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

[James Duffey]

Well Curt, I have the 10 element 432 version up and running FB. I
don't have a 432 MHz analyzer, but these antennas are pretty much
build and play. I wouldn't worry about tweaking them too much. - Duffey
On Nov 14, 2008, at 7:51 PM, Curt Nixon wrote:

> 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
>>
>>
>>
>>
>>
>>
>

--
KK6MC
James Duffey
Cedar Crest NM