[TowerTalk] Wind survival + load ratings... vs reality.

[Richard Thorne]

Matt,

I agree with the support.

I was on the phone with Ken on a Sunday resolving an end user mistake on 
the JK3040SR.  I had installed the phasing line backwards.

After fixing the initial problem,  he had me change a couple tip lengths 
on the 40m elements.  I raised the antenna on the tram, took some 
measurements,  which he then modeled, followed by a couple more tip 
length changes.  He was helping me hone it in for my specific 
location/ground conditions.

It's now a point and shoot affair on 30 and 40 meters.

Tough to beat.

Rich - N5ZC

On 10/31/2017 4:02 PM, Matt wrote:
> I have been extremely impressed with my JK antennas and more importantly...
> the support I've received when I had questions or wanted to make changes.
>
> Best,
>
> Matt
> K0KB
>
> On Tue, Oct 31, 2017 at 3:41 PM, Richard Thorne <rthorne at rthorne.net> wrote:
>
>> Jim,
>>
>> Good info.
>>
>> I don't have the #'s to back up my results as you do.
>>
>> I only have empirical info that coincides with your data.  I replaced an
>> M2 40mLLDD with a JK SR3040 due to a bent element from a wind event.
>>
>> This past summer I installed a JK801, JK SR3040 and a pair of Mid-Tri's.
>> Beefy is a understatement.
>>
>> Time will tell....
>>
>> Rich - N5ZC
>>
>>
>>
>>
>> On 10/31/2017 1:53 PM, Jim Thomson wrote:
>>
>>>     Has anybody tried stuffing yagi manufactures  ele dimensions into
>>> software  like  Yagi stress.....  and  or  Yagi max ????
>>>
>>> I have been doing just that on a bunch of them...and in several cases, Im
>>> not impressed with the results.
>>> And Im using the correct dimensions for exposed length tubing, and
>>> correct OD and wall thickness, and correct
>>> yield strength.    Im  using both the ... no spec..aka  wind tunnel
>>> spec.......and also the old  C spec.
>>>
>>> Some of these yagis that are rated at ...  100 mph are actually only good
>>> for a paltry  64 mph...and that’s  with NO ice,
>>> such is the case with the M2  80m yagis.   Their  3 el  80m yagi uses C
>>> specs for  wind area.  They rate it at 32 sq ft.
>>> Its actually 48 square foot of projected area.   Their combo truss  +
>>> LL  does nothing for ice loading, and nothing for
>>> horizontal deflection.    The LL reduces some ele sag, thats it.   Both
>>> YS + YM spit out 64 mph  using  no spec..and
>>> both spit out  69 mph, using C spec...and that’s with NO ice.
>>>
>>> Toss just .25 inch of ice into the mix, and it becomes   48 mph  using no
>>> spec....and    52 mph  using C spec.
>>>
>>> The optibeam 80m yagi doesnt fare much better.  Good for  72 mph, using C
>>> spec....and less using  no spec....and that’s with NO ice.
>>>
>>> I also tried the JK antennas   3 el 80m yagi in YM  + YS.   Using no
>>> spec, it comes in at  103 mph.  Using C spec, its good for  107 mph.
>>>
>>> Now that’s a helluva  big difference between  m2s  64 mph...and the JK’s
>>> 103 mph.   Considering the M2 is not cheap at  $9935.95
>>>
>>> I have also stuffed several other yagis, like 40m, and  20, and
>>> multibanders  etc  through the software.  Eye opener,  but not as bad as
>>> the 80m yagis above.   I tried Mosley, Hy-gain, old telrexs,  KLM, and
>>> anything else I could get exact dimensions for.
>>>
>>> Back in the day, ant makers could get away  quoting BS  gain and FB
>>> numbers...... until software came along.    They are still  doing it,
>>> but with BS wind load ratings, and max wind survival ratings.     The
>>> mechanical software is readily available, so why isnt anybody holding them
>>> accountable ?
>>> In a lot of cases, hams are being sold a... bill of goods.
>>>
>>> Jim   VE7RF
>>>
>>>    _______________________________________________
>>>
>>>
>>>
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