Re: Topband: Adding a parasitic reflector to a vertical

[Joel Harrison]

gt;>>> *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-boun...@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
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>> _
>>>> Topband Reflector Archives - http://www.contesting.com/_topband
>>> _
>>> Topband Reflector Archives - http://www.contesting.com/_topband
>>
>
>


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Re: Topband: Adding a parasitic reflector to a vertical

[W0MU Mike Fatchett]

I was going to try to phase 2 80m verticals but just could not find the 
room.  You get endfire and broadside.


I assume you have to put down the same radial field for a Parasitic 
element as a driven one?  Maybe I am wrong here.



On 2/9/2018 3:38 PM, Joel Harrison wrote:

Interesting question Mike!

Possibly, however my focus was to achieve maximum gain with minimal
effort. This direction allowed me to accomplish that objective.

Don't know if anyone has documented experience in doing what you pose. I
would certainly be interested in reading the work anyone conducted along
that line for amateur use. Would be interesting.

73 Joel W5ZN



Could you not get more out those elements if you had phased them?
Obviously there would be more work required for the phasing system.
One element short of a 4 square.


On 2/1/2018 6:01 PM, Joel Harrison wrote:

As Tim noted I built the K3LR version of the 3 element parasitic array
this past fall. I used my original and existing shunt fed tower as the
driven element. It is switchable in four directions and I have an
extensive radial system (120 radials)under each element.

My initial assessment indicates a forward gain of around 5 dB and a
minimum F/B of 25 dB. It performs very well from out here in fly over
country.

I am in the process of completing a paper detailing my construction and
experience with the array and will also be presenting this at the Dayton
Antenna Forum on Friday of Dayton.

I have spent the past 10 years improving my 160 meter RX systems here at
W5ZN and had reached a point of needing to improve the TX system beyond
a
single shunt fed tower. I struggled with whether to build a stand alone
4
square for 160 meters however the appeal of the parasitic array is that
I
could use the existing shunt fed tower to support the T elements without
having to erect an entirely new mechanical structure for a 4 square
while
achieving basically the same result. I have been pleased with the
performance for the short few months it has been in operation.

Obviously it doesn't provide the broad bandwidth a 4 square does. I have
about 40 KHz between 1.5:1 points however in reality a 4 square has
limited bandwidth since beyond the resonant points you dump a lot of
power
into the dump load!

73 Joel W5ZN



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-boun...@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
















_
Topband Reflector Archives - http://www.contesting.com/_topband

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Re: Topband: Adding a parasitic reflector to a vertical

[Joel Harrison]

Interesting question Mike!

Possibly, however my focus was to achieve maximum gain with minimal
effort. This direction allowed me to accomplish that objective.

Don't know if anyone has documented experience in doing what you pose. I
would certainly be interested in reading the work anyone conducted along
that line for amateur use. Would be interesting.

73 Joel W5ZN


> Could you not get more out those elements if you had phased them? 
> Obviously there would be more work required for the phasing system.  
> One element short of a 4 square.
>
>
> On 2/1/2018 6:01 PM, Joel Harrison wrote:
>> As Tim noted I built the K3LR version of the 3 element parasitic array
>> this past fall. I used my original and existing shunt fed tower as the
>> driven element. It is switchable in four directions and I have an
>> extensive radial system (120 radials)under each element.
>>
>> My initial assessment indicates a forward gain of around 5 dB and a
>> minimum F/B of 25 dB. It performs very well from out here in fly over
>> country.
>>
>> I am in the process of completing a paper detailing my construction and
>> experience with the array and will also be presenting this at the Dayton
>> Antenna Forum on Friday of Dayton.
>>
>> I have spent the past 10 years improving my 160 meter RX systems here at
>> W5ZN and had reached a point of needing to improve the TX system beyond
>> a
>> single shunt fed tower. I struggled with whether to build a stand alone
>> 4
>> square for 160 meters however the appeal of the parasitic array is that
>> I
>> could use the existing shunt fed tower to support the T elements without
>> having to erect an entirely new mechanical structure for a 4 square
>> while
>> achieving basically the same result. I have been pleased with the
>> performance for the short few months it has been in operation.
>>
>> Obviously it doesn't provide the broad bandwidth a 4 square does. I have
>> about 40 KHz between 1.5:1 points however in reality a 4 square has
>> limited bandwidth since beyond the resonant points you dump a lot of
>> power
>> into the dump load!
>>
>> 73 Joel W5ZN
>>
>>
>>> 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-boun...@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
>

Re: Topband: Adding a parasitic reflector to a vertical

[Roger D Johnson]

The one big problem with parasitic arrays is that you must have low enough
ground resistance to get the proper current to flow in the element. With a
driven array, you can force the elements to have the proper current 
distribution.

73, Roger


On 2/5/2018 4:18 PM, W0MU Mike Fatchett wrote:
Could you not get more out those elements if you had phased them? Obviously 
there would be more work required for the phasing system. One element short of a 
4 square.

_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Adding a parasitic reflector to a vertical

[W0MU Mike Fatchett]

Could you not get more out those elements if you had phased them?  
Obviously there would be more work required for the phasing system.   
One element short of a 4 square.



On 2/1/2018 6:01 PM, Joel Harrison wrote:

As Tim noted I built the K3LR version of the 3 element parasitic array
this past fall. I used my original and existing shunt fed tower as the
driven element. It is switchable in four directions and I have an
extensive radial system (120 radials)under each element.

My initial assessment indicates a forward gain of around 5 dB and a
minimum F/B of 25 dB. It performs very well from out here in fly over
country.

I am in the process of completing a paper detailing my construction and
experience with the array and will also be presenting this at the Dayton
Antenna Forum on Friday of Dayton.

I have spent the past 10 years improving my 160 meter RX systems here at
W5ZN and had reached a point of needing to improve the TX system beyond a
single shunt fed tower. I struggled with whether to build a stand alone 4
square for 160 meters however the appeal of the parasitic array is that I
could use the existing shunt fed tower to support the T elements without
having to erect an entirely new mechanical structure for a 4 square while
achieving basically the same result. I have been pleased with the
performance for the short few months it has been in operation.

Obviously it doesn't provide the broad bandwidth a 4 square does. I have
about 40 KHz between 1.5:1 points however in reality a 4 square has
limited bandwidth since beyond the resonant points you dump a lot of power
into the dump load!

73 Joel W5ZN



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-boun...@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

















_
Topband Reflector Archives - http://www.contesting.com/_topband


_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Adding a parasitic reflector to a vertical

[Joel Harrison]

As Tim noted I built the K3LR version of the 3 element parasitic array
this past fall. I used my original and existing shunt fed tower as the
driven element. It is switchable in four directions and I have an
extensive radial system (120 radials)under each element.

My initial assessment indicates a forward gain of around 5 dB and a
minimum F/B of 25 dB. It performs very well from out here in fly over
country.

I am in the process of completing a paper detailing my construction and
experience with the array and will also be presenting this at the Dayton
Antenna Forum on Friday of Dayton.

I have spent the past 10 years improving my 160 meter RX systems here at
W5ZN and had reached a point of needing to improve the TX system beyond a
single shunt fed tower. I struggled with whether to build a stand alone 4
square for 160 meters however the appeal of the parasitic array is that I
could use the existing shunt fed tower to support the T elements without
having to erect an entirely new mechanical structure for a 4 square while
achieving basically the same result. I have been pleased with the
performance for the short few months it has been in operation.

Obviously it doesn't provide the broad bandwidth a 4 square does. I have
about 40 KHz between 1.5:1 points however in reality a 4 square has
limited bandwidth since beyond the resonant points you dump a lot of power
into the dump load!

73 Joel W5ZN


> 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-boun...@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
>
>
>
>
>
>
>
>
>
>
>
>
>
>
>


_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Adding a parasitic reflector to a vertical

[Dan Maguire via Topband]

For AutoEZ users:  A model similar to the parasitic array that Tim described is 
available on this page:

http://ac6la.com/aecollection8.html

In the first section of that page, scroll down to topic "Parasitic Elements" 
and then look for the text "For a vertical parasitic example I chose a model 
described by N6LF ...".  The sample model is for 80m but everything is 
controlled via variables and there are instructions (within the model itself) 
on how to scale for other bands.

Links to several references are also included on the above page.

Dan, AC6LA
_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: 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:mpride...@yahoo.com] 
Sent: Wednesday, January 31, 2018 4:46 PM
To: k...@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 <k...@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-boun...@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
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> -- 
> W7RH DM35OS
> 
> 
> It has become appallingly obvious that our technology has exceeded our
> humanity.
> 
> Albert Einstein
> 
> _
> Topband Reflector Archives - http://www.contesting.com/_topband
> 
> _
> Topband Reflector Archives - http://www.contesting.com/_topband

_
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Re: Topband: Adding a parasitic reflector to a vertical

[Tim Duffy]

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-boun...@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















-- 
W7RH DM35OS


It has become appallingly obvious that our technology has exceeded our
humanity.

Albert Einstein

_
Topband Reflector Archives - http://www.contesting.com/_topband

_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Adding a parasitic reflector to a vertical

[W7RH]

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















--
W7RH DM35OS


It has become appallingly obvious that our technology has exceeded our humanity.

Albert Einstein

_
Topband Reflector Archives - http://www.contesting.com/_topband

Re: Topband: Adding a parasitic reflector to a vertical

[Tree]

Back about 10 years ago - I played around with a parasitic element and had
good results.

One method I used to determine how well - and where the antenna worked was
to use a wide band noise source.  You can build one - or I know Elecraft
has one.  For long distances - I would use my amplifier to make it louder
(only do this during the daytime).  You can then put a receiver on the back
side of the antenna and quickly find the frequency where you have the best
rejection (front-to-back).

I feel the main drawback of the parasitic elements is that they work over a
pretty small portion of the band.  This is probably okay for DX work - but
if you are doing contests and need to go up the band some, your performance
will quickly drop off.

Tree N6TR

On Mon, Jan 29, 2018 at 10:40 AM, N7DF via Topband 
wrote:

>
> From southcentral New Mexico working Europe on 160 meters is pretty much
> an exercise infrustration with a single vertical antenna. So I decided to
> see if I couldimprove on things by adding a parasitic reflector element to
> my cage antenna.  Since I could not find any specificinformation about
> doing this I decided to experiment a little and see what Icould come up
> with.  After looking at a lotof designs for two element antennas and taking
> into consideration the physicalparameters of being in a juniper forest I
> finally came up with a design that Icould build.  My antenna is a
> Collins27W-1X conical monopole fed with an MFJ 998 remote tuner located in
> a 120 footdiameter clearing. The parasitic reflector would be 88 feet
> southwest of the monopolein a small clearing.  From what I coulddetermine
> from various sources, in order for it to be effective at thatdistance, it
> would need to be resonant at 1.787 MHz to provide maximum gain at1.825
> MHz.  The reflector elementconsisted of a 30 foot tall section of 2 inch
> diameter irrigation pipe restingon a plexiglass sheet with a top hat wire
> strung at right angles to the linebetween the transmitting antenna and the
> reflector.  In the opposite direction a ground radial waslaid out along the
> ground surface.  Aftera lot of measuring with an antenna analyzer and
> cutting to length the top hatwire ended up as 86 feet 4 inches long and the
> ground radial at 112 feet 3inches to get resonance at 1.787 MHz. The bottom
> of the vertical is connectedto the ground radial with a clip lead so it can
> be taken out of the circuitwhen I want the monopole to be omnidirectional.
> The array turned out to be veryeffective in changing the pattern of the
> monopole and there is a markedimprovement on signals from the northeast
> both in North America and from Europeas realized in the recent 160 meter
> contest. The best measure, though, turned out to be courtesy of WD5COV who
> isabout 125 miles southwest from me.  Hissignal is usually about 40 over S9
> when he has his 4 square pointed myway.  After installing the
> parasiticelement his signal dropped to about 20 over S9 on peaks.
> Unfortunately the antenna has not improved mynoise problems but that is
> another story.
> N7DF
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