Given caveats stated below, the short answer is I'd bet with odds it
wouldn't make much difference.
Long answer:
One of the benefits of an end-fed half-wave L on 80 meters is the hi Z
feed, tolerating ghastly ground systems, and having all the current up high
at the bend. Arguably, this makes the 80EFHWL the best single wire 80m
antenna for a mix of DX and local (therefore also contesting) operation.
The huge drawback for most is the need for an out-in-in-the-weather tuning
device as you cannot feed it directly with a run of coax. It also is fairly
narrow band, except for CW only operators. Those who need the entire band
need to so something not-simple at the ground feed to cover a significant
range of the 75-80m band.
The half square is two of those end to end, coming together in the middle
of the 1/2 wave horizontal. On 160 that's 539 feet of wire up in the air.
If you got the space and support for that and you want that broadside
direction, that's going to be a killer antenna.
Many of the half-square illustrations show a low Z feed at one of the upper
corners. That would avoid some of the issues at ground with high Z feed.
BUT the feedline would need to be broken up at the feed and halfway going
down, and at the bottom with VERY robust common mode current blocks. See
some of K9YC's new RG400 on #31 ferrite choke designs with 15K+ ohms of
blocking for something that would actually do the job with very minimal
power loss.
The other answer, as you have implemented to to deal with the high
impedance feed at one of the ends. This requires that at the end the
antenna looks like an electrical full wave wire.
Equal coils at the corners have sometimes allowed smaller physical
dimensions. But as soon as you start modifying the antenna, then questions
emerge which need modeling to answer. So there is no certain
one-size-fits-all answer to your question without model analysis of the
not-quite-half-square you have in the air. Versions with modified
dimensions have to be carefully designed to avoid dropping back into ground
involvement and possible related losses.
Given your 2000 ohm end to ground feed Z of the "modified" version you have
up, you have PROBABLY managed to avoid issues that would kill its ground
independence.
To answer the question far more completely, model it along with any
antennas and conductors within a 500 foot radius, INCLUDING TOWERS AND
FEEDLINES.
The half square is a great idea that can be screwed up with less than full
implementation, or like many other excellent designs, can be totally
screwed to the wall by unconsidered nearby conductors.
73, Guy K2AV.
On Tue, Jan 8, 2019 at 3:45 PM Dick Bingham <dick.bingham@gmail.com> wrote:
> Hello Guy (and the group)
>
> I just finished reading your reply/observations on 160-Meter verticals -
> L's, etc - and wonder what your thoughts may be for the so-called
> "Half-Square" antenna (H-S) where the high current point is at the top of
> the array and the antenna is high-voltage-fed at the bottom.
>
> I have a terrible QTH situation where ground conditions are very poor -
> basically river deposited gravel
> and sand sub-soaked by glacier and snow-melt water covered by several feet
> of organic matter. It is an electrically quiet area - S-0 or so - with
> noise basically all propagated non-man made noise.
>
> The H-S antenna I use (actually a sloping H-S with top phasing wire at
> ~90-feet) has 5ea 136-foot radials and performs very well in contests using
> 100-watts or less.
>
> My question is, given the low current at-ground feed point with Zo ~
> 2000-ohms or so, what sort of improvement might one expect if the radial
> field was significantly improved?
>
> 73 to all - Dick/w7wkr at CN98pi
> =============================
> Message: 1
> Date: Mon, 7 Jan 2019 12:07:16 -0500
> From: Guy Olinger K2AV <k2av.guy@gmail.com>
> To: Todd Goins <tgoins@gmail.com>
> Cc: TopBand List <topband@contesting.com>
> Subject: Re: Topband: Inverted L improvement question
> Message-ID:
> <CANckpc26fGej-K2sQQ0iDkHu+73y+S8VJeKCtbkKv5F3ukzgjQ@mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> Apologies to all for delay in response.
>
> Losses related to ground and close dielectric materials remain the
> single monster gorilla in the room for improving TX performance of
> vertical antennas
> BIG SNIP
>
>
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