Mr Ryker, I hope I can share some light on those i355 Nextel phones and help you with your recent proposed purchase.
First a little background information on those devices: the Nextel i355 phones were originally designed to be operated on Nextel’s iDen cellular network. Out of all of the cellular technologies it can be argued that the iDen network is the closest to a trunking radio system, but it is still a “cellular” system and as such these i355 devices were originally designed to be used on cellular towers. The transmit power in these phones is around 1/2 watt due to FCC regulations. A lot of curious users (including myself) have taken old Nextel phones, inserted a blank SiM card, and used them “off network” as simplex walkie talkies.
Let’s go through the factors that sold you on these “phones”…
Cost
This is a perceived benefit of owning a cellular device vs a dedicated two way radio. Since cell phones normally require a service plan cell companies are willing to practically give their phones away (granted its not a smartphone :D). The i355s can be found for relatively cheap on the used market since they are an old Nextel model and the supply is much greater than the demand. When I purchased my i355s (set of two) about 2-3 yrs ago they were $45 each + SIM cards. I say “perceived benefit” because You are buying them to operate OFF of the cellular network. If your were to buy a new Sprint/Nextel phone without a cell contract you would end up paying $375-550 for the phone…more than most business two way radios.
Range
This one is tricky, the big question everyone wants to know, companies like to quote, and users are disappointed about. I’ll keep it brief: wattage isn’t everything, but you have to think-- the average handheld two way radio is 2-5 watts, these i355 phones are 1/2 watt. On to the facts: I own two i355 radios with standard extendable antennas. I originally bought them as a license free alternative to MURS, GMRS, and commercial radios. My experience has been 1/2 - 1 mile max outdoors, and <3 floors in a commercial building with the basement floor being underground (kind of upsetting to say the least). The longer upgraded antennas might give you an additional half mile, but nothing miraculous. In my experience, a UHF handheld such as your Kenwood TK3207 will always outperform the i355.
Functionality
No doubt the i355 phones have greater functionality than most two way radios. The caller ID feature is the best! Plus private talk options so you can call one person individually or your whole group. One thing to note: you cannot use GPS on the i355 unless it is activated on the cellular network. Also know that when using the “OFF” network walkie talkie feature, you cannot access any of the cellular network phone features (GPS, DirectConnect, Phone calls, texting, etc.)
Security
I355 wins here as it uses digital transmissions which are not legal to scan.
Durability
These phones are surprisingly very durable. I would put them on par with a commercial $300 radio. Batteries suck just like most cell phones; you will do great for about 6-12 months then you will experience a significant loss in battery life.
Overall these are a great pick for short range comms, perhaps in a small building or urban environment. Do not expect more than 1 1/2 miles max out of these though, and remember these were designed as a phone first, and radio second. This will affect what features are usable when the phone is off the Nextel network.
**Quick note for those who may be looking at these phones for cellular use as well as radio. Sprint will discontinue service to their iDen network in 2013 making these phones useless on the cell network. Look for a drastic decrease in price next year for these phones on the used market.