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N5YPJ
01-14-2013, 09:34 PM
Up until today my Cushcraft A3S had near 1:1 SWR readings on 20 - 10. Now all of a sudden I have a very high SWR on 10 meters, 15 & 20 meters are unaffected. Has anyone has this trouble before or have any ideas on how to troubleshoot what I assume is a problem trap in the driven element? I don't have much hands on experience with tribanders so any advice welcomed.

KO6WB
01-14-2013, 10:40 PM
Hum...well since 15 and 20 are okay then the 10 meter trap could be a problem. Could be the capacitor in the trap has a bad connection. Not sure which side is affected nor exactly which element. A high but usable SWR on 10 would indicate the director or reflector are likely the problem but if the SWR is nowhere near workable then I'd look at the driven element very carefully. The ten meter traps are the first ones from the center boom going out the element. If the traps are good enough when they do work then removing the trap will make the antenna only long enough to work the 10 meter band. It should block anything from the 10 meter band from going further. So remove the 15 -20 meter driven sections and place the 10 meter traps on the exposed ends. Check you SWR on 10. It should be good now. If not then remove the traps entirely. The resonant frequency will be a bit higher than it was but it should have a point where it's acceptable. One of the 10 meter traps is bad.
If the traps don't throw the SWR off then using a clip lead of wire or inserting the 15-20 meter section on one end of a 10 meter trap clip the wire to the end or slide the 15-20 meter section back in. Now check the SWR. Did it just jump up to a high level? If so that trap is the villain If not then try the other side. One of those should be the bad guy. Test it anyway. If it's a director or reflector causing the problem then just do exactly as you did for the driven element.
BTW the traps are all labelled as TA traps and as a result any TA trap can be used in place of any other TA trap. You can simply use just the driven element and find your problem that way.
Hope this helps
73
Gary

W9GB
01-14-2013, 11:57 PM
Refurbishing a Cushcraft A3S
George Szymanski, DU1GM
http://www.para.org.ph/membersarticles/A3S/

WB2WIK
01-15-2013, 01:57 AM
Sounds like a bad 10m trap to me.

I'd take it down, remove the covers from the 10m traps on the driven element, and see what's going on.

N5YPJ
01-15-2013, 10:59 PM
Problem found and corrected. Many thanks to all who replied!:)

WB2WIK
01-15-2013, 11:06 PM
Problem found and corrected. Many thanks to all who replied!:)

What was it? Was it a bird? Was it a plane?

<SPLAT!>

It was a bird...

N5YPJ
01-15-2013, 11:41 PM
What was it? Was it a bird? Was it a plane?

<SPLAT!>

It was a bird...

An aluminum DX bird with a cracked wing!!!
A strap that goes to the trap capacitor was broken causing an intermittent contact and I suppose the high SWR. I was able to fashion a temporary patch that hopefully will hold until a new trap arrives.

KD8W
02-09-2013, 04:58 PM
Up until today my Cushcraft A3S had near 1:1 SWR readings on 20 - 10. Now all of a sudden I have a very high SWR on 10 meters, 15 & 20 meters are unaffected. Has anyone has this trouble before or have any ideas on how to troubleshoot what I assume is a problem trap in the driven element? I don't have much hands on experience with tribanders so any advice welcomed.

From what you have described, I suspect one of your 10m traps has a bad connection from outer 'can'(12" long tube) to the elem sleeve. If you want a picture, of what this looks like when dissassembled- you can send me a PM message and I'll send you a 'pic' of the . I had this problem on a couple of mine, and its pretty common problem with cushcraft traps.

cheers

KQ9J
02-09-2013, 05:39 PM
An aluminum DX bird with a cracked wing!!!
A strap that goes to the trap capacitor was broken causing an intermittent contact and I suppose the high SWR. I was able to fashion a temporary patch that hopefully will hold until a new trap arrives.

If it is just the piece of the metal trap cover that bends down and connects to the element, the link a few posts up shows how you can fix it with a hacksaw and a drill. No expense involved.