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Author Topic: 13559 kHZ pips  (Read 15634 times)
N4EF
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Posts: 58




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« on: March 23, 2015, 04:11:27 AM »

There's a signal on 13559 kHz  which is  single "dit" or "pip" much like those heard on CHU or other time standard stations. The pips are a little more than 1 second apart and I count 54 single pips with the 55th pip  being a double pip at the end of 60 seconds.The pips per minute may vary according to other reports.

I hear it 24 hours per day on my attic dipole and others copy it in the west coast USA.

There's more discussion on hfunerground.com in the "beacons" forum, but if those of you with directional antennae would report what you get for a beam heading, it might be of some help pinning down more about this signal.
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K0OD
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Posts: 3030




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« Reply #1 on: March 23, 2015, 08:40:07 PM »

I'm hearing it nicely about 15 dB above the band noise right now in Saint Louis using a vertical (no beam here) and Flex-5000 which has a bandscope. 

There are two signals beeping. One narrow signal is on 13.560.698, measured using the Flex's scope and in the DSB mode.  I counted 49 beeps per minute on several one-minutes tests. There's a broader, more complex signal around 560.100 that produces about 59 beeps per minute. Not much QSB noted.

I'll keep the radio running in the background here.
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N3QE
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« Reply #2 on: March 24, 2015, 08:35:28 AM »

13.56 MHz is in the IFC band and is used for Bluetooth NFC and RFID tags.

A RFID tag reader will send out regular "pings" looking for a response from near-field tags.
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K0OD
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« Reply #3 on: March 24, 2015, 12:10:50 PM »


Quote
13.56 MHz is in the IFC band and is used for Bluetooth NFC and RFID tags.

A RFID tag reader will send out regular "pings" looking for a response from near-field tags.


So what exactly are all of us hearing? I presume those are extremely low power. Did my wife shoplift a blouse on her latest shopping trip and put it in the closet next to my radio? 
 
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K0OD
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Posts: 3030




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« Reply #4 on: March 24, 2015, 05:22:12 PM »

Turns out that 13.560 signal could be all sort of things, all legal and mostly mundane:

http://en.wikipedia.org/wiki/ISM_band
http://en.wikipedia.org/wiki/Near_field_communication

I was thinking that I heard more than one signal on 13.56 - like an echo - and that may be correct. Radio is shut down now due to storm but I'd love to determine the source of what I heard.
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N4EF
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Posts: 58




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« Reply #5 on: March 25, 2015, 04:03:06 AM »

Thanks for the comments about this signal.

Low power RFID:  the signal appeared recently and there aren't many other loggings of it.  My guess is that if it were an RFID device or NFC , we would have seen many previous reports of such a common device and it's emmissions, but these pips are new to me in over 2 years of ISM band scanning.  In addition, is it likely this RFID signal would be so strong as to be solid copy in W4, W6, and W7 areas at the same time?

I listen often to the ISM (industrial,  scientific,  medical) +/- 13500 kHz band and hear all the trashy noise that would be expected, but I have heard some very weak and occasional but deliberate hobbyist beacon CW signals, but the pips I hear are strong, consistent, and  readable nationally.
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K0OD
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« Reply #6 on: March 25, 2015, 06:48:02 AM »

Quote
but the pips I hear are strong, consistent, and  readable nationally.

But how do you know people are hearing the same transmitter, versus many similar, low powered signals scattered around the country?  Lack of QSB suggest the signals are local.

You might want to listen on one of those remote web receivers to see if the pulses match. Or drive around your neighborhood with a radio.

I'll do more research when our local thunderstorms move out.
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N3QE
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« Reply #7 on: March 25, 2015, 10:25:52 AM »


Quote
13.56 MHz is in the IFC band and is used for Bluetooth NFC and RFID tags.

A RFID tag reader will send out regular "pings" looking for a response from near-field tags.


So what exactly are all of us hearing? I presume those are extremely low power. Did my wife shoplift a blouse on her latest shopping trip and put it in the closet next to my radio?  

The low-power 13.56MHz RFID readers are generally using a 1-second poll cycle and they are *everywhere* now. Schools, businesses, even private residence security systems.

The near-field antenna loops generally do not have much far-field (by design!), but sometimes unintentional coupling into other more effective radiators will happen. It only takes milliwatts of effective radiated power to have CW communications across the continent.
« Last Edit: March 25, 2015, 10:52:58 AM by N3QE » Logged
WW7KE
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« Reply #8 on: March 27, 2015, 05:15:37 PM »

If you're really lucky, you'll hear Part 15 operations, either AM broadcasters or CW, in that band.  Part 15 allows about 2 mW ERP in this band (13553-13567 kHz).  But most activity is RFID or other ISM equipment.
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N9OGL
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Posts: 0




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« Reply #9 on: March 29, 2015, 02:30:35 AM »

If you're really lucky, you'll hear Part 15 operations, either AM broadcasters or CW, in that band.  Part 15 allows about 2 mW ERP in this band (13553-13567 kHz).  But most activity is RFID or other ISM equipment.

I want to know how you get 2 mw on 13553 -13567 MHz. which is 15,848 uV/m @30 meters when walkie - talkies are 10,000 uV/m@3 meter or 100 mw? Just curious.
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WW7KE
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« Reply #10 on: March 29, 2015, 07:54:15 AM »

If you're really lucky, you'll hear Part 15 operations, either AM broadcasters or CW, in that band.  Part 15 allows about 2 mW ERP in this band (13553-13567 kHz).  But most activity is RFID or other ISM equipment.

I want to know how you get 2 mw on 13553 -13567 MHz. which is 15,848 uV/m @30 meters when walkie - talkies are 10,000 uV/m@3 meter or 100 mw? Just curious.

Assuming a unity gain antenna (isotropic), the formula to determine ERP is (E2D2)/(30 * pi), where E is in volts per meter, and distance is in meters.  At 3 meters, it translates to 0.3 * E2, and at 30 meters, it's 30 * E2.  Check FCC OET 63 for the exact wording and formula.

At 15,848 uV/m (0.015848 V/m) and 30 meters, that comes out to 7.5 mW ERP, so I stand corrected there.  Maybe it was 2 mW under previous rules.

BTW, that 10,000 uV/m @ 3m field strength is actually about 30 microwatts ERP.  The old "100 mW input and a one meter build-in rod antenna" rule has been moot for years.  Since CB radio is no longer licensed, it was removed.  That rule still apples to devices operating in the 49.82-49.9 MHz band, other than cordless phones.
« Last Edit: March 29, 2015, 09:50:55 AM by WW7KE » Logged

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N9OGL
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Posts: 0




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« Reply #11 on: March 29, 2015, 10:34:23 AM »

Ok well I guess the Walkie-talkie companies are lying because they still put out 100 mw even on 49 MHz. Band. I do know Part 15 has changed since OET bulletin 63 (1993) in fact in December 2003 the FCC updated it. One of those updates was in regards to 13 MHz. where the power level was 10,000 uV/m@ 30 meter was increased to 15,848 uV/meter @ 30 meter because ISM were moving off those frequencies. So the FCC increased the electrical field strength
« Last Edit: March 29, 2015, 10:55:01 AM by N9OGL » Logged
WW7KE
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Posts: 942




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« Reply #12 on: March 29, 2015, 06:47:13 PM »

Ok well I guess the Walkie-talkie companies are lying because they still put out 100 mw even on 49 MHz. Band.

CB and 49 MHz walkie-talkes were/are rated on power drawn from the battery, aka the whole device, not RF power output or DC input to the final stage. 

Assuming the device has an oscillator and a stage or two of audio, maybe 40% of that 100 mW is drawn by the final amplifier.  That gives an actual RF output of about 15-20 mW on AM and 25-30 mW on FM. 

Add a single rod antenna close to the ground -- unless your name is Yao Ming, you won't be holding it even close to 1/4 wavelength above ground Grin -- with no counterpoise other than the ground traces on the PCB, and you have something that is not very efficient.
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