[TowerTalk] CushCraft A3

Bill Coleman aa4lr at arrl.net
Thu Sep 15 21:24:32 EDT 2005

On Sep 10, 2005, at 12:25 PM, nd8l at juno.com wrote:

> I have been offered a CushCraft A3
> and plan to use it on my tower fixed
> to Europe.  Anybody know where I can
> purchase or otherwise acquire a manual?

As other people have mentioned, these manuals are available on the  
Cushcraft web site.

> Any tips on re-habbing/testing the beam
> prior to installation?

Depending on how it was previously assembled, pulling the boom apart  
may be difficult. Since the boom is only 14 feet, I wouldn't bother.

Check the traps thoroughly. What's the condition of the end caps? If  
they are cracked or loose, I'd replace them. Cushcraft wants a fair  
amount for each one, so replacing them should be done judiciously. I  
spent almost $40 replacing all 24 on mine a few years ago.

One way to make them last a bit longer is to wrap a layer of black  
electrical tape around the cap. Just one layer to keep the sun off.

Make sure the traps don't have any insects, grass or other debris. If  
you pull the end caps off, run compressed air through the trap.  
Tighten the screws at both ends -- they provide the electrical  
connections for the trap and can loosen or corrode.

When assembled, point the A3S skyward with the reflector 3-4 feet off  
the ground. You should see some clean SWR curves on an antenna  
analyzer in this position. The resonant point should rise a few dozen  
kHz when mounted on the tower.

Oh, and when you assemble, considering using dimensions half-way  
between CW and Mid. This very effectively covers just about the  
entire width of 20m and 15 - with a good chunk of 10m to boot. If you  
are a CW-only buff, then use the CW dimensions.

> My inital plan
> is to replace all the hardware/clamps,
> scotchbrite and penetrox.

The A3S hardware is stainless, so it may not need replacing. Inspect  
it first. Penetrox is a great idea for re-assembly.

> One other thing...the tower is 50'...I'll
> have a two element Cubex quad at about 55'
> in a square configuration.  What sort of
> spacing would prevent the A3 from interacting
> with the quad?

That's going to be a problem. Any spacing you'd use is going to  
interact with the quad, or going to be so low as to affect the  
pattern of the A3S. I'd try about 15 foot spacing. Check the SWR  
curves of the quad before and after adding the A3S. That should give  
you some idea of the interaction.

At 40 feet, the A3S will have a pretty broad pattern on 20m, and the  
angles will be pretty high. You'll likely get almost no benefit from  
phasing it with the Quad.

Good luck.

Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr at arrl.net
Quote: "Not within a thousand years will man ever fly!"
             -- Wilbur Wright, 1901

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