[BVARC] 70cm J Pole SWR. Is it supposed to look like this?

[Daniel Poirot]

...aaaand, the best I can muster is this:

[image: Screenshot 2025-10-15 at 5.19.18 PM.png]

Very strange.

I moved the feed point to get a lower impedance and trimmed the driven
element quite a bit, but can't get it to come down at 444.3 MH.

At this rate, I am going to stick with 2 meters!

Dan KJ5IZK




On Wed, Oct 15, 2025 at 4:20 PM Daniel Poirot <dtpoirot at gmail.com> wrote:

> TL;DR  What does a 70cm VNA trace look like?
>
>
> Howdy y'all,
>
> The car is in the shop, so I had some time on my hands...
>
> I took a 16 cm section of 450 Ohm ladder line, shorted one end, soldered
> on a 32.5 cm length of wire and BOOM. I have another J Pole.
>
> I tacked on a short length of RG-8x, 1.6 cm from the end, and put a female
> BNC on the end. Closer still!
>
> I calibrated my NanoVNA for 420-450 MHz and made a trace of SWR and
> Resistance. I am looking to hit the 444.3 repeater.
>
> [image: Screenshot 2025-10-15 at 4.16.08 PM.png]
>
> This here is some messed up stuff. Do I have to tune to catch 50 Ohms as
> it goes by?
>
> The SWR minimum is to the left of 444.3, so my J Pole is long. I am about
> to nibble away.
>
> Should I expect a 25 MHz cycle like this? The middle of the cycle will be
> crazy SWR and terrible resistance, right?
>
> Comments welcome!
>
> 73
> Dan KJ5IZK
>
>
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