Fw: [Repeater-Builder] Re: 2M Vertical Dipoles
I think there are advantage to all metal plumber's delight antennas for VHF UHF. I would go for an all copper folded dipole. Split the far end dipole element feed it there using a balun made using a 1/2-wavelength piece of coax; run the coax feedline in from the grouinded antenna clamp. It'll give 4:1 Z transform but then you need to fiddle with the diameters of the dipole elements their spacing to get 200 ohms feedpoint Z. Then whole thing will be at DC ground vy sturdy broadbanded too, esp. if you use thick (say, 3/4) elements. Cheap too. I'd model it carefully using Eznec before-hand, get it maybe a bit long so you can cut it down when built (can't so easily _add_ pipe!) to get to resonance. Also, don't use a ruler to measure out the 1/2-wave piece of coax. Measure it out using an RF bridge or SWR analyzer, always more accurate. --John --- On Sat, 8/29/09, wb8vlc mas...@cableone.net wrote: From: wb8vlc mas...@cableone.net Subject: [Repeater-Builder] Re: 2M Vertical Dipoles To: Repeater-Builder@yahoogroups.com Date: Saturday, August 29, 2009, 9:39 PM I found some Plans on this groups page for a home made 4 pole array http://forums. radioreference. com/antennas- coax-forum/ 109144-4- bay-vhf-dipole- array-project. html scroll down a few responses and download the PDF document, I'm building one at this time. I just started to look at the spacings in EZNEC and it looks nice. Mike --- In Repeater-Builder@ yahoogroups. com, Eric Grabowski ejgrabowski@ ... wrote: I have used schedule 40 PVC for several antennas from HF thru 440 MHz without a problem. It does have a dielectric effect however that you must take into account. There is another plastic pipe called CPVC that does absorb RF at the higher frequencies. You don't want to use that. To make sure your plastic pipe will work ok, do the microwave test. Put a short length of the plastic pipe in a microwave along with a coffee mug filled with water. Run the microwave for a while. Then see if the plastic gets hot. If it does, you don't want to use it for RF. 73 and aloha, Eric KH6CQ --- On Wed, 8/12/09, AJ aj.grantham@ ... wrote: From: AJ aj.grantham@ ... Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles To: Repeater-Builder@ yahoogroups. com Date: Wednesday, August 12, 2009, 5:05 AM Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail. com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR _ _ _ _ __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail. yahoo.com
[Repeater-Builder] Re: 2M Vertical Dipoles
I found some Plans on this groups page for a home made 4 pole array http://forums.radioreference.com/antennas-coax-forum/109144-4-bay-vhf-dipole-array-project.html scroll down a few responses and download the PDF document, I'm building one at this time. I just started to look at the spacings in EZNEC and it looks nice. Mike --- In Repeater-Builder@yahoogroups.com, Eric Grabowski ejgrabow...@... wrote: I have used schedule 40 PVC for several antennas from HF thru 440 MHz without a problem. It does have a dielectric effect however that you must take into account. There is another plastic pipe called CPVC that does absorb RF at the higher frequencies. You don't want to use that. To make sure your plastic pipe will work ok, do the microwave test. Put a short length of the plastic pipe in a microwave along with a coffee mug filled with water. Run the microwave for a while. Then see if the plastic gets hot. If it does, you don't want to use it for RF. 73 and aloha, Eric KH6CQ --- On Wed, 8/12/09, AJ aj.grant...@... wrote: From: AJ aj.grant...@... Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles To: Repeater-Builder@yahoogroups.com Date: Wednesday, August 12, 2009, 5:05 AM Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail. com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail.com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR
RE: [Repeater-Builder] Re: 2M Vertical Dipoles
some does ,test a piece in the microwave To: Repeater-Builder@yahoogroups.com From: aj.grant...@gmail.com Date: Wed, 12 Aug 2009 09:05:55 -0600 Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail.com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR _ View photos of singles in your area Click Here http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fdating%2Eninemsn%2Ecom%2Eau%2Fsearch%2Fsearch%2Easpx%3Fexec%3Dgo%26tp%3Dq%26gc%3D2%26tr%3D1%26lage%3D18%26uage%3D55%26cl%3D14%26sl%3D0%26dist%3D50%26po%3D1%26do%3D2%26trackingid%3D1046138%26r2s%3D1_t=773166090_r=Hotmail_Endtext_m=EXT
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
The product I'm looking at specifically is branded as non metallic rigid PVC conduit sold locally at Lowes: http://www.carlon.com/Product_CarlonPlus4080.html On Wed, Aug 12, 2009 at 9:10 AM, Barry ate...@hotmail.com wrote: some does ,test a piece in the microwave -- To: Repeater-Builder@yahoogroups.com From: aj.grant...@gmail.com Date: Wed, 12 Aug 2009 09:05:55 -0600 Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail.com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR -- Click Here View photos of singles in your areahttp://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fdating%2Eninemsn%2Ecom%2Eau%2Fsearch%2Fsearch%2Easpx%3Fexec%3Dgo%26tp%3Dq%26gc%3D2%26tr%3D1%26lage%3D18%26uage%3D55%26cl%3D14%26sl%3D0%26dist%3D50%26po%3D1%26do%3D2%26trackingid%3D1046138%26r2s%3D1_t=773166090_r=Hotmail_Endtext_m=EXT
RE: [Repeater-Builder] Re: 2M Vertical Dipoles
Nuke a test piece and see if it gets hot. Chris Kb0wlf From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of AJ Sent: Wednesday, August 12, 2009 10:06 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail.com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR No virus found in this incoming message. Checked by AVG - www.avg.com Version: 8.5.392 / Virus Database: 270.13.45/2287 - Release Date: 08/12/09 06:09:00
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
I just happen to be today building a simple 12 meter 1/4 wave vertical using this PVC I picked up at Lowes yesterday. I am using the pipe for a sleeve to insulate the bottom 18 inches of the Aluminum tubing of the vertical from its mounting pipe. It says on the PVC pipe I purchased ..Rigid Nonmetallic Conduit Aboveground and Underground Schedule 40.. made by Cantex (http://www.cantexinc.com/ I am using a 1 inch diameter PVC with fairly thick walls. The antenna is fairly short and lightweight, being only 112 inches long, so it should hold up well. This is for my 12 meter beacon I will have on the air soon which will be next to my 10 meter beacon already going on 28.2185 MHz. Both antennas are on the top of my metal garage. Roger W5RDW Murphy, Texas - Original Message - From: AJ To: Repeater-Builder@yahoogroups.com Sent: Wednesday, August 12, 2009 10:13 AM Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles The product I'm looking at specifically is branded as non metallic rigid PVC conduit sold locally at Lowes: http://www.carlon.com/Product_CarlonPlus4080.html On Wed, Aug 12, 2009 at 9:10 AM, Barry ate...@hotmail.com wrote: some does ,test a piece in the microwave To: Repeater-Builder@yahoogroups.com From: aj.grant...@gmail.com Date: Wed, 12 Aug 2009 09:05:55 -0600 Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail.com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR Click Here View photos of singles in your area
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
There is a definite dielectric effect for slipping an antenna inside a PVC pipe. Here are a couple of antennas that I build to insert inside PVC and both have to be final tuned while inserted inside the support pipe. http://sbarcnm.org/forum/index.php?topic=83.0 http://sbarcnm.org/forum/index.php?topic=58.0 I built one version of the first one listed to slip inside a fiberglass radome from a defunct commercial antenna using RG-213 and one half inch copper tubing for the sleeves. I had to use a shorted matching stub to get a decent SWR from this setup. 73 - Jim W5ZIT --- On Wed, 8/12/09, AJ aj.grant...@gmail.com wrote: From: AJ aj.grant...@gmail.com Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles To: Repeater-Builder@yahoogroups.com Date: Wednesday, August 12, 2009, 10:05 AM Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail. com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
I see that YAHOO added spaces to the links in my last post. Remove the spaces to make the links work. 73 - Jim W5ZIT --- On Wed, 8/12/09, Jim Brown w5...@yahoo.com wrote: From: Jim Brown w5...@yahoo.com Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles To: Repeater-Builder@yahoogroups.com Date: Wednesday, August 12, 2009, 10:43 AM There is a definite dielectric effect for slipping an antenna inside a PVC pipe. Here are a couple of antennas that I build to insert inside PVC and both have to be final tuned while inserted inside the support pipe. http://sbarcnm. org/forum/index.php?topic=83.0 http://sbarcnm. org/forum/index.php?topic=58.0 I built one version of the first one listed to slip inside a fiberglass radome from a defunct commercial antenna using RG-213 and one half inch copper tubing for the sleeves. I had to use a shorted matching stub to get a decent SWR from this setup. 73 - Jim W5ZIT ,___
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
I have used schedule 40 PVC for several antennas from HF thru 440 MHz without a problem. It does have a dielectric effect however that you must take into account. There is another plastic pipe called CPVC that does absorb RF at the higher frequencies. You don't want to use that. To make sure your plastic pipe will work ok, do the microwave test. Put a short length of the plastic pipe in a microwave along with a coffee mug filled with water. Run the microwave for a while. Then see if the plastic gets hot. If it does, you don't want to use it for RF. 73 and aloha, Eric KH6CQ --- On Wed, 8/12/09, AJ aj.grant...@gmail.com wrote: From: AJ aj.grant...@gmail.com Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles To: Repeater-Builder@yahoogroups.com Date: Wednesday, August 12, 2009, 5:05 AM Does really PVC absorb or RF or just act as a dielectric? The reason I ask is I'm looking at encasing an antenna project for the sake of weatherproofing and PVC would fit the bill rather easily. 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:49 AM, AA8K73 GMail aa8...@gmail. com wrote: AJ, if you replace the steel mast with a fiberglass one, won't you still have the metallic feed line there? Doesn't PVC absorb RF? 73, Mike AJ wrote: On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR __ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
[Repeater-Builder] Re: 2M Vertical Dipoles
Hi Joe, Guess we are all telling our age. I had WR1AIK in 1975/76. Remember it took a note to my congressman to get the license assigned - seemed to take forever! I was in the AF in Northern Maine at the time. cu Tim W5FN --- In Repeater-Builder@yahoogroups.com, Joe k1ike_m...@... wrote: Jim Brown wrote: This plot was submitted to the FCC to get repeater license WR5ADU and WR5ADV back in the '70s when antenna patterns for a repeater had to be submitted. Wow Jim, your an old geezer! Me too. I remember plotting the antenna pattern for a ground plane back in the early 70's for a repeater application. Silly, but it had to be done to meet the requirements. We got the call WR1ABR. 73, Joe, K1ike
[Repeater-Builder] Re: 2M Vertical Dipoles
If you want Laird / Antenex does make a 2 and 4 dipole array for the 2 meter band the part number is YDA1362 for a 2 dipole 136-150 antenna and YDA1364 for the 4 dipole antenna. They don't come with a mast pipe like the cushcraft antennas from long ago. They have a YDA2004 for 200-225 MHZ and a YDA4304 for 430-450 MHZ. They all come with the dipoles and the harness and you supply the mast pipe or it can be ordered with the antenna. I am ordering one of the YDA1362 to check out how they work. Now that amateur line of Cushcraft has been absorbed by MFJ it will be interesting to see what happens to the line of Cushcraft antennas. Paul R. Dumdie Jr. 73 W9DWP/R IRLP-NODE-4455 443.025/2A 145.270/1B/1Z/NAC-293 ARC-Radio-8 KCARES KCAPS HERD546 EX WB9QWZ WQGG738-462.725 AAR5CU/T www.riflesandradios.com www.theherd.com
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower... On that same note, does anyone have construction plans for a dipole array (not necessarily folded dipoles)? I remember seeing a set of plans somewhere quite a while ago - we're thinking of constructing one but encasing the dipoles in fiberglass or PVC to try to protect from the weather and debris at our site (top of a large farm field)... 73, AJ, K6LOR On Mon, Aug 10, 2009 at 9:17 AM, Paul Dumdie w9...@sbcglobal.net wrote: If you want Laird / Antenex does make a 2 and 4 dipole array for the 2 meter band the part number is YDA1362 for a 2 dipole 136-150 antenna and YDA1364 for the 4 dipole antenna. They don't come with a mast pipe like the cushcraft antennas from long ago. They have a YDA2004 for 200-225 MHZ and a YDA4304 for 430-450 MHZ. They all come with the dipoles and the harness and you supply the mast pipe or it can be ordered with the antenna. I am ordering one of the YDA1362 to check out how they work. Now that amateur line of Cushcraft has been absorbed by MFJ it will be interesting to see what happens to the line of Cushcraft antennas. Paul R. Dumdie Jr. 73 W9DWP/R IRLP-NODE-4455 443.025/2A 145.270/1B/1Z/NAC-293 ARC-Radio-8 KCARES KCAPS HERD546 EX WB9QWZ WQGG738-462.725 AAR5CU/T www.riflesandradios.com www.theherd.com
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
If you mount the array on a non-conductive pole, won't you then have to model the effects of interaction with the outside of the coax shields of the feedline harness that would normally be insignificant when attached to the side of a conductive pole? - Original Message - From: AJ To: Repeater-Builder@yahoogroups.com Sent: Monday, August 10, 2009 9:27 AM Subject: Re: [Repeater-Builder] Re: 2M Vertical Dipoles On this same topic of the mast-less Antennex/Laird dipole arrays, has anyone attempted to top mount these from a fiberglass mast to minimize interaction with the normal steel pole? I have quite a few surplus fiberglass poles left that would likely work, even for side mounting on 1/2 wave spacing from the tower...
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
Paul Plack wrote: If you mount the array on a non-conductive pole, won't you then have to model the effects of interaction with the outside of the coax shields of the feedline harness that would normally be insignificant when attached to the side of a conductive pole? Be careful hereSome dipole arrays, like the cushcraft, requires a metallic support pole to obtain/maintain the 50 ohm feedpoint impedance. Kevin
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
Hmm, that would make sense... Back to the drawing board :) On Mon, Aug 10, 2009 at 11:15 AM, Kevin Custer kug...@kuggie.com wrote: Paul Plack wrote: If you mount the array on a non-conductive pole, won't you then have to model the effects of interaction with the outside of the coax shields of the feedline harness that would normally be insignificant when attached to the side of a conductive pole? Be careful hereSome dipole arrays, like the cushcraft, requires a metallic support pole to obtain/maintain the 50 ohm feedpoint impedance. Kevin
[Repeater-Builder] Re: 2M Vertical Dipoles
What was the spacing between the tower legs at the mounting location of the dipoles in your model? Allan Crites WA9ZZU -- In Repeater-Builder@yahoogroups.com, n...@... wrote: At 8/9/2009 05:47, you wrote: As frequency decreases, so does the importance of keeping the dipoles exactly above one another. This is why you can get away with mounting the bays of a LB array around a smaller tower (like Rohn 25) and still have very good omni-directional performance. Positioning the bays around a central supporting mast of a UHF array creates considerable pattern distortion and gain is lost. I once modeled this arrangement in NEC-Win: the resulting pattern looked like a warped pancake. On-horizon gain was all over the place. Bob NO6B
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
At 8/9/2009 16:41, you wrote: What was the spacing between the tower legs at the mounting location of the dipoles in your model? No tower. Only the rooftop-mounted mast 4 dipoles, which is what I was using at the time. Bob NO6B
Re: [Repeater-Builder] Re: 2M Vertical Dipoles
Comtech I believe has the modeling for antenna side mounting from tower and it's affect on gain... On Sun, Aug 9, 2009 at 7:14 PM, n...@no6b.com wrote: At 8/9/2009 16:41, you wrote: What was the spacing between the tower legs at the mounting location of the dipoles in your model? No tower. Only the rooftop-mounted mast 4 dipoles, which is what I was using at the time. Bob NO6B
