800 mgHz HATRED

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flydream777

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***Trunking systems aside***

What is the advantage of having a conventional 800 mghz system?? From my scanning experience, they are weaker signals, harder to pick up, shorter range... and not to mention the interference/rebanding issues...

Is this one of those "hey, it's new so I have to get it" fads, or is there a real substantial reason for using conv 800 mghz systems?
 
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N_Jay

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flydream777 said:
***Trunking systems aside***

What is the advantage of having a conventional 800 mghz system?? From my scanning experience, they are weaker signals, harder to pick up, shorter range... and not to mention the interference/rebanding issues...

Is this one of those "hey, it's new so I have to get it" fads, or is there a real substantial reason for using conv 800 mghz systems?
Yea, that it!:roll: ;)

It was "new" about 35 years ago.

What band you go on is usually determined by how many frequencies you need, where you need them, what frequencies you can get and what you need them for. (and how much $$ you have if you have to start buying them.)
 

JRichard

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I think it has something to due with urban environments (ie. buildings). Higher freqs like 400 and 800 have better potential to work inside buildings. At least that's what I've heard.
 

Gilligan

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Trunking systems shouldn't be any different than conventional systems in terms of power and reception. They are virtually the same w/ different data. Trunking is great because it allows many agencies to use only a few frequencies due to the fact that few of them talk on the radio at the same time. Take a look at the Trunking Basics and Other FAQs on the wiki here.
 

car2back

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An agency in the county where used to worked added a conventional 800mhz freq for both their Police & Fire as an addition to their trunked radio talk groups. Alot of times, there would be spots where there was no coverage on the TRS but they could communicate loud and clear when they switched to conventional. It was a good deal for them, becasue it required no extra radios or anything.
 

Gilligan

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phil_smith said:
there would be spots where there was no coverage on the TRS but they could communicate loud and clear when they switched to conventional.
Was that because all the trunked freqs were busy or just an effect of the system?
 

car2back

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Gilligan said:
Was that because all the trunked freqs were busy or just an effect of the system?
Just poor coverage. Sapulpa is allocating on the Tulsa Site of the Oklahoma DPS "state-wide" system, but there has been an FCC liscense issued for a Sapulpa site to be built. Unitil then, Dispatch will keep asking units to "switch to C" quite often :roll:

another idea I like is for FDs that use a trunked system to have a conventional fire tactical channel. From what I have seen, Trunked radio coverage is pretty weak inside a burning structure on a walkie.
 
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Alarms50

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The main reason FD's use conventional freq's on scene is that there is less to go wrong with conventional. If you get into a building where there is no trunked coverage or the system goes down, you have no communication. With conventional freq's you will more than likely be able to communicate with someone else, whether it is the IC outside or someone else in the building. I may be mistaken but I recall reading that NFPA recommends that all fireground comms be simplex, not trunked or repeated for just this reason.
 

Gilligan

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Haha. Funny how I read that differently the first time. He may be referring to simplex comms more than anything else (versus repeaters).
 

902

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flydream777 said:
***Trunking systems aside***

What is the advantage of having a conventional 800 mghz system?? From my scanning experience, they are weaker signals, harder to pick up, shorter range... and not to mention the interference/rebanding issues...

Is this one of those "hey, it's new so I have to get it" fads, or is there a real substantial reason for using conv 800 mghz systems?
The advantages of 7/800 MHz are not about scanning. In fact, the things that make scanning good for other bands, such as VHF are exactly what ruins its use.

I'm sure there are a lot of people who are going 'WTF?' right now because what I said is sacreligious for scanning, and maybe a handful of people who actually get it. I like monitoring, and it's been my hobby for over 30 years, but this is my profession, too. From the professional side, it's not about scanners. In fact, telecommunications technology may whiz past scanner technology. The market is not so great that Uniden and GRE make tons of money on research and development for the latest and greatest. It's about responders first, scale of economy second (most people leave that out, but I'm only being honest - money matters). Some people will also insert security, but that's a different can of worms.

So, "what's the advantage?"

Here goes:

Frequencies below 512 MHz are "shared use." The four public safety frequency coordinators (APCO, IMSA, FCCA and AASHTO) for the most part try to do their best to minimize interference, but as far as the FCC is concerned, all licenses below 512 have absolutely no regional exclusivity. You may, someday, get someone up on your frequency and have no recourse but to share it. The Rules and Regulations tell you to monitor before transmitting to make sure the channel is clear. That *always* happens, right?

VHF High Band has a legacy of haphazard assignment. There are inputs on outputs. Outputs on simplex channels. Many agencies have a legacy of putting the biggest tower on top of the highest mountain in their area and cranking the power to cover their 10 or so square miles. Recently, I saw a request for a system for 350 Watts effective radiated power to cover 3 square miles! To scannerists' delight, these systems can be heard for MILES, but they create tremendous interference and preclude the frequencies for reuse within 100 miles or so.

The 7 and 800 MHz band (you should consider them as one contiguous band from this point forward), is EXCLUSIVE to the one licensee within the service area. There is absolutely no way that the FCC will allow another system to be constructed over another. Elaborate engineering models (Longley - Rice formula) must be constructed to validate that there will be no interference. NPSPAC frequencies (currently 866 - 869, but moving down 15 MHz to 851 - 854 MHz) are even more restrictive. They allow for re-use within a certain area and are administered by a peer review committee, not the FCC. The FCC merely approves the plan. In most NPSPAC plans, the 40 dBu coverage contour must fall within three (rural) to five (urban) miles. This is important because signals are directed in toward the served jurisdiction AND NOT out to the horizon. This is why these systems typically don't get heard as far as the 'top of the mountain repeater' systems. Bad for scanners, but good for responders. 700 MHz assignment is even more restrictive (with the exception of several analog channels, the entire band MUST be digital... they DON'T have to be P25, only mutual aid channels must be P25; along with a greater mandate for channel efficiency pushing toward 1 voice path in a 6.25 kHz channelspace equivalent) and encourages regionalized deployment.

These other bands also mandate spectrum efficiency. VHF conventional is tremendously inefficient. Whenever another agency within city, county or state government needs a radio system to use, it must find a frequency (trust me, that's impossible in many areas), get concurrence from others who use it, and then must build a complete radio system just for themselves. If they work 9 - 5, like a building department may, that channel is idle for 16 hours of the day, but can't be used by anyone else. In a trunked environment (and you can have trunked VHF, but a public safety trunked system on VHF is highly unlikely in any populated areas) on a higher frequency band, the new user would procure radios, program them and the system manager would assign a talkgroup and priority. They'd share the handful of frequencies used by the system. It's tremendously more economical, although it seems more expensive up front. The decentralization of VHF and non-trunked UHF add up actually to more money spent for less efficiency.

So, that's why. When I build a system, the thing that's on my mind is not the people who listen - even though that's been my hobby for a long time - it's the people who use. It doesn't really matter if the system can be heard 10 miles out of town, as long as in town it is as close to 100% (on subscriber equipment, not scanners) as economically possible. These days that will mean that higher-technology initiatives will no longer be received on the old Bearcat. While that's unfortunate, needs for better coverage, better efficiency and better capacity demand their use.
 

LarrySC

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The state of SC has installed a statewide 800 mHz repeater system as a backup to the statewide trunking system. It employs the 5 nationwide I-TAC Ch's and an additional 5 Ch's operated by the state. It uses standard PL tones. There seems to be several reasons for this setup when it comes to emergency operations.
 

eyes00only

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902 said:
In a trunked environment (and you can have trunked VHF, but a public safety trunked system on VHF is highly unlikely in any populated areas) on a higher frequency band, the new user would procure radios, program them and the system manager would assign a talkgroup and priority. They'd share the handful of frequencies used by the system. It's tremendously more economical, although it seems more expensive up front. The decentralization of VHF and non-trunked UHF add up actually to more money spent for less efficiency.
I really have to disagree with that. UHF & VHF are far better for trunking. Why do you think the government uses UHF? MANY agencies are finally realizing this.

Jerry
 

flydream777

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Thank you, N_Jay, for pointing it out that I wasnt referring to trunking systems in my original post.

But to talk about trunking systems for a moment.....

I guess I'm trying to say that whenever an agency wants to upgrade and has the money to do so, they always opt for the 800 trunked system, maybe when it might not be absolutely necessary.... It seems like they do this just for the sake of having the latest and the greatest taxpaying money could buy (forgive me for being cynical). I could give many case examples from my area, but since this is not the IL forum, I'll spare you.

I hope I didnt give the impression that I was ignorant of the reasons many agencies choose to do so, and I do recognize that it is not about scanning, but about the needs of the agency and how their systems perform. However, since the scanner is essentially a one-way radio (even though it is not fine tuned to a specific freq), one could expect that the deficiencies heard via scanning of many 800 systems/freqs could also reasonably be applied to the actual public safety radio systems themselves.
 

902

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eyes00only said:
I really have to disagree with that. UHF & VHF are far better for trunking. Why do you think the government uses UHF? MANY agencies are finally realizing this.

Jerry
Jerry,

I never said that the propagation characteristics of VHF or UHF are not good. In diverse terrain, fewer VHF sites will cover areas compared to 7/800. There are many UHF systems already deployed, many are municipal or county systems, so it's used in more than federal application. The problem is twofold:

1) In order to trunk VHF or UHF, you need letters of concurrence from each of the co-channel users within the 19 dBu co-channel interference contour and 27 dBu adjacent channel interference contour - 90.187(b)(2) - OR the system must incorporate some sort of arbitration scheme that pulls the channel off-line while another system is using that frequency.

2) Trunking and digital radio systems both require a clear frequency, at least for talk-in. Talk-out can rely on some degree of capture, but a trunked system will disable the frequency if there is co-channel activity. Co-channel analog transmission on a frequency a digital system is used in may create holes in the decoded data. Another data signal may be destructive. Two P25 radios key up simultaneously, you will not hear heterodyne like analog would, chances are you will hear nothing. Co-channel issues don't lend well and the legacy of haphazard frequencies used for a repeater input here, a repeater output there, leads to unreliable operation while anomalous propagation is occurring. In those instances, a repeater output may kill the system's input for voice or control channels.

I won't even go into the difficulties of combining VHF. I have fourteen conventional VHF stations at each of five transmit sites. The walls are loaded with cans for combining. This leads to a 'usable'/ 'unusable' logic table for many frequencies, so the systems cannot be expanded when a possibly usable frequency is found.

IF VHF was responsibly managed over the years, and we had standardized inputs and outputs, VHF trunking would be fantastic. But we don't. To make matters worse, the FCC created 7.5 kHz channel centers when the signals that occupy them are wider (11.25 kHz in that 7.5 kHz channel, with overlap into the immediate adjacents), even with narrowband. To have made a positive impact, the Commission *SHOULD HAVE* gone from 15 kHz channel centers to 12.5 kHz channel centers and then should have gone through licenses and "right-sized" the ones which were grossly over-ERP. The 12.5 kHz channelspacing could have meant that a digital system could have been coordinated on an adjacent channel much closer than the 7.5 kHz channelspacing would allow. As it stands, in some places, narrowbanding has resulted in a net gain of zero, because adjacency issues remain. A NPSPAC-like requirement for service contour is a start. Requiring agencies that warehouse frequencies to conform to channel loading criteria and implement spectrum efficient technologies is the next progression. In that way, an agency with 32 conventional channels that are intermittently used can possibly be made into an effective trunked system using five to seven channels, and the other frequencies should be given back for general use. A mine sweeper game of this magnitude has the potential to dwarf the cost of Nextel rebanding.

For VHF trunking to work, there needs to be greenspace within which to implement it. This is going to come from only three sources - the Icom petition (free up the old IMTS/ VHF paging channel pairs for public safety), reclaiming VPC spectrum from MariTEL or getting a fresh infusion of spectrum from the NTIA either in spots adjacent to the 2 meter band or between 162 - 174 MHz. Most states cannot retask existing VHF allocations like several states have done.

Let's lobby for some greenspace and then start using VHF responsibly. Then we can use VHF for trunking. Absent that, it's just not feasible for many circumstances.

Edit: Oh, just a comment about 35 years... The earliest I remember 800 MHz was 1976. That has to be a few years after they took away TV channels 70 - 81. There was this absolutely terrible Motorola radio - an 800 MHz Maxar with a bumped out cover - that we called the pregnant guppy that was set up for PrivacyPlus trunking. There were also trunked Micor radios out there (the logic was in the control head assembly). 800's been around for a long time.
 
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902

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flydream777 said:
I guess I'm trying to say that whenever an agency wants to upgrade and has the money to do so, they always opt for the 800 trunked system, maybe when it might not be absolutely necessary.... It seems like they do this just for the sake of having the latest and the greatest taxpaying money could buy (forgive me for being cynical). I could give many case examples from my area, but since this is not the IL forum, I'll spare you.
Does this have something to do with an agency moving to Starcom21?
 

eyes00only

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Red* are Primary Control Channels, Blue* are alternate control channels

Site Description Freqs
1000 Rawlins 154.31750 154.33250 154.34750 155.61750 155.97750 156.14250 156.18750
1001 Beacon Hill 154.13000 154.72500 154.78500 155.07000* 155.19000* 155.58750 155.85000
1002 Strouss Hill 154.07750 154.17500 154.23500 154.35500 154.68750 154.86000
1003 Laramie 154.65750 154.92000 155.46000 155.97000 156.19500
1004 Torrington 154.17500 154.38500 154.93500 155.11500 155.37000
1005 Wheatland (South) 154.36250 154.91250 155.02500 155.13000 155.39250 155.82750 155.97750
1006 Wheatland (North) 154.09250* 154.40000 155.19750 155.35500 155.51250 155.67750 155.88750
1007 Wheatland 154.25000 154.71000 155.22000 156.06000 156.15750
1008 Albin 154.32500* 155.31750 155.50500* 155.82000 155.95500 156.12000 156.24000
1009 Cheyenne (South) 154.07000* 154.08500 154.69500 154.84500 155.43000* 155.85750 155.98500
1010 Russell Hill 154.01000* 154.35500 154.67250 155.45250 155.59500 155.62500 155.67000
Just a sample of the NEW Wyoming Wyolink VHF trunked system.

Jerry
 

Gilligan

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Just in comparing UHF to 800 MHz, I would have to say that many of the LTR around here on UHF have incredible coverage w/ one tower compared to many towers for the city's 800 MHz EDACS. I love UHF w/ the scanner because I don't need a real long antenna for my handheld and it receives it so good just about everywhere.
 

flydream777

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Haha no, my annoyance doesnt have anything to do directly with STARCOM. Thank God my hometown is not doing anything with it though...
 
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