I can't address whether the combined windload is within specs for your tower.
Someone else will have to comment.
But if the antennas are closer than about 10 feet apart, you will get
interaction between them. The SteppIR won't have much effect on the 40-2CD, but
the 40-2CD will definitely affect the pattern and SWR of the SteppIR on 15m and
17m. Best to get as much separation between the antennas as possible. When I
had the same antennas, I had about 14 feet between mine and there was still
some minor interaction. I use a full-size 2-el 40m beam now (a real monster),
and there's no interaction to speak of. My understanding is that the
interaction is especially bad with the 40-2CD and XM240, and similar
shorty-forty designs. Force12 claims their trapped shorty-forty doesn't
interact with tribanders, but I don't know if that's really true.
You say the crankup tower is guyed. Is that a feature provided by the
manufacturer, or did you add the guys yourself? It is not safe to guy a crankup
tower that hasn't been specifically designed for that. With most designs, the
guys will put too much downward pressure on the tower sections, with the likely
result being failure of the cable and collapse of the tower. The only way it's
safe is if the manufacturer has provided a way to take the load off the cable
when the tower is extended. I believe some people have modified crankup towers
for guying by putting lumber or metal bars between the sections to take the
load off the cable. But that's a very dangerous procedure and requires much
time to raise and lower the tower. You might as well have a guyed tower.
If the tower hasn't actually been designed to be guyed, I doubt that you will
be able to use a long enough mast to separate the antennas the required
distance without exceeding the windload rating on the tower.
Hope this helps.
73, Dick WC1M
From: Roger Cooke [mailto:email@example.com]
Sent: Friday, December 10, 2010 2:04 PM
Subject: [TowerTalk] Stacking a 402CD over a Steppir
Due to planning problems ( we have to live with those in the UK! ) I might
try putting the 402CD above my
4-el Steppir. I have a tilt-plate and wondered if anybody has done this, had
problems or has comments!
I am using a Westower 120ft tower, crank-up, guyed in place.
Regards from Roger, G3LDI
TowerTalk mailing list