Topband: Impedance of inv l?

Thu Nov 22 13:03:40 EST 2018

Frank and all,

I thought I would share a little real world experience I had today.  I have
a T, loaded vertical that is only something like 57 feet tall at the
moment.  The R should probably be in the neighborhood of 10. It is located
about 30 feet from the water.  I had about 40 radials and they ranged from
about 30 feet (ones going straight toward the water or sometimes in the
water) and perhaps 75 feet long.  I would say the average length is about
60 feet or so.  I added 8 more radials yesterday wanting to get the R down
to something I liked better.  I made a ring out of some 3/8 copper tubing,
scraped, soldered, generally made better connections than what I originally
had.  I moved the R by 1 ohm down from 22 to 21. :-)

Today, despite the fact that "my property" is about 100 feet wide, I first
added 6 radials that are well in excess of 100 feet long each - probably
115-125 feet long.  The R dropped from 21 to 14.  WOW.  Then I added 4 more
long radials.  The R dropped from 14 to 13.  I am stopping there.  I think
I would likely have to add another six going on the neighbors yard to drop
it by another 1 ohm.   I think I probably just picked up 3/4 dB - maybe
that's enough to work the EP6 that I have called for a couple hours.

In my particular case, I am not sure I could have reduced the 22 to 13 if I
had added another 30 radials x 70 feet long each.  The longer ones did the
trick in a big way.

73, Happy Thanksgiving and see you this weekend.

Stan, ZF9CW

On Sun, Nov 18, 2018 at 8:31 PM <donovanf at starpower.net> wrote:

>
> Hi Jamie,
>
>
> I use my AA-54 frequently in exactly the manner you're using your
> AA-23, I've never had any reason to be suspicious of any of its
> readings. I'm lucky to have no AM broadcast stations within ten
> miles.
>
>
> Your AA-230 is telling you that at least half of your power is being
> lost to ground resistance and need to at least double the number of
> radials to significantly reduce your resistive losses.
>
>
> The 2000 feet of wire in your radial system likely would have produced
> much better results with twice as many radials of half the radial length
> you used. Quarter wavelength radials aren't cost effective until many
> more than 60 radials are used.
>
>
> www.w0btu.com/Optimum_number_of_ground_radials_vs_radial_length.html
>
>
> 73
> Frank
> W3LPL
>
>
>
>
> ----- Original Message -----
>
> From: "Jamie WW3S" <ww3s at zoominternet.net>
> To: "Topband" <topband at contesting.com>
> Sent: Sunday, November 18, 2018 10:33:13 PM
> Subject: Re: Topband: Impedance of inv l?
>
> several have asked how I am measuring the impedance.....I'm using an
> AA-230,
> and am all the ALL PARAMS setting.....the 230 defaults to a series model,
> is
> that what I want, don’t see how to change it to parallel. I think the
> symbol
> for impedance is |Z|, correct?
>
> -----Original Message-----
> From: F Z_Bruce
> Sent: Sunday, November 18, 2018 3:20 PM
> To: wes_n7ws at triconet.org ; Topband
> Subject: Re: Topband: Impedance of inv l?
>
>
> The far end is high impedance voltage, and has minimum  horizontal
> current radiation.  The inverted L is a good trade off signal vs
> available height.  Not an expensive antenna to build. 
>
> 73
> Bruce-k1fz 
>  
> On Sun, 18 Nov 2018 12:31:38 -0700, Wes Stewart wrote:
>
> That also drives up the current in the horizontal wire with attendant
> increased
> horizontal radiation.
>
> I chose for a couple of reason to do the opposite; shorten the wire to
> make
> the
> feedpoint capacitive and use a shunt inductor to get a 50-ohm match. 
> This
> really doesn't improve the 2:1 VSWR, that I consider acceptable, however.
>
> Wes  N7WS
>
> On 11/18/2018 8:55 AM, F Z_Bruce wrote:
> > That sounds about right. As you put a good ground system under it,
> that
> value will come down, and the efficiency will come up.
> >
> > Many add extra antenna wire that pushes the current up the wire, this
> also raises  the impedance, hopefully to near 50 ohms with the right
> length.
> > A capacitor (variable, then fixed) in series at the feed point can
> cancel the added inductance.
> >
> > 73
> > Bruce-k1fz
> > https://www.qsl.net/k1fz/beverage_antenna.html
> >
> >  
> > On Sun, 18 Nov 2018 10:41:36 -0500, WW3S wrote:
> >
> > What should the Z be for a 1/4 wave inv l, with the radials attached
> to
> a radial plate? Mine seems to be 60 ohms or so....
> >
> > Sent from my iPad
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