Using the amplifier only

[Ross.Wheeler]

Detecting lightning within a certain radius of a location, with a single receiver, is almost impossible.

Lie!
Boltek's are single receiver's, and for beeing that and taking that in act, damn accurate if they are calibrated correctly

The Boltek is still only an educated guess. Yes, you can calibrate them, but they will still be subject to a large degree of inaccuracy - from those I've spoken to about their operation anyway. Yes, they probably give you a useful guess. No, they don't give you an accurate or reliable distance.

There is at least one study (Stanford?) that found lightning produces a typical signal, and the nature of the signal varies with distance due to phase velocity characteristics.

Yes, but that will require quite a lot of computational power, which the OP specifically wasn't going to be using.

Anyway, I would not be surprised if, for BO stations that use H-field coils that are properly set up at right angles to one another, some direction finding is also possible (see the X-Y plots on lightningmaps.org).

Yes, and it's quite accurate. While I was commissioning my first station, I used this to determine the source of some interference, by taking my sensor and a laptop and taking a few readings from different locations.

Even so, using DF will require multiple stations. If you're lucky, just two, but there will inevitably be lightning along the axis of those two resulting in no solution, and a third would be necessary. Again, it's not just using the receiver and plonking a counter on the output!

Just to clarify - yes, I agree a single receiver can certainly tell you if there's lightning-like activity around.
I was saying that a single receiver of the kind suggested (a BO amplifier with no external computing) cannot reliably discriminate between
noise or lightning, and cannot accurately be set to only pick up lightning with a (say) 50km radius (ignoring lighting >50km).

Yes, precision analysis of the waveform might give you enough additional information to make a reasonable estimate of distance under many (even most) atmospheric conditions, but that is not the configuration requested by the OP (which I thought would be a given in the context)