[UK-CONTEST] A3S

[G0JKZ]

Hmmm... if it is useless on all bands the surely something else is wrong.
The a3s is a full size half wave at 10m so surely the trap at the end of the
first section should not affect the operation on 10, but only 15 and 20...
I'm probably talking crap but that's what is flying through my head with
this problem.

George G0JKZ


> -----Original Message-----
> From: Steve Bunting [mailto:stephen.bunting at virgin.net]
> Sent: 01 February 2012 12:41
> To: uk-contest at contesting.com
> Subject: [UK-CONTEST] A3S
> 
> Guys,
> 
> The recent co-ax chat has reminded me of a problem that I have with a
> Cushcraft A3S (at www.gb2gp.org.uk) and I wonder if I can tap into the
> expertise on the list.
> 
> The antenna was being used with 400W CW on 20m when the SWR shot up
> from
> 1.4:1 to over 10:1 whilst transmitting. I swept the antenna with a miniVNA
> and it is u/s on 10,15 and 20m. The antenna is fed with 60m of
> LDF5-50 and ecoflex 10 around the rotator to the co-ax choke. I use
N-types
> or 7/16 connectors throughout so don't really expect there to have been
any
> failure there and have tested at the bottom of the tower to rule out a
co-ax
> fault where possible. My hypothesis is that a trap has failed in the
driven
> element. Does anyone know if this is common with pre-MFJ A3S's? Apart
> from a failed connector at the feed point, the traps are the only thing
that
> can break - aren't they? Perhaps someone here has experience with this
> antenna they can share with me off list.
> 
> In theory this is simple to solve, but the antenna is on top of a 30m tall
fixed
> tower so trips to the top need good planning and any substantial
mechanical
> work needs a posse assembling. I am trying to be as informed as I can be
> before embarking on tower top troubleshooting and hopefully a repair.
> 
> 73
> Steve
> M0BPQ
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> 
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