[TowerTalk] Increasing power capability of 6-meter yagi

[David Gilbert]

Cushcraft has been making antennas for a very long time.  I wonder if 
the design of that model simply dates back to when hams were only 
allowed 1 KW.  Maybe nobody bothered to update the rating.  The only 
other reason I can think of for why a standard yagi wouldn't be able to 
handle more power is if it had a gamma match with a smallish capacitor.  
Almost any other feed system should handle more than a KW unless the 
connections other than the SO-239 (straps, screws, etc) are really flimsy.

Dave   AB7E



On 7/31/2022 6:25 AM, Lux, Jim wrote:
> On 7/31/22 6:01 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?
>>
> The rating might be derived from "only tested to 1kW"
>
> But if it's design limited, it's either current at the feed point 
> (Yagis often have very low feed point resistance, which is transformed 
> up to 50 ohms by the matching network, or by using a folded dipole at 
> the feed) or voltage at the element tips (hard to model, usually 
> validated by testing).
>
> 1kW into 20 ohms is 7 Amps - Easily handled by a UHF connector, but 
> what does the rest look like?
>
>
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