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#1
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Velocity Factor of Coax
Hello all
What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 anyone have any input on this thanx howard |
#2
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Velocity Factor of Coax
sorry I should mention the RG-59 is used for impedance matching not feed
line thanks again Howard "Howard Kowall" wrote in message ... Hello all What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 anyone have any input on this thanx howard |
#3
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Velocity Factor of Coax
"Howard Kowall" wrote in message
news sorry I should mention the RG-59 is used for impedance matching not feed line thanks again Howard "Howard Kowall" wrote in message ... Hello all What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 anyone have any input on this thanx howard It's principally the relative permittivity of the dielectric that determines the velocity factor. Air alone would yield a value of unity but the presence of a spacer of some sort means practical values are smaller. Foam can get close to air. I wonder why you need a Lindenblad for 2 metres - do you really need good circular polarisation over a range of elevation angles (and omni HRP, of course)? Chris |
#4
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Velocity Factor of Coax
On Feb 9, 3:26*pm, "Howard Kowall" wrote:
What determines the *Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters. The velocity of propagation (v.p.) in each branch of the feed harness won't affect the relative field radiation pattern of such an antenna array as long as the same electrical lengths of coax are used between the power divider outputs and the feedpoint of each element of the array. The v.p. of the main transmission line from the tx to the input of of the antenna power divider in this scenario is irrelevant. RF |
#5
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Velocity Factor of Coax
"Howard Kowall" wrote in message ... Hello all What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 anyone have any input on this thanx howard Hi Howard I am interested in reception of CP signals from all points within the upper hemisphere. I am curious about your purpose for this Lindenblad. Jerry KD6JDJ |
#6
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Velocity Factor of Coax
"Jerry" wrote in message ... "Howard Kowall" wrote in message ... Hello all What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 anyone have any input on this thanx howard Hi Howard I am interested in reception of CP signals from all points within the upper hemisphere. I am curious about your purpose for this Lindenblad. Jerry KD6JDJ Ever tried crossed 'wilted' dipoles? Chris |
#7
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Velocity Factor of Coax
On Mon, 9 Feb 2009 15:30:50 -0600, "Howard Kowall"
wrote: sorry I should mention the RG-59 is used for impedance matching not feed line thanks again Howard "Howard Kowall" wrote in message ... Hello all What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 You might want to consider using RG-6/u instead of RG-59. These daze, the quality of RG-59 coax is rather marginal. I've seen 80% coverage shielding and cable unsuitable for outdoor use. Meanwhile, the CATV people have switched to RG-6/u for everything. Much of it is quad shielded and UV resistant. Velocity factor is usually 0.66 for solid dielectric and anywhere between 0.7 and 0.9 for various foam dielectric mixes. When you find a suitable piece of cable, grab the manufacturer and full part number. Then, lookup the VF on the mfg data sheet. -- # Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060 # 831-336-2558 # http://802.11junk.com # http://www.LearnByDestroying.com AE6KS |
#8
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Velocity Factor of Coax
hello all
thanks all who read and emailed back lot of good info came in and I have a good handle on it I am building this antenna for rhcp portable satellite antenna for LEO Ham Radio Sat thanks again Howard "Howard Kowall" wrote in message ... Hello all What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 anyone have any input on this thanx howard |
#9
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Velocity Factor of Coax
I've found quite a variation in foamed dielectric cable velocity factor
from lot to lot of the same brand and type, even with major brands. Apparently they don't control the density of the dielectric very well. So if you're planning on using foamed dielectric cable in an application where VF is important, I highly recommend that you measure the VF of a sample from the same piece you'll be using. Roy Lewallen, W7EL |
#10
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Velocity Factor of Coax
"Howard Kowall" wrote in message ... hello all thanks all who read and emailed back lot of good info came in and I have a good handle on it I am building this antenna for rhcp portable satellite antenna for LEO Ham Radio Sat thanks again Howard "Howard Kowall" wrote in message ... Hello all What determines the Velocity Factor of a coax cable. Is it the center conductor awg,dielectric,shield or all combined I am building a Lindenblad Antenna for 2 Meters its asked to use RG-59 polyethylene foam coax with stranded center conductor I think the VF is .66 I cant find any stranded center cond where I am,so I want to try it with Solid,but it seems all the solid is VF .88 anyone have any input on this thanx howard Hi Howard The Lindenblad has an overhead null that you might find anoying for some high elevation passes of LEOs. Are you open to trying to build a DCA (which is an antenna that I developed)? I make the claim that there is no other hemispheric coverage antenna design that performs better than a DCA. But, I sure am open to being corrected. The Feb 2008 QST contains an article on the DCA antenna design concept. It is my claim that a DCA is extreemely forgiving of construction errors and uses 4 wire dipoles and 50 ohm coax with 5 RFI type ferrites as "baluns'. Jerry KD6JDJ |
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