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@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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>>
>>
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