[TowerTalk] 40-meter GP resonance problem

[RLVZ at aol.com]

Hi Guys,
 
Hope you can give provide some wisdom on an antenna problem  I'm having on 
40-meters.  I'm operating at a temporary QTH and mounted  a Hustler 5BTV 
vertical up on the rooftop at 30' above ground.  Using  two 1/4 wave radials 
for 40-m. and four 1/4 wave radials for 20m. the SWR  across 40-m. was 1.3 to 
1.5 to 1.  The antenna radiated pretty well for  what it is.  ( a simple GP)
 
Since I'll be at this QTH for another month and I'd like  to work 
12-17-30m. I took the Hustler 5BTV down today and replaced it with a Big  SteppIR 
vertical.  Using the same radials at with the Hustler...  my SWR on 40-m. is 
now a terrible 5 to 1 and it doesn't  hear well either.  I'd say the reception 
is down about  4 S-units.
 
On 10-30 meters the Big SteppIR Vertical is  resonating aprx. 2 Mhz from 
the norm:
 
Transmit  Freg           SteppIR  Resonance
 
28mhz                        24mhz
21mhz                        18mhz
14mhz                        12.5mhz
10mhz                          8mhz
7mhz                            ?  (unfortunately I cannot add add'l length 
on 40-m. to find resonance but the SWR  is 5 to 1)
 
Since I can vary the antenna length I can make the SteppIR  work on 10-30 
meters.  But I'm wondering what I can do to make it work on  40-meters?  The 
SteppIR instructions say you can adjust a ground  planes resonance by 
changing the radial length.  I'm wondering if you  think increasing the length of 
the 40-meter radials would lower the SWR on  40-m?
 
I'd appreciate ideas on how to reduce the SWR and increase the  antennas 
efficiency on 40-m.  Such as: adding more radials to the GP  or increasing the 
radial length, etc.
 
Thanks & 73,
 
Dick K9OM/9