Re: Topband: Changes To My Shunt Fed Tower
Even if the beam is "insulated" from the mast or boom, any device insulating the support members of the antenna should be bypassed at these points: 1) Mast to Boom. 2) boom to longest elements farthest out on Boom. This may not be straightforward with a two element "shorty forty", but definitely connecting the reflector or director on a two element yagi may protect the insulation at the driven element from being arced over or carbon tracked at Remember also that if you have coax to the driven element through a balun of any kind, the half element + coax shield will be connected via the suppression path of the balun, which is NOT designed to stop the series impedance OR QRO voltage found 30 feet from the end of a 160 meter radiator. If anything, at QRO on 160, the suppression path will get heated up, UNLESS there is a more attractive path to the other element. The high beam IS the end of the radiator, whether you want it or not. Do targeted things to let the 160 energy get to the end of the longest elements farthest out on the boom. If not, you may find that it behaves one way with QRP or an analyzer, and quite another with power, all the while polluting your setup with carbon tracks. AND, if you change the stuff on the high half of the tower, it DOES change the 160 feed Z. Worry if it DOESN'T. 73, Guy. On Mon, Dec 12, 2011 at 10:29 AM, Mike & Coreen Smith wrote: > Hi Bob, > > If I recall (correctly). The D40 is completely > isolated from the mast, so it would be nearly invisible to your 160m > RF...given all the other loading you have going on there. > I don't know a thing about the Optibeam...is it also isolated or grounded? > I am guessing grounded, as you now have a change. > If that IS the case, you'll need more capacitance to counteract the loading > you've added. As to the amount, I could only hazard a guess. If you've > maxxed out your 1000pF air variable, you can add some random length of > RG-214 or other coax in parallel and start hacking off a foot at a time, > and > then tweak with the cap as neccessary. > It's cheap and saves climbing ! I forget at the moment how many pF RG-214 > or other similar dielectric coax is, but maybe 10-15pF per foot springs to > mind. Try adding 10 or 15' on and see what you can do with your cap. > > My brain is still numb from ARRL-10 CW this weekend...I keep hearing "T E S > T, V E 9 A A" in my ears , hi ! > > DIT dit, > > MIke > > - Original Message - > From: Bob Garrett > To: 'Jim F.' ; 'top Band' > Sent: Sunday, December 11, 2011 1:21 PM > Subject: Topband: Changes To My Shunt Fed Tower > > > Hello Topbanders, > > It is getting cold in the Northeast and as I get older, I dislike the cold > even more. > > In April of this year, I replaced my Cush craft D40 40 meter rotable > dipole > with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of > the > mast. The overall length of the antenna is about ten feet longer and I am > assuming that it has added some additional capacitance to my 100 foot > shunt > fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new > OptiBeam dipole. > > My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the > new antenna. In terms of loss, this isn't a huge change but my amplifier > doesn't like the change. Before I spend a lot of time running back and > forth to the tower making random changes, any thoughts as to what I can do > to improve the match. I'm currently using one series capacitor 1000PF for > the matching network. I have attempted to adjust this capacitor but it > looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase > or decrease the spacing of the shunt wire? Move the connection up or down > on the tower? > > Before I get to crazy, just wanted to look to the base of knowledge on > this > reflector for your input. > > 73 and tnx in advance. > > Bob K3UL > > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > > -- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 8.5.454 / Virus Database: 271.1.1/4071 - Release Date: 12/09/11 > 20:51:00 > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
The best way to handle the problem is to assume the new antenna made an impact on the match. The first step would be to measure the actual resistance and if it is not 50 ohms, reset the tap for 50 ohms. Then measure the J again and you can easily calculate the amount of C required to cancel the J. Anything else is just guessing. On 12/12/11 11:38 AM, DL2OBO wrote: > AFAIK all Optibeam elements are always isolated from the boom. So there > shouldn't be any additional toploading from them (elements), just the > loading from the boom should be considered > > 73 Tom > > > DL2OBO (T88DL) > Carsten-Thomas Dauer ( Tom ) > c/o Hotel Hellers Krug > Altendorfer Str. 19 > D-37603 Holzminden > > www.dl2obo.com Ham-Radio > www.hotel-hellers-krug.de my hotel / rent-a-shack > www.carstendauer.dephotografy > > -Ursprüngliche Nachricht- > Von: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] > Im Auftrag von Mike& Coreen Smith > Gesendet: Montag, 12. Dezember 2011 16:30 > An: topband@contesting.com > Betreff: Re: Topband: Changes To My Shunt Fed Tower > > Hi Bob, > > If I recall (correctly). The D40 is completely > isolated from the mast, so it would be nearly invisible to your 160m > RF...given all the other loading you have going on there. > I don't know a thing about the Optibeam...is it also isolated or grounded? > I am guessing grounded, as you now have a change. > If that IS the case, you'll need more capacitance to counteract the loading > you've added. As to the amount, I could only hazard a guess. If you've > maxxed out your 1000pF air variable, you can add some random length of > RG-214 or other coax in parallel and start hacking off a foot at a time, and > > then tweak with the cap as neccessary. > It's cheap and saves climbing ! I forget at the moment how many pF RG-214 > or other similar dielectric coax is, but maybe 10-15pF per foot springs to > mind. Try adding 10 or 15' on and see what you can do with your cap. > > My brain is still numb from ARRL-10 CW this weekend...I keep hearing "T E S > T, V E 9 A A" in my ears , hi ! > > DIT dit, > > MIke > >- Original Message - >From: Bob Garrett >To: 'Jim F.' ; 'top Band' >Sent: Sunday, December 11, 2011 1:21 PM >Subject: Topband: Changes To My Shunt Fed Tower > > >Hello Topbanders, > >It is getting cold in the Northeast and as I get older, I dislike the cold >even more. > >In April of this year, I replaced my Cush craft D40 40 meter rotable > dipole >with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of > the >mast. The overall length of the antenna is about ten feet longer and I am >assuming that it has added some additional capacitance to my 100 foot > shunt >fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new >OptiBeam dipole. > >My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the >new antenna. In terms of loss, this isn't a huge change but my amplifier >doesn't like the change. Before I spend a lot of time running back and >forth to the tower making random changes, any thoughts as to what I can do >to improve the match. I'm currently using one series capacitor 1000PF for >the matching network. I have attempted to adjust this capacitor but it >looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase >or decrease the spacing of the shunt wire? Move the connection up or down >on the tower? > >Before I get to crazy, just wanted to look to the base of knowledge on > this >reflector for your input. > >73 and tnx in advance. > >Bob K3UL > > >___ >UR RST IS ... ... ..9 QSB QSB - hw? BK > > > > -- > > > >No virus found in this incoming message. >Checked by AVG - www.avg.com >Version: 8.5.454 / Virus Database: 271.1.1/4071 - Release Date: 12/09/11 > 20:51:00 > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
Yuri, I would have to put this antenna on a different tower as I depend on my beam to give me toploading for 160...unless, they have away of connecting the elements at the center to the boom via small coils or chokes. Without top loading my vertical on 160 becomes about 25% shorter and less efficientHerb On 12/12/2011 12:38 PM, DL2OBO wrote: > AFAIK all Optibeam elements are always isolated from the boom. So there > shouldn't be any additional toploading from them (elements), just the > loading from the boom should be considered > > 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
AFAIK all Optibeam elements are always isolated from the boom. So there shouldn't be any additional toploading from them (elements), just the loading from the boom should be considered 73 Tom DL2OBO (T88DL) Carsten-Thomas Dauer ( Tom ) c/o Hotel Hellers Krug Altendorfer Str. 19 D-37603 Holzminden www.dl2obo.com Ham-Radio www.hotel-hellers-krug.de my hotel / rent-a-shack www.carstendauer.dephotografy -Ursprüngliche Nachricht- Von: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] Im Auftrag von Mike & Coreen Smith Gesendet: Montag, 12. Dezember 2011 16:30 An: topband@contesting.com Betreff: Re: Topband: Changes To My Shunt Fed Tower Hi Bob, If I recall (correctly). The D40 is completely isolated from the mast, so it would be nearly invisible to your 160m RF...given all the other loading you have going on there. I don't know a thing about the Optibeam...is it also isolated or grounded? I am guessing grounded, as you now have a change. If that IS the case, you'll need more capacitance to counteract the loading you've added. As to the amount, I could only hazard a guess. If you've maxxed out your 1000pF air variable, you can add some random length of RG-214 or other coax in parallel and start hacking off a foot at a time, and then tweak with the cap as neccessary. It's cheap and saves climbing ! I forget at the moment how many pF RG-214 or other similar dielectric coax is, but maybe 10-15pF per foot springs to mind. Try adding 10 or 15' on and see what you can do with your cap. My brain is still numb from ARRL-10 CW this weekend...I keep hearing "T E S T, V E 9 A A" in my ears , hi ! DIT dit, MIke - Original Message - From: Bob Garrett To: 'Jim F.' ; 'top Band' Sent: Sunday, December 11, 2011 1:21 PM Subject: Topband: Changes To My Shunt Fed Tower Hello Topbanders, It is getting cold in the Northeast and as I get older, I dislike the cold even more. In April of this year, I replaced my Cush craft D40 40 meter rotable dipole with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of the mast. The overall length of the antenna is about ten feet longer and I am assuming that it has added some additional capacitance to my 100 foot shunt fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new OptiBeam dipole. My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the new antenna. In terms of loss, this isn't a huge change but my amplifier doesn't like the change. Before I spend a lot of time running back and forth to the tower making random changes, any thoughts as to what I can do to improve the match. I'm currently using one series capacitor 1000PF for the matching network. I have attempted to adjust this capacitor but it looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase or decrease the spacing of the shunt wire? Move the connection up or down on the tower? Before I get to crazy, just wanted to look to the base of knowledge on this reflector for your input. 73 and tnx in advance. Bob K3UL ___ UR RST IS ... ... ..9 QSB QSB - hw? BK -- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.454 / Virus Database: 271.1.1/4071 - Release Date: 12/09/11 20:51:00 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
> If I recall (correctly). The D40 is > completely isolated from the mast, Any coax fed antenna is never isolated from the tower/mast unless the antenna switch/antenna relay is a double pole design and contained in an insulated (non-conductive) case. Even then, there is generally enough capacitive coupling between the tower and shield of the bundled coax that the "shield leg" of the antenna/driven element will top load the tower. 73, ... Joe, W4TV On 12/12/2011 10:29 AM, Mike & Coreen Smith wrote: > Hi Bob, > > If I recall (correctly). The D40 is completely > isolated from the mast, so it would be nearly invisible to your 160m > RF...given all the other loading you have going on there. > I don't know a thing about the Optibeam...is it also isolated or grounded? > I am guessing grounded, as you now have a change. > If that IS the case, you'll need more capacitance to counteract the loading > you've added. As to the amount, I could only hazard a guess. If you've > maxxed out your 1000pF air variable, you can add some random length of > RG-214 or other coax in parallel and start hacking off a foot at a time, and > then tweak with the cap as neccessary. > It's cheap and saves climbing ! I forget at the moment how many pF RG-214 > or other similar dielectric coax is, but maybe 10-15pF per foot springs to > mind. Try adding 10 or 15' on and see what you can do with your cap. > > My brain is still numb from ARRL-10 CW this weekend...I keep hearing "T E S > T, V E 9 A A" in my ears , hi ! > > DIT dit, > > MIke > >- Original Message - >From: Bob Garrett >To: 'Jim F.' ; 'top Band' >Sent: Sunday, December 11, 2011 1:21 PM >Subject: Topband: Changes To My Shunt Fed Tower > > >Hello Topbanders, > >It is getting cold in the Northeast and as I get older, I dislike the cold >even more. > >In April of this year, I replaced my Cush craft D40 40 meter rotable > dipole >with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of > the >mast. The overall length of the antenna is about ten feet longer and I am >assuming that it has added some additional capacitance to my 100 foot > shunt >fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new >OptiBeam dipole. > >My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the >new antenna. In terms of loss, this isn't a huge change but my amplifier >doesn't like the change. Before I spend a lot of time running back and >forth to the tower making random changes, any thoughts as to what I can do >to improve the match. I'm currently using one series capacitor 1000PF for >the matching network. I have attempted to adjust this capacitor but it >looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase >or decrease the spacing of the shunt wire? Move the connection up or down >on the tower? > >Before I get to crazy, just wanted to look to the base of knowledge on > this >reflector for your input. > >73 and tnx in advance. > >Bob K3UL > > >___ >UR RST IS ... ... ..9 QSB QSB - hw? BK > > > -- > > > >No virus found in this incoming message. >Checked by AVG - www.avg.com >Version: 8.5.454 / Virus Database: 271.1.1/4071 - Release Date: 12/09/11 > 20:51:00 > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
Hi Bob, If I recall (correctly). The D40 is completely isolated from the mast, so it would be nearly invisible to your 160m RF...given all the other loading you have going on there. I don't know a thing about the Optibeam...is it also isolated or grounded? I am guessing grounded, as you now have a change. If that IS the case, you'll need more capacitance to counteract the loading you've added. As to the amount, I could only hazard a guess. If you've maxxed out your 1000pF air variable, you can add some random length of RG-214 or other coax in parallel and start hacking off a foot at a time, and then tweak with the cap as neccessary. It's cheap and saves climbing ! I forget at the moment how many pF RG-214 or other similar dielectric coax is, but maybe 10-15pF per foot springs to mind. Try adding 10 or 15' on and see what you can do with your cap. My brain is still numb from ARRL-10 CW this weekend...I keep hearing "T E S T, V E 9 A A" in my ears , hi ! DIT dit, MIke - Original Message - From: Bob Garrett To: 'Jim F.' ; 'top Band' Sent: Sunday, December 11, 2011 1:21 PM Subject: Topband: Changes To My Shunt Fed Tower Hello Topbanders, It is getting cold in the Northeast and as I get older, I dislike the cold even more. In April of this year, I replaced my Cush craft D40 40 meter rotable dipole with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of the mast. The overall length of the antenna is about ten feet longer and I am assuming that it has added some additional capacitance to my 100 foot shunt fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new OptiBeam dipole. My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the new antenna. In terms of loss, this isn't a huge change but my amplifier doesn't like the change. Before I spend a lot of time running back and forth to the tower making random changes, any thoughts as to what I can do to improve the match. I'm currently using one series capacitor 1000PF for the matching network. I have attempted to adjust this capacitor but it looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase or decrease the spacing of the shunt wire? Move the connection up or down on the tower? Before I get to crazy, just wanted to look to the base of knowledge on this reflector for your input. 73 and tnx in advance. Bob K3UL ___ UR RST IS ... ... ..9 QSB QSB - hw? BK -- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.454 / Virus Database: 271.1.1/4071 - Release Date: 12/09/11 20:51:00 ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
Sounds like both of your ideas are good ones to try first. One other suggestion is to change from a gamma to an omega match. You're pretty close now so if the snow and cold doesn't impede your trips to the tower you ought to make that amp happy w/o too much problem Howard..K2HK > From: rgarre...@comcast.net > To: j_fit...@yahoo.com; topband@contesting.com > Date: Sun, 11 Dec 2011 12:21:56 -0500 > Subject: Topband: Changes To My Shunt Fed Tower > > > > My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the > new antenna. In terms of loss, this isn't a huge change but my amplifier > doesn't like the change. Before I spend a lot of time running back and > forth to the tower making random changes, any thoughts as to what I can do > to improve the match. I'm currently using one series capacitor 1000PF for > the matching network. I have attempted to adjust this capacitor but it > looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase > or decrease the spacing of the shunt wire? Move the connection up or down > on the tower? > > Before I get to crazy, just wanted to look to the base of knowledge on this > reflector for your input. > > 73 and tnx in advance. > > Bob K3UL > > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
Bob, To avoid the trips up and down the tower in the winter merely add an Omega cap from the shunt to ground, You can start with a bread slicer and replace with a fixed mica later when yu find what you need. IMHO I would replace, when you can, the shunt wire with a three or four wire cage feed as this will broaden out your B/W response significantly. If you don't want to try an Omega match then i recommend a CLC network rather than a straight series Cap. Herb, KV4FZ On 12/11/2011 1:21 PM, Bob Garrett wrote: > Hello Topbanders, > > It is getting cold in the Northeast and as I get older, I dislike the cold > even more. > > In April of this year, I replaced my Cush craft D40 40 meter rotable dipole > with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of the > mast. The overall length of the antenna is about ten feet longer and I am > assuming that it has added some additional capacitance to my 100 foot shunt > fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new > OptiBeam dipole. > > My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the > new antenna. In terms of loss, this isn't a huge change but my amplifier > doesn't like the change. Before I spend a lot of time running back and > forth to the tower making random changes, any thoughts as to what I can do > to improve the match. I'm currently using one series capacitor 1000PF for > the matching network. I have attempted to adjust this capacitor but it > looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase > or decrease the spacing of the shunt wire? Move the connection up or down > on the tower? > > Before I get to crazy, just wanted to look to the base of knowledge on this > reflector for your input. > > 73 and tnx in advance. > > Bob K3UL > > > ___ > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Changes To My Shunt Fed Tower
Bob: Before making physical changes to the shunt feed system, can you try changing the length of the StepIR element to see if that affects the match? If it does or doesn't make a difference, that would be valuable info for the group. 73 de Gene Smar AD3F - Original Message - From: "Bob Garrett" To: "'Jim F.'" ; "'top Band'" Sent: Sunday, December 11, 2011 12:21 PM Subject: Topband: Changes To My Shunt Fed Tower > Hello Topbanders, > > It is getting cold in the Northeast and as I get older, I dislike the cold > even more. > > In April of this year, I replaced my Cush craft D40 40 meter rotable > dipole > with an OptiBeam OB-4030 dipole for 30 and 40 meters right at the top of > the > mast. The overall length of the antenna is about ten feet longer and I am > assuming that it has added some additional capacitance to my 100 foot > shunt > fed tower with a Cush craft X7, A3WS, 5 EL M2 6 meter yagi and the new > OptiBeam dipole. > > My match on the tower went from 1.0 x 1. To 1.9 x 1 after I installed the > new antenna. In terms of loss, this isn't a huge change but my amplifier > doesn't like the change. Before I spend a lot of time running back and > forth to the tower making random changes, any thoughts as to what I can do > to improve the match. I'm currently using one series capacitor 1000PF for > the matching network. I have attempted to adjust this capacitor but it > looks like the 1.9 x 1 is the low point. Perhaps some thoughts - increase > or decrease the spacing of the shunt wire? Move the connection up or down > on the tower? > > Before I get to crazy, just wanted to look to the base of knowledge on > this > reflector for your input. > > 73 and tnx in advance. > > Bob K3UL > > > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
