When I trim an antenna I first measure the resonant frequency.? Then compute the ratio of that to the desired frequency.? Convert that to wavelength, divide by 4 (each side of a dipole is 1/4 wave) and that will give me the desired change.? To avoid overshooting, I will only change half that amount and then repeat the process.? Of course, in the stuck-in-the-mud USA, convert meters to inches.
You don't have to measure what you have.? The resonant frequency tells you that.
Bob K6DDX
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On Sunday, August 23, 2020, 06:12:01 PM PDT, Jerry Gaffke via groups.io <jgaffke@...> wrote:
Some antenna materials don't fold, bend, or mutilate.
Could cut long, measure the resonant frequency, then reduce in length
by a ratio proportional to? ? FreqResonant/FreqTarget.
Jerry, KE7ER
On Sun, Aug 23, 2020 at 05:20 PM, Jim Lux wrote:
On 8/23/20 3:07 PM, davidb1stein@... wrote:
<snip> As you get closer to your center frequency, start cutting a shorter
amount of wire off the end. Instead of 2-4 inches, now only cut 1 to 1/2 inch
off. If it turns out you went below your center frequency, you will need to
start over with new wire or add wire to your existing antenna.
This is why you crumple or fold the wire back, makes it easier to make it
longer.
