How to identify antennas?

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izeman   10 GW

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How to identify antennas?

Post by izeman » Aug 14 2019 12:01pm

Over the years I bought several antennas from ebay, aliexpress ... Some for 433Mhz projects, some for Wifi (2.4/5.8Ghz). Some for 868Mhz.
Of course after some time, if they where not installed, they ended all in one big box. They are all black or white, but other from that they look more or less the same.
How can i find out what antenna is for what frequency????

markz   100 GW

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Re: How to identify antennas?

Post by markz » Aug 14 2019 8:05pm

No markings at all on the antenna's?

I found this site, basically s.o.l. unless you want to open up the plastic housings.
https://physics.stackexchange.com/quest ... signed-for

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fechter   100 GW

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Re: How to identify antennas?

Post by fechter » Aug 14 2019 9:59pm

If there are no markings, it will be hard to know without using some expensive test equipment or ripping them apart.
"One test is worth a thousand opinions"

mark5   100 kW

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Re: How to identify antennas?

Post by mark5 » Aug 14 2019 10:44pm

Run them through a security X-ray machine like they have at criminal courts to try to see the antenna element lengths?

billvon   100 MW

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Re: How to identify antennas?

Post by billvon » Aug 14 2019 11:06pm

izeman wrote:
Aug 14 2019 12:01pm
How can i find out what antenna is for what frequency????
Borrow a network analyzer and check their S11 across frequencies. You'll see one frequency it is tuned for; it will work best around that frequency.

Alternatively you could do a very manual test with an RF frequency generator, a 50 ohm resistor and a power meter. A spectrum analyzer makes things a little easier.
--bill von

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amberwolf   100 GW

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Re: How to identify antennas?

Post by amberwolf » Aug 15 2019 3:50am

One basic test is to measure the actual antenna length, and calculate the wavelength that would be for. frequency is just wavelength inverted (1/x, IIRC) so you can see the frequency based on that.

They'll probably be made for some fraction of their actual wavelength. So you can multiply the frequency by some common ones to guess, so let's say they're 1/4 wavelength and measure out to be for 8.4ghz. That means tehy're rpobably for 2.1ghz, at 1/4 wavelength.

YOu won't know if they're 1/4, 1/2, or whatever, but there are common frequency bands so if the measurement comes out for something that's way higher than you'd expect, divide it by various fractions to see if it comes out to a band you recognize.

If you don't understand what I mean, go to some of the ham radio sites and they'll explain antennas/etc well enough to figure it out. (my brain is too tired to be sure I'm making sense).

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izeman   10 GW

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Re: How to identify antennas?

Post by izeman » Aug 15 2019 5:43am

Damn. I expected those answers, because it googled at bit before.
I don't want (and in some cases even can't) disassemble the antennas. Of course it could just add them to the receiver and see which one works best, but that is a bit to much guess work for me.
I hope the "one or two ring theory" is reliable. As all of the stuff comes from China, I'm not sure they care about this. Take any cover they have and call it a day.
Thanks everybody!!

kcuf   100 W

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Re: How to identify antennas?

Post by kcuf » Aug 15 2019 8:34am

best antenna is elevation
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izeman   10 GW

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Re: How to identify antennas?

Post by izeman » Aug 15 2019 9:12am

kcuf wrote:
Aug 15 2019 8:34am
best antenna is elevation
Sure. Just tell this to my devices in the basement and I'm fine?? 8) :lol:

kcuf   100 W

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Re: How to identify antennas?

Post by kcuf » Aug 15 2019 11:28am

don't talk to devices

put em where they do the most good
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HK12K   10 mW

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Re: How to identify antennas?

Post by HK12K » Aug 15 2019 1:49pm

If you can find a forum for Ham radio enthusiasts they may be able to identify them just by looking at them.

dustNbone   10 kW

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Re: How to identify antennas?

Post by dustNbone » Aug 15 2019 2:41pm

Yup. What you need is radio nerds. Or enthusiasts.

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izeman   10 GW

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Re: How to identify antennas?

Post by izeman » Aug 15 2019 3:13pm

kcuf wrote:
Aug 15 2019 11:28am
don't talk to devices
put em where they do the most good
Your help is really appreciated.

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fechter   100 GW

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Re: How to identify antennas?

Post by fechter » Aug 15 2019 3:33pm

Post some pictures.
Also look closely around the end for any markings.
"One test is worth a thousand opinions"

markz   100 GW

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Re: How to identify antennas?

Post by markz » Aug 16 2019 5:17pm

Perhaps find a Ham Radio person in your area, maybe they might be of help.

Look for some Ham Radio forums.

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izeman   10 GW

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Re: How to identify antennas?

Post by izeman » Aug 17 2019 8:59am

I have some 433 and 2.4 antennas and they look EXACTLY the same. So posting pics will make no sense. 🤮

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