On 11/27/2010 5:07 AM, Joe Subich, W4TV wrote:
>> &&& good point. So if the mfj ele's are snapping clean off..... then
>> the ultimate strength must have been reduced by a whole bunch..which
>> means xtal clear to me, that mfj CAN'T be using 6061-T6 or 6063-T832.
>> Other than 6061-T6 and also 6063-T832..... I don't know what else
>> will work [that's actually readily available]. There is all sorts of
>> junk AL tubing that obviously WON'T work... and MFJ has proven that
>> point.
> When the MFJ/Hy-Gain broke, it was generally not from a single event
> failure (one large wind) but from work hardening. The elements had
> mechanical resonance which was excited under certain wind conditions.
> The elements would oscillate/flex and the constant vibration would
> cause cracking with eventual failure.
>
> The Hy-Gain V-66 (as well as the other monoband antennas) includes
> rope dampers that are to be inserted into the element tips to prevent
> the "work hardening" and tip failure.
>
> Before speculating on the alloy/temper make sure the antenna was
> installed "as the manufacturer said" ... from my experience, the
> dampers have been part of Hy-Gain monoband antenna designs for 40
> years at least (they're certainly not something MFJ added so they
> could use lower quality aluminum).
>
> 73,
>
> ... Joe, W4TV
Yeah, Joe, I had that happen on an element tip for a pre-MFJ 103BA that
we stuck up at W8LT back in the mid 80-s.
73, Mike W4EF................
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