[UK-CONTEST] A3S

[Darren Collins]

I recall that the antenna should have a dip somewhere if you have blown 
a trap, check 30-40MHz  for some sort of dip and you should hear 
something on 10M. If your connector at the feed point is open circuit on 
the inner pin, or the feeder has a dead short then as you sweep through 
HF you should see the impedance swing from high to low to high etc. If 
the connection to the outer of the feeder is disconnected then I have no 
idea what you would see, but again you should hear something on HF on it.

I currently have an HR connection on a SO239 coupler, just a few watts 
of RF is enough to make the connection which may last a few seconds or a 
few days. One day I'll fix it.

73 Darren G0TSM


On 01/02/2012 17:32, Chris Tran GM3WOJ wrote:
> Hi Steve et al
>
> It most likely is a trap problem, but I would still take a small 50 ohm
> dummy load with me up the tower and have a friend test the SWR with this
> dummy load replacing the yagi - I have had trouble with 7/16 DIN connectors
> that I thought were perfectly fitted, but were not.
>
> In some trap yagis e.g. the TH7, the parasitic element traps use aluminium
> wire but the driven element traps use copper wire, so in the driven element
> trap you have a mild steel set-screw holding copper wire onto an aluminium
> element - corrosion is inevitable.
>
> Often trap covers are fixed in place by small dents - you maybe have to
> either drill these out (a drastic solution) or just force the trap cover
> off, taking as much care as possible to avoid damage.
>
> You'll probably find something corroded or melted.
>
> 73
> Chris
> GM3WOJ
>
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