[SOLVED] RF Emission from Piezoelectric Buzzer

[Audioguru]

A ferrite bar antenna is used for the AM broadcast band up to 1600kHz but might work at frequencies a little higher.
VHF and UHF need an antenna with a wire or whip at a suitable length for each frequency.

 

[vfone]

HRD (Ham Radio Deluxe) has an option for "Scan Frequencies".
Just connect HRD to your IC-R20 (it's in the ICOM list) and after that chose Scan Frequencies from the Scanning bar, tune manual the IC-R20 on desired frequency and press +Freq.
Repeat for all frequencies. The operation is much faster than you believe. After you enter all the frequencies for a band you can save them as a file, and use later.
HRD list shows the S (strength) level on each scanned frequency, and perhaps if you open the Digital Master you can see the signal in waterfall. The problem with waterfall window, has only 3kHz span.

 

[betwixt]

Sorry, I'm not familiar with the IC-R20, I have an Icom IC-756PRo2 here but that's completely different and several times the size of your phone!

The internal ferrite rod antenna will work at low frequencies but may not reach even as high as 5MHZ. The problem is eliminating all the other signals it normally picks up so you can listen for just the one within the shield perimeter. For that, if the frequency is one used by the ferrite rod, your only option is to put phone and the whole radio inside the screen. It may not be a drastic as it sounds, you can wrap baking foil around a cardboard box big enough to hold them both. In emissions testing for interference compliance it is quite normal to put a device, antenna, radio and the person operating it in a giant metal box. Even the incoming AC lines are filtered in case they leak signals into the room and the door usually has a signal absorbing gasket around it. Not good if you are claustraphobic !

Brian.

 

[EricaS]

HRD (Ham Radio Deluxe) has an option for "Scan Frequencies".
Just connect HRD to your IC-R20 (it's in the ICOM list) and after that chose Scan Frequencies from the Scanning bar, tune manual the IC-R20 on desired frequency and press +Freq.
Repeat for all frequencies. The operation is much faster than you believe. After you enter all the frequencies for a band you can save them as a file, and use later.
HRD list shows the S (strength) level on each scanned frequency, and perhaps if you open the Digital Master you can see the signal in waterfall. The problem with waterfall window, has only 3kHz span.

Do you know why the IC-R20 scans so slowly when connected to HRD?

The scanning speed is close to a hundred times slower.

When not connected to HRD the R20 scans at about 10 s/MHz. To sweep 3 GHz will about take 8 h.

I thought I could use HRD to automate this but the scanning becomes very much slower. I set the baud rate to max - 19200

Is it because I have a serial CI-V cable?
Should I get a USB CI-V cable?

- - - Updated - - -

It may not be a drastic as it sounds, you can wrap baking foil around a cardboard box big enough to hold them both.

That's a brilliant idea. I was having trouble wrapping the phone by itself.

- - - Updated - - -

Can CW carry audio?
And should I be scanning this channel?

 

[betwixt]

The speed is slower because of the data communication link. CI-V is a single wire system so it can only carry traffic one way at a time, it has to alternate between setting a frequency and returning the signal level so it can be displayed on the computer. I *think* (I have never checked) it sends the new frequency each time to the receiver rather than telling it to step by itself so obviously that takes longer and slows it down. In scanning mode, the receiver simply tunes to the next frequency and reads the strength of any signal it finds, when one exceeds the limit (squelch level) it stops scanning. Inside the receiver the frequency is set by sending a number to the oscillator circuit so all it has to do is add one to it to make the next frequency appear. A USB CI-V cable will not be quicker, the hold-up is the connection to the receiver and the data transfer which will still be at the same speed as a non-USB cable.

CW cannot carry any audio, it is just a plain simple unmodulated carrier as used for example in Morse code. If the receiver does pick up a modulated signal from the phone, all hell will break loose! The sound coming out of the loudspeaker will be picked up by the bug and transmitted again so you will get a feedback effect, similar to the howling you get if you hold a microphone close to a loudpeaker in a PA system.

Brian.

 

[vfone]

You can try the USB interface.
On my ICOM I am using a home made serial CI-V interface and the scanning speed is about 1 second for each frequency, even if I set the minimum time interval in HRD to 100 msec.
On HRD you can set the scanning modulation to any modulation supported by the remote radio. CW should give better information about the power level in that channel, and if something is there, you can use different demodulator available.

 

[EricaS]

Let's say I find a bug at frequency X.
Will I be able to hear it at 2X or 0.5X?

 

[betwixt]

A pure signal (which is rare to find!) will only appear at one frequency. Almost all transmitters produce some distortion in their output waveforms which creates harmonics. These will be at multiples of the fundamental frequency. For example, if a transmission is on say 10MHz, you might hear it's second harmonic on 20MHz and third harmonic on 30MHz. In good transmitter designs, the output signal passes through a low pass filter with a cut-off frequency set below the second harmonic so it reduces unwanted radiation as much as possible.

You can look at it the other way though, if you see a signal at 20MHz you should check it is isn't also present and stronger on 10MHz. You could be seeing a harmonic instead of the original. In general, the lowest occurrence will be the fundamental one.

Brian.

 

[EricaS]

I know this is really off topic.
But does anyone have a reference/link to the first instance of laptop spyware (webcam/microphone) being reported on in the media?

 

[D.A.(Tony)Stewart]

Java, Flash, JS based apps may exceed your desired permissions and give options to disable each by security levels of OS.

Obviously any trojan apps are capable of using admin resources.

 

[EricaS]

I've been making tremendous progress, thanks to you lot.

I've been scanning using 1 kHz step sizes. As I mentioned earlier it takes 10 s to sweep 1 MHz at this interval size.

Though 5 and 10 kHz intervals allow for a quicker sweep. So I've began playing around with these intervals.

The R20 can scan as low as a 0.01 KHz interval. Is it really necessary to have such a small interval?

What is the smallest interval I could use without "skipping" the bug frequency?

 

[D.A.(Tony)Stewart]

CISPRE and FCC invented the Quasi-peak bandwidth of 15kHz to match hearing response during WWII because unintentional radiators interfered with RF radios. That is still used today for radiated emissions with from 10k to 100k resolutions for slow or fast sweeps.

 

[betwixt]

Translated: to carry voice the transmission width will be at least twice the highest modulation frequency. If you assume "just intelligible" quality and that the transmitter is simple enough to hide, it needs a transmission bandwidth of about 7.5KHz. The receiver also has a reception bandwidth, (guessing) 10KHz on AM and 15KHz for narrow band FM so even if you step at 10KHZ you should get some overlap between transmission and each channel. The worst case is there is no modulation and only a single frequency carrier is present but I would be surprised if 10KHz steps didn't pick it up. I experimented with weak signals on an ancient FRG9600 I have here and nothing escaped 10KHz steps in scan mode.

Brian.

 

[D.A.(Tony)Stewart]

I think EricaS is wasting his time with paranoia scans when the leak must be somewhere else, including anywhere between the phone and the CO with a high impedance transmitter and choke to block RF going to source but radiating outside.

 

[Audioguru]

I think Erica S is a girl:
"www.urbandictionary.com/define.php?term=Erica
The most beautiful queens to ever walk the face of this earth...women named Erica are fierce by nature and generally quite sassy."

 

[EricaS]

10 kHz intervals are such a relief. It makes scanning so much faster.

The R20 sensitivity is given here
https://www.icomamerica.com/en/products/RECEIVERS/HANDHELD/R20/specifications.aspx

It specifies sensitivity as volts per frequency interval. What does this mean physically?

Could the RF from the phone be below the sensitivity of the R20?
Will a premaplified antenna help detect a signal if it is below detection threshold?

And I am a female.

 

[betwixt]

And I am a female.

Hey - one problem resolved :lol:

The sensitivity isn't 'per frequency interval', the figures are telling you that the sensitivity varies across the frequency range and is guaranteed to meet the figure when receiving between the lower and upper frequencies quoted. Very wide band receivers are difficult to make so typically, the radio would have several different 'front ends', one for each part of the band, switched in automatically as you adjust the tuning. The different sensitivity numbers are for each of the 'front ends' and maybe also over parts of the coverage each of them works in.

The actual numbers are meaningless in themselves although they give an indication of how weak a signal might be resolved. The numbers are microvolts at the antenna input point but it doesn't say what that level achieves in terms of reception. It's probably safest to say that a signal of that strength or stronger would be intelligible but a weaker one might not be. To give a definitive answer it would have to specify, for example, how much background quietening that voltage would produce. Look up "SINAD" for examples.

The figures quoted are very tiny (1uV = 1/1,000,000 V) so if the R20 can't pick it up at close range, there is pretty much zero chance something more distant could. The signal drops very quickly (inverse square of the distance) away from the source and the problem with amplified antennas is they also pick up and amplify other noise sources so there is an ever diminishing return as the gain is increased. If there is a bug inside the phone I would expect a thundering great signal to be picked up nearby - you wouldn't miss it!

Brian.

 

[EricaS]

During scanning my R20 usually skips from FM to AM or WFM automatically.

How do i stop this?

 

[betwixt]

I have never seen an R20 so I can't say for certain but it's likely it adapts to the most common modes used within that frequency range. There is also a point that as the frequency gets higher, especially in radios with PLL tuning like the R20, the stability of the received frequency gets worse. Essentially this means the actual frequency you pick up may 'wobble' around what you think it is. The amount is very small and in most cases won't be noticed but some modes, particularly narrow bandwidth ones, may show poor results so the receiver automatically switches to wide bandwidth modes. My VHF/UHF receiver here for example, disables SSB mode above 300MHz even though it covers up to 960MHz in AM, FM and WFM modes. To get good results in all modes at all frequencies you are looking at receivers like the R8500 and R9000 which are very expensive!

Brian.

 

[davenn]

During scanning my R20 usually skips from FM to AM or WFM automatically.

How do i stop this?

don't think you can ... it is p-reprogrammed to default modes of particular freq bands

Could the RF from the phone be below the sensitivity of the R20?
Will a preamplified antenna help detect a signal if it is below detection threshold?

not likely