[amsat-bb] Re: Question re WA5VJB "Cheap Yagiis"
cptcurt at flash.net
Fri Nov 14 18:51:26 PST 2008
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
Now I just thave to get a 300.00 antenna analyzer to figure out if the
match is good on the $10.00 antenna!! ;)
James Duffey wrote:
> Curt - I have built lots of there. I use the 1/2 inch as the inside
> 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
>> Is this a result of the computer design for easily progressive build, or
>> perhaps some error in the dimensions posted on-line??
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> James Duffey
> Cedar Crest NM
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