On 11/29/2010 02:09 PM, Rick Karlquist wrote:
> Rik van Riel wrote:
>> On 11/27/2010 09:08 PM, Rick Karlquist wrote:
>>
>>> VK1OD did a nice analysis. Unfortunately, many hams are simply
>>> in a mode of "don't bother me with facts". They desperately want to
>>> believe in the paradigm of a tuner in the shack and a simple all band
>>> antenna at the other end of the line, such as a plain vertical
>>> conductor,
>>> or a random wire, or a "loop skywire", a "G5RV," or some sort of
>>> "Windom"
>>> antenna. All continue to live on in ham folklore.
>>
>> The big horizontal loop antenna seems decent, provided it is
>> cut at a length that gives it a good match on not just the
>> primary band but also the others:
>>
>> http://surriel.com/radio/multi-band-hf-loop-antenna
>
> Are you kidding me? The pattern breaks up into a multitude
> of lobes on the higher frequencies. This is the fundamental problem
> with any simple conductor used on many bands with a shack based tuner.
Definitely agreed there. On 15 and up the nulls are
often noticable.
On 20 and 17, the lobes are still very broad and the
nulls are very narrow, but I do suspect a null on 20
towards Antarctica and another one towards New Caledonia.
I suspect there's one towards the Faroe Islands, too.
On 20m the nulls are narrow to the point that the Faroe
Islands are hard to work, but Iceland and Scotland are
fine. Antarctica is hard, but South America seems to
be just fine (with the possible exception of Bolivia).
In fact, after using the antenna for a year I am still
not completely sure where exactly the nulls are on 20m
and 17m...
On 40 & 30 the nulls are so shallow the antenna might
as well be omnidirectional.
I do plan on adding other antennas later: first something
to work 160, probably a double L (aka lazy U) since it is
somewhat decoupled from ground and New Hampshire has very
poor ground...
For 80m I'm thinking of building a 2 element bruce array,
so I get good gain east (africa, middle east) and west
(continental US & pacific). Incidentally one of those
also works well on 60m, with gain east/west.
For 20 and up I'd like a hex beam at some point, but I
might end up with fixed in-phase dipoles instead (lazy
H configuration).
I know the 80m loop is not a miracle antenna, but you
do not need miracles to get decent performance on 8 of
our 10 HF bands.
--
All rights reversed.
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