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December/2013
Mt Duncan VK7RMD UPGRADE
Tower is to be installed with new solar panels and cabinet.  The old mast
 has reached the end of its useful life and a new sturdy tower structure is to
be installed. The panels totalling 1kw will capable of maintaining battery
charge over winter.  

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Tripod Support for Portable Masts
Details

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Projects under way


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Mt Duncan VK7RMD battery replacement - Completed 1/7/2012
The old batteries have reached the end of their life and have been replaced.


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Welcome to the first of our construction  projects
END FED 1/2 HALF WAVE DIPOLE for 2M


All you need are the materials as follows-


* 1.5m long, 10mm dia. fibreglass electric fence pole - available from any farm material supplier
(For local builders - Sargents rural supplies, Wellington st,
 South Burnie Tasmania). Cost $5


* A short (1-3m long)  RG58 coax  with PL259 connector attached one end. A second piece of RG58, 100mm
long (no connectors) for capacitive tuning stub.


* Braid (maybe from old  RG8, RG213 coax, etc) to fit over and cover
the fibre glass rod for a distance of  at least 1metre. 


* A supply 0.85mm enameled wire.


* 16mm dia. heat shrink tubing 1.2m long. Jaycar have in catalogue
at
less than $4 and so should be available at Leading Edge, Burnie, etc.

http://www.jaycar.com.au/heatshrink

Will need a heat gun (or hairdryer) for the heatshrink.

At less than $15 total cost, this works out to be a cheap, sturdy, lightweight
2m ground independent  vertical, ideal for home or portable use.

To get best SWR the coaxial capacitor is made about 100mm long and cut a
few mm off at a time. This is the tuning capacitor and brings circuit to resonance.

My stub ended up about 25mm long. If you cut off too much
then you will need a new peice of coax and have to start trimming again.   

Also adjust the spacing of the coil turns below the feed point
tapping or move tapping point around to bet the best match at the same time.

Another technique is to use a trimmer capacitor  to see if you get a 1:1 match.
If not then then adust the lower turns spacing or tap point until a 1:1 can be
achieved  by adjusting the capacitor. Once this is achieved the the trimmer
can be removed and coax tuning stub can then be trimmed to the same value
as the trimmer. The coax is used as it is more structurally unobtrusive under
the heatshring which is applied and less likely to be damaged.
Heatshrink is applied over the whole antenna and coil for
 the waterproofing. The heatshrinking process may have an adverse
effect on the final SWR
 

I have already built the prototype and found it performing well,
and has VSWR of  less than 1.2/1 across 2 metre band..



   Construction details


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