ok i have a question

[scnradio]

I went away for a couple of days and took one of my work radios wit me. I went throw imp co and sd co and in both cos i was picking up rso and perris. In imp co i went as far as i8 in holtville and still heard traffic. In sd co i was as far as 905 and 805 and had traffic coming across the radio. Does someone know if it was just skip going on or was i a lucky person.

[sp1989]

Imperial County and San Diego County are both adjacent to Riverside County. The radio coverage for their radio system extends beyond the geographical boundaries by a good amount I would imagine. It would make no sense to have a system that didn't work outside the county borders...imagine a pursuit and radio comms quit right at the border going into the next county. Skip only happens with low VHF freqs, not 800 mhz.

[scnradio]

over 60 miles south of the co line?

[zz0468]

In sd co i was as far as 905 and 805 and had traffic coming across the radio. Does someone know if it was just skip going on or was i a lucky person.

Neither, but probably leaning more toward lucky than "skip". Riverside County has some high elevation sites that get out a long way. In some cases, efforts are made to control the signals outside the county line, and in other cases, it's not necessary. You just happen to hear parts of the system that get out a long way.

[zz0468]

Skip only happens with low VHF freqs, not 800 mhz.

The term "skip" is a misnomer that most people misuse these days. That said, as soon as you declare that propagation enhancements don't take place at 800 MHz, you'd be wrong. Things can and do happen that can cause 800 MHz signals to go a lot further than you'd think.

[cvrules90]

Imperial County and San Diego County are both adjacent to Riverside County. The radio coverage for their radio system extends beyond the geographical boundaries by a good amount I would imagine. It would make no sense to have a system that didn't work outside the county borders...imagine a pursuit and radio comms quit right at the border going into the next county. Skip only happens with low VHF freqs, not 800 mhz.

I totally agree with this statement. Radio coverage must be expanded as far as possible into bordering counties because you never know where a chase will take you. A chase could start on the on-ramp to I10 from Cook Street, and the escaping driver could take you throughout the entire LA County.

[zz0468]

I totally agree with this statement. Radio coverage must be expanded as far as possible into bordering counties because you never know where a chase will take you. A chase could start on the on-ramp to I10 from Cook Street, and the escaping driver could take you throughout the entire LA County.

It's not that easy.

Back when the 800 MHz NPSPAC frequency assignments were first being released, there were FCC requirements to limit coverage to no further than 5 miles outside a licensee's political boundary. This proved to be impractical and, so far as I know, is no longer being so strictly enforced. What is being enforced is co-channel requirements which frequently prevent 800 MHz coverage from being expanded into adjacent cities and counties.

For example, there are frequencies that are licensed by Riverside County in the west end that are co-channel with County of Los Angeles frequencies at sites as close as San Dimas. The interference potential is huge. If either county changes to a site antenna that doesn't have the right amount of downtilt, then too much signal overlaps where it's not needed and the co-channel frequencies become unusable for at least one of the two agencies. If you go to some moderately high ground and put your scanner in conventional mode on just about any NPSPAC frequency, you'll hear a minimum of 2 systems, if not 3 or more.

Not only that, most public safety 800 MHz trunked systems in Southern California are simulcast. Engineering considerations for simulcast require careful control of antenna patterns, transmitter power, and careful timing of the audio distribution. Outside the primary coverage area, a simulcast system could sound so bad as to be completely unusable. Any coverage outside a county is pure dumb luck, and probably not by design. A notable exception to that is 700 MHz and VHF coverage from the PSEC system. In out-of-county areas where RSO deputies frequently travel, radio coverage in adjacent counties has been provided by design.

Chases that extend outside an agency's borders often wind up on cellphones because of coverage problems. There are also several systems in area counties intended to provide some measure of coverage outside the area covered by their simulcast trunked systems but few, if any, agencies know how to use them.

[cvrules90]

That's too bad. It is a lot harder to pull out a phone than hold a button to talk to an officer in another patrol car.