RFID read distance and frequency

In RFID (according to this source: Understanding RFID and RFID Operating Ranges) there are :

  • Low Frequency RFID :
  • has the shortest read distance, about 10 centimeters between the reader and the tag.
  • Low frequency covers ranges from 30 to 300 KHz .
  • High Frequency RFID:
  • The read distance ranges from 10 centimeters to 1 meter .
  • operates in a frequency range from 3 to 30 MHz.
  • Ultra-High Frequency RFID :
  • can read at ranges as far as 12 meters with a passive RFID tag, whereas active tags can achieve ranges of 100 meters or more.
  • The operating frequency of UHF RFID tags ranges from 300 MHz to 3 GHz

so, if I resume the lower the frequency the lower the transmission distance.

However, I thought in radio frequency the lower the frequency the greater the transmission distance.

picture source: Radio Frequency Bands | TeraSense

Why in radio frequency the lower the frequency the greater the transmission distance but in RFID the lower the frequency the lower the transmission distance.

*** 30 to 300 KHz – 10 centimeters**
*** 3 to 30 MHz – 10 centimeters**
*** 300 MHz to 3 GHz – 12/100 centimeters**

I’m sure there’s something I misunderstood. So could you help me to understand? please.

Thank you

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I don’t see a question per se

But rfid in at least LF and HF is not emissive radio,

Think magnetics,

The field of the reader needs to couple with the antenna of the transponder

Antenna size and how BOTH antenna fields couple is going to largely effect the distance

An important note here, part of the main factor here is what type of wave the radio signal takes
Ground wave
Sky wave
Space wave

Ground waves will slowly follow the curvature of the earth over the radio horizon

Sky waves are Line of sight, but will bounce off the ionosphere… permitting some over the horizon communication, depending on angles

Space waves will punch straight thru so they are limited to line of sight, and radio horizon


Thank you for your response

Here is my question

I answered your question above

why are you asking?

Thank you for your help



Hey. So RFID “antennas” are not like transmission antennas. They are inductors, and the magnetic fields they produce loop back into the coil and are never allowed to escape and become electric waves or photons. They operate only in the near field.

The RFID reader communicates with the tag when the tag enters the magnetic field and draws energy from it. In LF(125kHz) and HF(13.56MHz) lower frequency means longer range because inductors attenuate high frequencies while letting lower frequencies pass.

UHF RFID readers operate differently. They transmit electric waves, which is why they travel so far. Unfortunately that means they’re unable to transition through skin because of the dielectric properties.

Everything you know about low frequencies traveling farther in electric transmission is correct though. Those types of antennas are fundamentally different in that they toss electric waves off into space. They operate in the far field.


stop being a weirdo erie theyre obvs jsut abit confusd



I asked why they wanted to know, to gain context to try to help them with their actual goal

They said thanks for the help
Which left me also confused, thus my gif

You are confusing wavelength with “transmission distance”. You are trying to figure out why your apples don’t taste like oranges.


Even with your answer, I still haven’t understood but I guessed that you did respond me as you said (I answered your question above. why are you asking?) so I thanked you for your effort, your answer, for the time you dedicated to answer me, it is very appreciated.

Indeed, I am confused, I am not an expert or professional in this field, but I am a student trying to understand.

I am not an expert or professional in this field, but I am a student trying to understand.
So I don’t know the taste of apples neither the taste of oranges.

Anyway, Thank you for your great help.

thank you

That’s fine, but is there a reason that you want to know?

Trying to pick what implant you want?
Trying to limit implants range?
Passing curiosity?

(Passing curiosity) but I have to understand it :slight_smile:
For a study project, we use an Arduino card (RFID reader) and an RFID tag. For the purposes of the project everything works well.

However, I noticed that with RFID the lower the frequency the lower the transmission distance, but in general we know that the lower the frequency the greater the transmission distance that s why I asked the question.

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Have you considered other variables?

Such as as coil size, shape, power, tuning, materials and associated effects on tag- such as metal in close proximity

One of my LF systems has one of the best ranges I’ve seen, by double the best I’ve gotten out of HF

I appreciate that you are trying to help me but I think that I find it difficult to explain my question to you given my lack of knowledge in the field.

maybe it will be clearer with these pictures

picture 1 (Why You Should Care About RFID Frequencies)


picture 2 (What are Radio Frequency bands and its uses? - RF Page)


What is the difference between : Range (picture 1) and Wavelength (picture 2) ?

Thank you

Wavelength is the distance from peak to peak of the wave. Range is the distance at which the RFID tag can be used.

Like radio, sound has a wavelength and a frequency, but they also have an amplitude. So here is a thought experiment.

You take two people and put them on a stage. Now you stand at the back of the theatre. You get one of them to sing a low note, and the other to sing a high note at the same volume (amplitude). You can hear them both from the back of the auditorium.

Now you get one of them to whisper. You can’t hear them. Then you get the other to whisper. You still can’t hear them.

The wavelength hasn’t changed but the amplitude has and thus the range has.

The speed of a wave is calculated as the frequency multiplied by the wavelength. As the frequency drops, the wavelength increases. But the range is more to do with the amplitude.

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The lower the frequency, the greater the wavelength

The lower the power, the lower the transmission distance (excluding other factors).