Approximately what frequency should my UHF Pi-Star be set on in the US? Is there a standard?
Given that it has been established that there is no 'standard', the main criteria for picking a frequency are:
- Find a frequency where the mode you are using is permitted
- Find a frequency where you will not interfere with an existing user of the band
- Make sure you use as little power on your handheld as necessary to get into your hotspot. The hotspot is already probably only using around 10mW or similar, so it is not really the problem.
So the thing you are most worried about is that your handheld is going to be interfering with other users of the band.
I would recommend finding a frequency in the 'digital modes' portion of the band, and see if there are any people already using it. If so, pick another, until you find one where your handheld transmitting on 500mW will not bother anyone.
Remember to turn your handheld power down as low as it will go, while still being able to get into your hotspot.
EDIT: It should be obvious, but in case it isn't ... please avoid the part of any band that is allocated to satellite operation. Satellites are very low signal devices (due to power and size constraints), and so even a very low signal transmission can ruin someone's day if they are trying to communicate with a satellite.
A web search revealed nothing, so I would suspect that there is no standard UHF frequency for D-STAR hot spots, in Kansas or anywhere else. The ARRL Band Plan for the 70cm band reveals that 433–435 MHz is for "Auxiliary/repeater links", which seems like the category that hot spots would fall in. Typical UHF/VHF channel spacing is 20 kHz, and you wouldn't want your signal to bleed into another channel outside the 433–435 sub-band, so I'd pick a frequency somewhere in the range of 433.02–434.98 Mhz, on a multiple of 20 kHz. (433.02, 433.04, 433.06, ..., 434.94, 433.96, 433.98) That gives quite a few possibilities.
That advice is for the US. You didn't ask about Canada, but just to make this a more complete answer I checked the RAC UHF band plan, which says that 433–434.8 MHz is for digital modes, including links, and that the recommended channel spacing there is 25 kHz.
Be in a legal band allowed by your license.
Follow any band plan that has been published for your area.
Do not use a frequency that interferes with others. I want to emphasize this one. There have been reports of interference between hotspots and satellite links. Just because you don't hear anyone on the frequency this instant does not mean someone does't already use it.
Before I get a large number of comments, "no one owns any frequency", that is true, but it is also true that you don't have to be a self center jerk believing you can interfere with others any time you feel like it. I'd like to think that most Amateur Radio operators are considerate.