Re: Topband: Inverted-L question

[Guy Olinger K2AV]

Hi Steve,

5300 pF is way large. It indicates *something *else is going on.
"Something" needs to be determined.

One thing for sure, after nearly a decade of correspondence with this as a
frequent subject, there is no one single "silver bullet" to fix this in all
cases. It is complicated and with several distinctly different causes, each
one by itself capable of causing the symptoms you report. Only *one *of the
several causes is* not* also causing significant RF loss that minimizes
your radiated TX power.

Worse, quite often two or three of them are in effect at the same time. And
excellent reports and suggestions by those trying to help out seem like an
argument about which solution is "the one". In fact, all of the respondents
may be making an excellent suggestion about *one *of the* several ways* the
problem reported above can be caused.

Very unfortunately, one may have to fix all two or three or four to get the
antenna acting with an ideal modeled result.

*So, apologies for the length*, but this one possibly takes a silver
bullet, plus a gold bullet, plus a platinum bullet, plus a depleted uranium
bullet to solve all the possibles responsible for this report. So on to the
stuff

The *large* capacitor needed means that the amount of inductive X being
tuned out *is getting small.* If what you did was lengthen the Inv L
horizontal to get 50Ω R and then use a series capacitor to tune out the
inductive X, the method has a blind spot where the* inductive reactance at
R=50Ω is so low that the cap has to be huge. *

This is usually caused with an Inv L because there is* a lot of **fixed RF
loss R somewhere* added to the L's natural 20-35Ω radiation R at X=0Ω. The
Inv L is decidedly not a natural 50Ω antenna. X=0Ω should not be close to
R=50Ω

If you take away the added loss, the now needed extra length to get R=50Ω
all from radiation resistance (lengthening the horizontal) is substantial.
The longer length has a lot larger inductive X to tune out. This *reduces *the
size of the cap needed. *Smaller *pF value caps produce the *larger
*capacitive reactance
to cancel out that larger inductive X.

And of course it could be that something in the environment is giving you
an "X push" one way or the other.

So exactly *what *is the added RF loss, or X push, and *what *is causing
it?

To start, you have an *undefined* tower involvement which is capable of
producing a very large RF loss addition to that tower-supported 1/4
wave-ish L, *and at the same time *also capable of producing a very large X
push in a capacitive *or *inductive direction.

Anything in the k2av.com "Loss List"
 could
be adding ohms to the feedpoint R.

One of the splendidly frustrating things about 160 meter antennas is,
unless we can put up a 160 dipole at 250', we probably need to go vertical
oriented.

We can't do problem-solving on vertical-antennas-for-160 accurately or
effectively without considering several overwhelming factors on 160: Loss,
ground effects, and a monstrous wavelength which multiplies miscellaneous
conductor involvement.

These can't be reliably determined or solved by tuning for SWR. You're only
trying to match* (antenna + problems)* to 50Ω.

The inverted L with the bend supported by the tower, and fed at the
radials, is really a transformer in disguise. *The L is one winding of the
"transformer". The tower and each coax shield and control conductor on the
tower are separate windings in this multi-winding ad-hoc "transformer".*

Somewhere in my stuff I have a NEC 4 model of an L supported at the bend by
a tower that has more induced current in the tower than there is in the L.
This transformer situation has an *effective *turns ratio that keeps the
tower with lower voltage and higher current. This higher current is then
driven into and dissipated in the ground.

If your tower cabling has:

All its shields and unused conductors in the cable grounded to the tower at
the base...

And all active control conductors bypassed to the tower at the base…

Then Tree's suggestion to detune the tower works to its maximum
effectiveness.

But tower detuning has to be done well. Otherwise the induction to the
tower will still drive a lot of current into the ground. The induced RF
current in ungrounded or unbypassed coax shields and control conductors
will be driven into ground via capacity effect all along their lengths
laying on or buried in the ground between the tower and the shack This loss
adds to the R of the L feed through the above transformer effect.

A second issue is whether the radial's center is solidly connected to the
tower's cable grounding point. That will substantially reduce the dirt's R
that the induction is forcing RF into.

One case I was involved in violently changed the feed Z when the tower base
was bonded to the radial feed. The performance picked up substantially and
he only needed a 5:4 turns ratio transformer to get close to 50 ohms after
pruning the L for X=0. Until t

Re: Topband: Inverted-L question

[Michael Tope]

Remember, Steve, for a given frequency more capacitance equals less 
capacitive reactance [Xc = 1/(2*pi*f*c)]. At 1825 KHz, 5300 pf is only 
16.5 ohms reactance. That means you are only offsetting a small amount 
of inductive reactance. Where you should be more concerned is when the 
series capacitance is very small. That is when capacitive reactance (Xc) 
gets large and the RF voltage across the series capacitor can get very 
high.


73, Mike W4EF..

On 12/20/2023 5:43 PM, Steve Muenich wrote:

I have an Inverted-L question that hopefully someone can answer for me.

I  installed the 160m  wire to the 80 ft level on a 100 ft Rohn 45 tower
with top mounted yagis.
The horizontal (sort of) portion is approx 45ft long.
The wire starts at 80 ft down approx 5 ft from tower and when it gets to
the match box the bottom of the wire is about 10ft away from tower.

I have about 50 or so 120 ft long radials.

I am able to get a X=0, R=52. SWR 1.19:1 tune according to my RE Zoom using
load shunt match at base of tower.

My question is why do I need so much series capacitance (5300pf) with
parallel inductance approx 8uh?

Everything is working fine, but I am wanting to understand why I am needing
so much series capacitance? Does this indicate an issue I need to resolve?

TIA,

Steve, NA5C
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Re: Topband: Inverted L Question

[Pete Smith N4ZR]

FWIW, for 160 I used my old 97-foot Rohn 25 tower, with 2 tribanders and 
a 40M 2-el on it, shunt fed at about 50 feet.  I had a pair of 300 uf 
variable caps at the bottom, one in series with the feed and the other 
in parallel.  It proved to be easy to tune to low SWR once I discovered 
that the local 500-watt radio station on 1500+ KHz went to low power at 
6 pm, so my MFJ analyzer didn't freak out from the received signal.


73, Pete N4ZR

On 12/21/2023 4:55 PM, Jim Brown wrote:

On 12/21/2023 12:54 PM, Paul Dulaff via Topband wrote:
Ran a basic EZNEC model with no tower present for your 80 ft X 45 ft 
inverted L at 1.825 Mhz. The base impedance for this is 28.5 - j 130 
ohms.  The get rid of the reactance I extended the top wire an 
additional 20 ft so 80 X 65 ft and base impedance is 37.2 + j0. The 
tower is definitely influencing the inverted L.


Neighbor K6RB described a 160 vertical running next to his tower, and 
I don't remember him do anything to detune the tower. Yes, the tower 
becomes part of the antenna, but that isn't a bad thing as long as we 
take it into account to match it to the line. AND -- unless the line 
is quite long or uses lossy coax (like RG58), excess loss on 160M is 
quite low.


I've seen (and used) a simple equation for determining the effective 
diameter of a triangular tower. An NEC model should include that, as 
well as aluminum at the top.


For my Tee, I adopted the ancient and accepted practice of making the 
horizontal element long enough that the feedpoint Z became 50 +jX at 
the desired center of operation, and added series C at the feedpoint 
to equal -jX. I can do this because my Tee is strung between tall 
redwoods.


I ended up with C in the range of 800-900 pF. What's required here is 
capacitors with very low loss, but not particularly high voltage, 
because they're at a high current point, not a high voltage point. So 
their voltage rating is tied to peak value of TX power. I had a stash 
of low loss caps in the 2-3kV range, and used those in parallel, in a 
weatherproof box.


73, Jim K9YC

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Re: Topband: Inverted L Question

[Jim Brown]

On 12/21/2023 12:54 PM, Paul Dulaff via Topband wrote:
Ran a basic EZNEC model with no tower present for your 80 ft X 45 ft 
inverted L at 1.825 Mhz. The base impedance for this is 28.5 - j 130 
ohms.  The get rid of the reactance I extended the top wire an 
additional 20 ft so 80 X 65 ft and base impedance is 37.2 + j0. The 
tower is definitely influencing the inverted L.


Neighbor K6RB described a 160 vertical running next to his tower, and I 
don't remember him do anything to detune the tower. Yes, the tower 
becomes part of the antenna, but that isn't a bad thing as long as we 
take it into account to match it to the line. AND -- unless the line is 
quite long or uses lossy coax (like RG58), excess loss on 160M is quite 
low.


I've seen (and used) a simple equation for determining the effective 
diameter of a triangular tower. An NEC model should include that, as 
well as aluminum at the top.


For my Tee, I adopted the ancient and accepted practice of making the 
horizontal element long enough that the feedpoint Z became 50 +jX at the 
desired center of operation, and added series C at the feedpoint to 
equal -jX. I can do this because my Tee is strung between tall redwoods.


I ended up with C in the range of 800-900 pF. What's required here is 
capacitors with very low loss, but not particularly high voltage, 
because they're at a high current point, not a high voltage point. So 
their voltage rating is tied to peak value of TX power. I had a stash of 
low loss caps in the 2-3kV range, and used those in parallel, in a 
weatherproof box.


73, Jim K9YC

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Topband: Inverted L Question

[Paul Dulaff via Topband]

Steve

Ran a basic EZNEC model with no tower present for your 80 ft X 45 ft 
inverted L at 1.825 Mhz. The base impedance for this is 28.5 - j 130 
ohms.  The get rid of the reactance I extended the top wire an 
additional 20 ft so 80 X 65 ft and base impedance is 37.2 + j0. The 
tower is definitely influencing the inverted L.


Best 73's

Paul - W2NMI



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Topband: Inverted-L Question

[Tom Boucher]

Steve,
For comparison my inverted-L is similar to yours with a 94 ft vertical
section and 43 ft horizontal (ish). It is on a tall tree, not a tower.

Like you, I use an L-network to match it and get a feed impedance on 1826.5
KHz of 50+j0. I have a 1600pF capacitor in parallel but no inductor as I
simply extended the antenna length to make it slightly inductive.

73,
Tom G3OLB
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Re: Topband: Inverted-L question

[Tree]

Without getting into the measurements - I think you need to detune the
tower if that is going to work at all.  Probably put a trap in the bottom
20 feet.

Tree N6TR

On Thu, Dec 21, 2023 at 6:27 AM Noel Lopez via Topband <
topband@contesting.com> wrote:

> Here is my 2 cents worth.  First of all, I am not an antenna expert nor do
> I know how to use antenna modeling software.These are my thoughts based on
> my experience and what I remember reading.  My low band system is an
> inverted L under a SteppIr yagi that can be retracted.  This avoids the
> capacitance hat effect on the inverted L.
> The capacitative top hats you have on your tower make the inverted L
> "appear" longer thus requiring morecapacitance to match the inverted L.
> If there were no yagis to create capacitance over the inverted L,
> the antenna would appear shorter and require less capacitance to match.
> Capacitative matching is less lossy and more efficient than inductive
> matching from what I remember.
> I am posting this to see if anyone can add-to or correct my comments.
> Noel Lopez NR5R
> On Wednesday, December 20, 2023 at 07:52:00 PM CST, Steve Muenich <
> srmuen...@gmail.com> wrote:
>
>  I have an Inverted-L question that hopefully someone can answer for me.
>
> I  installed the 160m  wire to the 80 ft level on a 100 ft Rohn 45 tower
> with top mounted yagis.
> The horizontal (sort of) portion is approx 45ft long.
> The wire starts at 80 ft down approx 5 ft from tower and when it gets to
> the match box the bottom of the wire is about 10ft away from tower.
>
> I have about 50 or so 120 ft long radials.
>
> I am able to get a X=0, R=52. SWR 1.19:1 tune according to my RE Zoom using
> load shunt match at base of tower.
>
> My question is why do I need so much series capacitance (5300pf) with
> parallel inductance approx 8uh?
>
> Everything is working fine, but I am wanting to understand why I am needing
> so much series capacitance? Does this indicate an issue I need to resolve?
>
> TIA,
>
> Steve, NA5C
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> Reflector
>
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>
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Re: Topband: Inverted-L question

[Noel Lopez via Topband]

Here is my 2 cents worth.  First of all, I am not an antenna expert nor do I 
know how to use antenna modeling software.These are my thoughts based on my 
experience and what I remember reading.  My low band system is an inverted L 
under a SteppIr yagi that can be retracted.  This avoids the capacitance hat 
effect on the inverted L. 
The capacitative top hats you have on your tower make the inverted L "appear" 
longer thus requiring morecapacitance to match the inverted L.    If there were 
no yagis to create capacitance over the inverted L, the antenna would appear 
shorter and require less capacitance to match.  Capacitative matching is less 
lossy and more efficient than inductive matching from what I remember.
I am posting this to see if anyone can add-to or correct my comments.
Noel Lopez NR5R
On Wednesday, December 20, 2023 at 07:52:00 PM CST, Steve Muenich 
 wrote:  
 
 I have an Inverted-L question that hopefully someone can answer for me.

I  installed the 160m  wire to the 80 ft level on a 100 ft Rohn 45 tower
with top mounted yagis.
The horizontal (sort of) portion is approx 45ft long.
The wire starts at 80 ft down approx 5 ft from tower and when it gets to
the match box the bottom of the wire is about 10ft away from tower.

I have about 50 or so 120 ft long radials.

I am able to get a X=0, R=52. SWR 1.19:1 tune according to my RE Zoom using
load shunt match at base of tower.

My question is why do I need so much series capacitance (5300pf) with
parallel inductance approx 8uh?

Everything is working fine, but I am wanting to understand why I am needing
so much series capacitance? Does this indicate an issue I need to resolve?

TIA,

Steve, NA5C
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Topband: Inverted-L question

[Steve Muenich]

I have an Inverted-L question that hopefully someone can answer for me.

I  installed the 160m  wire to the 80 ft level on a 100 ft Rohn 45 tower
with top mounted yagis.
The horizontal (sort of) portion is approx 45ft long.
The wire starts at 80 ft down approx 5 ft from tower and when it gets to
the match box the bottom of the wire is about 10ft away from tower.

I have about 50 or so 120 ft long radials.

I am able to get a X=0, R=52. SWR 1.19:1 tune according to my RE Zoom using
load shunt match at base of tower.

My question is why do I need so much series capacitance (5300pf) with
parallel inductance approx 8uh?

Everything is working fine, but I am wanting to understand why I am needing
so much series capacitance? Does this indicate an issue I need to resolve?

TIA,

Steve, NA5C
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Re: Topband: Inverted L question

[Jim Brown]

On Tue,2/3/2015 1:55 PM, Art Snapper wrote:

How important is it for the top part to be led away at a right angle?

I was considering running it vertically 80ft, then about 25 feet at a 45
degree up angle and 25 feet at a 45 degree down angle, over the top of the
supporting tree.


That shape should work just fine, BUT -- the end of an inverted L is a 
high voltage point (VERY high voltage if you're running an amp), so it's 
easy to get arcing to the tree. I had a 160 dipole up for several years, 
and the first rigging had one end in contact with foliage of the tall 
redwood that held it up. When I took it down for maintenance, the 
insulation was heavily scorched.


Another suggestion. Do you have skyhooks that you might use to turn it 
into a Tee? If you can, it will work as well or better than the L. Both 
configurations are simple ways of providing top-loading.


Bottom line -- run it through the tree with caution. It will work, but 
things can go wrong. :)


73, Jim K9YC
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Re: Topband: Inverted L question

[Guy Olinger K2AV]

The most important part of an inverted L is the counterpoise, be it raised
radials, buried or on-ground radials or an FCP. Be sure you can do a
counterpoise well. Otherwise the counterpoise can be a huge RF loss, easily
negating anything done well with the L wire itself.

Next the vertical part of the wire is most important. 80 feet up will do
very well, and will carry the large majority of total RF current density.

The horizontal will fill in the hole in the doughnut pattern of a vertical,
but more useful, you can use its length to help tune the antenna. Adding or
taking away from the far end of the horizontal can be a very useful tuning
device. The shape, slope, "straightness" of the "horizontal" are fairly
immaterial. Dropping down at 45 degrees will produce a lower feed Z and a
narrower bandwidth than the same pulled away parallel to the ground.

The pattern of an L always has a mild to moderate weakness in the otherwise
omnidirectional pattern, in the direction that the horizontal pulls away
from the bend in the L. In the Southeast US, you want the horizontal wire
of an L to pull away toward the SE, so the weak quadrant is not to the SW,
W, NW, N or NE.

73, Guy K2AV

On Tue, Feb 3, 2015 at 4:55 PM, Art Snapper  wrote:

> I have been looking at locations on my property to install an Inverted L
> for 160.
>
> How important is it for the top part to be led away at a right angle?
>
> I was considering running it vertically 80ft, then about 25 feet at a 45
> degree up angle and 25 feet at a 45 degree down angle, over the top of the
> supporting tree.
>
> de Art NK8X
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Re: Topband: Inverted L question

[James Bennett]

Art, from what I’ve read, I understand that the non-vertical part of the 
Inverted L does not have to be completely horizontal - it can slope with little 
detriment to it’s radiation pattern. I have two - one for 80 and one for 160. 
Both of ‘em slope away from the top support.

Jim / W6JHB


> On   Tuesday, Feb 3, 2015, at  Tuesday, 1:55 PM, Art Snapper  
> wrote:
> 
> I have been looking at locations on my property to install an Inverted L
> for 160.
> 
> How important is it for the top part to be led away at a right angle?
> 
> I was considering running it vertically 80ft, then about 25 feet at a 45
> degree up angle and 25 feet at a 45 degree down angle, over the top of the
> supporting tree.
> 
> de Art NK8X
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Topband: Inverted L question

[Art Snapper]

I have been looking at locations on my property to install an Inverted L
for 160.

How important is it for the top part to be led away at a right angle?

I was considering running it vertically 80ft, then about 25 feet at a 45
degree up angle and 25 feet at a 45 degree down angle, over the top of the
supporting tree.

de Art NK8X
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Re: Topband: Inverted L question

[Guy Olinger K2AV]

On Thu, Dec 27, 2012 at 10:12 AM, Ashton Lee 
 wrote:

> Several of us here in Western Colorado run slopers off the tower, which I
> believe is essentially loading the tower with an elevated lead. It works
> for us.


Sloper is really not the same thing as a parallel vertical wire at four
feet as with the original poster.  The vertical wire parallel to the tower
at four feet has a much higher degree of coupling to the tower than your
sloper.

The tower is induced to a degree either way, but if the tower to dirt
resistance is high, the impedance of the sloper is not changed nearly to
the extent that the L's is.  The close coupling of the L works harder on
the tower's base resistance.   This is very easy to model.  Varying a load
resistance at the base of the tower in either case will show the dependence
of either antenna.  The worst losses occur when the tower, plus all its
antennas viewed as top loading, is close to natural resonance on 160.

Once the tower current gets down to a third or a fourth of the current in
the driven antenna, the antenna should be out of the deep woods for induced
loss.  As usual, those with really good conductive dirt are far less
affected than those with poor soil.

It is a very good exercise to model the tower and its entire antenna and
its conductors, along with all the other antennas, with feedlines
explicitly included.  Once you get that model done, a bit of a PITA the
first time, you hang on to it, and keep it current. You turn on the
feedpoints (EZNEC "sources") one at a time and see what happens.  There
should be a "load" in the bottom of the tower to account for the base
resistance to the dirt.   The devil is in the details.   Some folks come
out fairly clean, others have surprising interactions paid for in loss.  If
you are the latter, it's a very useful thing to know.

73, Guy
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Re: Topband: Inverted L question

[Guy Olinger K2AV]

On Wed, Dec 26, 2012 at 3:08 PM, Tom W8JI  wrote:

>
> At any distance less than 1/4 wave or so, which is around 130 feet, the
> inverted L is coupled very tightly to the tower. At wider spacings, like
> 50-100 feet, the tower and things on the tower **sometimes** won't have
> much interaction. Of course if you are unlucky, interaction can be severe
> even at a hundred feet spacing or more.
> [Several more paragraphs of good stuff.]


Completely agree with Tom.

Tom didn't elaborate on just how BAD that loss can be.  Think of your L and
your tower as being two windings on the same transformer.  If the base of
your tower is just in the ground, and directly tower connected steel guys
go to steel anchors in the ground, that basically is a close-coupled
transformer winding connected to a big resistor.

Some have moved the feed, supporting the far end of the L horizontal with
the tower, and using a tree to support the bend in the L.

If your tower is the only possible support and you can't relocate the L,
 you will have to prep the tower just the same as if you were going to feed
it with a gamma match.  Among all the other stuff, the L feed and the tower
base must share the radial field.  If you have to do all the work to prep
the tower, maybe forget the L and just load the tower.  Lot of loud
stations out there loading  up their tower over a quality radial system.

Even if you keep the feed at the tower, don't skimp on the radials.  Do
them right.  Take the time.  The radials/counterpoise is always the most
important performance detail.  Nothing in second place.

73, Guy
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Re: Topband: Inverted L question

[ZR]

- Original Message - 
From: "Tom W8JI" 

To: "Herb Krumich" ; 
Sent: Wednesday, December 26, 2012 3:08 PM
Subject: Re: Topband: Inverted L question


I am right now using an inverted L which is spaced about 4 feet away from 
my tower. The vertical leg is about 85 feet. I only have 6 radials at the 
present time

Now here is the question
The horizontal leg is about 50 feet and goes to my back yard. Since the 
trees are not that high, it probably slopes down to 40 feet at the far end

The horizontal wire faces west..
Would it help me to face that wire to the south for east west signals on 
transmit. I am hearing very well with a 550 foot beverage. >>>


At a prior QTH I had a 100' tower with a Christmas tree of HB 4 el wide 
spaced yagis for 10-15-20M and a 4 el KLM 40M on another tower about 60' 
away.


The 100' tower was shunt fed on 160. Several months after the KLM was 
installed the VSWR went haywire and I used a coax balun until moving several 
years later. Never considered the possibility of another antenna causing the 
problem BUT KLM also suggested later to connect the parasitic elements to 
the boom with aluminum strap.


In the 60's I had baluns burn out twice on a TH6 and finally went with a 
coil of coax. A 6 el 6M yagi was about 4' above it and fed with the legal 
limit. Coincidence? Both were similar construction I believe.


Carl
KM1H




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Re: Topband: Inverted L question

[Tom W8JI]

I am right now using an inverted L which is spaced about 4 feet away from my 
tower. The vertical leg is about 85 feet. I only have 6 radials at the 
present time

Now here is the question
The horizontal leg is about 50 feet and goes to my back yard. Since the 
trees are not that high, it probably slopes down to 40 feet at the far end

The horizontal wire faces west..
Would it help me to face that wire to the south for east west signals on 
transmit. I am hearing very well with a 550 foot beverage. >>>


At any distance less than 1/4 wave or so, which is around 130 feet, the 
inverted L is coupled very tightly to the tower. At wider spacings, like 
50-100 feet, the tower and things on the tower **sometimes** won't have much 
interaction. Of course if you are unlucky, interaction can be severe even at 
a hundred feet spacing or more.


You have a particularly close situation. For all purposes, at less than a 
few dozen feet spacing, the tower and inverted L are really just one big 
antenna system. The tower characteristics, including ground system and 
cables leaving the tower, and all the guy wires and things on the tower, are 
all part of that inverted L system. The tower can suck up a lot of RF and 
divert it to places that hurt your signal, even if the tower system is not 
resonant. This would include lossy ground below the tower, and all the 
cables and wires leaving the tower.


Much more critical than the direction you run the flattop, which is probably 
only worth part of single dB, is how the tower is constructed and wired. If 
the tower has no radials, or has uninsulated guy wires going to anchors, a 
considerable amount of energy can be dissipated in lossy earth. How much of 
a problem it is really depends on details of the tower installation more 
than anything else.


73 Tom


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Re: Topband: Inverted L question

[N1SV]

Snip: I am right now using an inverted L which is spaced about 4 feet away
from my tower. The vertical leg is about 85 feet. 

I remember a number of years ago  talking with Jeff Briggs (K1ZM) about
ideas for my first inverted-L while we were both waiting for flights out of
the Dayton Hamvention.  Like you I wanted to use my tower as a support and
Jeff suggested that the vertical wire be at least 15-feet away from the
tower.  In short I did what Jeff suggested and the antenna worked well.  As
an alternative you can also detune the tower.

Snip: I only have 6 radials at the present time Now here is the question The
horizontal leg is about 50 feet and goes to my back yard. Since the trees
are not that high, it probably slopes down to 40 feet at the far end The
horizontal wire faces west.. Would it help me to face that wire to the south
for east west signals on transmit.  

I would not lose too much sleep on your horizontal wire and the specific
direction that’s its pointing.  In theory there is a very small amount of
gain in the opposite direction to that of the horizontal wire.  If you model
this there is only about a 1.5 DB F/B ratio, certainly nothing to write home
about.  Since the inverted-L is a shortened vertical it benefits from a good
ground system so I would definitely add some more radials.

73,

Les, N1SV

___
Stew Perry Topband Distance Challenge coming on December 29th.

Re: Topband: Inverted L question

[Clive GM3POI]

Herb, 
Your best bet is to add another 50ft and make a T rather than inverted L.
The L will only be of use on very local (out to 200 miles) QSOs.
With a T it will remove the Horizontal and I suggest unnecessary component.
Mine has the T dropping to about 33ft with 51ft Vertical but over a serious
ground system. 73 Clive GM3POI  

-Original Message-
From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Herb
Krumich
Sent: 24 December 2012 19:14
To: topband@contesting.com
Subject: Topband: Inverted L question

I am right now using an inverted L which is spaced about 4 feet away from my
tower. The vertical leg is about 85 feet. I only have 6 radials at the
present time
Now here is the question
The horizontal leg is about 50 feet and goes to my back yard. Since the
trees are not that high, it probably slopes down to 40 feet at the far end
The horizontal wire faces west.. 
Would it help me to face that wire to the south for east west signals on
transmit.  I am hearing very well with a 550 foot beverage. But missing many
stations that I call.  My power is not to high with the old Drake L7.. About
600 watts
Thanks Guys and Merry Christmas
Herb K2LNS
___
Stew Perry Topband Distance Challenge coming on December 29th.



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___
Stew Perry Topband Distance Challenge coming on December 29th.

Topband: Inverted L question

[Herb Krumich]

I am right now using an inverted L which is spaced about 4 feet away from my 
tower. The vertical leg is about 85 feet. I only have 6 radials at the present 
time
Now here is the question
The horizontal leg is about 50 feet and goes to my back yard. Since the trees 
are not that high, it probably slopes down to 40 feet at the far end
The horizontal wire faces west.. 
Would it help me to face that wire to the south for east west signals on 
transmit.  I am hearing very well with a 550 foot beverage. But missing many 
stations that I call.  My power is not to high with the old Drake L7.. About 
600 watts
Thanks Guys and Merry Christmas
Herb K2LNS
___
Stew Perry Topband Distance Challenge coming on December 29th.

Re: Topband: Inverted L Question

[Guy Olinger K2AV]

"and radial"  is that really singular or a typo?   73, Guy.

On Mon, Apr 30, 2012 at 11:16 AM, Jim WA9YSD  wrote:

> My feed point impedance with every thing grounded and measuring against
> the tower ground and radial is 27 ohms.
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[Jim WA9YSD]

I have been playing with and reading about inverted L, and verticals Since 
November 2011.  I had very little experience with them before that time.

I have the feed point mounded next to the tower where I could make measurements 
and the sort. My feed point impedance with every thing grounded and measuring 
against the tower ground and radial is 27 ohms. My 1:2 balun from Balun Design 
was ordered and should be here today. :-)

If you want to add an 80M section to your inverted L,  Leave around 15 feet of 
it going out in the opposite direction or add a trap, be careful and be 
observant that the resonant point on 160M may change.  The key it to match the 
impedance and let the tuner do the work to match the SWR.

What I have done was half way up I attached and insulator and a rope to it I 
pulled it about 10 feet away from the tower.

If this does not work I will try to gamma match the tower.  I ran test using 
the Reverse Beacon system and found out what devices and setups worked and do 
not work.

My next trek is to Use the Reverse Beacon System again and compare some one 
else's signal with mine at the same time and see how I compare.
 
Stay on course, fight a good fight, and keep the faith. Jim K9TF/WA9YSD
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question - Reply

[Ulrich Weiss]

hello Guy,

I have been using a 3/8 Lambda Inverted Vee on my telescoping 55 foot tower 
(with a 5 Band Quad on top) for a couple of years now... I'm well aware of 
the fact that there is a significant amout of coupling between the 
Inverted-L and the tower... but as they are connected to the same ground 
system, I do not see where power ("5 or 10 db lost") should be wasted...
considering to try your FCP on the Inverted-L I have obtained the cores for 
the transformer, but the current discussion makes me doubt that it will be 
helpful as the tower is still connected to my (buried) ground system... do 
you think that detuning the tower (with the lines going up bonded to the 
tower) might improve the situation???
BTW, I do not mind the horizontal part of the radiation as it seems to help 
me a lot in 160m-contestst to work the numerous EU-multipliers... DX-wise I 
am not entirely unhappy as I have be able to work almost all the rare stuff 
in and outside of contests, but, of course, the better is the enemy of the 
good...
kind regards

Uli, DJ2YA

- Original Message - 
From: "Guy Olinger K2AV" 
To: "Lloyd Korb" 
Cc: 
Sent: Sunday, April 29, 2012 10:22 PM
Subject: Re: Topband: Inverted L Question - Reply


> The normal innocent presumption would be that your feedlines and other
> miscellaneous conductors are not involved in your patterns.  But if your L
> and your 6BTV are engaged in a horse race on 160, your tower/L is really
> not doing well, and has the typical loss problems for that setup.
>
> My personal inverted L is out in the woods away from everything, without
> radials for that matter, uses an FCP.  It simply blows away anything I 
> have
> ever used on 160 on this property, nothing close.  There is nothing
> intrinsically inferior about an L.  Yes there is something about a few
> tenths of a dB down from a completely vertical 1/4 w radiator,  but your
> case sounds more like 5 dB lost or 10 dB lost.
>
> You are likely hearing a LOT off the OTHER feedline shields (because they
> are also close coupled to the L vertical) and effected by miscellaneous
> conductors in the vicinity.  You shouldn't have any real expectation of a
> clean vertical doughnut pattern, and miscellaneous conductors NOT sturdily
> blocked for common mode current will have you listening everywhere,
> including to all the garbage on the safety wire of your house wiring.
>
> 73, Guy.


___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question - Reply

[Guy Olinger K2AV]

The normal innocent presumption would be that your feedlines and other
miscellaneous conductors are not involved in your patterns.  But if your L
and your 6BTV are engaged in a horse race on 160, your tower/L is really
not doing well, and has the typical loss problems for that setup.

My personal inverted L is out in the woods away from everything, without
radials for that matter, uses an FCP.  It simply blows away anything I have
ever used on 160 on this property, nothing close.  There is nothing
intrinsically inferior about an L.  Yes there is something about a few
tenths of a dB down from a completely vertical 1/4 w radiator,  but your
case sounds more like 5 dB lost or 10 dB lost.

You are likely hearing a LOT off the OTHER feedline shields (because they
are also close coupled to the L vertical) and effected by miscellaneous
conductors in the vicinity.  You shouldn't have any real expectation of a
clean vertical doughnut pattern, and miscellaneous conductors NOT sturdily
blocked for common mode current will have you listening everywhere,
including to all the garbage on the safety wire of your house wiring.

73, Guy.

On Sun, Apr 29, 2012 at 8:51 AM, Lloyd Korb  wrote:

> To everyone how replied to my Inverted L question, a big THANKS!  I really
> learned a lot from the replies.
>
> I know that what I have is not an ideal situation for the Inverted L but
> it's all I have available to me.  I live on a very standard one third of an
> acre city lot.  My 60 foot tower is used to support a multitude of VHF/UHF
> yagis used for weak signal operation.  Prior to a friend giving me an old
> 6BTV vertical, last year, the Inverted L was my best shot for getting on
> 160
> meters.
>
> As one fellow said, "If it's not broke, don't fix it".  It is a great
> antenna for me.  I am able to use it on 160 through 10 meters using my
> tuner.  Maybe ignorance is bliss!!
>
> What is interesting to me is the fact that at times the L seems to have a
> different polarity than the 6BTV.  I can switch back and forth between the
> two antennas, on bands other than 160 meters, and see quite a difference in
> signal strength.  So, If the L is actually just inducing current to the
> tower, on 160, it should be vertically polarized.  Then I really shouldn't
> see a difference between to vertically polarized antennas!  Could this
> difference be because of the horizontal part of my Inverted L radiating!
>
> After being a Ham for over 55 years I'm still learning something new!
>
> Thanks again for all of your replies.
>
> 73,  Lloyd  K8DIO
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question - Reply

[Herb Schoenbohm]

The "L" most likely has a significant amount of horizontal component.  
It is not a bad antenna on 160 but neither is it a great antenna.  It is 
better than and inverted Vee most of the time but there are time like ar 
SS and SR when the horizontal antenna will work very well for DX.  That 
period of time is only a few minutes before and after those events.  For 
working someone up to 1000 miles away many times the horizontal antenna 
or one like you describe with a horizontal component will work better.

Herb, KV4FZ




On 4/29/2012 9:13 AM, chacuff wrote:
> - Original Message -
> From: "Lloyd Korb"
> To:
> Sent: Sunday, April 29, 2012 7:51 AM
> Subject: Topband: Inverted L Question - Reply
>
>
>> What is interesting to me is the fact that at times the L seems to have a
>> different polarity than the 6BTV.  I can switch back and forth between the
>> two antennas, on bands other than 160 meters, and see quite a difference
>> in
>> signal strength.
> cut
>
> I have no way at this point to model antennas but I would guess on bands
> other than 160 you are seeing lobes in the radiation patern of the L/tower
> due to it being closer to and over a wavelength depending on what frequency
> it is being used at.  The 6BTV being more omni.  Both should still be
> vertical...  It's always nice to have more than one antenna option in a
> given situation.
>
> Cecil
> K5DL
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question - Reply

[chacuff]

- Original Message - 
From: "Lloyd Korb" 
To: 
Sent: Sunday, April 29, 2012 7:51 AM
Subject: Topband: Inverted L Question - Reply


> What is interesting to me is the fact that at times the L seems to have a
> different polarity than the 6BTV.  I can switch back and forth between the
> two antennas, on bands other than 160 meters, and see quite a difference 
> in
> signal strength.

cut

I have no way at this point to model antennas but I would guess on bands 
other than 160 you are seeing lobes in the radiation patern of the L/tower 
due to it being closer to and over a wavelength depending on what frequency 
it is being used at.  The 6BTV being more omni.  Both should still be 
vertical...  It's always nice to have more than one antenna option in a 
given situation.

Cecil
K5DL 

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[chacuff]

- Original Message - 
From: "Mike(W5UC)" 
To: 
Sent: Sunday, April 29, 2012 6:55 AM
Subject: Re: Topband: Inverted L Question


> Good Morning Lloyd & All:
>
> You have described my 160 & 80 meter antennas almost exactly.  The
> vertical part of my L is about 3 feet away from the tower at the top,
> and approximately 2 feet away at the bottom.  I also have a 80 meter
> vertical wire on the other side of my tower.  The 80 meter wire is
> approximately 3 feet from the tower at both ends.

---cut---

Hi Mike and the Group

Sounds like mine as well with the exception of the 80 meter wire and fewer 
radials.   Which concerns me a bit because I had considered loading the 
tower after I put it up but didn't because I was told the Force 12 yagi was 
not well suited for that and that I would probably blow something up. 
(insulated elements and ferrite bead balun) With that in mind I placed all 
the coax on the outside of the tower5 runs of LMR 600 and abandoned that 
idea. (strike two)...

So I ran the L and it has worked OK with 1kw. But what am I doing to the 
other antennas and feedlines?

What to do now...

Cecil
K5DL 

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Topband: Inverted L Question - Reply

[Lloyd Korb]

To everyone how replied to my Inverted L question, a big THANKS!  I really
learned a lot from the replies.

I know that what I have is not an ideal situation for the Inverted L but
it's all I have available to me.  I live on a very standard one third of an
acre city lot.  My 60 foot tower is used to support a multitude of VHF/UHF
yagis used for weak signal operation.  Prior to a friend giving me an old
6BTV vertical, last year, the Inverted L was my best shot for getting on 160
meters.  

As one fellow said, "If it's not broke, don't fix it".  It is a great
antenna for me.  I am able to use it on 160 through 10 meters using my
tuner.  Maybe ignorance is bliss!!

What is interesting to me is the fact that at times the L seems to have a
different polarity than the 6BTV.  I can switch back and forth between the
two antennas, on bands other than 160 meters, and see quite a difference in
signal strength.  So, If the L is actually just inducing current to the
tower, on 160, it should be vertically polarized.  Then I really shouldn't
see a difference between to vertically polarized antennas!  Could this
difference be because of the horizontal part of my Inverted L radiating!

After being a Ham for over 55 years I'm still learning something new!

Thanks again for all of your replies.

73,  Lloyd  K8DIO

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[Mike(W5UC)]

Good Morning Herb;

In years past, when I was living about 30 miles north of Dallas, I had a 
shunt fed tower, and it worked very well.  However, when I tried the 
same configuration here, I got my fanny kicked on a regular basis, and 
that was why I decided to put up the Inverted L.  Occasionally I am 
tempted to re-establish the shunt fed  configuration.  I am about to 
plunk down $200 for an instrument to measure the complex impedance at 
the feed point of the "gamma" match, and at that point I may  go back & 
try the shunt configuration again.  However, for the moment, I am 4 or 5 
entities away from DXCC on 160, and untill I get that done I will stay 
in "If it ain't broke, don't fix it"  Mode.

73,
Mike, W5UC



On 4/29/2012 7:09 AM, Herb Schoenbohm wrote:
> Mike,  You would be much better off by feeding the tower with a shunt or
> cage feed.  As K2AV so accurately pointed out...an inverted "L"
> supported by a metal tower is not the answer for an efficient system on
> 160.  With the amount of radials you have at the base you could do much
> better by feeding the grounded tower.  I presume the tower has a beam on
> the top and that will really make you system even more efficient by
> providing some good toploading.  An inverted L supported by a steel
> tower is not the best solution. It is probably the worst of all compared
> to a Marconi "T" out in the clear even with the same tower used to
> support one end as far away a possible from the vertical wire.
>
>
> Herb Schoenbohm, KV4FZ
>
>

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[Herb Schoenbohm]

Mike,  You would be much better off by feeding the tower with a shunt or 
cage feed.  As K2AV so accurately pointed out...an inverted "L" 
supported by a metal tower is not the answer for an efficient system on 
160.  With the amount of radials you have at the base you could do much 
better by feeding the grounded tower.  I presume the tower has a beam on 
the top and that will really make you system even more efficient by 
providing some good toploading.  An inverted L supported by a steel 
tower is not the best solution. It is probably the worst of all compared 
to a Marconi "T" out in the clear even with the same tower used to 
support one end as far away a possible from the vertical wire.


Herb Schoenbohm, KV4FZ


On 4/29/2012 7:55 AM, Mike(W5UC) wrote:
> Good Morning Lloyd&  All:
>
> You have described my 160&  80 meter antennas almost exactly.  The
> vertical part of my L is about 3 feet away from the tower at the top,
> and approximately 2 feet away at the bottom.  I also have a 80 meter
> vertical wire on the other side of my tower.  The 80 meter wire is
> approximately 3 feet from the tower at both ends.
>
>

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[Mike(W5UC)]

Good Morning Lloyd & All:

You have described my 160 & 80 meter antennas almost exactly.  The 
vertical part of my L is about 3 feet away from the tower at the top, 
and approximately 2 feet away at the bottom.  I also have a 80 meter 
vertical wire on the other side of my tower.  The 80 meter wire is 
approximately 3 feet from the tower at both ends.

I modeled the Inverted L in EZ Nec, and determined that the Z at the 
base is approximately 5 ohms.  I built a T network to feed the antenna 
and it works well. I'm not the biggest dog on the porch, but I work my 
share of DX running 500 watts. I just have to stand in line a bit longer 
than the big dogs.  The same applies for the 80 meter vertical.  I have 
approximately 70 radials of varying length.

I'm confident that the farther you place the L from the tower, the 
easier it would be to match, otherwise I believe it will perform well.  
The trick appears being able to accurately determine the complex 
impedance of the antenna. EZ Nec probably gets you in the neighborhood, 
but there will probably still be some cut & try with the matching 
network,  If you can increase the number of radials to 65 - 70 you may 
see better performance.  I did a significant amount of reading on this 
subject, and the consensus was that this number radials is near the 
point of diminishing returns when you don't have the real estate to put 
down a large number of full length radials.

73,
Mike, W5UC


On 4/27/2012 8:07 PM, Lloyd Korb wrote:
> Hello, I have used an Inverted L, on 160 meters, for many years and have
> always been curious if I am okay with my present spacing.  The spacing
> between the vertical portion of the L and my 60 foot tower is 18 inches.
> The spacing was picked for the ease of feeding the wire at the base of my
> tower.  The horizontal part, of the L, is around 85 feet and goes from the
> top of the tower to a pole that is 6 feet above the ground.  Does anyone
> know of any studies done on the performance of the L versus the spacing of
> the vertical wire to the tower?
>
>
>
> I'm also wondering if I could run another wire, on the opposite side of the
> tower, for an L on 80 meters.  It would be nice to be able to have two bands
> available.  Will there be any interaction between the two wires?  My present
> radial system is 24 wires of various lengths to fit in my yard.
>
>
>
> 73,
>
>
>
> Lloyd  K8DIO
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[Guy Olinger K2AV]

Hi, Lloyd,

Using an L with the vertical running next to a tower like that means that
your tower is FULLY coupled to the L as if they were both transformer
windings.  The principal determination of performance in this situation is
the tower, not the L.  You will find that all conductors on the tower are
fully induced.  For all practical purposes, the L is just another way to
load a tower.

This is very easy to model.  In quite a few situations, there will actually
be more current in the tower than in the L, particularly for shorter towers.

My collection of stories about running L's next to towers, alas, mostly has
poor outcomes.

My personal advice on L's includes "Never use a tower to support the
vertical rise of an inverted L --  there are better ways to load a tower."

There ARE ways to make the L work.  Problem is that most people don't want
to ground and bypass tower conductors and run radials, etc, and by the time
you've done that, the tower is perfectly prepared to load the tower itself
and the L is not needed for anything.

73, Guy.

On Fri, Apr 27, 2012 at 9:07 PM, Lloyd Korb  wrote:

> Hello, I have used an Inverted L, on 160 meters, for many years and have
> always been curious if I am okay with my present spacing.  The spacing
> between the vertical portion of the L and my 60 foot tower is 18 inches.
> The spacing was picked for the ease of feeding the wire at the base of my
> tower.  The horizontal part, of the L, is around 85 feet and goes from the
> top of the tower to a pole that is 6 feet above the ground.  Does anyone
> know of any studies done on the performance of the L versus the spacing of
> the vertical wire to the tower?
>
>
>
> I'm also wondering if I could run another wire, on the opposite side of the
> tower, for an L on 80 meters.  It would be nice to be able to have two
> bands
> available.  Will there be any interaction between the two wires?  My
> present
> radial system is 24 wires of various lengths to fit in my yard.
>
>
>
> 73,
>
>
>
> Lloyd  K8DIO
>
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Topband: Inverted L Question

[Lloyd Korb]

Hello, I have used an Inverted L, on 160 meters, for many years and have
always been curious if I am okay with my present spacing.  The spacing
between the vertical portion of the L and my 60 foot tower is 18 inches.
The spacing was picked for the ease of feeding the wire at the base of my
tower.  The horizontal part, of the L, is around 85 feet and goes from the
top of the tower to a pole that is 6 feet above the ground.  Does anyone
know of any studies done on the performance of the L versus the spacing of
the vertical wire to the tower? 

 

I'm also wondering if I could run another wire, on the opposite side of the
tower, for an L on 80 meters.  It would be nice to be able to have two bands
available.  Will there be any interaction between the two wires?  My present
radial system is 24 wires of various lengths to fit in my yard.

 

73,

 

Lloyd  K8DIO

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[Guy Olinger K2AV]

Given that you have the 70-90 vertical rise as a given (not in play as
maybe or maybe not), what the shape of your L will do to
improve/worsen your signal will be overwhelmingly swamped (not close
at all) by what you do or don't with your counterpoise. Unintended
coupling of lossy ground by a dozen different unfortunate counterpoise
issues have resulted in installations with as much as 15 dB gone to
ground losses.

Tell us about what you intend to do for a counterpoise.  Radials?
Buried, elevated?  How many? How long?  Miscellaneous length and angle
according to opportune support?  Uniform in length and angular
distribution?  How high above ground?

Those will determine how well you get out.

73, Guy.

On Thu, Jan 6, 2011 at 9:08 PM, Scott Meister  wrote:
> First year on Top Band and I have a question regarding my inverted L.  I now
> have it 55 foot vertical with the remainder horizontal with elevated
> radials.  It works well, but the neighbors will not be happy in the spring
> when they come back to their summer cottages! Hihi.  I am going to move it
> to a permanent home in the woods.  My question is:  I can get the vertical
> portion up about 80-100 feet with the remainder horizontal.  The issue is
> the horizontal part will have to slope if I put the vertical that high.  Is
> this ok, or should I put it vertically high enough to make the horizontal
> portion level.  And last maybe I should load it with a coil and make it only
> 100 feet tall.  Your experience will be appreciated.
>
> Scott
> WB2REI
> ___
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[Mel Crichton]

By all means make the vertical portion as tall as possible, even if the 
horizontal part slopes downward a bit. My 90 footer is really an "inverted J" 
over a hickory tree with the horizontal part sloping downward at about 20-30 
degrees angle it plays fine with 100 watts Better than my short 
beverages can hear

Mel KJ9C

My question is:  I can get the vertical portion up about 80-100 feet with the 
remainder horizontal.  The issue is the horizontal part will have to slope if I 
put the vertical that high.  Is this ok, or should I put it vertically high 
enough to make the horizontal portion level. 
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: Inverted L Question

[DAVID CUTHBERT]

Scott,

let's compare the radiation resistance of the three antennas at 1.8 MHz.

55' x 82' Inverted-L is 16 ohms
100' x 36' Inverted-L with the 36' wire sloping downward at 45 deg is 28
ohms
100' base-loaded vertical with 22 uH inductor is 18 ohms

The antenna with the highest radiation resistance will be more efficient and
exhibit greater VSWR bandwidth.

  Dave WX7G
___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Topband: Inverted L Question

[Scott Meister]

First year on Top Band and I have a question regarding my inverted L.  I now
have it 55 foot vertical with the remainder horizontal with elevated
radials.  It works well, but the neighbors will not be happy in the spring
when they come back to their summer cottages! Hihi.  I am going to move it
to a permanent home in the woods.  My question is:  I can get the vertical
portion up about 80-100 feet with the remainder horizontal.  The issue is
the horizontal part will have to slope if I put the vertical that high.  Is
this ok, or should I put it vertically high enough to make the horizontal
portion level.  And last maybe I should load it with a coil and make it only
100 feet tall.  Your experience will be appreciated.

Scott
WB2REI
___
UR RST IS ... ... ..9 QSB QSB - hw? BK