HI,
I am looking for options for an organization that have multiple agents across a city that has an area of of 35 square kilometers. Most of the employees will be in the field and we are looking at means to make communication easier. I was looking at the Motorola MR350R as its said that it has a range of 35 miles. So in a real life scenario with all trees and buildings I am assuming it will be broken down to 5 miles? Any other heavy duty option would you recommend?
Always ignore published range specifications as advertised, do your research, get a topographical map and look at the lie of the land. Some countries like the UK it is also possible to get a propagation map related to frequencies and bands giving a comprehensive idea as to coverage. Any decent supplier, Hytera or Motorola along with others , if there is enough value in the project will do that research for you and suggest if a remote base station or repeater is needed . Again I reiterate do not look at range figures . I can give you a classic example, here I use a 25 watt Hytera base unit (DMR) on a small end fed antenna at about 15 feet agl and portable 4 watt units . I patchily cover more than your 35 sq miles . I intend to have that antenna raised to about 60 feet agl and fully expect to remove 90% of the patchiness. It is all about the variables and overcoming them. Do the proper research and you won’t go far wrong
The range is “up to 35 miles” - so take it as very much a couple of miles if you are lucky, radio to radio. When I set a portable radio to the power these things run, with my repeater, with the antenna fairly high on high ground for the locality, I can get about 2 miles reliably - as in when the radio is in the pocket, NOT when it’s in my hand, held up high. This is the snag. You want the radio to respond, and tucked into pockets, inside coats, or being sat on in a back pocket, the range can be tiny radio to radio.
It VHF, the topography of the surrounding area and tropospheric (low-mid altitude) weather effect on propagation is what defines, with sig field density degradation over distance as your main enemy in all radio use, your usable range.
At UHF upwards, it’s the above but with a lot more dependency and less latitude in how much those factors can be compromised - but at UHF, you can take more advantage of the multi-path effect of signals bouncing off buildings or being channelled down valleys etc.
At very high UHF into SHF, you add in that it gets even more critical to assess the terrain for siting your stations, and note that upwards of 1Ghz, as easily demonstrated with wifi and bluetooth, anything more dense than fresh air has a marked attenuation effect and rapid degradation of sig field density. If the attenuating substance has notable reflective characteristics, it’s even worse.
For example, you won’t distinctly notice it too badly on SHF frequency cell phones and cellular dongles because unless you’re in the back of nowhere, in a proverbial RF ‘black hole’ or somewhere where population makes putting in much cell site coverage unviable, you’ll see artificially high sig quality on cellular. Don’t let that fool you.
At SHF, even water and slight damp on a window pane has a notable indoor usage range effect (due to attenuation), because regular glass has (due to it’s silicon content) capacitive effect which makes it a sort of non-resonant antenna element which actually reflects a lot of RF energy back at you, water is also a good attenuator at all frequencies but really brick wall attenuation grade at SHF.
If you’ve got a sat receiver - go outside with a paper town, put it over the dish facing feedhorn on the LNB and go check your reception, either your reception goes to ■■■■ or (in the event you’ve normally way more sig level than the receiver needs) a marked deterioration. Repeat this with a wet paper towel and you’d be lucky to have anything remotely resembling a received sig level.
So focusing on VHF/UHF, look at the types of terrain and extremes of range you’ll need and notably for HT you’ll find your best option is probably going to be VHF if extremes are notable and using vertical antennas. Assuming the TA and license allows for it, you could be looking at needing single or dual band (depending on which way you jumped or both) antennas that are a collinear in nature and those can be pricey for multi-band portable/HT use, highly not very practical, and choice being pretty slim unless you build them.
Antenna setups get more usable, within license and TA restrictions, when you are talking mobile ops (vehicle installations) and base stations. For mobiles, you can buy what are often described as range extenders (mini repeaters) which can be fitted in vehicles and use the mobile antenna (or two paired) to repeat traffic on frequency too and from the HT via the mobile. Classically, in police mobile setups, they threw a switch on the radio kit to switch it between internal mobile use and into repeater/extender mode for when they left the vehicle and were on HT’s. But again, legit options for that depend much on the license you’ll be working under, if they are permitted, and given their relatively limited demand, certified items for LMR use are pretty pricey.
Beyond that stuff, the previous postings stand in good ground and put it all in perspective. I just fely a bit more detail could help - since VHF and UHF are still sort of ‘dark magic’ bands in the eyes of many - who would find the quirks and added considerations pretty hard to get perspective on.
It helps when you started on VHF/UHF, to get a grip on it at the underlying level as, as us former B ham licensees knew, a lot of it was still relatively ‘dark magic’ even back in the 90’s like SHF still is to many and will probably remain so in general before i fall off my proverbial perch …