I can tell you that generally FCC wants to see the ability to have a conversation with another ham. Most other hams would tell you that if you found a clear frequency that is not a calling or weak signal channel, and paused periodically to listen, you might just be alright. Provided your not in some dense area like California where spectrum management is a pain. What you will conflict with if your not careful is the rule about using the minimum power for a QSO. The other rule is do not interfere with existing systems or repeaters. There is no firm rule, but bands like 1296 do have other users, ie FAA long range search radars. Three point five, which we just lost in an FCC vote, is Navy Surface Search Radar.. WISPs just got in a lot of trouble for interfering with WSR-88, and I mean a LOT of trouble. 440 is shared with space tracking radars of considerable importance.
So how long are you going to emit on a given day, what is your target, and how close are you to the coasts? Are you below the horizon of any Air Search Radars in your area? What kind of peak power are we talking here? Are you clear of the the government and commercial users in the band?
Will you transmit your ID in a way an offended user can find you?
Have you looked at the FCC special rules for given areas, Ie no repeaters near the three Pave Paws (they have a new name now) space search radars, or in my case, because I am north of line "A", I can't use 420 to 430 because it is commercial and government land mobile in Canada.
BTW, It is difficult to find who is using what if they are Federal users.
Generally unless your transmitting a beacon or RC , most hams are going to say no to blind one sided QSOs with no intent to answer. I can guess what your regional, voluntary, frequency coordinator is going to say, which is NO.
Do you have a spectrum analyzer for the band you wish to use?
This gets complex quickly. Its one thing to rig a fixed directional antenna and do some pinging. Its another to set a scanning antenna.
I think the rule that will get you is the bandwidth limitations. The shorter the pulse you radiate, the more your spectral width increases.
Also keep in mind that if there is one group of RF users with the ability to rapidly hunt you down, it is your fellow Hams. FCC has many, many, automated remote monitoring stations that they don't talk about. Last I checked there were around 30 regional automated systems that were publicly mentioned.
Look, here is an example of a home made radar, if not the pinnacle of a simple home made radar.. He needs 150 Mhz of bandwidth to accomplish his goal of making a decent radar altimeter using FMCW at 400 mS per sweep. He's actually using the designated aircraft band for this, and considering whom he is in his home country, probably knew whom to call to get permission. He heads a RF research institute as a day job.
http://s53mv.s56g.net/vnr/theory.htm Looking at his numbers, and being locked out of X-band, I think you'll run out of bandwidth within the terms of your license if you want to go beyond backyard distances.
Steve