Preamps lead to front-end overload, front-end overload leads to AGC limiting, mixing products, etc.
For a repeater site on a hill without much of anything in the neighborhood, that's not a bad idea. But if there's anything within five miles, the preamp will need cavity filters itself, not to mention protecting it from the transmitter you're running rather close to it. The radio has much better rejection characteristics without the preamp than with preamp. Or, to say that another way, power is a better idea than power + preamp. One cannot "hear" below the site noise floor, and bringing the noise floor up reduces the signal to noise ratio, leading to scratchy signals, etc.
Since everything has a preamp, one doesn't need to be on the frequency exactly to effect a denial of service, one only needs to be on a nearby frequency. And the closer one is to a given receiver, the less on frequency they need to be to cause front-end overload and put the radio's gain stages into limiting, which leads to zero signal apparent on frequency (since all the gain has been turned down).
And from the mountaintop, a DB-228 would be a better idea for large area coverage (>= 30 miles from repeater to mobile). 350W into a 4-bay antenna is excessive (ERP is then 1400W), and results in co-channel interference as well as a footprint the FCC doesn't want to support or license (> 40 mile radius). 350W ERP total sounds reasonably normal for a 30 mile radius repeater inclusive of losses.
I still wouldn't put a preamp on a repeater; Motorola and GE only used 6dB gain preamps. A typical receiver noise figure is about 7dB; the preamp, having a NF of 0.5 - 1.5dB can make up the 6dB NF difference, but any gain above 6dB will reduce the receiver's dynamic range as shown above. The effects are similar to the "Extender" functionality of some radios -- a 60MHz RX that detects atmospheric noise and reduces the front-end gain of the radio to eliminate noise.
And then there's OET65.
Not to mention power-to-weight ratio. (And driving faster than the max efficiency point of most cars (60MPH) effectively raises your cost per mile or cost of gas per gallon for the tank.) But the Prius is best suited for city driving; the power train has limitations -- speeds above 60-70MPH result in electrical motor issues due to shorted turns in the motor, etc.
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