[TowerTalk] XM240

[WD0M]

Ummm....I push a button on my SteppIR and the 40M 
element tunes to a 1:1 SWR....oops...sorry - no more SteppIR stuff.  ;-)

73,

Joe
WDØM

At 10:10 AM 6/14/2007, Bill Parry wrote:
>I am really tired of the Steppir stuff...let's talk about something else.
>
>I have a 2 element Cushcraft XM240. It has been up for about 5 years at
>about 40 Meters high and has always been a fine antenna. I have had one
>problem with the antenna. I set the point at which I have the lowest SWR at
>about 7.075. I knew that the antenna was fairly broad and I wanted to be
>sure that the SWR was OK in the CW band. I didn't realize the SWR curve was
>not going to be symmetrical and the SWR was going to rise very quickly
>toward the bottom of the band. As a result the 2:1 points are about 7.020
>and 7.285. The antenna still works nicely in the 7.000 - 7020 range but it
>creates problems with my amplifier.
>
>I have always just put up with this, the antenna works well and I am
>certainly capable of retuning the amp. A friend was over the other day and
>suggested putting a 1/4 wave section of 75 ohm coax inline at the shack to
>broadband what the amp sees. I was amazed that I hadn't thought of this
>before. I have a full size 80 sloper from the top of the tower and I did
>this very thing to it. It works fine and the SWR is good across the entire
>band.
>
>So the question is:  Are there any drawbacks to using this procedure on a
>yagi? I have lost my notes on the exact frequency that I would chose to cut
>the 1/4 for...(yes I know I need to include in the velocity factor.) I
>assume that I would choose +/- 7.025.
>
>It is definitely not worth the time and expense of taking the antenna down
>to lengthen the driven element a few inches!
>
>Any thoughts?
>
>Bill, W5VX