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| 15 Apr 2008 21:41:32 |
| Cathy |
| Tuning VHF Antenna |
I have purchased a new VHF Antenna and then decided to also get a Glomex Wind Indicator that fits on the antenna in an effort to slightly tidy up all the garbage at the top of the mast. Afte following the assembly instructions for the Wind Indicator, at the end it suggests I need to cut a length of the Antenna off. The problem is that the Antenna I have fitted this onto is not a Glomex Antenna and I am wondering if the distance to be cut of would be the same if this Antenna is different. I assume the length of Antenna needs to be cut off to compensate for the Chrome ball fitted to the centre of the Antenna where the Wind Indicator sits. Thinking back to my Childhood CB days, we used to use an SWR meter to tune a CB Antenna which I assume is very similar to a VHF Radio. Would it help if I went and bought an SWR meter to try and tune this VHF Antenna? Any advice would be greatly appreciated. Regards C |
| 15 Apr 2008 22:56:39 |
| Andy Champ |
| Re: Tuning VHF Antenna |
Cathy wrote: > I have purchased a new VHF Antenna and then decided to also get a Glomex > Wind Indicator that fits on the antenna in an effort to slightly tidy up > all > the garbage at the top of the mast. > > Afte following the assembly instructions for the Wind Indicator, at the end > it suggests I need to cut a length of the Antenna off. The problem is that > the Antenna I have fitted this onto is not a Glomex Antenna and I am > wondering if the distance to be cut of would be the same if this Antenna is > different. > > I assume the length of Antenna needs to be cut off to compensate for the > Chrome ball fitted to the centre of the Antenna where the Wind Indicator > sits. > > Thinking back to my Childhood CB days, we used to use an SWR meter to > tune a > CB Antenna which I assume is very similar to a VHF Radio. > > Would it help if I went and bought an SWR meter to try and tune this VHF > Antenna? > > Any advice would be greatly appreciated. > > Regards > C > Cathy, I suggest you look for a radio-oriented group. Andy |
| 16 Apr 2008 00:18:16 |
| Chris |
| Re: Tuning VHF Antenna |
"Cathy" <Cathy@Nospam.com > wrote in message news:DPOdnfWFjqygjpjVnZ2dnUVZ8uidnZ2d@plusnet... > I have purchased a new VHF Antenna and then decided to also get a Glomex > Wind Indicator that fits on the antenna in an effort to slightly tidy up all > the garbage at the top of the mast. > > Afte following the assembly instructions for the Wind Indicator, at the end > it suggests I need to cut a length of the Antenna off. The problem is that > the Antenna I have fitted this onto is not a Glomex Antenna and I am > wondering if the distance to be cut of would be the same if this Antenna is > different. > > I assume the length of Antenna needs to be cut off to compensate for the > Chrome ball fitted to the centre of the Antenna where the Wind Indicator > sits. > > Thinking back to my Childhood CB days, we used to use an SWR meter to tune a > CB Antenna which I assume is very similar to a VHF Radio. > > Would it help if I went and bought an SWR meter to try and tune this VHF > Antenna? > > Any advice would be greatly appreciated. > > Regards > C > > See http://www.glomex.it/files/Catalogue2008.pdf I think page 55 has the answer you require I actually checked my vhf swr a few years back with a cb meter (on 1 watt due to the meters 4w limit) gave virtually 1:1 swr Chris |
| 16 Apr 2008 00:45:32 |
| Phasmatis |
| Re: Tuning VHF Antenna |
Hi Cathy, Marine antennas are pre cut to a specific length to have the lowest VSWR (Voltage Standing Wave Ratio) over the 156-163 MHz frequencies, normally reaching less than 1.2:1 at 160MHz. If you were to shorten the antenna this would result in a reduced perfomance throughout the 156-163 MHz frequencies as in general the smaller the antenna the higher the frequency it is best tuned for. You can buy a 'matching' box, this is a small box full of coiled copper wire where you can technically shorten or lengthen your antenna to match the frequency in theory, by moving a slider on the box. My best advice is avoid cutting the antenna unless you can check the VSWR, you could purchase an antenna matching box to compensate or accept the reduced performance. Funnily enough I have recently bought a new VHF antenna/windex, didn't get much change out of £60 but didn't have to mess on cutting the antenna to make it fit. Hope this helps... "Cathy" <Cathy@Nospam.com > wrote in message news:DPOdnfWFjqygjpjVnZ2dnUVZ8uidnZ2d@plusnet... >I have purchased a new VHF Antenna and then decided to also get a Glomex > Wind Indicator that fits on the antenna in an effort to slightly tidy up > all > the garbage at the top of the mast. > > Afte following the assembly instructions for the Wind Indicator, at the > end > it suggests I need to cut a length of the Antenna off. The problem is that > the Antenna I have fitted this onto is not a Glomex Antenna and I am > wondering if the distance to be cut of would be the same if this Antenna > is > different. > > I assume the length of Antenna needs to be cut off to compensate for the > Chrome ball fitted to the centre of the Antenna where the Wind Indicator > sits. > > Thinking back to my Childhood CB days, we used to use an SWR meter to tune > a > CB Antenna which I assume is very similar to a VHF Radio. > > Would it help if I went and bought an SWR meter to try and tune this VHF > Antenna? > > Any advice would be greatly appreciated. > > Regards > C > |
| 16 Apr 2008 10:14:39 |
| 666 |
| Re: Tuning VHF Antenna |
AFAIK do not cut anything, todays' vhf radios have in-build automatic antenna tuning. JaC ----- > I assume the length of Antenna needs to be cut off to compensate for |