Posted by
Martin Gillen on
Jan 04, 2006; 11:06pm
URL: http://elecraft.85.s1.nabble.com/T1-Antenna-Considerations-tp385235p385248.html
Hi, Mick.
> please can someone explain why this is important
As previously stated a halfwave end fed wire
represents a very
high impedance which is outside of the matching range
of the
T1.
But thats with no counterpoise or fed against a ground
stake.
I have found that a halfwave long wire works as long
as it is fed
against a raised counterpoise, ie. a wire lying over
some nearby
bushes. In this case it works because the two wires
are really an
off center fed dipole with the radio in the middle.
The end fed halfwave wire does have some interesting
characteristics and people do use them, for example
they are
quick to erect DX antennas because they gave a very
low angle
of radiation. You just have to make another matching
circuit to bring the imedance into the matching range
of the T1.
Check these web pages for details:
http://www.aa5tb.com/efha.htmlhttp://www.njqrp.org/n2cxantennas/halfer/index.htmlhttp://www.angelfire.com/electronic2/qrp/efhwt.htmlhttp://hometown.aol.com/n0lx/triband_tuner.htmlhttp://www.arsqrp.com/ars/pages/back_issues/2000_text/1100_text/phased.htmlFor excellent antenna information in general try:
http://www.cebik.com/radio.html> i wish to use this tuner on the following bands
20/15/10m
> so a suggested wire length would be appreciated I
only have
> 40ft of space to play with.
Is that 40ft by 40ft or is it 40ft by 10ft :) ... Are
there any
trees or other antennas in that space? What kind of
contacts
are you interested in making? QRP? QRO? Local? DX?
One antenna for all bands or separate antennas?
For example if you are interested in DX, you can
probably fit
a full wave loop for 10m into your lot, or even a
cubical quad
which would give excellent performance.
For local contacts you could consiter a doublet fed
with twinlead
or even a fan dipole fed with twinlead.
If it's just a single wire length, are you planning on
feeding
it at the end? Or in the centre? Against a
counterpoise or
against ground? For a quick throw-wire I'd use 42
feet with
a 14ft counterpoise. Bend the extra 2 or 3 feet at 90
degrees
if you have to make it fit into your 40 feet. You
could also
use linear loading by using twinlead to put up a
folded dipole,
or many other ideas.
Martin.
VA3SIE.
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