[UK-CONTEST] : A3S

[Colin Wilson]

George
you might well be right on that one unless its the 10m trap thats gone?

73

Colin CT7ACG/G3VCQ
www.sheffield-live.co.uk
e. colin at sheffield-live.co.uk
t. +351912884618

----- Original Message ----- 
From: "G0JKZ" <g0jkz at terminalcomputers.com>
To: <steve at m0bpq.com>; <uk-contest at contesting.com>
Sent: Wednesday, February 01, 2012 2:33 PM
Subject: Re: [UK-CONTEST] A3S


> 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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