[TowerTalk] [Bulk] A4S questions/INFO

[Grant Saviers]

I have an A4S, used for Field Day.  The tuning - element lengths and 
spacings are critical - so check and recheck them, something may have 
slipped.  You won't get accurate measurements of swr at 7' off the 
ground, probably 25' height is needed.  I also have to be at least 50' 
from my steel shop to have it work ok when up 45' on a pneumatic 
Will-Burt mast.  The driven element insulator deteriorates from UV (FR4 
tube) so replacing it with a new solid rod may help. If the trap rubber 
boots are cracked you can get new ones from MFJ at a reasonable price.  
Are all of the trap drain holes pointing down?

There are some other mechanical improvements I've made in the boom and 
element clamps   I sleeved the boom at the mast clamp, it is very easy 
to flatten it.  Same for a couple of the elements inside and outside 
sleeves after an overly enthusiastic FD assembler flattened the element 
center.  I cut out the damaged center and sleeved about 18" so now they 
are triple wall.

The stamped element to boom clamps can be improved as the elements 
always seemed to get skewed when it was permanently installed in a high 
wind environment..  They tend to splay out, so I drilled them for a 
stainless 6-32 machine screw and nut on both sides of the boom to 
prevent that from happening.  You can get 3' lengths of tubing from DX 
Engineering in the sizes needed.  My boom filled with water so I notched 
the caps for a small drain hole, too small for wasps etc.

Grant KZ1W


On 11/10/2014 2:12 PM, Yuri wrote:
> I have Cushcraft A4S which I haven't been using for a while. It worked perfectly and was tuned to CW portion of the 20,15 and 10 m bands.
> Few days ago I noticed that SWR on 10 meters went up (to approximately 4:1) and antenna started to resonate well above 29.0 MHz. At the same time the resonant frequency moved higher on 15 m, but is still tolerable in the CW portion (1.6:1).
> 20 m remains unchanged.
> I took it down today and examined the traps. They all look O.K. except I found few small spider nests inside. Also checked them for dc which appears to be fine.
> It's on the step ladders about 7 feet above ground level now.
> Is there anything I can do? Anybody experienced same problem before?
> Any tip would be appreciated.
>
> Thanks.
>
> Yuri  VE3DZ
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