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Measuring the frequency of a signal WIFI

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etness

New Member
Hello,

I have bought a frequency counter IBQ2006ST (a Chinese product), but I think, it is not good product. I tried to measure a Wifi signal of 2.4GHz but the strument give me always 0 (zero). I tried to measure a signal of GSM Phone but it's very variable from 400 MHz to 700 MHz.
Someone has this product? Is it normal this behavior? It work only with low frequency.

Thanks very much for the help.
 

Leftyretro

New Member
etness said:
Hello,

I have bought a frequency counter IBQ2006ST (a Chinese product), but I think, it is not good product. I tried to measure a Wifi signal of 2.4GHz but the strument give me always 0 (zero). I tried to measure a signal of GSM Phone but it's very variable from 400 MHz to 700 MHz.
Someone has this product? Is it normal this behavior? It work only with low frequency.

Thanks very much for the help.

I thought wifi used a spread spectrum or frequency hopping method within a channel band of frequencies, rather then using one specific frequency. If that is a case a frequency counter would be of little use even if it was sensitive enough to respond to such a low level signal. Are you trying to read it wirelessly ?

Don't know about GSM.

A spectrum analyzer is the appropriate instrument for what you want to do.

Lefty
 

ecerfoglio

New Member
Leftyretro said:
I thought wifi used a spread spectrum or frequency hopping method within a channel band of frequencies, rather then using one specific frequency. ......
Don't know about GSM.

Lefty

GSM also uses spread spectrum / frecuency hopping
 

etness

New Member
Leftyretro said:
I thought wifi used a spread spectrum or frequency hopping method within a channel band of frequencies,

ecerfoglio said:
GSM also uses spread spectrum / frecuency hopping

Sorry, :) I have not thought to frequency hopping. So this frequency counter is not util with high frequency.
 

Leftyretro

New Member
etness said:
Sorry, :) I have not thought to frequency hopping. So this frequency counter is not util with high frequency.

Not a counter problem, some frequency counters work fine at high frequency, it depends on their design and specifications. The problem is that the signals you want to measure are not stable at a single specific frequency but move around within a band of frequencies. Such a signal measured with a frequency counter would just show random measurements that would not represent the actual signal.

A spectrum analyzer sweeps a whole range of frequencies and shows all the signals that occupy the range.

Lefty
 

Papabravo

Well-Known Member
etness said:
Hello,

I have bought a frequency counter IBQ2006ST (a Chinese product), but I think, it is not good product. I tried to measure a Wifi signal of 2.4GHz but the strument give me always 0 (zero). I tried to measure a signal of GSM Phone but it's very variable from 400 MHz to 700 MHz.
Someone has this product? Is it normal this behavior? It work only with low frequency.

Thanks very much for the help.
How much did you pay for the counter and what is the maximum specified frequency reading? I'd be surprised if it was in excess of a couple of hundred MHz.
 

Leftyretro

New Member
Papabravo said:
How much did you pay for the counter and what is the maximum specified frequency reading? I'd be surprised if it was in excess of a couple of hundred MHz.


**broken link removed**
 

Super_voip

New Member
if all you are after is 2.4GHz frequency readings then the Wi-Spy USB dongle will do, it will definately give more info the that freq meter.
 

etness

New Member
Papabravo said:
How much did you pay for the counter and what is the maximum specified frequency reading? I'd be surprised if it was in excess of a couple of hundred MHz.
I pay 60 €, the range is 10Hz - 2.6GHz, it is not for professional use.
I tried it with wifi 802.11g on channel 1.
 

etness

New Member
Leftyretro said:
Such a signal measured with a frequency counter would just show random measurements that would not represent the actual signal.

It's always 0, it's very strange for me.
I tried it with reader/writer smart card RFID 13.56 MHz and give me 13.557MHz.
 

RadioRon

Well-Known Member
The counter is rated to count up to 2.6 GHz, but at that frequency, there must be quite a lot of signal going into it. At 1GHz, the rated sensitivity is 10mV which is -27 dBm, and the impedance is 50 ohms. This is a high level of signal. To count a signal off-air, you would need to use a proper antenna and put the antenna very close to the transmitting antenna. It is likely that at 2.4 GHz, the sensitivity is worse than at 1 GHz, so we might assume that signals need to enter the counter at about -15 to -20 dBm, which is a fairly strong signal.

You should be able to count a spread spectrum signal as well as any other depending on the protocol used. A counter of this type will end up counting the average signal frequency and this average will depend on the modulation. If the modulation is entirely symmetrical around a carrier, such as with analog FM for example, then the counter averages the frequency to the center frequency of the signal which happens to be the carrier. If a spread spectrum modulation is applied to a carrier, the average frequency is still counted and this average is certain to be somewhere within the bandwidth of the signal itself, perhaps not exactly at its center though.

The larger problem with many data signals is that they are not transmitting steadily at a constant power, so a frequency counter may not capture enough cycles of signal within its timing gate to count anything useful. Many protocols have the transmitter turning on and off rapidly over time. GSM is an example where the basic GSM voice call has the transmitter turning on and off very rapidly at a 220 Hz rate (approx) following a TDMA protocol. The transmitter only stays on for a very short time (can't remember exactly, but I think it was about 570 microseconds per burst). CDMA signals, including WCDMA, vary their power a great deal as they transmit and some of them also burst their signals vs time. I'm not sure how WiFi signals behave, but they may also burst their transmitters on and off rapidly, making it difficult for a counter to complete its count correctly.

If the counter is showing 0 then the problem is probably not enough level. In this case, you must try and couple a lot of signal into the counter and if you can't make a direct coax cable connection to the transmitter you are measuring, you must use a proper 2.4 GHz antenna and bring it very very close to the transmitter. If the counter shows a number but the number is rubbish, then it is quite possible that the signal you are trying to measure is pulsing on and off and/or is varying a great deal in amplitude vs time. The only thing you can do is shorten your gate time to the absolute minimum that the counter is capable of and hope to capture one burst. Otherwise there isn't much you can do. I think that it is hopeless for GSM since each burst is too short for your counter's minimum gate time.
 
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Rolf

Member
Input specifications ........

etness said:
It's always 0, it's very strange for me.
I tried it with reader/writer smart card RFID 13.56 MHz and give me 13.557MHz.

After quickly reading through all the replies here i didn't find any that mentioned that freq. counters have input sensitivity ratings and it usually degrades as the freq. goes up. So you have to have a signal input that meets these RMS or peak to peak voltage specifications before you can get a accurate reading. Also some have a 50 ohm input impedance that you cant feed a high impedance signal into and expect a reading.
And of cause, as it has been mentioned several times already you have to have a steady freq. to read.
 

mneary

New Member
It's also important to remember that a frequency counter counts cycles for a period of time and reports its findings. This assumes continuous transmission. For wifi and GSM this is not a valid assumption.
 
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