[TowerTalk] Stacking distance?

[Grant Saviers]

Paul,

There are now three versions of the 40m Moxon by Dave Leeson, W6NL.  The 
original XM240 (v1) mods, an strengthened XM240 "100 mph W6NL/Moxon for 
K3LR" (v2), and a scratch build "120 mph" (v3).  K6KR and I are building 
two of the v3s from scratch.  If your location is wind or ice challenged 
you might want to make the v2 mods which adds some 1 1/4" sch 40 6061-T6 
pipe in the center to strengthen the elements.  Some other parts and 
dimensions also change a bit.

I found that DX Engineering has much better prices (50% less!) for 
0.058" wall and 0.120" wall telescoping tubing than any commercial 
supplier in the Seattle area (if they stock it).  However, the schedule 
40 pipe is readily available locally at good prices.  On-Line Metals has 
good prices on 6061 flat stock (also has the sch 40) you might need for 
element or boom mounts.  We are using the DX Eng element clamps 
throughout since they appear to really grip well.

As for your stack distance, see 
http://www.ifwtech.co.uk/g3sek/stacking/stacking2.htm  for some 
guidance.  You can join 2" mast, but ought to use the mast calculators 
to check the loads.  You don't mention your current tower size, but 
these two antennas are a lot for 25G with a tall mast.  K6KR is using a 
3" mast for a stack on 45g and my 4L SteppIR and 40m Moxon are going on 
separate towers with 2" mast.  Your mast should also be high strength 
alloy steel e.g. 4130 etc.

Grant KZ1W

On 7/3/2011 7:51 AM, Paul Staupe wrote:
>   I'm going to be building  Moxon elements this week for my Cushcraft XM240.
> I just received a SteppIR from the same W4 who sold me the XM240, so I'm
> excited to get started.
>
> I'd like to get a feeling from the group as to the proper stacking distance
> from my 4L SteppIR.  I can get 17' lengths of 2" by 1/4" wall steel tubing
> locally which would put the distance about 10' apart.  That's probably not
> enough.
>
> I suppose that I could retract the SteppIR ribbons when I'm on the Moxon so
> it wouldn't be an issue on 40, but the Moxon can't be retracted, so it would
> affect the pattern of the SteppIR at all times.
>
> I'm reading "Array of Light" by Tom Schiller,  N6BT (the guy who founded
> Force 12) and up until now I never realized why my  "Christmas Tree" of a
> HyGain 20/40 four element duobander, a five element 15M Yagi and a 5 element
> 10M Yagi never played up to my expectations.  I put this up when I was 18 on
> top of a 90' stick of Rohn 25G using a 20' water pipe for a mast and turned
> by a Ham II.... What did I know!!!)  . According to Schiller, the F/B and
> gain of such a system was less effective than rotatable dipoles!
>
> Any ideas?
>
> 73,
>
> Paul W0AD
>
> Happy 4th of July to everyone....
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