[NLRS] [BC'ers] Fwd: Re: Anybody have experience with multi-band feeds?

[Dr. Gerald N. Johnson]

I know I've seen more detailed data on looper gains vs length, but I 
haven't found it lately.

2.5 dB for doubling the length is usually achievable, 3 isn't usually, 
nor is it always possible to get more than 2.8 for stacking a pair of 
yagis. In stacking there is always a conflict between greater main lobe 
gain and the strength of side lobes.

73, Jerry, K0CQ

On 3/20/2011 7:22 PM, tom ring wrote:
>
>
> On 15 Mar 2011 at 18:18, Dr. Gerald N. Johnson wrote:
>
>>
>> At 1296, N6CA says 6' of boom gets 18 dBi and 12' of boom gets 20.5 dBi.
>>
>
>> From my studies of buildable high gain V/UHF yagis and the equation I derived,
> this seems about right.  I used over 100 yagis and a significant percentage
> were K1FO.  Gain of long yagis (>1WL) expressed as a multiplier is linearly
> related to boom length.  Interestingly it intercepts 0 length at very nearly
> 6dB.  I've always wondered about that.
>
> So double the length can give you at best 3dB if the yagi is very long and the
> design is perfect.  +2.5 for double the length isn't bad if correct.
>
> tom
> K0TAR
>
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