In article , Tom wrote:

I am looking to cut an antenna for 70cm. I have seen lot of designs for the
dual band like Slim Jim or J Pole or Ladder Line. Lots online but they are
dual banders.

Anyone have a good recommendation for a single band 70cm antenna? I have
ladder line (450ohm) and I have RG8u coax with bnc connector on one end
(about 25ft.)

Any ideas for a single band 70cm? Can someone post a good link or good
dimension? I don't have a "Dip meter or antenna analyser".

Take a look at the following.

http://www.repeater-builder.com/ante...20-440-mhz.pdf

It shows simple ground-plane antennas for several bands. As drawn it
uses a SO-239 "UHF" socket connector as the basis for the antenna.
You could also use a female BNC connector, which would connect easily
to your RG8u BNC cable. The mounting plate can be aluminum (as they
suggest) or a scrap of single- or double-sided PC board material.

One useful tweak, is to cut the upper radiator wire an inch or so
longer than you need, and bend the upper end into a closed loop
and solder it. If you cut the wire so that the entire length from
connector to loop matches the dimensions in the article, it'll behave
the same way electrically... and you can run a length of heavy-duty
fishing line or some other insulating string through the loop and use
this to hang the antenna.

Ground-plane antennas of this sort can be very effective. The gain
towards the horizon differs very little from that of a J-pole or other
half-wave radiator, and the construction is easy and non-critical.
Cut the wire lengths to match the dimensions in the article (this sets
the resonant frequency), assemble, hang it up in the clear, and you're
good to go. If you do get ahold of an antenna analyzer or 440-capable
SWR meter you can tweak it for the best match (trim the radiator
and/or radials, and adjust the downwards bend-angle of the radials)
but this really shouldn't be necessary in practice.


--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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