WA2ZKD

ERP the result of antenna gain I'll guess. Rockwell-Collins has a WBHF waveform that goes to 48 KHz. http://www.hfindustry.com/meetings_presentations/presentation_materials/2012_sept_hfia/presentations/RC_WBHF_UK_Trial_2012.pdf

I posted some howto in another thread for making AMBC notch filters

NVIS paths have proven tricky for me.

a surefire solution at a decent price
https://www.ebay.com/itm/Lucent-GPS-40dB-High-Gain-Timing-Antenna-Lightning-Surge-Protection-Mount-Kit/323346523135?epid=10008077643&hash=item4b48f463ff:g:-yEAAOSwjkdZ81n5&_sacat=0&_nkw=40+gps+antenna&_from=R40&rt=nc&_trksid=m570.l1313&LH_TitleDesc=0

It seems like VOACAP and its online frontend variants have evolved as a Gold Standard for some. However, during my professional work I find that the answers are not always right with regards to MUF for the NVIS and NVIS+ paths I am interesting in. I find that REC533 may be a better model. Also, there's always debate as to what to use for SSN in any of those programs. Greg Hand, who wrote the latter variants of the xxxCAP programs says to use:

http://www.sws.bom.gov.au/Solar/1/6

The xxxCAP programs themselves may be downloaded here:

http://www.greg-hand.com/hf.html