Obsolete Article - maintained for historical purposes only.
REC has been working on adding a better service contour dataset across the various REC tools and services.
Until now, service contour in REC systems has been defined by power, antenna height and directional pattern. This new functionality takes this one step farther by using a different FCC dataset that not only shows an FM station's service contour, but it also takes terrain into consideration.
In the REC Broadcast Query Tool, many "current" FM faciltiy records have had their maps enhanced to show this new service contour data. When "View Map" is clicked, the map will now show the actual 60 (or 57 or 54) dBu service contour.
Below are two maps generated by REC's Broadcast Query Tool for KXOL-FM in Los Angeles. The map on the left is the older style map that did not take terrain into consideration. The map on the right uses the recently added FCC dataset.
This will become especially useful for LPFM applicants who are seeking second adjacent waivers involving a station that may be blocked by substantial terrain.
Let's take an example of how this change in the dataset impacts some Southern California LPFM applicants who may otherwise blocked by KXOL being on a second adjacent channel.
In the Antelope Valley, the city of Palmdale is shielded by the Los Angeles basin by a significant amount of terrain. KXOL's transmitter is located on Verdugo Peak, which is a lower elevation compared to the popular Mount Wilson transmitter site. Because of this, you will notice that KXOL's signal barely reaches areas to the north and northeast.
In Palmdale, 95.9 may be available for LPFM but under 73.807, it is short spaced to KXOL on 96.3 and KLOS on 95.5.
But now, if we look at the REC Second Adjacent Channel Waiver Report for 95.9 in Palmdale in myLPFM, you will now notice that we are using the new style maps and that while KXOL may be short spaced under 73.807 due to station class and distance separation, there is no overlap of the LPFM 100dBu interference contour and KXOL's service contour. Therefore, an argument can be made that in the case of KXOL, there is no interference. However, in this case, we still are having to work with KLOS, which is on Mount Wilson and has a better chance of being heard in Palmdale. An LPFM applicant will still need to show a lack of population overlap with KLOS but the nice thing is that they can totally disregard the estimated overlap zones in respect to KXOL.
While the REC tool may show an estimated overlap zone in respect to KLOS at 44 meters, the overlap zone may be larger based on the distance from KLOS to the lobe in the direction to the LPFM transmitter. If it is shorter (which is likely the case here), the overlap zone will be larger. This functionality will be in the next release of the myLPFM tool. For now, please check with a qualified consulting engineer. As an alternative to a consulting engineer, you may also use REC's Premium Search service as a preliminary check prior to engaging an engineer or consultant.
We are still working ways to integrate this dataset across the REC family of products.
This new functionaly is not yet available on the mobile version of myLPFM, but that will be next.
