2ghz pulsed transmission? - Page 1
Forum section: electronics / rf-microwave

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 05:56:20 pm
content: I have a bicone hooked up to my SA and I found a weird pulsed signal on almost exactly 2GHz. It appears to be a very slow amplitude(on off) modulation, almost like a beacon. Like it turns on every 2 seconds for a second and turns off. Very slow. Literary like human seconds.Any idea what this might be? I looked at it for a while and it appeared to be repetitive.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: August 15, 2017, 06:36:13 pm
content: Check you router or wireless modem , sometimes they can have certain features enabled. For example on my router there is a WiFi feature that in a way works like a beacon for WiFi reciever.

author: Yansi
author_rank: Super Contributor
timestamp: August 15, 2017, 06:44:03 pm
content: Wifi is not 2Ghz, so... what?

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 06:58:09 pm
content: yes, it does not appear to be a frequency related to cell phones or wifi. appears to be fairly powerful too.I will try to find it again. I saw it last month and its been bugging me since.ok, thats different. it appears to be a bunch of spikes when I center around 2 GHz with 50MHz bandwidth. Kind of looks like some kind of digital communications.Before there was just a pulse that went on and off. Maybe I remembered the frequency wrong...What is the purpose of beacons anyway? I figure anything computer related would be alot faster then a few Hz frequency.

author: StillTrying
author_rank: Super Contributor
timestamp: August 15, 2017, 07:32:06 pm
content: Mobiles, sat phones and space according to:https://www.ntia.doc.gov/page/2011/united-states-frequency-allocation-chart

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 15, 2017, 08:12:06 pm
content: There's GSM bands at 1850.2 – 1909.8 and 1930.2 – 1989.8 (MHz, uplink and downlink respectively).I've seen GSM-850 around here, that looks like a picket fence of carriers with digital (flat topped) bands appearing within them from time to time.Hmm, I didn't try demodulating it, I should. It ought to be that freakingbit-bit-beep-bit-bipGSM sound that bleeds into freaking everything...Tim

author: metrologist
author_rank: Super Contributor
timestamp: August 15, 2017, 08:24:00 pm
content: This is what I get off my specially tuned 2GHz paperclip.

author: w2aew
author_rank: Super Contributor
timestamp: August 15, 2017, 08:36:02 pm
content: Most likely cellular downlink (tower to handset).

author: TheSteve
author_rank: Unknown
timestamp: August 15, 2017, 08:59:19 pm
content: I doubt it ever turns off. Check out band 2 LTE - 1930-1990 MHz, as w2aew mentioned this is the cellular base station to handset link.If it is LTE you can expect carriers 5/10/15 or 20 MHz wide.

author: CopperCone
author_rank: Super Contributor
timestamp: August 15, 2017, 09:47:45 pm
content: Quote from: metrologist on August 15, 2017, 08:24:00 pmYes, I see something similar on those frequency ranges, but with more resolution (maybe its my RBW?)This signal I speak of was just a spike that appeared and disappeared. I believe I even put my instrument into receiver mode (0 Hz span) to check for modulation. It just appeared and disappeared with a very low frequency in the seconds.When I look at the cell/wifi bands, I see spikes that dance around (probably because its only 10mS maximum update rate). I assume each is a data channel that someone is using. 2 modulated carriers per connection right, so its duplex. Digital stuff looks like... well its doing something fast.This thing was slower then someone keying morse code.

author: metrologist
author_rank: Super Contributor
timestamp: August 16, 2017, 12:21:47 am
content: 50 MHz span and 30kHz RBW, IIRC. Not sure about VBW.

author: Lord of nothing
author_rank: Super Contributor
timestamp: August 24, 2017, 11:10:04 am
content: What I know in the US the use ~2ghz for Sat Radio and Sat Phones.There are more thinks like Zigbee for example.