[TowerTalk] Increasing power capability of 6-meter yagi

[Mpridesti]

Joe

You make perfect points here!

No doubt the gamma was designed around a KW power level but the reality is, it was probably ok for 500 watts. Power limit was 1 KW input with 50% efficiently, a 500 watt design target was the case. Now envision 1500 output to the antenna feed point. Yep you will have problems!

Other related Cushcraft power limits come with the A3/A4 tribanders- no more than 1200 watts here. 

Regards,

Mark, K1RX


> On Jul 31, 2022, at 9:51 AM, Joe Subich, W4TV <lists at subich.com> wrote:
> 
> 
>> On 2022-07-31 9:01 AM, Pete Smith N4ZR wrote:
>> It looks to me that this limitation might relate to the feedline connection, which is a bulkhead SO-239 (mounted with a big nut) bracketed to the center of the driven element.
> I would bet that the limitation is due to the breakdown of the
> dielectric in the gamma match (capacitor).  CushCraft used a
> rod from the center conductor of the UHF connector through a
> dielectric tube inside an aluminum tube that formed the outside
> of the gamma match.
> 
> If 1KW is a real limitation, I doubt that you can do anything
> to improve it except redesign the antenna for a split driven
> element and 50 Ohm feed.  That 7' boom would make a nice 4 element
> OWA.
> 
> 73,
> 
>   ... Joe, W4TV
> 
>> On 2022-07-31 9:01 AM, Pete Smith N4ZR wrote:
>> I have just bought a small Cushcraft 3-element 6-meter yagi.  Only small fly in the ointment is that it is *only* rated at 1 KW.  It looks to me that this limitation might relate to the feedline connection, which is a bulkhead SO-239 (mounted with a big nut) bracketed to the center of the driven element.
>> My question is, do I need another connector here, or maybe insulation between the bracket and the element?  If so, what material makes sense? Any other advice?
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