Interference Sources on OTA, Radio, WiFi Signals

[ProjectSHO89]

700-800MHz is not listed as either passed or stopped. This is the roll-off zone for the filter I take it. Question is how much it would attenuate nearby LTE services in the 700-800MHz band.

Depends on the rate of roll-off. If P-M doesn't have a frequency chart, all we can do is speculate.

[ota_canuck]

Originally Posted by insider22

Do you what Whitespace mean ? it does not mean freespace.
Whitespace is specific technology it's 802.22 ( 802.11 is the base of WIFI and 802.16 is the base of Wimax)

http://en.wikipedia.org/wiki/White_spaces_%28radio%29

White space certainly does mean any unused space or small buffer spaces found between currently occupied frequencies.

[white space device aka:WSD]A portable white space device [eg: wireless microphone]must be capable of determining if there is any white space available in the area and then determine if it is unoccupied by any other devices or broadcasts before allowing access to the white space and the device must vacate the white space if it detects that the space is being used by another device or broadcast. To explain it in simple terms,.. A WSD must essentially roam to find a piece of free radio spectrum to use.

http://news.cnet.com/White-space-spe...?tag=mncol;txt
Most broadcast channels are separated by small swaths of spectrum, or unused channels called white space, which limit interference from other stations.

Here's another example of white space:

http://www.prometheusradio.org/white_spaces
White spaces are sections of the radio spectrum allocated for a certain use (e.g. radio or television) that are not being used in a particular area. For example, a city might have a TV station broadcasting on channel 6 but not channel 5—a common situation because channels 5 and 6 interfere with each other. In this example, there would be white space on channel 5 (from 76-82 MHZ) in that city. Since radio signals do not interfere with TV, this white space could safely accommodate ten FM radio stations, or thousands of wifi Internet connections, or tens of thousands of cell phone calls.

[insider22]

Obvioulsy you did not read the wikipedia article.

I repeat White Space equal 802.22.

Also look at our website:
http://www.ic.gc.ca/eic/site/smt-gst...g/sf10058.html

[ota_canuck]

Is 802.22 a frequency? The number 802.22 is not a specific description of white space. The number 802.22 is just a number.

Yes,.. I did read that wikipedia article. What is 802.22?

I had also previously posted the same IC link:
http://www.ic.gc.ca/eic/site/smt-gst...g/sf10058.html

Definition of 'white space' in the television spectrum is not a specific 'number'.... it's a term referencing any available unoccupied radio spectrum spaces, some big, some small,... but most certainly not pertaining to a fixed number or frequency.

http://whatis.techtarget.com/definit...189510,00.html

White space, in a communications context, refers to underutilized portions of the radio frequency (RF) spectrum. Large portions of the spectrum are currently unused, in particular the frequencies allocated for analog television and those used as buffers to prevent interference between channels.

Detail discussions on 'white space' is off-topic in this thread.
Forum discussion regarding 'white space should continue on the appropriate thread:
http://www.digitalhome.ca/forum/show...t=white+spaces

[insider22]

I will try another way.
If white space is use in Canada it will be only in the broadcasting band. And it will use 802.22 as base to handle the potential interference issues.

There a lot of unused frequencies, just look at the ham band. When people
use the term White Space in tech news, it's for the FCC project of white space not to refer to generic avaible frequencies.

[ota_canuck]

'802.22 WRAN' is a standard of 'white space' usage protocols,... it's is not 'white space'. The term 'White Space' is the unassigned, unused, buffer zones, simply referred to as being underutilized spectrum space that is found to be available within the radio spectrum. The argument is that WRAN usage will not interfere with licensed tv broadcasts because the devices are supposedly vertically polarized and the tv spectrum is using horizontal polarization. The truth of the 'interference risk' is that most mobile [hand-held] devices will need to be circular [or horiz & vert] polarized to be effective.

'WRAN/802.22 is a standard protocol' intended for 'on-the-fly self regulation' of wireless usage of any random white spaces that may be available within the busy television spectrum.

http://m2m.tmcnet.com/news/2011/07/27/5663438.htm
This new standard for Wireless Regional Area Networks (WRANs) takes advantage of the favorable transmission characteristics of the VHF and UHF TV bands to provide broadband wireless access over a large area up to 100 km from the transmitter. Each WRAN will deliver up to 22 Mbps per channel without interfering with reception of existing TV broadcast stations, using the so-called white spaces between the occupied TV channels. This technology is especially useful for serving less densely populated areas, such as rural areas, and developing countries where most vacant TV channels can be found.

[insider22]

I admire you confidence in your knowledge. I will not argue with you.

For my part I am more afraid of people using UHF preamp. All of thoses preamps were design prior to 2009 and have a bandwith that exceed 700Mhz.
When the first 4G cell site will be active at their full power, those preamps will amplify the cell radiowaves and it could be a disaster.

We need to have new preamp with a cutoff a 700Mhz.

[ota_canuck]

I absolutely agree with that! Pre-amps and distribution amps that would be suitable for the new DTV spectrum should have a band pass of 54-700MHZ. Also, another high risk interference is that antenna manufactures have essentially simply re-labeled their antenna product bandwidth specs, adding a HDTV/Digital antenna moniker, but have not physically changed the working VHF/UHF bandwidth spectrum of the antenna products to exclude +700MHZ.

[Jase88]

insider22, they already sell pre-amps that amplify to 700MHz only. For example, there's a UK company (it's name escapes me at the moment) that sells them.

It's rare for a cell site to transmit at greater than 50 watts. Most are less than 20 watts maximum; likely not enough to generate interference.

I'm sure there are also other radio services that fall within the range of amplification for most pre-amps...and these don't appear to cause too many issues.

I've used drop amps that amplify up to 1000MHz for a temp pre-amp. There were no issues for my weak 700MHz stations from 850MHz cellular (which is in use in my area).

A member here (gerryb?) in Ottawa did have some interference issues with a 700MHz test LTE site for Rogers. The problems were with TV stations in the 700MHz band. The site was atop his apartment building (or a nearby building) and within 50m or so of his antenna. Though this test site was transmitting at a much higher ERP than what's normal.

[insider22]

About that the uk company selling preamp, that a good new, I did not knew that.

about the other forms of transmssion, no there no other radio transmission in the UHF band except low power wireless mic. The 4G station will be High Power.

What are you talking about with you 50 Watts the ERP on many cell site is 500-3000 Watts. 50 Watts would be a femtocell not a normal cell.
Even Radio mobile Repeater will operate at a least 60 Watts of ERP, just look at a typical licensed, you will see.
By the way, Rogers also have LTE test site in MTL right now.

[Jase88]

I've never heard of such a powerful cell site in operation. If you have a link to information on such high ERP levels for cell sites, I'd be interested in reading up on it.

I didn't say other services within the UHF band...rather, that some pre-amps amplify more than just TV spectrum.

[insider22]

Here are example result for cell stations (some of them emit a 5000 watts):
the link is broken.

Here a screenshot of the results:

[Jase88]

That link doesn't work.

[insider22]

you are right.
You must do your own search, because the results are not linked in the url.

Go there:
http://sd.ic.gc.ca/pls/engdoc_anon/w...raphical_input

Choose you own geocode, put a 10 km radius and
choosse ie 1000 Mhz to 4000 Mhz. Dont Forget to tick the Tx Effective Radiated Power (ERP) (dBW) in the lower page.

Then press search and you will see resul like this:


Please not that the ERP are in DbW (20 dBW = 100 Watts, 30 dBW = 1000 watts...) to convert them you can use an online tool like this one:
http://www.giangrandi.ch/electronics...l/decibel.html

[Jase88]

I did a search for AWS/PCS/cellular stations in Ottawa as an example. The highest power station I found was 18dBW, which--if my math is correct--equals just over 63 watts. Most stations were between 8 and 14dBW.

I see the test LTE stations licensed for up to 34dBW--but they're few and far between and likely won't operate at that power in the future once in "production" mode.

By the way, here is the thread regarding the LTE 700MHz interference issue for GerryB in Ottawa.

And Research Communications of the UK is the company which sells pre-amps which amplify to channel 51 only, for those interested in avoiding possible interference issues once 700MHz telcos begin using the spectrum. See the Signal Amplifier thread for discussion on this company's products.