[bars] 40M Dipole?

[Paul Pellegrini]

Willie –

Mike has covered this very well.  Here are a couple additional ideas.  The ends of the antenna can droop down theside of your house and it will still work OK.

If you cut the wires long, say 35 feet, you can loop each wireend back on itself.  The loop backportion will not radiate.  This way youwon’t need to solder a foot of wire to the existing length to get a 40 meterresonance (low vswr).

Feeding the same center insulator with 16 foot wires is agood way to get 20 meters.  If you dothis you should try to angle the wires away from the 40 meter wires.  This will reduce interaction between the twoantennas.  Interaction can cause theresonance frequency to shift in both antennas.

A vswr meter will be useful.
de K1VK

    On Friday, September 4, 2020, 09:03:54 AM EDT, Mike Raisbeck via bars <bars at w1hh.org> wrote:  
 
  Hi Willie,
A couple of observations:
1 - it doesn't need to be super straight.  any angle greater than 60 should do it.
2 - if you have choices on which point can be the highest, go for the center.  The center portion of the dipole carries most of the current, so the higher the better.

 3 - shoot for the middle of the band - it's a squeeze, but you might get most or all of the band at less than 2:1 SWR.  If you have a tuner on your rig, it hardly matters at this fequency

4 - depending on where your coax enters the house, you have the opportunity to base feed the whole thing as an 80m vertical
5 - might as well have a 20m dipole on the same feed points as well.  That way you get 20.  Though the SWR may be a bit over 2:1,  you will get 15m as well.
 
-----Original Message-----
From: William Smith <w_smith at compusmiths.com>
To: bars at w1hh.org
Sent: Thu, Sep 3, 2020 7:11 pm
Subject: [bars] 40M Dipole?

Hi All,
As I mentioned last night during the Zoom meeting, I'm looking at building a 40M dipole out of some wire, insulators, and an SO-239 connector, using essentially the instructions at:
https://dcasler.com/2011/02/17/ham-radio-40-meter-dipole-your-first-antenna/
I'm hoping to stretch it out across the roof peak of my house, which has lots of space:

The ridge of the larger side is 40 feet, and the smaller side is 25 feet, so 66 feet ought to be do-able.
I have a couple of questions for the experts:
1) Does it make much difference if the antenna is straight?  I might do something like:

To stay away from the ridgelines, where I know there's a lot of wiring (the point of the "Vee" is where I have a couple of antenna poles.)
2) Obviously I want to start out long and shorten the wires, so as to avoid the "I cut it three times and it's still too short!" problem, but I'm not sure if I have to cut the (insulated) wire at the ends, or if I can wrap it back around itself (which would allow me to lengthen it if I overshoot).
3)  Should I aim for one end of the band or the middle?  Or is it going to be pretty good throughout the band?
Is there anything else I should know before I start?
Many thanks in advance!
73,
WillieN1JBJ
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