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 > > > > > > > > > > > > > > > > > > > > > > > >
