[amsat-bb] Re: Question re WA5VJB "Cheap Yagiis"
JamesDuffey at comcast.net
Fri Nov 14 18:58:32 PST 2008
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!! ;)
> 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
>>> so decided to build one for 435.
>>> Couple of questions:
>>> For the driven element "hairpin" or J, it shows 1/2" dimension for
>>> spacing--knowing this might be critical on 435, is that INSIDE
>>> or OUTSIDE spacing??
>>> Also, I noticed what appears to be unusual element spacing for the
>>> 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??
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>> James Duffey
>> Cedar Crest NM
Cedar Crest NM
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