Thanks. I agree that the idea of a tuner would be a solution but as I
mentioned earlier, this is not a big problem. The purchase of a tuner for my
station doesn't seem like a good use of a lot of money. A 26 foot piece of
75 Ohm coax and a couple of coax connecters is a far simpler and less costly
fix for a fairly small problem.
The problem that you mention with the amplifier is exactly what I am trying
to avoid. The drive for my 87A is relatively the same on all bands but 40.
On 40 the same amount of drive is far to much drive and the large amount of
reflected power immediately trips the safety. Adding a tuner to the system
just adds complexity to the system.
I know that the really simplest way to fix this is to always remember to
reach over and turn the drive back when I change to 40 M and this is exactly
what I have been doing. (Except when I forget---I'm old!! :-)
>From: email@example.com [mailto:towertalk-
>firstname.lastname@example.org] On Behalf Of Ron Todd
>Sent: Thursday, June 14, 2007 3:46 PM
>Subject: [TowerTalk] Fw: XM240
>I have the same antenna you do. XM240 and what I did is put a tuner in
>circit that I can switch in and out.
>The Alpha 87a will not give me full out put on CW unless I add the tuner
>The X;M240 is a great antenna and with my 3 ele SteppIR under it all works
>----- Original Message -----
>From: "WD0M" <email@example.com>
>Sent: Thursday, June 14, 2007 12:17 PM
>Subject: Re: [TowerTalk] XM240
>Ummm....I push a button on my SteppIR and the 40M
>element tunes to a 1:1 SWR....oops...sorry - no more SteppIR stuff. ;-)
>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
>>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
>>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
>>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
>>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!
>TowerTalk mailing list
>TowerTalk mailing list
TowerTalk mailing list