Technical Topics > Propagation

Question about the ionosonde charts

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TheRelayStation:

--- Quote from: ChrisSmolinski on May 14, 2018, 1106 UTC ---Speaking of propagation above the MUF... my logging of The Relay Station the other night: https://www.hfunderground.com/board/index.php/topic,42507.0.html

Based on foF2 values I shouldn't have heard anything. But I was actually getting a fairly decent signal at times. He said he was running 500 watts, so significantly more than the typical 20 plus/minus watts of a MOSFET type transmitter. Several S units right there, plus a decent antenna on each side of the circuit.

--- End quote ---
so this would be considered "ground wave scatter" ?
i suspect this type of ground wave propagation would only occur with a certain amount of TX power ?
because i was receiving my signal on many SDR's in the US-west and abroad quite well actually.

ChrisSmolinski:

--- Quote from: TheRelayStation on May 14, 2018, 1606 UTC ---
--- Quote from: ChrisSmolinski on May 14, 2018, 1106 UTC ---Speaking of propagation above the MUF... my logging of The Relay Station the other night: https://www.hfunderground.com/board/index.php/topic,42507.0.html

Based on foF2 values I shouldn't have heard anything. But I was actually getting a fairly decent signal at times. He said he was running 500 watts, so significantly more than the typical 20 plus/minus watts of a MOSFET type transmitter. Several S units right there, plus a decent antenna on each side of the circuit.

--- End quote ---
so this would be considered "ground wave scatter" ?
i suspect this type of ground wave propagation would only occur with a certain amount of TX power ?
because i was receiving my signal on many SDR's in the US-west and abroad quite well actually.

--- End quote ---

It's possible that is the mechanism for my reception. For the more distant receiving sites, normal propagation would suffice, as foF2 was high enough so the MUF was above 6880.  As the incident angle becomes more shallow, higher frequencies can propagate, for a given foF2 value. Once you get out of the skip zone, the signal can be heard (via normal propagation).

If it was ground wave scatter in my case, the signal was hitting the Earth some distance away from me, then getting scattered/reflected back to me. Think of it as another hop, where that hop is more distant, vs being between the transmitter and receiver sites. I guess you could even think of it along the lines of multipath reception for VHF/UHF? Not quite the same thing, but maybe that helps to visualize it?

The more I learn about propagation, the less I feel I know  ;D

Josh:
There's also the old method of simply pointing the beam at a region of propagation a few hops away and using that, very common on 10m. I suppose sans beams at both ends it just becomes luck if one can hear a given signal that "shouldn't" be there.

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