[K3PZN-List] Mobile Antenna Question

[John Hoge]

The whip at the end of the ATAS-120 provides a capacitive element that  
resonates with the coil. If it's too short, the antenna may not be  
able to tune to a sufficiently low SWR. That's most likely to happen  
on 40, 30, and 20 m.

73 de W3JJH

Quoting Curt Milton via K3PZN-List <k3pzn-list at mailman.qth.net>:

> Nick
> well there might be advantages to avoiding those places -- but I get  
>  your need. 
>
> I am not familiar with the mechanical construction, so I can't speak  
>  to that - but if the whip is merely aluminum then there is no  
> impact. 
>
> I am thinking the only loading coil is at the bottom so then its   
> merely the percentage difference of this antenna, so this is a loss   
> of something like 10%.  You would notice a 25% difference in   
> efficiency, but this sounds a bit smaller impact.  I guess there is   
> no practical way to tilt it a bit, as I would also consider that   
> option. 
>
> yes do obtain some more answers before cutting. 
>
> 73 Curt
>
>
>
>      On Tuesday, June 16, 2015 7:15 PM, Nick Proy (WT3O)   
> <wt3o at proylaw.com> wrote:
>
>
>  Good Evening Everyone,
>
> I have a mobile antenna question. I think I know the answer, but I   
> wanted to see if anyone else had any thoughts.
>
> I just got a new F-150 and want to install my FT-857 and ATAS-120   
> antenna. This year's F-150s are a little taller than previous years.  
>  If I put my ATAS-120 on the bed rails via a bed stake pocket mount,  
>  the antenna will be about 9 1/2 feet from the ground to the top of   
> the antenna. I'd still like to go through drive thru (banks, fast   
> food, etc...), but most clearances are about 9 feet. I was thinking   
> of cutting off about 8" of the ATAS whip and let the loading coil   
> pick up the difference. I can't imagine 8" would make a huge   
> difference on 20M or 40M (or even VHF with the auto-tuning antenna).
>
> Does anyone see any problems (other than a slight performance   
> decrease) with cutting off a few inches of the whip?
>
> Thanks and 73!
>
> -Nick (WT3O)
>
> Sent from my iPhone
> ______________________________________________________________
>
> 73 de K3PZN Westminster, MD
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> ______________________________________________________________
>
> 73 de K3PZN Westminster, MD
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73 de W3JJH
John