Okay, but would these Base Transceiver Station signals to a GSM mobile phone typically be above 50dB during the middle of the night and hence able to trigger the alarm logs I saw? And why is it I don't see these BTS to GSM signals during the day? And what sort of information would be transferred between a BTS and a GSM mobile during the middle of the night anyway when the phone is completely idle? And there's also the WiFi and Bluetooth alarm logs I saw which were above 50dB. Some WiFi networks can be connected to a BTS but what about Bluetooth?
Because -50 dB is a normal signal level and they are constantly communication with all the handsets in their sectors, that's just normal operation. Also keep in mind with - readings the higher the reading the lower the signal levels. Again normal operation of the system. Incorrect WiFi is not served out of cellular BTS's.
But I had set the threshold for generating an alert log at +40dB on the first night and +50dB on the second. According to the Wiki page Base transceiver station, computers with a wireless internet connection can be connected to a BTS.
First of all dB is a ratio not a fixed amount, as such a field strength meter, which is what you should be using would indicate power levels in dBm, not DB and to get such a reading as what you are claiming to be reading you would need to be living in a hammock hanging in front of the transmitting antenna of a cell site. Wiki is full of crap BTS's do not use WiFi nor are they connected to the internet. How do I know that? Simple I am a wireless technician for a U.S. based Tier 1 carrier. See that brown hut in the background with it's door open? That is what one of my many homes away from home looks like. Now if you do actually live up in the halo of a cell site hanging from the antennas I would strongly recommend you purchase a powered ascender it can make getting to bed a lot easier.
I'm a bit confused here. Are saying my readings are normal or not normal? You seem to have changed what you are saying somewhat. Where I'm living the background signal is around an average of +15dB, with a max of +18dB. That's why I set the alerts to +40dB and +50dB, which are well above the background. Here's a screenshot of one of the pages from the alert logs. Does it make any sense?
That is incorrect as if you look carefully all of your readings are negative which is what I would expect and in that case the greater the number the weaker the signal You are also reading the E-field which means those readings are dBm not dB, also keep in mind dBm is reference ratio to 1 mW which is a very small amount of power as -85 dBm is the lower limit for cellular reception. Another thing that is puzzling why are the frequencies not listed? Knowing that would make real easy to determine the source of the signal.
It's confusing that the quoted units at the top of columns 5, 6, 7 and 8 in the log report are actually dB and not dBm. The frequencies aren't listed presumably because the signal type has already been identified, i.e. that it's Bluetooth or WLAN. But if the signal threshold for the alert had been set at +50dB, why is a signal level of -55dB, for example, listed in the log report? Can I also ask why you commented as follows in #229, "to get such a reading as what you are claiming to be reading you would need to be living in a hammock hanging in front of the transmitting antenna of a cell site." Did you really mean to say this and if you did, what were you actually referring to?
That's a typo or the manufacturer doesn't understand what the meter is actually displaying, but it is recorded as a E-field measurement so the measurements should by dBm if what you have is designed properly. . That I don't like because I want to decide for myself what is interfering with my site which is why I use a spectrum analyzer when chasing down something that is causing harmful interference to a site. . Without having my hands on the instrument I cannot answer that question, but it could be the setting you entered is the upper threshold limit, not the lower threshold, it seems to me you are working with a consumer device not a professional instrument like a Rohde and Schwarz FPL1003 which is what the company assigned to me for chasing down interference.. The reason I made that statement is because you stated the readings where positive not negative and to get a reading that high you would need to be in front of a transmitting antenna within a few feet. With RF each time the distance from the source is doubled the signal is reduced by 50%. Also keep in mind a field strength of -50 dBm is well below the human permissible exposure level and because RF is non-ionizing radiation it can only cause tissue heating it can not break or modify DNA strings. I have more than once accidentally walked in front of active cellular antennas and the effect is like walking out of a air conditioned building into sunlight, however unlike sunlight the energy cannot be seen but it sure can be felt, in fact the first time it happened it puzzled me do I walked back in front of the antenna again. The result I could feel myself warming up as it I was laying on a beach getting a tan, after a short amount of time I walked away from the antennas and touched my arms and they where actually warmer than normal, again like laying in the sun getting a tan but it is a very strange feeling because the source of the warmth cannot be seen, just felt. Another thing we get called out to do is complaint resolution and everyone I have had to investigate has been due to a cell site near a school. The typical complaint is a parent will contact the FCC with a claim their child or children are becoming ill due to RF from the site, it is commonly the result of the parent(s) searching the internet and finding information that to someone outside the world of RF seems to be dangerous, it actuality has been given a name electrosmog. When such a complaint I or another tech has to go to the site and do a RF survey, to do that I use a Narda MBM-550 with a GPS receiver. The procedure used is to start at the tower inside the fence or with a roof top site on roof where the general public does not have access, this is referred to by the FCC as a controlled area where only properly trained personal have access, the next part of the survey is just outside the fence or the on the floor just below the roof where the general public does have access, this is known as a non-controlled area. The next measurement I take if possible is at 50 to 100 feet from the site again a non-controlled area, the reason for that measurement is cellular antennas are down tilted and many times I have measured a higher signal strength at that location then at the site, my final measurement is where the complaint originated from, most commonly at the school. Now my experience with schools has been very positive, quite often they are rather surprised that the company actually sent out a tech to address the problem and out of the couple dozen investigations I have done, four times I have found a tech from a competitor doing the same thing s such we go to the school as a multi-company team. At the school commonly I am escorted by the principal or assistant principal to whom I explain how to interpret the readings displayed on my instrument and what they cannot exceed and if that person is willing I will hand them the meter to record the measurements. Once complete I download the measurements from the Narda and forward them to my manager and a color coded map is made from them. The color coding makes it very easy for the general public to understand what was measured, red indicates a area where only trained tech's are allowed into, yellow indicates where it is safe for the general public to be but RF was detected and green indicates areas where RF was detected but at levels so low they don't matter. That stated based on your measurements you are in a green zone. I hope that clarifies your questions and findings. Now if you really want to drill down on the RF and if your device has antennas that can be disconnected get your hands on a dummy load that can be used to terminate one of the antenna connectors and a directional antenna such as a log-periodic which is a wide band directional antenna. Now most LP's are rather expensive because they are calibrated to a traceable source which is required by FCC regulations for certain proof of performance filings, but for what you are trying to figure out a UHF TV antenna mounted to a non-conductive pole will do the job, te only modifications you will have to make is drilling two more holes where the U-bolt attaches so you can change the antenna from horizontal to vertical polarization as required for your signal hunting.[/QUOTE]
It's a foreign manufacturer, so perhaps the country in question has a different standard? It's definitely a professional instrument. It's described as a bug hunter professional. Interesting idea and might be worth a try. My antennas are removeable. However log-periodic wide band directional antenna don't all look that expensive in the UK. What about the following on eBay which covers 0.6 - 12 GHz for £37.98? Log Periodic Antenna 0.6-12GHz Analysis Wideband
That's a stripline antenna so it should work you will just need a adapter to match it to the connector on your receiver and don't forget you need a 50 ohm dummy load for the second antenna connector. .
Thanks for the advice. I'll put an order in for both items. The sensitivity of your receiver goes up many fold with directionality as it cuts down on background noise. Also I'd be interested to see where that GSM signal is coming from and if it is a cell phone tower or not.
Actually the sensitivity of the receiver doesn't change, it's the antenna is providing more power to the receivers input that makes the difference.
