[TowerTalk] Imperial vs. metric tube size

HA3LN list at ha3ln.hu
Tue Sep 16 18:30:56 EDT 2014


Hi,

I'm wondering if I find a Yagi taper schedule (imperial) like this for 
6el 20m
how I should "translate" them into European tube diameters?

...for example:
         1       0.875   0.75    0.625   0.5
0.00    48      24      44      36      65.73
90.00   48      24      44      36      58.70

1 inch (25.4mm) is easy, we have D25mm tube.
0.875 inch (22.225mm) is still OK, we have D22mm

But, what I should use in case of
0.75 inch (19.05mm), we have 18mm or 20mm diameter.
0.625 inch (15.875mm), we have 15mm and 16mm (I think this should go for 
16mm).
1.25 inch (31.75mm), we have 30mm and 32mm. Should it be 32mm?

In general:
How critical the tube diameters are when I match them from the imperial 
model to the metric?
Can I maintain the same modeled performance if I have ~5% difference 
between metric and
imperial modeled diameters?
Is there any % tolerance?

I know re-modeling would be the best but I'm not an expert in that which 
I could rely on...


Thanks a lot for your help in advance.


73!
Csaba  HA3LN



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