[TowerTalk] What are est of frequency chg for ten meters?

[N5MT at aol.com]

Keith just made this comment and it sounds accurate.  Ten feet is a bit low 
for tuning.  A 40 meter dipole tuned at 15-20 feet will resonate about 10-15 
KHz higher at 78 feet.

Now lets change frequency to ten meters.  A ten meter dipole antenna tuned at 
15 ft would resonate about ( What ) KHz higher at say 75-78 feet?  
Now lets change antenna to a 4 el yagi moving from/to same heights?

Thanks.  73 Mike  N5MT