Wavelength and matching components.

Discussion in 'Radio and Wireless' started by Rajinder, Apr 29, 2019.

1. Rajinder

434
7
Jan 30, 2016
Hi all,
I was trying to find the difference of wavelength of 868MHz compared to 928MHz.
Using a online calculator i found that the wavelength if 868MHz is 34.5cm and 928MHz is 33cm.
If i wanted to use a printed antenna, would i simply make the length of the track 33cm? What hapoens to matching components for 50R matchibg, will they change for a 928MHz compared to 868MHz? Finally, please could you explain what quarter wavelength means with resoect to 33cm, is it 33cm/4? Why is this important?

2. davennModerator

13,598
1,875
Sep 5, 2009
34.5 yes 33 no should be 32.3

no. you never use a full wave antenna plus those figures above don't take into account the velocity factor of the antenna on the board

matching at the feedpoint is another whole different ball game

A 3/4 way is the usual length .... yes 34.5 /4 or 32.3 / 4 BUT as I previously said, you still have to find out what the velocity factor will be

so for an example the Vf = .65 then you will have

34.5 / 4 = 8.625cm
then
8.625 x .65 = 5.60cm as a final tuned length

because if you do di it like that, it will never tune up on the correct frequency

time for you to go do some searching and study of PCB antennas

Dave

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3. Harald KappModeratorModerator

10,079
2,153
Nov 17, 2011
e.g. these:

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