[amsat-bb] Re: Question re WA5VJB "Cheap Yagiis"

[Curt Nixon]

Thanks James.

Yes that is the way I layed them out--using a long rule.  I'm an old 
gage designer so understand cumulative error stackup.

Those are the same differences I have, but when the chart is used for 
the next two elements for a ten element unit, the spacings just look odd.

I'm going to build it as specified.  It is that way on several pages so 
probably OK.



Now I just thave to get a 300.00 antenna analyzer to figure out if the 
match is good on the $10.00 antenna!! ;)

Curt


James Duffey wrote:
> Curt - I have built lots of there. I use the 1/2 inch as the inside 
> dimension.
>
> It is best to measure the spacing as cumulative from the rear, not 
> incremental. That eliminates cumulative errors. ANd you don't have to 
> subtract. Use a tape measure, or you can buy a 5 or 6 ft steel rule 
> pretty cheaply at Lowes or HOme Depot.
>
> Here is the referencce I use for LEO antennas:
>
> < http://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf >
>
> Here is what I get for the spacings when I subtract: 5.75, 6.25, 6.5, 
> 6.5, 7.25. I think that this is reasonable.
>
> But don't subtract measure it all from a single reference point, the 
> reflector. The antennas work great. - Duffey
> On Nov 14, 2008, at 11:47 AM, Curt Nixon wrote:
>
>> Good afternoon:
>>
>> Hi have liked the way the WA5VJB Kent Britain 144Mhz cheap yagi worked
>> so decided to build one for 435.
>>
>> Couple of questions:
>>
>> For the driven element "hairpin" or J, it shows 1/2" dimension for the
>> spacing--knowing this might be critical on 435, is that INSIDE spacing
>> or OUTSIDE spacing??
>>
>> Also, I noticed what appears to be unusual element spacing for the last
>> directors in both the 435 and 432 versions.  The spacing increments seem
>> to follow an increasing spacing trend but then the last couple are
>> different.  ie  spacing goes ...6.25, 6.5, 6.5, 7.25, 7.25, 7.0, then 
>> 7.5.
>>
>> Is this a result of the computer design for easily progressive build, or
>> perhaps some error in the dimensions posted on-line??
>>
>> Thanks,
>>
>> Curt
>>
>> KU8L
>>
>>
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>
> -- 
> KK6MC
> James Duffey
> Cedar Crest NM
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