Heard a couple of units on 1B Zone around 10:45PM. One of them was saying he was in the San Bernardino mountains, and was pretty stoked he was able to get out on NextGen from several counties away! :-D
Paul
Paul
NextGen San Bernardino coverage
- Thread starter Anderegg
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Elevation helps range. A San Diego City radio engineer once told me he was able to hit the city system with a portable from the San Bernardo mountains.
Yeeeup!
Alain
Member
Yes, elevation does help, but I think what is the major contributor to the "DX", is an atmospheric phenomenon called tropospheric ducting. There is a great website which shows the world conditions, western U.S conditions, and in particular, the Southern California area, as currently being under a very strong ducting influence. There is a forum on RR that addresses tropo.
It is a great guide and resource for VHF/UHF ham radio operators. I use it quite often, particularly when our "monsoonal flow season" [usually the end of June thru the end of August]. Some ham radio operators have spoken to folks in Hawaii, from the Santa Monica Pier, in Los Angeles via tropo; that 2,500 miles over salt water!
Here's the website: http://www.dxinfocentre.com/tropo_wam.html
In the upper L/H corner is a drop down menu in which you can scroll to the "Western North America" site. I won't attempt to explain the phenomenon here, because Gordon West, WB6NOA [who wrote a book on the subject called "VHF Propagation"] explains it in his own inimitable way. Hope this helps.
It is a great guide and resource for VHF/UHF ham radio operators. I use it quite often, particularly when our "monsoonal flow season" [usually the end of June thru the end of August]. Some ham radio operators have spoken to folks in Hawaii, from the Santa Monica Pier, in Los Angeles via tropo; that 2,500 miles over salt water!
Here's the website: http://www.dxinfocentre.com/tropo_wam.html
In the upper L/H corner is a drop down menu in which you can scroll to the "Western North America" site. I won't attempt to explain the phenomenon here, because Gordon West, WB6NOA [who wrote a book on the subject called "VHF Propagation"] explains it in his own inimitable way. Hope this helps.
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It figures....You can make it into the system from San Berdo but dozens of dead spots exist in North County for portables such as the area around Lawrence Welk village, north old 395 and Fallbrook which I've personally experienced. Listen to how many "Entering 10-1 area" are announced by Deputies in a normal shift. We have to announce that we would be out of coms before we passed the gatehouse at Lawrence Welk Village as coms became 10-1 50 feet inside of the residential area. More than once I had Station M or the Duty Shift Sergeant call me on my cell phone because I broke up without knowing it.
dmills1
Member
Where in the world did you get the idea that the 800 MHz System is nearly 30 years old? The current 800 MHz trunking system was commissioned in 2008.
Also, the licensed ERPs are lower in the 700 MHz band width different adjacent and co-channel frequency use criteria with other licensee's.
Also, the licensed ERPs are lower in the 700 MHz band width different adjacent and co-channel frequency use criteria with other licensee's.
Ehh...uhh, nooo...the SD city 800 system is a lot older than 12 years! I remember back in the early to mid 90's I think when it was being brought online. At the time I had no 800MHz trunking scanner and I used to be able to hear the old 158.970 MHz North conventional site really well at my home in Carlsbad! Better sometimes than the, more local to me, local Carlsbad PD transmitter! Once the 800MHz trunking system took over that went away (SD City easy listening).
-Mike
dmills1
Member
To be more clear. The original 800 MHz trunked system for San Diego City was built as a Variable Density analog Simulcast system using MSF5000 base stations. It was commissioned in 1993. It was analog only. In 2008, the system was upgraded to a Smartzone 4.1 platform with Quantar base stations and all 20 channels were Simulcast. It was also a mixed mode. ( Analog and P25). The inital phase of the 700 MHz system was commisioned in 2010. As time went on more channels were added to the 700 MHz system. The ASTRO 7.7 core which was the platform for the 700 MHz system was upgraded to release A7.9 and the 800 system was merged using SmartX converters for the 800 MHz system into a single system and commissioned in 2012. The same equipment from the 800 MHz 4.1 platform is still used today in the current A7.17 system release.
So it is not the same system built in 1993.
So it is not the same system built in 1993.
SDBud
Member
The radios may have changed, the SITES for the antennas haven't.
If you change the tires on your car, is it a NEW car??
The city 800 system back in the 90's, worked in a weird way. The four control channel group frequencies were the only far north and far south available frequencies (antenna sites), so only certain PD and FD talkgroups were allowed on them.
Paul
Paul
I think Alameda county did this too on their old 800 MHz “ALCO” Smartnet system. It was single-site simulcast, but had “local” and “wide area” talkgroups, and only the wide area talkgroups would be carried on all the simulcast transmitters. I imagine if you looked at the control channel data you’d see the call in progress but just not hear it if you were out of range of the site it was being carried on. Weird way to implement that.
Thanks for the history @dmills1 !
I think I remember when the system cut over to Smartzone 4.1, because the SDPD emergency traffic tone changed from the goofy DTMF telephone tones to the regular standard Motorola beep they have now. The analog audio quality of mobile units and dispatchers was very good.
Upgrading the zone controller to ASTRO 7.x was also a memorable event, because the audio quality of the dispatch consoles changed and for a while the dispatchers sounded very “digital” while the units continued to sound analog. I believe this has improved with later versions as I can barely notice it now.
I remember a communication between Able and a dispatcher on a tac channel shortly after the cut over to 4.1. Able had the dispatcher play the different hot tones -- because one of the tones was the same as engine failure alarm on the helicopter -- tends to cause the crew's heart to skip a beat.
That would definitely be problematic! Haha!
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