Replacing Wiscom

[NVAGVUP]

I am a bit late to the discussion, but I wanted to add that in addition to the excellent summation by @trumpetman for reasons to go with 700/800 MHz is the fact that the VHF spectrum has seen a significant increase in the level of the noise floor caused by countless electronic devices that now pollute the spectrum just about everywhere and thanks to the incompetence and miss management at the FCC.

I am personally aware of at least one county in Wisconsin that is battling RFI at one of their VHF sites that so far has had no resolution and is driving that local government entity to also consider moving 700/800 MHz. So, while arguments that VHF has greater range is true, it also true that this potential has been greatly diminished over the past 20-25 years by electronic pollution that extends well above VHF.

Ding. Ding. VHF may have great tower site talk out range. But when you calculate/measure the amount of floor noise (Site and mobile/portable) on RX, effective RX sensitivity is fair to very poor. This causes terrible system talk in/talk out imbalances.

The benchmark of public safety communications is portable coverage. (And more specifically in building coverage) Not a DOT plow. Even without overall RX degradation of VHF band, the laws of physics favor 700/800 band for in building coverage. 700/800 sites (Stand alone or simulcast) can be optimized for optimum portable performance. VHF requires additional sites (Voting) to even have a chance of good portable coverage. And once you enter buildings, propagation is still worse than 700/800.

VHF Portable antenna gain=-6 to -9 db typical
700/800 Portable antenna gain= +3db typical

And for any buildings with coverage issues, a 700/800 BDA/DAS can be designed and installed at a fraction of VHF BDA.

Those are the laws of physics.

(Last time I checked, MN and MI have a few trees and river valleys.)

Per wgbecks. I know of a large county in one of the above states. When they migrated from VHF to 800, the range throughout the county was comparable with the relative same number of RF sites. (For reasons noted above) And inbuilding coverage improved.

And I won't delve into issues with VHF spectrum above Line A (Canada). PIA is an understatement.

Kudos to WI for looking forward to where they need to be.

 

[kb9mwr]

My thought is how many counties already built their own.. sorta late now. Might as well just let firstnet do the rest anway.

 

[OpSec]

My thought is how many counties already built their own.. sorta late now. Might as well just let firstnet do the rest anway.

Two FirstNet users can't even do PTT between themselves, let alone anyone else. FirstNet isn't the answer to anything.

 

[dmchalmers]

As always they want a 700/800 mHz system. Works great in the urban centers. How about all the forrested northern counties? Why do they always insist on not using VHF?! Get ready for the excuses of why they will need to spend our tax money to put up tons more towers. It's the MPSCS in Michigan all over again.

Wi will use all the Biden bucks its got for a new MPSCS system that still has high costs for users just like MI

 

[gman1971]

I concur that the VHF noise threshold has gone up substantially over the last few years. Traffic lights at intersections are some of the worst offenders and the noise floor can go from a -118dBm RSSI to -89dBm RSSI in a snap.

The only effective way I've found to combat this was by raising the TX tower height. So, IMO, you don't need 800mhz, you just need higher towers, which will take care of most high noise floor areas, and allow portables to work better inside buildings too. There is no amount of gain in a portable that can compare to the gains from raising the tower transmitter 150 feet higher in the air.

So, 800 Mhz has a -15 dB deficit in propagation in free space vs VHF. Sure, you get some extra gain on the portables, but again, you are starting with a -15dB deficit to begin with. I've also found that UHF 462 to be vastly inferior to a VHF 150mhz system: No matter how hard I've tried to get UHF to work long range, VHF always wins. Even with the higher VHF noise floor.

For building penetration I've had a lot of success using VHF-VHF vehicular repeaters. Works well even deep inside crowded places like malls.

I really think 800 mhz is a sucker money trap. 800mhz has absolutely piss poor propagation over long distances, it sucks in the forest, it sucks in the rain, snow will reflect the crap out of it, and then it has -15 dB deficit at equal distance, so you'll need more towers to cover the same area, for what? hoping that you can improve some "inside building" reception?

VHF works just fine, even with my current limited budget system I have a 30 mile solid coverage, with just a handful of dead spots, which BTW will get addressed in the upcoming tower upgrade this spring.

If the WI government can't get a VHF system to work properly, it sounds to me like they are doing something wrong.

Now, if more bandwidth is the requirement then that is perhaps a valid reason to migrate, but I have no experience there so I can't comment to that.

G.

 

[R8000]

I have no experience there so I can't comment to that.

You must not have read the documents the state released. It explains many things.

 

[gman1971]

You must not have read the documents the state released. It explains many things.

I did not.