**Pascal CASTRATARO** 2021/03/17 16:15
As I have explained, whether I shorten or extend my antenna, the middle

point, therefore, the minimum value of TOS 1.1 is kept at 433 MHz. It is

impossible to have the minimum value of 446 MHz as the frequency I am

interested in.

Le mer. 17 mars 2021 à 14:05, Ken Sejkora <kjsejkora@comcast.net> a écrit :

> Here’s an online calculator to give an approximate length of a

> quarter-wave antenna based on frequency:

>

>

>

> https://m0ukd.com/calculators/quarter-wave-ground-plane-antenna-calculator/

>

>

>

> Perhaps you didn’t incorporate the velocity factor into the equation when

> you calculated the target antenna length.

>

>

>

> If your current resonant frequency is 440 MHz and you want it to be 446

> MHz, then your current antenna is 1.35% too long. For example, if your

> current antenna length is 16.5 cm, then you would need to shorten it by

> 16.5 cm * 0.135 = 0.22 cm = 2.2 mm.

>

>

>

> You might try clipping off 1 mm, and then rechecking the resonant

> frequency with the NanoVNA. That should move the resonant frequency up to

> around 443 MHz, but the NanoVNA will be a better indication.

>

>

>

> One other thought – are you measuring the resonant frequency with a

> suitable groundplane under the vertical element? That will also affect the

> NanoVNA results.

>

>

>

> Ken -- WBØOCV

>

>

>

>

>

> *From: *Pascal CASTRATARO <pcast.fr@gmail.com>

> *Sent: *Wednesday, March 17, 2021 07:27 AM

> *To: *NanoVNAV2@groups.io

> *Subject: *Re: [nanovnav2] ROS Problème on H4

>

>

>

> I do not understand, what I would like is to move the frequency from 440

> to 446 Mhz. Wouldn't that be possible with a 1/4 wave?

>

>

>

> Le mer. 17 mars 2021 à 04:45, Terry Nixon <TLNixon357@gmail.com> a écrit :

>

> I hope I am not saying what others have said, but a 1/4 wave antenna at 2

> meters (146 MHz)is an effective 3- 1/4 waves on the 440 MHz. band. That is

> why you are getting that response. It is correct and verifying what I am

> telling you.

>

>

>

>

>