The antenna is mounted at the tip top. The meter im using im sure is not top of the line accurate. It's a basic cheap radio shack model 144/440 band watt/swr meter. I can get a hold of a Bird 43 meter pretty easy to check with if you think that would be better. Also im running 40 ft of lmr 400 feedline
--- In [email protected], Ralph Mowery <ku...@...> wrote: > > > > > --- On Sun, 5/24/09, agrimm0034 <agrimm0...@...> wrote: > > > From: agrimm0034 <agrimm0...@...> > > Subject: [Repeater-Builder] Re: New Transmitting Antenna SWR Question > > To: [email protected] > > Date: Sunday, May 24, 2009, 11:36 AM > > It came with some cutting charts to > > cut the 3 inside elements inside of a plastic tube. I cut > > those and checked the SWR with 10 ft piece of RG-58 25 watts > > input and it read 1.5-1. Assumed everything was okay. Cable > > was put on a dummy load and cable tested great with no > > shortages and very low loss. 3-4 watts from 40 watt input. > > After testing several times the more power that was put into > > the feedline the higher the SWR was. The lower power I put > > in the lower the SWR was. My tower that it is on is not > > grounded and the antenna calls for DC ground for lightning > > protection so I might need to ground the antenna. Anyone > > think that will help SWR any? > > > > > > I have not been following the whole thread,but it seems that something is > wrong with your meter. I guess that you are using about 50 feet or more of > the lmr400. It has a loss of over 2 db (almost 3 db) per 100 feet. That is > a loss of 1 db for 50 feet which should give you around a 10 watt loss or > more with 40 watts input. > Many inexpensive meters (and some expensive ones) will show lower swr at > lower power. This is a false reading due to the way the detecting diodes > work. What kind of meter are you using ? > When you used the rg58 to test the antenna, it has too much loss at 450 mhz > to make a good swr measurment. I think if it shows the swr to be 1.5 it will > really be over 2 at the antenna due to the loss in the coax. > > Grounding a 40 foot will have no effect on the swr of an antenna mounted to > it. Atleast if it is anywhere near the top. It should be grounded for > lightning protection if possiable. > > Is the antenna at the very top of the tower or is it side mounted ? If side > mounted, this could have some effect on the swr. >
