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A 2.4GHz balun for antenna measurement?


Leif M 2020/12/14 07:26

I would like to test some WIFI antennas. Is balun always needed? I have noticed it is needed for lower frequency antennas. Simplest antenna I would test is two sticks soldered to end of coaxial. Where do I get a cheap 2.4GHz or 5GHz balun. Do ferrites work. And of course, where do I get a 6GHz Nano VNA?

Leif M 2020/12/27 18:14

I would like to test some WIFI antennas. Those with thin cable probably do not have any gain because of cable losses. So I'll just see what happens. At lower frequencies I have had to use a balun. But where do I get a 2.4GHz or WIFI balun. How else should I do it?
What if I cut a dipole for 2.4GHz, do I need a balun.

Leif M 2020/12/27 18:50

Well, this is still an idea. And after some thinking I noticed that if a commercial antenna uses coaxial cable, it should not need a balun. But if I make simple dipole for reference, I'll probably need a balun. But what and how.

Reinier Gerritsen 2020/12/28 10:54

Make a groundplane antenna with an sma connector and 5 pcs of 35 mm
solid copper wire. Just google for some images. This antenna does not
need a balun. The 4 radials need to be bent down for 50 Ohm impedance
matching, the radiator needs to be trimmed to 2.45 GHz. Theoretical
length is 31 mm @ 2.45 GHz. With a nanoVNA V2 you have the right tool to
do that. I you build 2 identical antennas, you can measure and calculate
the gain of the antenna and with this reference antenna, you can measure
the gain of any 2.4 GHz antenna.
For antennas that need a balun, I sometimes put some ferrite sleeves
over the coax, as close to the antenna feedpoint as possible to suppress
coax influence. Many small antennas are difficult to measure. You have
to include the environment like a pcb, a battery, the casing, etc.

Reinier

Op 28-12-2020 om 03:50 schreef Leif M:

Leif M 2020/12/28 07:09

A good idea. I have measured that kind of antenna at VHF and got good results. About ferrite "balun", does it matter that ferrite, toroids and such are very lossy at 2.4GHz.

Reinier Gerritsen 2020/12/28 16:17

Op 28-12-2020 om 16:09 schreef Leif M:
> A good idea. I have measured that kind of antenna at VHF and got good
> results. About ferrite "balun", does it matter that ferrite, toroids
> and such are very lossy at 2.4GHz.
Yes, the ferrite should be as lossy as possible in order to dissipate
any current in the outer side of the coax shield.

Don Bomer, W5MML 2021/01/03 13:16

Hi Leif,
There are many Excellent YouTube Videos regarding 2.4 GHz antennas.
Especially those by Andrew McNeil. I believe you will find what you need
there.
Don, de W5MML...🤠

On Sun, Dec 27, 2020 at 8:14 PM Leif M <leif.michaelsson@gmail.com> wrote:

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