smeezekitty wrote:I think FM might be a better way to send NBTVA standard video due to it's better low frequency performance? (technically DC I think?)
As a generalisation that's true, but as ever there are compromises to be made. We could go into a discussion about this, but the HAARP transmitter is AM so that's that. A sub-carrier could be used to achieve FM-type results as per SSTV but at this stage I don't know the transmitters capability in terms of modulation frequency response, it would need to be beyond 20kHz to accommodate a sub-carrier that could convey a 10kHz NBTV signal.
In addition the receiver would need a similar response, I doubt they exist unless designed and built specifically for this application.
Without the transmitters specifications, esp. modulation capabilities, it's somewhat of an uphill battle...
Steve A.
In addition to the above, the antenna array/RF distribution arrangements may also conspire to limit the modulation bandwidth. With it's intended application the array may have a very narrow bandwidth, we just don't know.
...later, I've seen a note (somewhere) that HAARPs modulation bandwidth is up to 100kHz, that would need verification...