There are several observations that I have made over a period of time that augment that conclusion. 1. Short wave stations are not a lot different than long wave.
I have seen many SW stations that provide low levels of modulation day in and
day out. You wonder what the engineering staff thinks this practice yeilds.
2. Short wave stations will warm up their transmitter (not every station is the
same) over long periods of time. Why I don't know. I worked in radio
stations when I was young and a few minutes of warmup were all that you were
asked to do.
3. In the US we are dealing with much lower levels of LW signal than Europeans
experience on their radios. If a carrier is present in low levels
sometimes you will not hear the modulation. Depends on the type of detection
you have in your radio.
4. I have also noticed that frequency control in some of the long wave/NDB
equipment that we encounter is not always tightly controlled. The power
company SCADA emissions that I recently described to you are the worst. These
channels will drift while in operation sometimes more than 1 Khz. I think it
due to them not utilizing the equipment for long periods of time. When I see
them turn on the SCADA the channels constantly drift until they reach
equilibrium.
5. I see a lot of maintenance issues in NDB equipment. Transmitters off the air,
drift from assigned frequency, and many with no identifiers. It makes you
wonder about the state of this radio gear.
6. When I first started searching the low frequencies I finally figured out the
fading that can occur. To me it's not like shortwave. It can fade out
within minutes and not be seen for a long time. There are times that it can
change the carrier strength quickly. I am betting that in Indiana that you
don't get as much fading as I do in Texas. Texas is a great place to live
but you are stuck in the middle.