Re: [Repeater-Builder] Commercial VHF antenna on 2m
Dave, I thought I'd do a bit of investigation using the rough VSWR numbers you provided earlier, and here is what I calculated with my trusty Smith Chart and calculator: 1) the length of the o.c.coax (I used RG-214/U in my calculations) you used on your 1st try to reduce the VSWR to 1.5 was about 3.7. 2) the VSWR being 2.0 relates to a Z=51+j35 ohms 3) the impedance matching line needed to be added to the existing coax is 23.6 of RG-214/U. 4) the o.c. stub needed to be added at the Tee adapter on the xmtr end of the additional line is 5.18 of RG-214/U 5) if one wanted to use a s.c. stub then the impedance matching line needed to be added to the existing coax is 13.325 of RG-214/U 6) and the s.c. stub length needed is 8.14 of RG-214/U at the Tee adapter All impedance matching was done here with only VSWR measurements which can be obtained using a Bird WM and an arbitrary length of o.c.coax (o.c. coax is preferred because one can easily shorten it by cutting with a side cutters or I use a hand held hedge clipper) and the aid of a Smith Chart, a compass for drawing VSWR circles, and a 4 function calculator. Are you listening Norm? AC --- On Sun, 5/9/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Sunday, May 9, 2010, 11:20 PM Thanks, I'll get back to you but it won't be immediately. The site is secured and access is very limited. Dave - Original Message - From: allan crites To: Repeater-Builder@ yahoogroups. com Sent: Monday, May 10, 2010 12:17 AM Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, maybe I can help you with your impedance matching if you could provide me with some information. I need to know: 1) the freq of operation 2) the VSWR at the xmtr end of the coax line feeding the antenna 3) the VSWR of the line when you added the Tee adapter and open circuit coax stub 4) the type of coax used for the stub (50 ohms, solid dielectric, foam, polyethylene or teflon, the impedance, and the length in inches. When I get this I will put it into my Smith Chart program and see what I can find. AC --- On Sun, 5/9/10, WA3GIN wa3...@comcast. net wrote: From: WA3GIN wa3...@comcast. net Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@ yahoogroups. com Date: Sunday, May 9, 2010, 10:09 PM DB224... no access to the antenna. We got to live with it as it is ... just trying to make the transmitter happy till a time comes when we can either tweak the antenna or replace it. Thanks , dave - Original Message - From: allan crites To: Repeater-Builder@ yahoogroups. com Sent: Sunday, May 09, 2010 10:13 PM Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast. net wrote: From: WA3GIN wa3...@comcast. net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@ yahoogroups. com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
Re: [Repeater-Builder] Commercial VHF antenna on 2m
Dave, You're probably right that the new location probably makes up for a lot. Have you been able to confirm that the antenna still works up at it's rated freqs? How much feedline loss are you dealing with? Most 'good' sites have significant feed line runs and therefore loss. While I haven't spotted where you indicated this, it sounds like a tower site. Feedline loss improves your apparent match by twice the loss of the feedline. 2:1 is 9.5 db return loss. If you have 3 dB of feedline loss, that's a 6 dB improvement and the RL at the antenna is 3.5 dB (~5:1) this might expalin why you can't stub tune it out. One of your earlier posts indicates that this is a PD-220-3A. This is a collinear with a beamwidth of 18 degrees. It's low enough gain where the beam tilt out of band isn't likely to be a factor. The up (or down) tilt of a collinear is dependent on frequency. At UHF and 800 with high gain antennas this can be a real factor. You can get great match but put all of your energy into the ground (or into space.) It's also a reason that a lot of antennas don't work well upside down. This is a real problem with high gain collinear wireless LAN antennas. N1OZ -- mailto:o...@ozindfw.net Oz POB 93167 Southlake, TX 76092 (Near DFW Airport)
Re: [Repeater-Builder] Commercial VHF antenna on 2m
Not to throw a monkey wrench into things, but... Is that 4 dipole array antenna an Andrew db-224a? If so, and it was made in Mexico in the last 6 or 7 years the harness may leak... The leaks seem to be happening where the coax of the harness enters the molded Y where 3 coaxes are joined. There are at least 3 of these on each harness and some have 4 if you have an open stub factory installed in the harness near where the top and bottom halves come together. Andrew (now part of Commscope) has changed the harnesses to address this problem... I have gotten free replacement harnesses from them, but I have had to send the old harness back to them first. I sent one to them just over a month ago, but haven't gotten a new one back for it yet... Good luck. Norm - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Sat May 08 23:13:40 2010 Subject: [Repeater-Builder] Commercial VHF antenna on 2m Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
Re: [Repeater-Builder] Commercial VHF antenna on 2m
Hello Dave, You may be able to improve the VSWR match, but the antenna may still not perform well. What kind of an antenna is it? If it is the typical fiberglass collinear antenna, the internal elements will be too short. Using a 154MHz antenna on 146.745MHz will mean that the elements will be about 5% too short. It is my understanding that when you shorten the elements on a collinear array by 2% you will get about a 3% down-tilt off the horizon of the antenna angle of radiation. Your antenna (if it is a collinear) will have quite a serious down-tilt with the 5% shorter elements. This may not be bad on a very high site covering very low terrain around it, or if you are trying to keep the signal from propagating much farther from the horizon. If the terrain that you are trying to cover is not much lower than the repeater site elevation you may have a coverage issue. Look At: www.ad4c.us/Antennas/collinearantenna.doc and look at his comments about down-tilt. 73, Joe, K1ike = On 5/9/2010 12:13 AM, WA3GIN wrote: Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
RE: [Repeater-Builder] Commercial VHF antenna on 2m
Norm, Whenever I install an antenna that uses molded Y joints, I take the time to seal them with 3M Scotchkote electrical sealant. I also ensure that all nuts are tight- a few new antennas had loose terminals, right out of the box. When applying the Scotchkote, I first do all upward-facing joints and allow the sealant to set, then invert the antenna and do the remaining joints. If I have the time, I give each joint a second coat. I use a small stiff brush to apply the sealant only where the cable jacket enters the splice block. This is a messy job, so I do it at the shop a few days before making the trip to the site. I have several Scotchkote-treated exposed-dipole antennas in service, both VHF and UHF, and none of them has suffered a leaky harness. I have a mixture of Andrew (Decibel Products), Celwave, Sinclair, Comprod, and Telewave antennas, and I believe that the Scotchkote routine has prevented any water ingress problems. Disclaimer: I have no association with 3M; I am simply a satisfied customer. More info is here: http://tinyurl.com/2cdrdnm 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of NORM KNAPP Sent: Sunday, May 09, 2010 4:34 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Not to throw a monkey wrench into things, but... Is that 4 dipole array antenna an Andrew db-224a? If so, and it was made in Mexico in the last 6 or 7 years the harness may leak... The leaks seem to be happening where the coax of the harness enters the molded Y where 3 coaxes are joined. There are at least 3 of these on each harness and some have 4 if you have an open stub factory installed in the harness near where the top and bottom halves come together. Andrew (now part of Commscope) has changed the harnesses to address this problem... I have gotten free replacement harnesses from them, but I have had to send the old harness back to them first. I sent one to them just over a month ago, but haven't gotten a new one back for it yet... Good luck. Norm - Original Message - From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Sat May 08 23:13:40 2010 Subject: [Repeater-Builder] Commercial VHF antenna on 2m Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
Re: [Repeater-Builder] Commercial VHF antenna on 2m
div class=plainMailInserting a tee connector in an arbitrary point on a transmission line with an open or short circuited stub to obtain an acceptable reduction in the VSWR on the line is next to impossible and is typically an exercise in futility (which you apparently have learned).BRBRThe only way to guarantee having a substantial reduction in VSWR is to first measure the Z=R+/-jX at the connector, plot the measured R+/-jX on a Smith Chart or into a Smith Chart computer program, determine if there needs to be a modification in the line length and then add a Tee adapter with a shorted or open circuit stub of a length indicated by the Smith Chart. This is not a simple or easy process for the uninitiated user.BRBRAllan Critesnbsp; wa9zzuBRBRBRBR--- On Sat, 5/8/10, WA3GIN lt;a ymailto=mailto:wa3...@comcast.net; href=/mc/compose?to=wa3...@comcast.netwa3...@comcast.net/agt; wrote:BRBRgt; From: WA3GIN lt;a ymailto=mailto:wa3...@comcast.net; href=/mc/compose?to=wa3...@comcast.netwa3...@comcast.net/agt;BRgt; Subject: [Repeater-Builder] Commercial VHF antenna on 2mBRgt; To: a ymailto=mailto:Repeater-Builder@yahoogroups.com; href=/mc/compose?to=repeater-buil...@yahoogroups.comRepeater-Builder@yahoogroups.com/aBRgt; Date: Saturday, May 8, 2010, 11:13 PMBRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt;nbsp; BRgt; BRgt; BRgt; BRgt; BRgt;nbsp;nbsp;nbsp;BRgt; BRgt; BRgt;nbsp; nbsp;nbsp;nbsp;BRgt;nbsp; nbsp; nbsp;nbsp;nbsp;BRgt;nbsp; nbsp; nbsp;nbsp;nbsp;BRgt;nbsp; nbsp; nbsp;nbsp;nbsp;BRgt; BRgt; BRgt; Hi folks,BRgt; BRgt; Several weeks ago I posedBRgt; the question of using a BRgt; Commercial VHF antenna that was resonant on 154Mhz onBRgt; 146.745Mhz. We tried BRgt; it today. The SWR was a bit over 2:1 on the repeater freq.BRgt; We installed a T BRgt; connector after the cans and used an open stub to try toBRgt; match the line...got it BRgt; down to 1.5:1, wouldn't go any lower. BRgt; BRgt; We think the height of theBRgt; antenna makes up for BRgt; what we suspect is a lot of loss in the antenna. TheBRgt; previous location of the BRgt; repeater antenna was 100ft ASL and this location is 525ftBRgt; ASL. Maybe one day BRgt; we'll get a chance to retune the four dipoleBRgt; antenna.BRgt; BRgt; Thanks to all thatBRgt; provided ideas for this BRgt; project.BRgt; BRgt; 73,BRgt; daveBRgt; wa3ginBRgt; BRgt; BRgt; BRgt;nbsp; nbsp;nbsp;nbsp;BRgt;nbsp; nbsp; nbsp; BRgt; BRgt;nbsp; nbsp;nbsp;nbsp;BRgt;nbsp; nbsp;nbsp;nbsp;BRgt; BRgt; BRgt;nbsp; BRgt; BRgt; BRgt; BRgt;nbsp;nbsp;nbsp;BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt; BRgt;BR/div
Re: [Repeater-Builder] Commercial VHF antenna on 2m
Hi Eric. That is a good idea. You shouldn't have to do it, but you got to do what you got to do. When I replaced the harness on the 3 year old db224a that we use on our 147.225 repeater, I used scotch C130 tape, followed by 88T and the double scotch coated that over every single joint or connection on that thing. No way I want to have to go back up there (270') again and swap antennas. I too have seen those screws and or nuts get loose and need tightening. After all was said and done, I ended up with a SWR of 1:43 : 1 at the polyphaser according to the Anrisu Site Master I am now working on two more DB224a antennas. I plan on making my own db224e by modifying loops and harness from an A model and also one with a modified A harness.. 73 Norm - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com Sent: Sun May 09 10:15:03 2010 Subject: RE: [Repeater-Builder] Commercial VHF antenna on 2m Norm, Whenever I install an antenna that uses molded Y joints, I take the time to seal them with 3M Scotchkote electrical sealant. I also ensure that all nuts are tight- a few new antennas had loose terminals, right out of the box. When applying the Scotchkote, I first do all upward-facing joints and allow the sealant to set, then invert the antenna and do the remaining joints. If I have the time, I give each joint a second coat. I use a small stiff brush to apply the sealant only where the cable jacket enters the splice block. This is a messy job, so I do it at the shop a few days before making the trip to the site. I have several Scotchkote-treated exposed-dipole antennas in service, both VHF and UHF, and none of them has suffered a leaky harness. I have a mixture of Andrew (Decibel Products), Celwave, Sinclair, Comprod, and Telewave antennas, and I believe that the Scotchkote routine has prevented any water ingress problems. Disclaimer: I have no association with 3M; I am simply a satisfied customer. More info is here: http://tinyurl.com/2cdrdnm http://tinyurl.com/2cdrdnm 73, Eric Lemmon WB6FLY -Original Message- From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com [mailto:Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com ] On Behalf Of NORM KNAPP Sent: Sunday, May 09, 2010 4:34 AM To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Not to throw a monkey wrench into things, but... Is that 4 dipole array antenna an Andrew db-224a? If so, and it was made in Mexico in the last 6 or 7 years the harness may leak... The leaks seem to be happening where the coax of the harness enters the molded Y where 3 coaxes are joined. There are at least 3 of these on each harness and some have 4 if you have an open stub factory installed in the harness near where the top and bottom halves come together. Andrew (now part of Commscope) has changed the harnesses to address this problem... I have gotten free replacement harnesses from them, but I have had to send the old harness back to them first. I sent one to them just over a month ago, but haven't gotten a new one back for it yet... Good luck. Norm - Original Message - From: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com To: Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Repeater-Builder@yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com mailto:Repeater-Builder%40yahoogroups.com Sent: Sat May 08 23:13:40 2010 Subject: [Repeater-Builder] Commercial VHF antenna on 2m Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
Re: [Repeater-Builder] Commercial VHF antenna on 2m
Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
RE: [Repeater-Builder] Commercial VHF antenna on 2m
What ever the radiator is one word springs to mind which if adjusted correctly makes the harness much less important and explains the vwsr imbalance Resonance To: Repeater-Builder@yahoogroups.com From: wa9...@arrl.net Date: Sun, 9 May 2010 19:13:20 -0700 Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin _ New, Used, Demo, Dealer or Private? Find it at CarPoint.com.au http://clk.atdmt.com/NMN/go/206222968/direct/01/
Re: [Repeater-Builder] Commercial VHF antenna on 2m
DB224... no access to the antenna. We got to live with it as it is ... just trying to make the transmitter happy till a time comes when we can either tweak the antenna or replace it. Thanks , dave - Original Message - From: allan crites To: Repeater-Builder@yahoogroups.com Sent: Sunday, May 09, 2010 10:13 PM Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
RE: [Repeater-Builder] Commercial VHF antenna on 2m
Barry, I think you're dreaming. --- On Sun, 5/9/10, Barry ate...@hotmail.com wrote: From: Barry ate...@hotmail.com Subject: RE: [Repeater-Builder] Commercial VHF antenna on 2m To: repeater-builder@yahoogroups.com Date: Sunday, May 9, 2010, 9:49 PM What ever the radiator is one word springs to mind which if adjusted correctly makes the harness much less important and explains the vwsr imbalance Resonance To: Repeater-Builder@ yahoogroups. com From: wa9...@arrl. net Date: Sun, 9 May 2010 19:13:20 -0700 Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast. net wrote: From: WA3GIN wa3...@comcast. net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@ yahoogroups. com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin Find it at CarPoint.com. au New, Used, Demo, Dealer or Private?
Re: [Repeater-Builder] Commercial VHF antenna on 2m
I see. If you knew the impedance at the end of the coax then one could make an impedance matching section which would enable the xmtr to see a resistive load of 50 ohms, thus negating the need to replace the antenna. AC --- On Sun, 5/9/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Sunday, May 9, 2010, 10:09 PM DB224... no access to the antenna. We got to live with it as it is ... just trying to make the transmitter happy till a time comes when we can either tweak the antenna or replace it. Thanks , dave - Original Message - From: allan crites To: Repeater-Builder@ yahoogroups. com Sent: Sunday, May 09, 2010 10:13 PM Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast. net wrote: From: WA3GIN wa3...@comcast. net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@ yahoogroups. com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
Re: [Repeater-Builder] Commercial VHF antenna on 2m
Dave, maybe I can help you with your impedance matching if you could provide me with some information. I need to know: 1) the freq of operation 2) the VSWR at the xmtr end of the coax line feeding the antenna 3) the VSWR of the line when you added the Tee adapter and open circuit coax stub 4) the type of coax used for the stub (50 ohms, solid dielectric, foam, polyethylene or teflon, the impedance, and the length in inches. When I get this I will put it into my Smith Chart program and see what I can find. AC --- On Sun, 5/9/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Sunday, May 9, 2010, 10:09 PM DB224... no access to the antenna. We got to live with it as it is ... just trying to make the transmitter happy till a time comes when we can either tweak the antenna or replace it. Thanks , dave - Original Message - From: allan crites To: Repeater-Builder@ yahoogroups. com Sent: Sunday, May 09, 2010 10:13 PM Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast. net wrote: From: WA3GIN wa3...@comcast. net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@ yahoogroups. com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
Re: [possible spam] RE: [Repeater-Builder] Commercial VHF antenna on 2m
I am going to have to disagree with you. Take it from me. I have tried everything under the sun when it comes to manipulate the size of or tuning of the loops but to no avail. In my opinion, and Allen might disagree (listen to him) the harness seems to have more to do with the match than the size of the loops. I have gone to great length (no pun intended) to modify the lengths of the loops to no avail... The harness is the key. 73 Norm - Original Message - From: Repeater-Builder@yahoogroups.com Repeater-Builder@yahoogroups.com To: repeater-builder@yahoogroups.com repeater-builder@yahoogroups.com Sent: Sun May 09 21:49:59 2010 Subject: [possible spam] RE: [Repeater-Builder] Commercial VHF antenna on 2m What ever the radiator is one word springs to mind which if adjusted correctly makes the harness much less important and explains the vwsr imbalance Resonance To: Repeater-Builder@yahoogroups.com From: wa9...@arrl.net Date: Sun, 9 May 2010 19:13:20 -0700 Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin Find it at CarPoint.com.au New, Used, Demo, Dealer or Private? http://clk.atdmt.com/NMN/go/206222968/direct/01/
Re: [Repeater-Builder] Commercial VHF antenna on 2m
Thanks, I'll get back to you but it won't be immediately. The site is secured and access is very limited. Dave - Original Message - From: allan crites To: Repeater-Builder@yahoogroups.com Sent: Monday, May 10, 2010 12:17 AM Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, maybe I can help you with your impedance matching if you could provide me with some information. I need to know: 1) the freq of operation 2) the VSWR at the xmtr end of the coax line feeding the antenna 3) the VSWR of the line when you added the Tee adapter and open circuit coax stub 4) the type of coax used for the stub (50 ohms, solid dielectric, foam, polyethylene or teflon, the impedance, and the length in inches. When I get this I will put it into my Smith Chart program and see what I can find. AC --- On Sun, 5/9/10, WA3GIN wa3...@comcast.net wrote: From: WA3GIN wa3...@comcast.net Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@yahoogroups.com Date: Sunday, May 9, 2010, 10:09 PM DB224... no access to the antenna. We got to live with it as it is ... just trying to make the transmitter happy till a time comes when we can either tweak the antenna or replace it. Thanks , dave - Original Message - From: allan crites To: Repeater-Builder@ yahoogroups. com Sent: Sunday, May 09, 2010 10:13 PM Subject: Re: [Repeater-Builder] Commercial VHF antenna on 2m Dave, Is this a 154 MHz colinear antenna you are wanting to use on 146 MHz or one like a DB 224 with 4 exposed dipoles? If the 4 exposed dipole type, just what makes you suspect that there is a lot of loss when an antenna made for 154 MHz is used at 146 MHz and how do you expect to tune the dipoles without compensating for the harness impedance matching sections mismatch also. Allan Crites wa9zzu --- On Sat, 5/8/10, WA3GIN wa3...@comcast. net wrote: From: WA3GIN wa3...@comcast. net Subject: [Repeater-Builder] Commercial VHF antenna on 2m To: Repeater-Builder@ yahoogroups. com Date: Saturday, May 8, 2010, 11:13 PM Hi folks, Several weeks ago I posed the question of using a Commercial VHF antenna that was resonant on 154Mhz on 146.745Mhz. We tried it today. The SWR was a bit over 2:1 on the repeater freq. We installed a T connector after the cans and used an open stub to try to match the line...got it down to 1.5:1, wouldn't go any lower. We think the height of the antenna makes up for what we suspect is a lot of loss in the antenna. The previous location of the repeater antenna was 100ft ASL and this location is 525ft ASL. Maybe one day we'll get a chance to retune the four dipole antenna. Thanks to all that provided ideas for this project. 73, dave wa3gin
RE: [Repeater-Builder] Commercial VHF antenna on 2m
To: Repeater-Builder@yahoogroups.com From: wa9...@arrl.net Date: Sun, 9 May 2010 20:14:19 -0700 Subject: RE: [Repeater-Builder] Commercial VHF antenna on 2m Barry, I think you're dreaming. Ok explain to me why making the thing resonant won't make it be a better antenna assisting several of the issues mentioned t Activity: New Members 17 Visit Your Group Switch to: Text-Only, Daily Digest • Unsubscribe • Terms of Use . _ View photos of singles in your area! Looking for a hot date? http://clk.atdmt.com/NMN/go/150855801/direct/01/
RE: [possible spam] RE: [Repeater-Builder] Commercial VHF antenna on 2m
To: Repeater-Builder@yahoogroups.com From: nkn...@twowayradio.net Date: Sun, 9 May 2010 23:21:43 -0500 Subject: Re: [possible spam] RE: [Repeater-Builder] Commercial VHF antenna on 2m I am going to have to disagree with you. Take it from me. I have tried everything under the sun when it comes to manipulate the size of or tuning of the loops but to no avail. In my opinion, and Allen might disagree (listen to him) the harness seems to have more to do with the match than the size of the loops. I have gone to great length (no pun intended) to modify the lengths of the loops to no avail... The harness is the key. 73 Norm Sigh ... see my other post om _ New, Used, Demo, Dealer or Private? Find it at CarPoint.com.au http://clk.atdmt.com/NMN/go/206222968/direct/01/
