Topband: How much ground independence?

[Bruce]

Hi Don,

Congratulations on your nice set up and your new height above ground.  ( I 
now have my receiving Delta receiving antenna up  to easily drive the car 
under. hi)
Thank you for the wealth of information on your WEB site, and utube.

On 80 meters wonder if you, at low TX power, have checked the RF at the end 
of your radials with a field strength meters ?

Do you have a perimeter wire around the ends of you radials ?

73
Bruce-K1FZ



----- Original Message ----- 
From: "Don Kirk" <wd8dsb at gmail.com>
To: "Bruce" <k1fz at myfairpoint.net>
Cc: "topband" <topband at contesting.com>; "chetmoore" <chetmoore at cox.net>
Sent: Wednesday, December 11, 2013 11:16 AM
Subject: Re: Topband: How much ground independence?


> Hi Bruce,
>
> I'm using 3 small Pennant RX antennas (51.6% the size of full size
> pennants), one pointing 40 degrees, one pointing 160 degrees, and one
> pointing 300 degrees (sharing the same feedpoint).  Originally bottom of
> them were 2 feet off the ground and then after a year of encouragement 
> from
> my wife I raised them up so the bottom are 8 feet above ground.
>
> My buried radial field (55 short radials, average length 60 feet) runs
> right under my pennants, and my 68 foot base loaded TX vertical is
> approximately 40 or 45 feet (as I recall) from the feedpoint of the
> pennants.
>
> No difference in performance between the 2 foot and the 8 foot above 
> ground
> mounting positions (no noticeable difference in signal to noise using my 
> TX
> vertical as a reference antenna for signal to noise improvement, and no
> noticeable difference in front to back ratio).
>
> Originally I took steps to detune my TX antenna during receive, but to my
> surprise detuning was not necessary on 160 meters in my installation.  On
> the other hand something is destroying the pattern (noticeable on front to
> back) of my pennants when used on 80 meters, and detuning of my TX antenna
> helps slightly, but the TX antenna is not the main cause of my 80 meters
> problem (I even removed (took down) my TX antenna to make sure it was not
> the TX antenna causing the problem).  I've always suspected the problem is
> the proximity of the RX array to my house and interaction with house
> wiring, rain gutters, metal I beams, metal chimney flue, etc, but never
> considered the ground radials.  Since my primary interest is 160 meters 
> I'm
> very happy with my system (installed summer of 2011).
>
> This morning I recorded AA1K calling CQ on 160 meters and uploaded the
> recording to youtube so you (and others) can experience one example of the
> directional properties of my pennants.  Since my pennants are not pointing
> exactly 180 degrees from each other it's impossible to fully capture the
> front to back properties, but you can certainly compare the performance to
> the expected plots of my array.  There was a lot of QSB during my
> recordings this morning, and suspect (based on the variation in front to
> back ratio during the recording) that the arrival angle was changing
> considerably over time but the QSB might have also been due to a different
> propagation phenomena.
>
> The youtube link for the AA1K recording is
> http://www.youtube.com/watch?v=TWlBy5ypMIU
> (Note : AA1K is 564 miles from my QTH at a heading of 93.6 degrees)
>
> The link to my website where you can see the expected directional
> properties (pattern plots overlay) when receiving AA1K from my QTH is
> http://sites.google.com/site/pennantflagantennas/
>
> You will definitely see periods where I'm experiencing 18 to 20 dB front 
> to
> back directional properties in the AA1K youtube recording (and AA1K is not
> lined up exactly with the back of my 300 degree pennant), but then you 
> will
> also see times where the directional properties are much less.  My plot
> overlays predict approximately 15 dB in directional properties when
> receiving AA1K (if arrival angle is 31 degrees), and think the 15 dB is
> close to the average experienced in my recording.
>
> Also on my website I show a plot for predicted front to back ratio versus
> arrival angle for pennants, and think you will find this interesting 
> (front
> to back ratio is very dependent on arrival angle).  On the average I would
> say I notice front to back to be 18 to 20 dB if the back of one of my
> antennas is close to being lined up with the station I'm receiving (not
> exactly front to back since my antennas are not facing exactly 180 degrees
> from each other, but close since the forward pattern is so broad).
>
> Sorry for the long posting, but very complicated topic.  I also have lots
> of comments about the overall characteristics of pennants (performance
> compared with a vertical TX antenna), but won't complicate this posting
> with them.
>
> 73,
> Don (wd8dsb)
> _________________
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>