Thank you for the detailed explanation, it's educating. :)
Faisal Imtiaz Snappy Internet & Telecom 7266 SW 48 Street Miami, FL 33155 Tel: 305 663 5518 x 232 Help-desk: (305)663-5518 Option 2 or Email: [email protected] > From: "Mike Black" <[email protected]> > To: [email protected] > Sent: Tuesday, October 20, 2015 11:35:46 AM > Subject: Re: [AFMUG] Mimosa B11: Exactly what does the mounting look like? > ..... Today, one cannot use the same channel/polarity on the same site > anyway... > Actually, you can if the azimuths are sufficiently different and you choose > antennas carefully. > The difference is distance. Say you built a new path between points A and B > using the traditional FDD licensed equipment, and for simplicity, there are no > other 11GHz systems anywhere close to your new link. Your coordinator would be > free to choose any frequency pair for you because there is no interference to > avoid. At 11GHz the frequency pairs generally have a 490MHz split, so at site > A > you may be instructed to transmit at 11015MHz which means you will also have a > receiver operating at site A at 11505MHz. Your system works fine. > You now decide you need a link from A to C. Once again, there are no other > 11GHz > systems in the area, so the only potential interference is from your A/B link. > The A/C link coordinator now has an established Hi/Lo regimen at site A, with > site A transmitting "Lo" to B, so he would normally pick another "Lo" > frequency > for transmitting to site C, which would bring along another high band receiver > at site A. Doing so maximizes the frequency separation between the > transmitters > continually transmitting from A and the receivers continually receiving at A. > The nearest receiver operating in the low half of the band would be at a > distance equal to the shorter of path A/B and path A/C. Any third party link > would ideally follow the established Hi/Lo regimen. > Now you introduce a TDMA link between A and D. If you choose a frequency pair > that follows the Hi/Lo regimen you will again go with a Lo band transmitter, > but it is only a transmitter for the duty cycle of the TDMA link -- say 50% of > the time. The other 50% of the time you have a low band receiver at site A > with > the nearest transmitter only feet away. NSMA has a paper that suggests the > pattern of an 11GHz antenna isn't predictable until you get about 0.55km away > from the antenna, so you probably can't assume the antenna will protect you. > Polarization may help, but the systems under discussion seem to use both > polarizations, so at best only one polarization may be affected. Ah, but you > still have _ some _ frequency separation, right? Well, when we run a frequency > analysis we will look for interferers at not only the frequency of interest, > but at a minimum, anything falling within the adjacent and second adjacent > channels to cover the potential impact of out-of-band emissions. For a 40MHz > system this means looking at everything within +/- 100MHz, and for a 80MHz > system, +/- 200MHz. > So again, if you are running an isolated system you shouldn't have any issues. > However, given the current licensing process, if there are third parties > involved and they are reviewing the PCNs that they receive, you should expect > them to flag your links as unacceptable due to bucking with, perhaps, some > accommodation if you agree to a post-installation test of some sort. > Mike Black > Black & Associates > 727-773-9016 > www.bamicrowave.com > black & associates > Frequency Coordination ● FCC Licensing ● Engineering Design > From: Af [ mailto:[email protected] ] On Behalf Of Faisal Imtiaz > Sent: Tuesday, October 20, 2015 7:07 AM > To: [email protected] > Subject: Re: [AFMUG] Mimosa B11: Exactly what does the mounting look like? >>>> Instead, the challenge is in assessing and accepting the risk of possibly >>>> bucking your own 11GHz links or other operator's 11GHz links on or near >>>> your >>>> two endpoints. As there is no reliable way to calculate this type of >>>> interference, you may only become aware of the problem after you have >>>> installed > >>> and turned up your TDMA system. > Call me stupid, and please explain how that is ......I can understand the > issue > of channel/polarity availability...however how is this potential interference > different from current ..... Today, one cannot use the same channel/polarity > on > the same site anyway... > The B11, actually opens up the possibility of channel reuse, on the same site > with angular separtion ...(possibility being a key word). > Regards > Faisal Imtiaz > Snappy Internet & Telecom > 7266 SW 48 Street > Miami, FL 33155 > Tel: 305 663 5518 x 232 > Help-desk: (305)663-5518 Option 2 or Email: [email protected] >> From: "Mike Black" < [email protected] > >> To: [email protected] >> Sent: Tuesday, October 20, 2015 12:45:25 AM >> Subject: Re: [AFMUG] Mimosa B11: Exactly what does the mounting look like? >> +1 to Tim's remarks in this thread. The challenge isn't in coordinating the >> same >> frequency pair in H and V between two sites, in both directions. Instead, the >> challenge is in assessing and accepting the risk of possibly bucking your own >> 11GHz links or other operator's 11GHz links on or near your two endpoints. As >> there is no reliable way to calculate this type of interference, you may only >> become aware of the problem after you have installed and turned up your TDMA >> system. >> If there are no other 11GHz systems within about a half km of either site and >> you don't plan to expand either site with additional 11GHz equipment from >> other >> vendors, you may be ok. If not, then ? >> Mike Black >> Black & Associates >> 727-773-9016 >> www.bamicrowave.com >> black & associates >> Frequency Coordination ● FCC Licensing ● Engineering Design >> -----Original Message----- >> From: Af [ mailto:[email protected] ] On Behalf Of Hardy, Tim >> Sent: Monday, October 19, 2015 8:29 PM >> To: [email protected] >> Subject: Re: [AFMUG] Mimosa B11: Exactly what does the mounting look like? >> In the olden golden days building the MCI route with full block systems, we >> would have "bucks" or "bumps" in frequency plans when required, and we >> learned >> first hand how important it was to use ultra high performance antennas or >> better in such situations. With very little free space loss, antenna >> performance is key and there is very little reliable data on close-coupling >> antenna performance, so it is extremely difficult to accurately calculate >> expected interference levels in these situations. With the prevalence of 2&3' >> antennas these days, antenna isolation will be an even larger challenge. >> Sent from my iPhone >> > On Oct 19, 2015, at 8:03 PM, Seth Mattinen < [email protected] > wrote: >> >> On 10/19/15 16:56, George Skorup wrote: >> >> To make Tim's point, we're co-located on a couple towers with other >> >> 11GHz users and using both the high and low of a channel pair at both >> >> ends is unpossible. (yes, that's a word :) >> > It's a perfectly cromulent word. >> > ~Seth
