Ed G wrote in
92.196:



Our ARES station has had a NVIS antenna on the roof of the
building
we are in. It is a large, one story structure with a rubber coated
on steele roof.

The dual dipole type antenna, center at 14' and ends at about 3'
high, was fed with a long run of coax and has historically exhibited
a large SWR when operating below about 3825 KHz.

We recently replaced the entire antenna assy with a 122' half
wave
dipole, fed with 600 ohm ladder line to an SGC antenna coupler at the
base of the center mast. Heights are the same as previous.

The SGC 237 coupler tunes the antenna well above 3825, and all
other
bands, too. However, we still exhibit a very high SWR when going
below about 3825 and the tuner fails to tune... in fact the Radio's
power drops way down, possibly preventing the tuner from working
properly. A different radio shows the same problem.


QUESTION: Can anyone offer reasons we may be having this
tuning
problem below 3825?

Thanks.


Ed K7AAT


Ed,

The way in which you dealt with the transition from the open wire
feedline to the SGC237 unbalanced tuner is relevant. As is whether or not
you bonded the tuner 'ground' terminal to the roof.

Your description is short on relevant detail.

Owen