[TowerTalk] [CQ-Contest] 40-2-CD

[Grant Saviers]

The common personal printer FDM (Filament) printing has some properties 
that make it not a good choice outdoor RF applications.

Filament printing is a bit porous layer to layer, so moisture ingress is 
likely.  Add to that that the infill is commonly a grid, so there are 
big internal spaces for moisture.  Solvent sealing can help with the 
first issue and solid infill printing with the second, but that can take 
a lot of print time.

The laser or UV solidification printing technology from liquid or powder 
is claimed better for moisture absorption. Of course need a resin with 
good RF properties.  I have no experience with them but have printed a 
some temporary outdoor use RF parts with my FDM printer.

There are lots of interesting FDM filaments available, new ones every 
month, but it is hard to find RF properties for some of them.  Some data 
I've found shows large variations among suppliers, I think due to additives.

If new insulators need turned, I would suggest black acetal (Delrin) as 
the material.  Excellent mechanical properties and much nicer to machine 
than PVC or ABS or UHMW.  Costs more though.

Grant KZ1W

Not committed to saving electrons.

On 2/28/2020 08:18, Richard (Rick) Karlquist wrote:
> Is there any chance that custom tubing can be
> 3D printed instead of made on a lathe?
> 
> Rick N6RK
> 
> On 2/28/2020 6:04 AM, john at kk9a.com wrote:
>>
>> You can purchase plastic tubing at McMaster-Carr in a variety of types 
>> and sizes.  If you cannot find something that fits the 1 1/4" 
>> Cushcraft element you may have to bore the inside diameter of the 
>> insulator on a lathe.
>>
>> John KK9A
>>
>>
>> Shelby K4WW wrote:
>>
>> insulator, for 40-2-CD?  If not, an alternative mounting solution? After
>> "only" 32 years mine has disintegrated. To save band width, please reply
>> off list
>>
>>
>> 73, Shelby - K4WW
>>
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