Genesee Co. APCO25 (antenna directivity)

[Old4rd]

Originally Posted by SEMTTP
"nobody can say 100% what the problem is"

That comes with a lot of things. But in reference to the Detroit MPSCS Simulcast system.

The System is designed to only transmit toward the city. The city has put up 10 tower sites. The antenna's are designed to have forward power, but off the back door of the antenna's only transmit 1-2 miles.

This is part of the reason why we are having so much difficulty hearing the detroit system. It is not the Scanners 100% but a mixture of the two. So what is the problem? I dont know but I would venture to say it is the way that the SIMULCAST systems are put up.

Keep you scanner as it will be one of the few that will be around after rebanding and still be able to be used

Eric



I'm replying to this month old posting by Eric to relay my recent monotoring experience, that for me, confirms what he was saying in regards to the designed directional capabilities of these 800 MHz. APCO 25 antennas. Here in Genesee Co. our problems with the system have been reported on RR numerous times, and they are the same complaints as Detroit's and Monroe County. I live in and close to Gen. Co's. eastern border. About 4 miles due south of me I can see the Goodrich tower, and it is also near the eastern Gen. Co. line. From my home location you would think I'd receive the system well. Not so. I have to use the Holly tower (Oakland Co.) and the Columbiaville tower (LapeerCo.), with excellent Gen. Co. simulcast results. On a recent trip south on M-15 I monitored the Gen. control system only, and discovered that the Goodrich tower appeared to have a narrow radiation beam width towards the west, and maybe a bit south. Reception grew better as I approached the "beam", maxed out, and then deterioated rapidly as I drove south. Checking the online FCC records http://wireless2.fcc.gov/UlsApp/Uls...?licKey=2650664 for Genesee County I found that there were at least two antennas on the tower. Beamwidths for these two antennas were 105 & 65 degrees. I assume they are indicating the transmitted signals' radiation pattern???? There are six other towers in the county on the system. Three had specific beam widths on record and three listings for beamwidth were blank. Maybe the blank ones radiate omni directional???? I'll have to check FCC records further sometime for the Columbiaville & Holly towers to see if there are obvious differences in antenna height and ERP, that might explain why I receive them so well, even though they are much farther away.... Does anybody know if there are FCC records that would show a mapped radiation pattern of these antennas? That'd sure be useful information for us monitorists...

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[Thunderbolt]

There is a saying that a photo is worth a thousand words. If we could see some high resolution photos of the tower sites in Genesee County, it would be easy to identify what kind of antennas they are using; thus, we can figure out what kind of radiation pattern they are producing.

For instance, three out of the four tower sites in the current Monroe County simulcast system are omni-directional, but the one located in the very southwest part of the county, in Whiteford Twp. uses a very unique, directional antenna design that radiates the signal out in a 90 degree pattern. This was done to keep the signal out of neighboring Lenawee County and the state of Ohio, so as to not cause any harmful interference to the latter of the two, as Eric's photo shows below:




It would be really interesting to see how the antennas are configured on the towers in Genesee County? I am sure that they would tell a lot about what direction the signals radiate from them. Then we can make a conclusion about how to solve this problem on our end.

73's

Ron

[Thunderbolt]

Originally Posted by Old4rd

I found that there were at least two antennas on the tower. Beamwidths for these two antennas were 105 & 65 degrees. I assume they are indicating the transmitted signals' radiation pattern????

Yes, that is correct! You can plot that on a map and see how if affects the areas that it covers. This will well you a lot about how the system is set-up and how the engineers designed it to operate in conjunction with other radio sites in nearby areas.


73's

Ron

[Old4rd]

Originally Posted by Thunderbolt

Yes, that is correct! You can plot that on a map and see how if affects the areas that it covers. This will well you a lot about how the system is set-up and how the engineers designed it to operate in conjunction with other radio sites in nearby areas.


73's

Ron

Has anyone ever seen a signal plot map in FCC records??