Topband: Adding a parasitic reflector to a vertical

[Tim Duffy]

Hi Mark:

The tower (driven element) sits on a base insulator. So it is series fed.

73
Tim K3LR

-----Original Message-----
From: Mpridesti [mailto:mpridesti at yahoo.com] 
Sent: Wednesday, January 31, 2018 4:46 PM
To: k3lr at k3lr.com
Subject: Re: Topband: Adding a parasitic reflector to a vertical

Hi Tim

Following this thread. Assume the tower is grounded so just how are you
connecting your L network to the tower?  A gamma wire?  Tapped where?

Appreciate your help!

Regards,
Mark, K1RX


> On Jan 31, 2018, at 2:28 PM, Tim Duffy <k3lr at k3lr.com> wrote:
> 
> I have been using a 3 element parasitic vertical beam on 160 for at least
20
> years. K9CT, NR5M, AA1K*, VE3EJ and most recently W5ZN have the same
array.
> It has instant switching in 4 directions.
> 
> With 4 parasitic cut directors around the center driven element tower - it
> is pretty easy to get over 5 dB of forward gain (over 40 KHz wide) and
over
> 30 dB of front to back (over a narrow bandwidth). Easy driven element
match
> with an L network at the base. Each parasitic has 3 modes. Director,
> Reflector or float. Going from directional to Omni is easy as well.
> 
> *AA1K has an additional director toward Europe. So he has 4 elements!
> 
> As was pointed out - the magic in any vertical antenna is all about the
> radials. Each parasitic wire (4) and the center driven element tower has
120
> radials that are 130 feet long (unless they cross the junction bus). I
have
> 67,000 feet of radials under my 160 array.
> 
> I use a 120 ft 24 inch face solid leg tower as the driven element. The
tower
> sections are welded together to decrease any joint loss. The parasitic T
> wires are #12 Copperweld.
> 
> The last three editions of the Low Band DXing book describe this antenna
in
> the Yagi chapter.
> 
> 73
> Tim K3LR
> 
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of W7RH
> Sent: Tuesday, January 30, 2018 11:39 PM
> To: Topband
> Subject: Re: Topband: Adding a parasitic reflector to a vertical
> 
> I've played with parasitic elements in antenna arrays for almost three 
> decades and the current antenna system I have used parasitic elements 
> both director and reflectors.
> 
> With very careful tuning performance that of a all driven array can be 
> achieved. Tree is correct they due tend to be somewhat limited in in 
> bandwidth with relation to F/B ratio. Gain remains fairly constant.
> 
> The tuning procedure that Tree suggested is absolutely correct. You 
> detune all unused elements and adjust the center frequency of the 
> parasitic for best F/B one element at a time. Parasitic elements I might 
> add are no different than driven and must have extensive ground system 
> to be effective. No exceptions. You know you have right by F/B ratio. 
> You can go one step further and measure the actual antenna currents 
> which I have done. In my system the parasitic elements achieve 80-85% of 
> the theoretical current at the base.
> 
> de Bob W7RH
> 
> 
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> 
> -- 
> W7RH DM35OS
> 
> 
> It has become appallingly obvious that our technology has exceeded our
> humanity.
> 
> Albert Einstein
> 
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