VSWR meter, and that is a very limited view! Owen The SGC-237 is on order! I appreciate the help in making my decision. John Ferrell W8CCW |
Auto tuners & verticals
Nice tuner... Just remember John, no one can be too rich, too thin, or
have too many radials... denny / k8do |
Auto tuners & verticals
On 5 Dec 2006 06:25:25 -0800, "Denny" wrote:
Nice tuner... Just remember John, no one can be too rich, too thin, or have too many radials... denny / k8do I will never have any of those problems...! John Ferrell W8CCW |
Auto tuners & verticals
On Mon, 04 Dec 2006 20:50:54 -0500, John Ferrell
wrote: On Mon, 04 Dec 2006 06:49:11 GMT, Owen Duffy wrote: On Sun, 03 Dec 2006 23:13:38 -0500, John Ferrell wrote: I am considering purchasing a remote auto tuner for my continuing tinkering with verticals. My current focus is on 80-160 meters with 33+ foot verticals. The auto tuners specs claim a max inductance of .... The SGC-237 is on order! I appreciate the help in making my decision. If you want to improve efficiency on 160m, think about raising the radiation resistance and / or reducing the earth loss. Possibilities to raise Rr include inductive loading high up, longer radiator, capacity hat, more than one of the above. Owen -- |
Auto tuners & verticals
On Mon, 04 Dec 2006 09:18:47 -0500, chuck wrote:
John Ferrell wrote: I am considering purchasing a remote auto tuner for my continuing As others have noted, the auto tuners will have no trouble matching a 33 foot vertical on either 80 or 160 meters, even over sea water. Using one at the antenna may reduce losses in your coax since the swr will always be low. The auto tuners will introduce their own losses, as will any antenna tuners, although with shorter antennas the losses may be greater. QST had an article in which auto tuner losses and matching ranges were measured and I think compared with conventional tuners. If I recall, the results were less unfavorable toward auto tuners than I had expected. To reduce auto tuner matching losses to insignificant levels, you might consider adding some lumped inductance at the base of your vertical (or even better, part way up as in center-loading). You can add a capacitance hat as well. If you cause the 33 foot antenna to appear resonant at either 80 or 160, you will see reduced auto tuner matching losses on both bands. Just a rough approximation to the required number of turns ought to work. You're only trying to provide enough external loading to reduce the tuner's losses. Resonance really doesn't matter much. If you do this, you should be able to enjoy the ease of QSY without a serious loss penalty and without a need to switch taps or retune manually. Of course your 33 foot vertical resonant at 80 or 160 meters may not perform well at 40 meters and above, or worse, may not provide an impedance your tuner can handle at those frequencies. Chuck, NT3G I have updated the 28 foot vertical web page for those who may be interested in my experience. I is at http://www.dixienc.us/28FtVert/SGC237.htm I am very pleased with the results using the tuner but it has only been a few days, I am still in the "honey moon" phase. I outline the considerations for me and a larger vertical at the web site. John Ferrell W8CCW |
Auto tuners & verticals
John Ferrell wrote in
: On Mon, 04 Dec 2006 09:18:47 -0500, chuck wrote: John Ferrell wrote: I am considering purchasing a remote auto tuner for my continuing As others have noted, the auto tuners will have no trouble matching a 33 foot vertical on either 80 or 160 meters, even over sea water. Using one at the antenna may reduce losses in your coax since the swr will always be low. The auto tuners will introduce their own losses, as will any antenna tuners, although with shorter antennas the losses may be greater. QST had an article in which auto tuner losses and matching ranges were measured and I think compared with conventional tuners. If I recall, the results were less unfavorable toward auto tuners than I had expected. To reduce auto tuner matching losses to insignificant levels, you might consider adding some lumped inductance at the base of your vertical (or even better, part way up as in center-loading). You can add a capacitance hat as well. If you cause the 33 foot antenna to appear resonant at either 80 or 160, you will see reduced auto tuner matching losses on both bands. Just a rough approximation to the required number of turns ought to work. You're only trying to provide enough external loading to reduce the tuner's losses. Resonance really doesn't matter much. If you do this, you should be able to enjoy the ease of QSY without a serious loss penalty and without a need to switch taps or retune manually. Of course your 33 foot vertical resonant at 80 or 160 meters may not perform well at 40 meters and above, or worse, may not provide an impedance your tuner can handle at those frequencies. Chuck, NT3G I have updated the 28 foot vertical web page for those who may be interested in my experience. I is at http://www.dixienc.us/28FtVert/SGC237.htm I am very pleased with the results using the tuner but it has only been a few days, I am still in the "honey moon" phase. I outline the considerations for me and a larger vertical at the web site. John Ferrell W8CCW John, re the lighting protection issue with the tuner. I don't need or want to operate when there is a high risk of lightning, so I disconnect the tuner. The last picture in this article shows how the tuner is mounted and the simplicity of an effective isolating switch. In the event of lightning strike, the inverted L wire will probably side flash to the support mast where it is much closer. One could of course build a sturdy arrestor near the tuner if you don't have such an alternative. http://www.vk1od.net/InvertedL/InvertedL.htm Pleased it is all working well for you. Owen |
Auto tuners & verticals
On Tue, 02 Jan 2007 02:07:57 GMT, Owen Duffy wrote:
I have updated the 28 foot vertical web page for those who may be interested in my experience. I is at http://www.dixienc.us/28FtVert/SGC237.htm I am very pleased with the results using the tuner but it has only been a few days, I am still in the "honey moon" phase. I outline the considerations for me and a larger vertical at the web site. John Ferrell W8CCW John, re the lighting protection issue with the tuner. I don't need or want to operate when there is a high risk of lightning, so I disconnect the tuner. The last picture in this article shows how the tuner is mounted and the simplicity of an effective isolating switch. In the event of lightning strike, the inverted L wire will probably side flash to the support mast where it is much closer. One could of course build a sturdy arrestor near the tuner if you don't have such an alternative. http://www.vk1od.net/InvertedL/InvertedL.htm Pleased it is all working well for you. Owen After reading your web pages I have begun to imitate your set up. I will be using a 44 foot wire radiator. It will (is) angling down to one of the ground rods. That will permit the tuner to be installed inside the house. This set up is physically much simpler for me. The tower is a crank-up/tilt over arrangement with no guys so the actual rigging must allow for a lot of movement. John Ferrell W8CCW |
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