[amsat-bb] my 435 helix

["Mark L. Hammond" <hammond@xxxxxxxxxxxxxx>]

Hi Douglas,

The helix is a 9 turn RHCP helix for 435 MHz using hollow copper 
tubing.  It was loving crafted in the G3RUH tradition over 6 years 
ago.  (Actually, mine looks more like a red-headed stepchild than the 
beautiful work he does ;-)

I never coated the copper tubing, so is has lost its luster--but not its 
effectiveness.  My first contact on AO-40 was uplinked with that antenna :)

That was a fun antenna to build....I found a plastic bucket (seems like a 
large dish washing detergent bucket was used??) and wrapped the coil around 
it, then stretched it out.  The standoff insulators are PVC pieces; I put 
end caps on the end close to the boom, and used nuts and bolts through it 
to fasten it to the boom (which is an old TV antenna boom).  I cut notches 
in the end so the copper helix "snapped" down onto the PVC.  Then I filled 
the ends with silicone caulking.

The reflector is regular wire mesh/hard ware cloth with some galvanized 
straps to support it.  The match is a piece of flat brass from the end of 
the helix to the end connector, with the distance between the brass strap 
and the reflector varied for best SWR.  It's VERY broad banded, and easy to 
tune.

I love it.  And, it doesn't mind sitting in front of a metal cross boom on 
the array, either!  It does require some counter balance.  I used some old 
scuba diving lead for that ;-)

73,

Mark

At 05:41 PM 5/13/2001, you wrote:
>Mark,
>
>    Is that a 435 MHz Helix made of *coax* next to the dish ?
>It looks like it's a black helix and looks like it might be 435 MHz.
>
>    Details, please.
>
>Douglas KA2UPW
>dquagliana@aol.com
>
>
>
>In a message dated 01-05-13 12:05:59 EDT, you write:
>
> > The 2'x3' dish seems to work great.  It's a bit heavy, but worth it's
> >  weight.  They are ready to go for AO-40.  I bought a TranSystem
> >  downconverter and dish from him for about $80 (plus shipping) as I
> >  recall?  Bought it via eBay when he was selling them there.
> >
> >  http://camel.campbell.edu/~hammond/ham/array/dish1.JPG
> >  http://camel.campbell.edu/~hammond/ham/array/dish2.JPG
> >  http://camel.campbell.edu/~hammond/ham/array/dish3.JPG
> >
> >  73,
> >
> >  Mark N8MH
> >


Mark L. Hammond  [N8MH]

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