Topband: Inverted J antennas?

[Mike Smith VE9AA]

Hi Dave and thank you.  That was quick.

I guess I should’ve been clearer with my question.

What does the elevation pattern look like please?

 

Mike, Coreen & Corey

Keswick Ridge, NB

 

From: Dave Cuthbert [mailto:telegrapher9 at gmail.com] 
Sent: January 11, 2021 5:35 PM
To: Mike Smith VE9AA
Cc: topband
Subject: Re: Topband: Inverted J antennas?

 

Hi Mike,

 

your inverted-J in EZNEC shows a radiation resistance at 1850kHz of 10 ohms. It is resonant at 1800kHz. 

 

With the 50' vertical wire removed it is resonant at 2.7MHz and has a radiation resistance at 1850kHz of 11 ohms. 

 

   Dave KH6AQ

 

 

 

On Mon, Jan 11, 2021 at 10:52 AM Mike Smith VE9AA <ve9aa at nbnet.nb.ca> wrote:

Has anyone modeled an inverted J on 160m ? (almost an inverted U, really)



I currently have only one left (the other half of my 2-el array blew down
and I've been lazy to replace it) and it "works" but not as good as it could
I think if I had better supports (ie: taller trees, wider yard).  I am quite
constrained on my property boundaries, so it goes up crookedly and also at a
slight angle about 60', over maybe 35'in broad arc and then nearly straight
down vertically 40', with the far end maybe only 10' off the ground (just
like an inverted J or U).

It has 2 full size 1/4wl radials 180* apart raised up about 6' off the
ground.  The radials are perpendicular to the direction the far end of the
vertical is headed..which is to say, the 'vertical' is not directly above
any part of the radials.

(a little bit like an Aki-special but not nearly as 'good', hi)



What concerns me MOST is the far end is mostly vertical on its way down and
it being barely off the ground at the far end.



  I can't do anything now that there's a foot of snow down in the woods with
lots of rocks sitting right on top of the ground (too dangerous to
walk.especially on a bit of slanted ground,)  however if I believed I could
do better by keeping the far end up off the ground some more, I might
re-route it somehow in the spring. Because of the lack of trees I doubt I
could get anything resembling a true inverted L, but I might be able to
zig-zag the far end here and there in the tree tops and some branches on its
way back to earth a little bit to keep the far end away from the ground some
more.



Has anyone done any modeling of this type of antenna or even have anecdotal
evidence to share?



p.s.- at times it works gangbusters..fr'instance I was testing it the other
day at 0.9watts (900mW) and it was still daylight here and about 45mins
before SS in New England and 2 skimmers (about 340miles/550kms away) picked
me up at 2-9dB..maybe that only means it's a cloud warmer?



Tnx in advance.



CU (all of a sudden) on Top Band.



Mike VE9AA , NB





Mike, Coreen & Corey

Keswick Ridge, NB



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