Re: Topband: T-loaded vertical

[Edward via Topband]

That's good news. I am in Saudi Arabia on a small lot. My plan is to use my 
ladderline-fed Cobra Ultralite dipole (73' long), tying the 100' ladderline 
together, making a T.  Will load it against a decent ground via a wide range 
tuner. 

Thoughts?

Thanks,
Ed 7Z1ES

> On 20 Feb 2020, at 7:45 AM, GEORGE WALLNER  wrote:
> 
> The T has another advantage: it is better on 80 (and 40) if you can match 
> it. A 160 m inverted L, with a substantial length horizontal wire, makes a 
> poor 80 meter radiator because of high angles. A T will give you more low 
> angle radiation.
> 
> 73,
> George,
> AA7JV
> 
> 
>> On Wed, 19 Feb 2020 15:31:21 -0500
>> "Ed Sawyer"  wrote:
>> Rick said it better.  Thanks Rick.  The T has been a great performer for me 
>> in 4 different locations over the years.  I swear by it for 55 - 70 ft 
>> vertical sections.
>> 
>> Ed  N1UR
>> 
>> -Original Message-
>> From: Richard (Rick) Karlquist [mailto:rich...@karlquist.com] Sent: 
>> Wednesday, February 19, 2020 3:04 PM
>> To: Ed Sawyer; donov...@starpower.net; topband@contesting.com
>> Subject: Re: Topband: T-loaded vertical
>> 
>> 
>>> On 2/19/2020 11:50 AM, Ed Sawyer wrote:
>>> I have personally found that for Ts that are only 70 ft vertical, like 
>>> mine, the ground losses of the long topped L are not as desirable as the 
>>> cancelled out horizontal lobes of the T.  If the T were say 90 ft of 
>>> vertical, I don’t think the T adds as much value.
>>> Ed  N1UR
>>> 
>>> 
>> When you model an inverted L, the driving point resistance
>> goes up when you lengthen the top.  This it appears that
>> you decreased ground losses and your efficiency goes up.
>> However, if model vertical polarized radiation vs input
>> power, you find that your effective efficiency actually
>> goes down.
>> 
>> Extending the inverted L top out to where you have a 1/4
>> wavelength of wire seems very elegant.  The antenna
>> reaches resonance at 1830 and you get a low VSWR without
>> using a tuner.  If you model that vs a T vertical, there
>> is no comparison. The T wins.
>> 
>> Rick N6RK
>> 
>> _
>> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
> 
> _
> Searchable Archives: http://www.contesting.com/_topband - Topband Reflector

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

Re: Topband: T-loaded vertical

[GEORGE WALLNER]

The T has another advantage: it is better on 80 (and 40) if you can match 
it. A 160 m inverted L, with a substantial length horizontal wire, makes a 
poor 80 meter radiator because of high angles. A T will give you more low 
angle radiation.


73,
George,
AA7JV


On Wed, 19 Feb 2020 15:31:21 -0500
 "Ed Sawyer"  wrote:

Rick said it better.  Thanks Rick.  The T has been a great performer for me in 
4 different locations over the years.  I swear by it for 55 - 70 ft vertical 
sections.

Ed  N1UR

-Original Message-
From: Richard (Rick) Karlquist [mailto:rich...@karlquist.com] 
Sent: Wednesday, February 19, 2020 3:04 PM

To: Ed Sawyer; donov...@starpower.net; topband@contesting.com
Subject: Re: Topband: T-loaded vertical


On 2/19/2020 11:50 AM, Ed Sawyer wrote:

I have personally found that for Ts that are only 70 ft vertical, like mine, 
the ground losses of the long topped L are not as desirable as the cancelled 
out horizontal lobes of the T.  If the T were say 90 ft of vertical, I don’t 
think the T adds as much value.
Ed  N1UR



When you model an inverted L, the driving point resistance
goes up when you lengthen the top.  This it appears that
you decreased ground losses and your efficiency goes up.
However, if model vertical polarized radiation vs input
power, you find that your effective efficiency actually
goes down.

Extending the inverted L top out to where you have a 1/4
wavelength of wire seems very elegant.  The antenna
reaches resonance at 1830 and you get a low VSWR without
using a tuner.  If you model that vs a T vertical, there
is no comparison. The T wins.

Rick N6RK

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


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

Re: Topband: T-loaded vertical

[w5zn]

So, what impact will the yagi have on the T element???

73 Joel W5ZN



On 2020-02-19 12:57, donov...@starpower.net wrote:

Hi Ed,


A T-top at right angles to a Yagi will have little affect, but anything
close to broadside is very bad within 500 feet or less on 40 meters.
Fortunately a 60 foot top is just short enough to have minimal affect.
70 feet would be much worse.


Any top longer than 40 feet should have little affect on a 20 meter 
Yagi.



Happy modelling!


73
Frank
W3LPL

- Original Message -

From: "Ed Sawyer" 
To: donov...@starpower.net, topband@contesting.com
Sent: Wednesday, February 19, 2020 7:50:13 PM
Subject: RE: Topband: T-loaded vertical



Frank, You will have me grabbing my EZNEC tonight and playing around.
In my case my tops are around 60 ft long and they are thankfully
perpendicular to my 20M yagi and about 120 ft away. However if I beam
west on my 40M yagi. I am 100 ft away and parallel to the wire. I need
to take a look at that.

It gets me thinking about the reverse. Could it “enhance” a direction
if properly designed?

My back T is 250ft even further so almost 400 ft from either tower.
Same T design.

I have personally found that for Ts that are only 70 ft vertical, like
mine, the ground losses of the long topped L are not as desirable as
the cancelled out horizontal lobes of the T. If the T were say 90 ft
of vertical, I don’t think the T adds as much value.

Ed N1UR



From: donov...@starpower.net [mailto:donov...@starpower.net]
Sent: Wednesday, February 19, 2020 2:13 PM
To: topband@contesting.com
Subject: Re: Topband: T-loaded vertical


Hi Ed,




The affect of the T-vertical on a nearby HF Yagi is easily modeled in

EZNEC or your favorite antenna modelling program. You'll be surprised

by the results if the horizontal top is +/- 15% of resonance on 40 or 
20


meters, for example. HF Yagi performance degradation occurs within ten

(yes, ten) wavelengths, but its especially severe within a few 
wavelengths


(wavelengths in terms of the HF Yagi, not 160 meter wavelengths).



There's no magic distance beyond which parasitic effects no longer 
occur.


If any conductor carries RF current, its magnitude and phase enters 
into


the determination of the radiation pattern of the antenna system, even 
if that


conductor is ten wavelengths away from the main radiator. Ask any

AM broadcast antenna engineer about this... (if you can still find 
one).


Maybe K3LR...



For many hams, installing a nearby second tower sets back their station

performance. Why? Because the antennas on the second tower degrade

the performance of antennas on the first tower and visa-versa. Exactly

the same situation occurs when a parasitic element -- in this case the

flat top of a T-vertical -- is installed within several wavelengths of 
HF Yagis


(wavelengths in terms of the HF Yagis, not 160 meter wavelengths).



We learn from our mistakes... I've made exactly the same mistakes with

T-verticals, multiple towers with HF Yagis for the same band, and HF 
Yagi


booms that are resonant within an HF band (e.g., when I installed a

72 foot boom 20 meter Yagi a few hundred feet from a 40 meter Yagi

on another tower).



For example, I have 20 meter Yagis on two towers spaced 300 feet apart.

The Yagis on the rear tower are badly degraded when pointing into the

the 20 meter Yagis 300 feet in front of it. They work perfectly well

when pointed at least +/- 30 degrees away from the 20M Yagis 300 feet

in front.



HF Yagi performance degradation is insignificant when an HF Yagi points

away from the horizontal top of a T-vertical. But when the Yagi is 
turned so


its the 3 dB beamwidth intercepts the horizontal top of a T-vertical, 
all hell


breaks loose with:

- significantly degraded HF Yagi front-to-back ratio,

- additional sidelobes,

- splitting of the main beam of the HF Yagi into two or more lobes,

- reduced gain




The bottom line: If you care about the performance of your HF Yagis,

select the length of the horizontal section of a T-vertical so its not

within +/- 15% of resonance on any HF band you care about. 40 to

60 feet lengths do not interfere with any HF band other than 30 meters.



Or use an inverted-L rather than a T-vertical and you'll have no 
problem


at all, and -- from practical on the air performance -- an inverted-L 
is


imperceptibly worse than a T-vertical.



I no longer have any T-verticals...



73

Frank

W3LPL



- Original Message -


From: "Ed Sawyer" 
To: topband@contesting.com
Sent: Wednesday, February 19, 2020 6:13:02 PM
Subject: Re: Topband: T-loaded vertical

The answer to the top loading is that the top is essentially the same 
as if
it was an L on the antenna - just with the connection point moved to 
the
center. I would add maybe 5 ft on either side of the top to that 
equation
and see what it looks like when you install. And, like other verticals. 
If
it gives you a good SWR right off the bat, then your ground 

Re: Topband: T-loaded vertical

[Ed Sawyer]

Rick said it better.  Thanks Rick.  The T has been a great performer for me in 
4 different locations over the years.  I swear by it for 55 - 70 ft vertical 
sections.

Ed  N1UR

-Original Message-
From: Richard (Rick) Karlquist [mailto:rich...@karlquist.com] 
Sent: Wednesday, February 19, 2020 3:04 PM
To: Ed Sawyer; donov...@starpower.net; topband@contesting.com
Subject: Re: Topband: T-loaded vertical



On 2/19/2020 11:50 AM, Ed Sawyer wrote:

> I have personally found that for Ts that are only 70 ft vertical, like mine, 
> the ground losses of the long topped L are not as desirable as the cancelled 
> out horizontal lobes of the T.  If the T were say 90 ft of vertical, I don’t 
> think the T adds as much value.

> Ed  N1UR
> 
>   

When you model an inverted L, the driving point resistance
goes up when you lengthen the top.  This it appears that
you decreased ground losses and your efficiency goes up.
However, if model vertical polarized radiation vs input
power, you find that your effective efficiency actually
goes down.

Extending the inverted L top out to where you have a 1/4
wavelength of wire seems very elegant.  The antenna
reaches resonance at 1830 and you get a low VSWR without
using a tuner.  If you model that vs a T vertical, there
is no comparison. The T wins.

Rick N6RK

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

Re: Topband: T-loaded vertical

[Richard (Rick) Karlquist]

On 2/19/2020 11:50 AM, Ed Sawyer wrote:


I have personally found that for Ts that are only 70 ft vertical, like mine, 
the ground losses of the long topped L are not as desirable as the cancelled 
out horizontal lobes of the T.  If the T were say 90 ft of vertical, I don’t 
think the T adds as much value.



Ed  N1UR

  


When you model an inverted L, the driving point resistance
goes up when you lengthen the top.  This it appears that
you decreased ground losses and your efficiency goes up.
However, if model vertical polarized radiation vs input
power, you find that your effective efficiency actually
goes down.

Extending the inverted L top out to where you have a 1/4
wavelength of wire seems very elegant.  The antenna
reaches resonance at 1830 and you get a low VSWR without
using a tuner.  If you model that vs a T vertical, there
is no comparison. The T wins.

Rick N6RK
_
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector

Re: Topband: T-loaded vertical

[donovanf]

Hi Ed, 


A T-top at right angles to a Yagi will have little affect, but anything 
close to broadside is very bad within 500 feet or less on 40 meters. 
Fortunately a 60 foot top is just short enough to have minimal affect. 
70 feet would be much worse. 


Any top longer than 40 feet should have little affect on a 20 meter Yagi. 


Happy modelling! 


73 
Frank 
W3LPL 

- Original Message -

From: "Ed Sawyer"  
To: donov...@starpower.net, topband@contesting.com 
Sent: Wednesday, February 19, 2020 7:50:13 PM 
Subject: RE: Topband: T-loaded vertical 



Frank, You will have me grabbing my EZNEC tonight and playing around. In my 
case my tops are around 60 ft long and they are thankfully perpendicular to my 
20M yagi and about 120 ft away. However if I beam west on my 40M yagi. I am 100 
ft away and parallel to the wire. I need to take a look at that. 

It gets me thinking about the reverse. Could it “enhance” a direction if 
properly designed? 

My back T is 250ft even further so almost 400 ft from either tower. Same T 
design. 

I have personally found that for Ts that are only 70 ft vertical, like mine, 
the ground losses of the long topped L are not as desirable as the cancelled 
out horizontal lobes of the T. If the T were say 90 ft of vertical, I don’t 
think the T adds as much value. 

Ed N1UR 



From: donov...@starpower.net [mailto:donov...@starpower.net] 
Sent: Wednesday, February 19, 2020 2:13 PM 
To: topband@contesting.com 
Subject: Re: Topband: T-loaded vertical 


Hi Ed, 




The affect of the T-vertical on a nearby HF Yagi is easily modeled in 

EZNEC or your favorite antenna modelling program. You'll be surprised 

by the results if the horizontal top is +/- 15% of resonance on 40 or 20 

meters, for example. HF Yagi performance degradation occurs within ten 

(yes, ten) wavelengths, but its especially severe within a few wavelengths 

(wavelengths in terms of the HF Yagi, not 160 meter wavelengths). 



There's no magic distance beyond which parasitic effects no longer occur. 

If any conductor carries RF current, its magnitude and phase enters into 

the determination of the radiation pattern of the antenna system, even if that 

conductor is ten wavelengths away from the main radiator. Ask any 

AM broadcast antenna engineer about this... (if you can still find one). 

Maybe K3LR... 



For many hams, installing a nearby second tower sets back their station 

performance. Why? Because the antennas on the second tower degrade 

the performance of antennas on the first tower and visa-versa. Exactly 

the same situation occurs when a parasitic element -- in this case the 

flat top of a T-vertical -- is installed within several wavelengths of HF Yagis 

(wavelengths in terms of the HF Yagis, not 160 meter wavelengths). 



We learn from our mistakes... I've made exactly the same mistakes with 

T-verticals, multiple towers with HF Yagis for the same band, and HF Yagi 

booms that are resonant within an HF band (e.g., when I installed a 

72 foot boom 20 meter Yagi a few hundred feet from a 40 meter Yagi 

on another tower). 



For example, I have 20 meter Yagis on two towers spaced 300 feet apart. 

The Yagis on the rear tower are badly degraded when pointing into the 

the 20 meter Yagis 300 feet in front of it. They work perfectly well 

when pointed at least +/- 30 degrees away from the 20M Yagis 300 feet 

in front. 



HF Yagi performance degradation is insignificant when an HF Yagi points 

away from the horizontal top of a T-vertical. But when the Yagi is turned so 

its the 3 dB beamwidth intercepts the horizontal top of a T-vertical, all hell 

breaks loose with: 

- significantly degraded HF Yagi front-to-back ratio, 

- additional sidelobes, 

- splitting of the main beam of the HF Yagi into two or more lobes, 

- reduced gain 




The bottom line: If you care about the performance of your HF Yagis, 

select the length of the horizontal section of a T-vertical so its not 

within +/- 15% of resonance on any HF band you care about. 40 to 

60 feet lengths do not interfere with any HF band other than 30 meters. 



Or use an inverted-L rather than a T-vertical and you'll have no problem 

at all, and -- from practical on the air performance -- an inverted-L is 

imperceptibly worse than a T-vertical. 



I no longer have any T-verticals... 



73 

Frank 

W3LPL 



- Original Message -


From: "Ed Sawyer"  
To: topband@contesting.com 
Sent: Wednesday, February 19, 2020 6:13:02 PM 
Subject: Re: Topband: T-loaded vertical 

The answer to the top loading is that the top is essentially the same as if 
it was an L on the antenna - just with the connection point moved to the 
center. I would add maybe 5 ft on either side of the top to that equation 
and see what it looks like when you install. And, like other verticals. If 
it gives you a good SWR right off the bat, then your ground losses are too 
high. It ideally wants to be around 20 Ohms. I can'

Re: Topband: T-loaded vertical

[Ed Sawyer]

Frank, You will have me grabbing my EZNEC tonight and playing around.  In my 
case my tops are around 60 ft long and they are thankfully perpendicular to my 
20M yagi and about 120 ft away.  However if I beam west on my 40M yagi. I am 
100 ft away and parallel to the wire.   I need to take a look at that.

 

It gets me thinking about the reverse.  Could it “enhance” a direction if 
properly designed?

 

My back T is 250ft even further so almost 400 ft from either tower.  Same T 
design.

 

I have personally found that for Ts that are only 70 ft vertical, like mine, 
the ground losses of the long topped L are not as desirable as the cancelled 
out horizontal lobes of the T.  If the T were say 90 ft of vertical, I don’t 
think the T adds as much value.

 

Ed  N1UR

 

From: donov...@starpower.net [mailto:donov...@starpower.net] 
Sent: Wednesday, February 19, 2020 2:13 PM
To: topband@contesting.com
Subject: Re: Topband: T-loaded vertical

 

Hi Ed,

 

The affect of the T-vertical on a nearby HF Yagi is easily modeled in

EZNEC or your favorite antenna modelling program.  You'll be surprised

by the results if the horizontal top is +/- 15% of resonance on 40 or 20

meters, for example.   HF Yagi performance degradation occurs within ten

(yes, ten) wavelengths, but its especially severe within a few wavelengths

(wavelengths in terms of the HF Yagi, not 160 meter wavelengths).

 

There's no magic distance beyond which parasitic effects no longer occur.

If any conductor carries RF current, its magnitude and phase enters into

the determination of the radiation pattern of the antenna system, even if that

conductor is ten wavelengths away from the main radiator.   Ask any

AM broadcast antenna engineer about this... (if you can still find one).

Maybe K3LR...

 

For many hams, installing a nearby second tower sets back their station

performance.  Why?   Because the antennas on the second tower degrade

the performance of antennas on the first tower and visa-versa.   Exactly

the same situation occurs when a parasitic element -- in this case the

flat top of a T-vertical -- is installed within several wavelengths of HF Yagis

(wavelengths in terms of the HF Yagis, not 160 meter wavelengths).

 

We learn from our mistakes...  I've made exactly the same mistakes with 

T-verticals, multiple towers with HF Yagis for the same band, and HF Yagi

booms that are resonant within an HF  band (e.g., when I installed a

72 foot boom 20 meter Yagi a few hundred feet from a 40 meter Yagi

on another tower).

 

For example, I have 20 meter Yagis on two towers spaced 300 feet apart.

The Yagis on the rear tower are badly degraded when pointing into the

the 20 meter Yagis 300 feet in front of it. They work perfectly well

when pointed at least +/- 30 degrees away from the 20M Yagis 300 feet

in front.

 

HF Yagi performance degradation is insignificant when an HF Yagi points

away from the horizontal top of a T-vertical. But when the Yagi is turned so

its the 3 dB beamwidth intercepts the horizontal top of a T-vertical, all hell

breaks loose with:

   - significantly degraded HF Yagi front-to-back ratio,

   - additional sidelobes,

   - splitting of the main beam of the HF Yagi into two or more lobes,

   - reduced gain

 

The bottom line:  If you care about the performance of your HF Yagis,

select the length of the horizontal section of a T-vertical so its not

within +/- 15% of resonance on any HF band you care about.  40 to

60 feet lengths do not interfere with any HF band other than 30 meters.

 

Or use an inverted-L rather than a T-vertical and you'll have no problem

at all, and -- from practical on the air performance -- an inverted-L is

imperceptibly worse than a T-vertical.

 

I no longer have any T-verticals...

 

73

Frank

W3LPL

 

  _  

From: "Ed Sawyer" 
To: topband@contesting.com
Sent: Wednesday, February 19, 2020 6:13:02 PM
Subject: Re: Topband: T-loaded vertical

The answer to the top loading is that the top is essentially the same as if
it was an L on the antenna - just with the connection point moved to the
center.  I would add maybe 5 ft on either side of the top to that equation
and see what it looks like when you install.  And, like other verticals. If
it gives you a good SWR right off the bat, then your ground losses are too
high.  It ideally wants to be around 20 Ohms.  I can't get mine down past 30
Ohms because of the really poor ground in Vermont.  I started with 24 and
kept adding 6 radials (1/4 wave) at a time until I saw no difference with
the feed point impedance adding the next 6.  That had me end at 48 radials
per T on a 2 el phased array.

 

I was surprised by Frank's comments.  I would get 50 - 75 feet away - but
"hundreds of feet away" would seem too far to have a parasitic element have
effect on a yagi.  Especially a 10, 15, or 20M yagi.  I guess it would be
easily modelled to see.

 

Ed  N1UR

_
Searchable Archives: http:

Re: Topband: T-loaded vertical

[donovanf]

Hi Ed, 



The affect of the T-vertical on a nearby HF Yagi is easily modeled in 
EZNEC or your favorite antenna modelling program. You'll be surprised 
by the results if the horizontal top is +/- 15% of resonance on 40 or 20 
meters, for example. HF Yagi performance degradation occurs within ten 
(yes, ten) wavelengths, but its especially severe within a few wavelengths 
(wavelengths in terms of the HF Yagi, not 160 meter wavelengths). 


There's no magic distance beyond which parasitic effects no longer occur. 
If any conductor carries RF current, its magnitude and phase enters into 
the determination of the radiation pattern of the antenna system, even if that 
conductor is ten wavelengths away from the main radiator. Ask any 
AM broadcast antenna engineer about this... (if you can still find one). 
Maybe K3LR... 


For many hams, installing a nearby second tower sets back their station 
performance. Why? Because the antennas on the second tower degrade 
the performance of antennas on the first tower and visa-versa. Exactly 
the same situation occurs when a parasitic element -- in this case the 
flat top of a T-vertical -- is installed within several wavelengths of HF Yagis 
(wavelengths in terms of the HF Yagis, not 160 meter wavelengths). 


We learn from our mistakes... I've made exactly the same mistakes with 
T-verticals, multiple towers with HF Yagis for the same band, and HF Yagi 
booms that are resonant within an HF band (e.g., when I installed a 
72 foot boom 20 meter Yagi a few hundred feet from a 40 meter Yagi 
on another tower). 


For example, I have 20 meter Yagis on two towers spaced 300 feet apart. 
The Yagis on the rear tower are badly degraded when pointing into the 
the 20 meter Yagis 300 feet in front of it. They work perfectly well 
when pointed at least +/- 30 degrees away from the 20M Yagis 300 feet 
in front. 


HF Yagi performance degradation is insignificant when an HF Yagi points 
away from the horizontal top of a T-vertical. But when the Yagi is turned so 
its the 3 dB b eamwidth intercepts the horizontal top of a T-vertical, all hell 
breaks loose with: 
- significantly degraded HF Yagi front-to-back ratio, 
- additional sidelobes, 
- splitting of the main beam of the HF Yagi into two or more lobes, 
- reduced gain 



The bottom line: If you care about the performance of your HF Yagis, 
select the length of the horizontal section of a T-vertical so its not 
within +/- 15% of resonance on any HF band you care about. 40 to 
60 feet lengths do not interfere with any HF band other than 30 meters. 


Or use an inverted-L rather than a T-vertical and you'll have no problem 
at all, and -- from practical on the air performance -- an inverted-L is 
imperceptibly worse than a T-vertical. 


I no longer have any T-verticals... 


73 
Frank 
W3LPL 


- Original Message -

From: "Ed Sawyer"  
To: topband@contesting.com 
Sent: Wednesday, February 19, 2020 6:13:02 PM 
Subject: Re: Topband: T-loaded vertical 

The answer to the top loading is that the top is essentially the same as if 
it was an L on the antenna - just with the connection point moved to the 
center. I would add maybe 5 ft on either side of the top to that equation 
and see what it looks like when you install. And, like other verticals. If 
it gives you a good SWR right off the bat, then your ground losses are too 
high. It ideally wants to be around 20 Ohms. I can't get mine down past 30 
Ohms because of the really poor ground in Vermont. I started with 24 and 
kept adding 6 radials (1/4 wave) at a time until I saw no difference with 
the feed point impedance adding the next 6. That had me end at 48 radials 
per T on a 2 el phased array. 



I was surprised by Frank's comments. I would get 50 - 75 feet away - but 
"hundreds of feet away" would seem too far to have a parasitic element have 
effect on a yagi. Especially a 10, 15, or 20M yagi. I guess it would be 
easily modelled to see. 



Ed N1UR 

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

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

Re: Topband: T-loaded vertical

[Ed Sawyer]

The answer to the top loading is that the top is essentially the same as if
it was an L on the antenna - just with the connection point moved to the
center.  I would add maybe 5 ft on either side of the top to that equation
and see what it looks like when you install.  And, like other verticals. If
it gives you a good SWR right off the bat, then your ground losses are too
high.  It ideally wants to be around 20 Ohms.  I can't get mine down past 30
Ohms because of the really poor ground in Vermont.  I started with 24 and
kept adding 6 radials (1/4 wave) at a time until I saw no difference with
the feed point impedance adding the next 6.  That had me end at 48 radials
per T on a 2 el phased array.

 

I was surprised by Frank's comments.  I would get 50 - 75 feet away - but
"hundreds of feet away" would seem too far to have a parasitic element have
effect on a yagi.  Especially a 10, 15, or 20M yagi.  I guess it would be
easily modelled to see.

 

Ed  N1UR

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

Topband: T-loaded vertical

[Paul Christensen]

>"With respect to current distribution with the lowered resonance -- N6BV
modeled it in his NEC-4 licensed software, and found no increase in the far
field compared to a resonant antenna."

Looks like I accidentally cross-posted to the TowerTalk list, so I'll bring
it back...

Jim,

I didn't see any change either until I ran a "what if" analysis with several
types of compromised radial systems.  The change wasn't too significant, but
4Nec2 with NEC4 did show improvement when running the surface wave model.
With a reasonably good radial system, I didn't find a modeled change in
field strength.

With our current 80 ft. T, we've not experienced any discernable pattern
distortion to the HF Yagis, including a full-size 4L 40m monobander at 140
ft. but going to a 100 ft length may further reduce any mutual coupling.
With the T resonated at 1400 kHz, that also helps to minimize mutual
coupling to our 200 ft. diameter Hi-Z 8 on 160m.  We've not seen a need to
use a relay to open-circuit the base feed.  The Hi-Z 8 is capable of some
extraordinary F/B but I find big changes throughout the evening.  There are
times when F/B rejection is 30+ dB and other times it may be on the order of
12 dB depending on arrival angles and probably some other factors that are
unknown to me.

Paul, W9AC   

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

Re: Topband: T-loaded vertical

[Richard (Rick) Karlquist]

On 2/18/2020 8:45 AM, N4ZR wrote:
I keep seeing references to people using symmetrical wire top loading 
instead of the single wire of an inverted L.  My question is how to 
calculate the appropriate length for the two top-loading wires.




At least 3 different answers:

1.  If you want the antenna to be resonant on 160 as is (without a
loading coil, etc), then as a rule of thumb, the length of the
vertical section plus the length of ONE of the legs of the top
loading should be about 1/4 wavelength.

2.  If you want to move the current maximum above ground,
you can make the top wire even longer than in #1 above.  You
will need a series capacitor to tune it to 160.  The limit
to this is when the vertical section plus one leg
equals a 1/2 wavelength.  This configuration is difficult
to match, but gets out well if you go to the trouble.

3.  If you are limited in the size of the top loading, you
can install just enough to get near uniform current in the
vertical section.  Then use a loading coil to tune it to
160 meters.  W8JI advocated this.  Perhaps his posts are
in the top band archive.

You really need to model your system and consider all the
tradeoffs including your grounding/radial system.

Rick N6RK
_
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector

Re: Topband: T-loaded vertical

[dj7ww]

Hi Frank,

I just simulated a T vertical 50m away from my 38m high 3L 40m yagi with
EZNEC.
Pattern and gain did not change on the yagi when it beamed 90° away from the
yagi.
Only when I turned the yagi to point to the T antenna gain went down by
0.4dB and front to back by 9dB (was 39). Director parallel to the top load.
Vertical simulated with 30m vertical and 2x 15m horizontal toploads.
No difference with the vertical connected to ground or lifted by 10cm.

73
Peter

-Original Message-
From: Topband [mailto:topband-bounces+dj7ww=t-online...@contesting.com] On
Behalf Of donov...@starpower.net
Sent: Dienstag, 18. Februar 2020 19:01
To: topband reflector
Subject: Re: Topband: T-loaded vertical

Hi Pete, 


Symmetrical T-verticals offer a performance improvement over 
inverted-L verticals but with a major downside if you operate on the 
higher bands. If the flat top of the T-vertical is near resonance on any 
HF band is will significantly degrade the performance of any Yagi 
antenna within hundreds of feet of the flat top. 


My recommendation: if you're serious about the HF bands don't use 
a T-vertical unless you can locate it far from your Yagis. 


I learned this lesson the hard way years ago with a 70 foot flat top 
on my T-vertical I totally trashed my 3 element 40 meter Yagis 
hundreds of feet away. 


73 
Frank 
W3LPL 

- Original Message -

From: "N4ZR"  
To: "topband reflector"  
Sent: Tuesday, February 18, 2020 4:45:27 PM 
Subject: Topband: T-loaded vertical 

I keep seeing references to people using symmetrical wire top loading 
instead of the single wire of an inverted L. My question is how to 
calculate the appropriate length for the two top-loading wires. 

-- 
73, Pete N4ZR 
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster. 

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

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

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

Re: Topband: T-loaded vertical

[Jim Brown]

Yet another example of Frank coming up with excellent advice about 
things we hadn't thought of. At least I hadn't. Thanks Frank.


73, Jim K9YC

On 2/18/2020 10:00 AM, donov...@starpower.net wrote:

If the flat top of the T-vertical is near resonance on any
HF band is will significantly degrade the performance of any Yagi
antenna within hundreds of feet of the flat top.


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

Re: Topband: T-loaded vertical

[donovanf]

Hi Pete, 


Symmetrical T-verticals offer a performance improvement over 
inverted-L verticals but with a major downside if you operate on the 
higher bands. If the flat top of the T-vertical is near resonance on any 
HF band is will significantly degrade the performance of any Yagi 
antenna within hundreds of feet of the flat top. 


My recommendation: if you're serious about the HF bands don't use 
a T-vertical unless you can locate it far from your Yagis. 


I learned this lesson the hard way years ago with a 70 foot flat top 
on my T-vertical I totally trashed my 3 element 40 meter Yagis 
hundreds of feet away. 


73 
Frank 
W3LPL 

- Original Message -

From: "N4ZR"  
To: "topband reflector"  
Sent: Tuesday, February 18, 2020 4:45:27 PM 
Subject: Topband: T-loaded vertical 

I keep seeing references to people using symmetrical wire top loading 
instead of the single wire of an inverted L. My question is how to 
calculate the appropriate length for the two top-loading wires. 

-- 
73, Pete N4ZR 
Check out the Reverse Beacon Network 
at <http://reversebeacon.net>, now 
spotting RTTY activity worldwide. 
For spots, please use your favorite 
"retail" DX cluster. 

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

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

Re: Topband: T-loaded vertical

[Jim Brown]

On 2/18/2020 8:45 AM, N4ZR wrote:
My question is how to calculate the appropriate length for the two 
top-loading wires.


An NEC model. It's a pretty simple one, and can be done in the free 
version that comes with the ARRL Antenna Book.


73, Jim K9YC
_
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector

Topband: T-loaded vertical

[N4ZR]

I keep seeing references to people using symmetrical wire top loading 
instead of the single wire of an inverted L.  My question is how to 
calculate the appropriate length for the two top-loading wires.


--
73, Pete N4ZR
Check out the Reverse Beacon Network
at , now
spotting RTTY activity worldwide.
For spots, please use your favorite
"retail" DX cluster.

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