Simple Match for Inverted L 80m?
 

This is a source run for an inverted L antenna for 80m that is 43 feet
vertical and 23 feet horizontal.

What would be the simplest matching network to use to produce a flat match.
My primary use would be 80m low angle work at 3.7 and 3.5 Mhz, but also want
to be able to use it (with a tuner, of course) for a local net at 3.97 megs.

While a 1.7:1 vswr at resonance is usable, I would like to get my starting
point as low as possible to maintain some sort of reasonable vswr at the
band edges, for those times when I need to check into the net.

By simple I mean no caps...they are not all that easy to find (in a hurry)
any longer. I need power handling of 500w. My two thoughts are some sort of
1/4 wave transformer (although that's a lot of coax), or a simple toroidal
transformer.

Any suggestions? Core material for the toroid (including availability),
turns ratio, etc? Or is a toroid a bad idea for this app?

TIA,

....hasan, N0AN


EZNEC ver. 3.0

Vertical over real ground 5/28/2005 6:39:29 AM

--------------- SOURCE DATA ---------------

Frequency = 3.71 MHz

Source 1 Voltage = 29.15 V. at 0.61 deg.
Current = 1 A. at 0.0 deg.
Impedance = 29.15 + J 0.308 ohms
Power = 29.15 watts
SWR (50 ohm system) = 1.715 (75 ohm system) = 2.573

Well, you can make it a little short and add a base inductor to tap to get
the high end of the band, or you can make it a little long and shorten it
with a variable cap.

W4ZCB
"hasan schiers" wrote in message
...
This is a source run for an inverted L antenna for 80m that is 43 feet
vertical and 23 feet horizontal.

What would be the simplest matching network to use to produce a flat
match.
My primary use would be 80m low angle work at 3.7 and 3.5 Mhz, but also
want
to be able to use it (with a tuner, of course) for a local net at 3.97
megs.

While a 1.7:1 vswr at resonance is usable, I would like to get my starting
point as low as possible to maintain some sort of reasonable vswr at the
band edges, for those times when I need to check into the net.

By simple I mean no caps...they are not all that easy to find (in a hurry)
any longer. I need power handling of 500w. My two thoughts are some sort
of
1/4 wave transformer (although that's a lot of coax), or a simple toroidal
transformer.

Any suggestions? Core material for the toroid (including availability),
turns ratio, etc? Or is a toroid a bad idea for this app?

TIA,

...hasan, N0AN


EZNEC ver. 3.0

Vertical over real ground 5/28/2005 6:39:29 AM

--------------- SOURCE DATA ---------------

Frequency = 3.71 MHz

Source 1 Voltage = 29.15 V. at 0.61 deg.
Current = 1 A. at 0.0 deg.
Impedance = 29.15 + J 0.308 ohms
Power = 29.15 watts
SWR (50 ohm system) = 1.715 (75 ohm system) = 2.573

Thanks Harold, but that's not what I'm trying to do. I'm not trying to
broadband the antenna...I'm trying to simply match it...so that starting out
at 1:1 instead of 1.7 : 1 will broaden the 2:1 vswr points a bit. I'm going
to use a tuner on the band edges anyway.

So the only question is:

Simplest way (without caps) to match 29 ohms to 50 ohms at the feedpoint.

....hasan, N0AN

"Harold E. Johnson" wrote in message
news:q1Zle.15771$IC6.11043@attbi_s72...
Well, you can make it a little short and add a base inductor to tap to get
the high end of the band, or you can make it a little long and shorten it
with a variable cap.

W4ZCB
"hasan schiers" wrote in message
...
This is a source run for an inverted L antenna for 80m that is 43 feet
vertical and 23 feet horizontal.

What would be the simplest matching network to use to produce a flat
match.
My primary use would be 80m low angle work at 3.7 and 3.5 Mhz, but also
want
to be able to use it (with a tuner, of course) for a local net at 3.97
megs.

While a 1.7:1 vswr at resonance is usable, I would like to get my
starting
point as low as possible to maintain some sort of reasonable vswr at the
band edges, for those times when I need to check into the net.

By simple I mean no caps...they are not all that easy to find (in a
hurry)
any longer. I need power handling of 500w. My two thoughts are some sort
of
1/4 wave transformer (although that's a lot of coax), or a simple
toroidal
transformer.

Any suggestions? Core material for the toroid (including availability),
turns ratio, etc? Or is a toroid a bad idea for this app?

TIA,

...hasan, N0AN


EZNEC ver. 3.0

Vertical over real ground 5/28/2005 6:39:29 AM

--------------- SOURCE DATA ---------------

Frequency = 3.71 MHz

Source 1 Voltage = 29.15 V. at 0.61 deg.
Current = 1 A. at 0.0 deg.
Impedance = 29.15 + J 0.308 ohms
Power = 29.15 watts
SWR (50 ohm system) = 1.715 (75 ohm system) = 2.573

"hasan schiers" wrote in message
...
Thanks Harold, but that's not what I'm trying to do. I'm not trying to
broadband the antenna...I'm trying to simply match it...so that starting
out
at 1:1 instead of 1.7 : 1 will broaden the 2:1 vswr points a bit. I'm
going
to use a tuner on the band edges anyway.

So the only question is:

Simplest way (without caps) to match 29 ohms to 50 ohms at the feedpoint.

...hasan, N0AN

"Harold E. Johnson" wrote in message
news:q1Zle.15771$IC6.11043@attbi_s72...
Well, you can make it a little short and add a base inductor to tap to
get
the high end of the band, or you can make it a little long and shorten
it
with a variable cap.

W4ZCB
"hasan schiers" wrote in message
...
This is a source run for an inverted L antenna for 80m that is 43 feet
vertical and 23 feet horizontal.

What would be the simplest matching network to use to produce a flat
match.
My primary use would be 80m low angle work at 3.7 and 3.5 Mhz, but also
want
to be able to use it (with a tuner, of course) for a local net at 3.97
megs.

While a 1.7:1 vswr at resonance is usable, I would like to get my
starting
point as low as possible to maintain some sort of reasonable vswr at
the
band edges, for those times when I need to check into the net.

By simple I mean no caps...they are not all that easy to find (in a
hurry)
any longer. I need power handling of 500w. My two thoughts are some
sort
of
1/4 wave transformer (although that's a lot of coax), or a simple
toroidal
transformer.

Any suggestions? Core material for the toroid (including availability),
turns ratio, etc? Or is a toroid a bad idea for this app?

TIA,

...hasan, N0AN


EZNEC ver. 3.0

Vertical over real ground 5/28/2005 6:39:29 AM

--------------- SOURCE DATA ---------------

Frequency = 3.71 MHz

Source 1 Voltage = 29.15 V. at 0.61 deg.
Current = 1 A. at 0.0 deg.
Impedance = 29.15 + J 0.308 ohms
Power = 29.15 watts
SWR (50 ohm system) = 1.715 (75 ohm system) = 2.573

A Twelfth-Wave transformer. QST June 1997. pp43

W4ZCB

"hasan schiers" wrote in message
...
Thanks Harold, but that's not what I'm trying to do. I'm not trying to
broadband the antenna...I'm trying to simply match it...so that starting
out
at 1:1 instead of 1.7 : 1 will broaden the 2:1 vswr points a bit. I'm
going
to use a tuner on the band edges anyway.

So the only question is:

Simplest way (without caps) to match 29 ohms to 50 ohms at the feedpoint.

...hasan, N0AN

hasan schiers wrote:
Any suggestions?

For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.
--
73, Cecil http://www.qsl.net/w5dxp


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hasan schiers wrote:

What would be the simplest matching network to use to produce a flat match.
My primary use would be 80m low angle work at 3.7 and 3.5 Mhz, but also want
to be able to use it (with a tuner, of course) for a local net at 3.97 megs.


EZNEC ver. 3.0

Vertical over real ground 5/28/2005 6:39:29 AM

--------------- SOURCE DATA ---------------

Frequency = 3.71 MHz

Source 1 Voltage = 29.15 V. at 0.61 deg.
Current = 1 A. at 0.0 deg.
Impedance = 29.15 + J 0.308 ohms
Power = 29.15 watts
SWR (50 ohm system) = 1.715 (75 ohm system) = 2.573

Hi hasan, If you don't want to use capacitors in your matching
circuit, just shorten the antenna a couple of feet. That will add some
capacitive reactance at the frequency of interest. Then you can use a
shunt inductor to get a 50 ohm match. What you will really have is an
"L" network with a series cap and shunt inductor. You tune the
capacitor by changing the length of the radiator, and tune the inductor
by adding or removing turns.
An example, if you shorten the antenna until the impedance is around
29-j25 at 3.71mhz, a 2.5uH shunt inductor will give a 50 ohm match.
Gary N4AST

On Sat, 28 May 2005 06:49:15 -0500, "hasan schiers"
wrote:

This is a source run for an inverted L antenna for 80m that is 43 feet
vertical and 23 feet horizontal.

What would be the simplest matching network to use to produce a flat match.
My primary use would be 80m low angle work at 3.7 and 3.5 Mhz, but also want
to be able to use it (with a tuner, of course) for a local net at 3.97 megs.

First of all, changing the match doesn't make the antenna change from
a "low angle" radiator to a radiator for local work.


While a 1.7:1 vswr at resonance is usable, I would like to get my starting
point as low as possible to maintain some sort of reasonable vswr at the
band edges, for those times when I need to check into the net.

By simple I mean no caps...they are not all that easy to find (in a hurry)
any longer. I need power handling of 500w. My two thoughts are some sort of
1/4 wave transformer (although that's a lot of coax), or a simple toroidal
transformer.

You can use a 1/4 transformer of two parallel RG-59 to get a nearly
perfect match at 3.7 MHz. But, you must realize that by doing this
you actually *increase* the SWR at the band edges. Any reactive
solution will do the same.

If you have a tuner anyway, I fail to see why you want to do this.

a 2:1 balun should get you close.

"hasan schiers" wrote in message
...
Thanks Harold, but that's not what I'm trying to do. I'm not trying to
broadband the antenna...I'm trying to simply match it...so that starting
out
at 1:1 instead of 1.7 : 1 will broaden the 2:1 vswr points a bit. I'm
going
to use a tuner on the band edges anyway.

So the only question is:

Simplest way (without caps) to match 29 ohms to 50 ohms at the feedpoint.

...hasan, N0AN

"Harold E. Johnson" wrote in message
news:q1Zle.15771$IC6.11043@attbi_s72...
Well, you can make it a little short and add a base inductor to tap to
get
the high end of the band, or you can make it a little long and shorten
it
with a variable cap.

W4ZCB
"hasan schiers" wrote in message
...
This is a source run for an inverted L antenna for 80m that is 43 feet
vertical and 23 feet horizontal.

What would be the simplest matching network to use to produce a flat
match.
My primary use would be 80m low angle work at 3.7 and 3.5 Mhz, but also
want
to be able to use it (with a tuner, of course) for a local net at 3.97
megs.

While a 1.7:1 vswr at resonance is usable, I would like to get my
starting
point as low as possible to maintain some sort of reasonable vswr at
the
band edges, for those times when I need to check into the net.

By simple I mean no caps...they are not all that easy to find (in a
hurry)
any longer. I need power handling of 500w. My two thoughts are some
sort
of
1/4 wave transformer (although that's a lot of coax), or a simple
toroidal
transformer.

Any suggestions? Core material for the toroid (including availability),
turns ratio, etc? Or is a toroid a bad idea for this app?

TIA,

...hasan, N0AN


EZNEC ver. 3.0

Vertical over real ground 5/28/2005 6:39:29 AM

--------------- SOURCE DATA ---------------

Frequency = 3.71 MHz

Source 1 Voltage = 29.15 V. at 0.61 deg.
Current = 1 A. at 0.0 deg.
Impedance = 29.15 + J 0.308 ohms
Power = 29.15 watts
SWR (50 ohm system) = 1.715 (75 ohm system) = 2.573

For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.
--
73, Cecil http://www.qsl.net/w5dxp

===============================

Cec, it seldom works. You forgot to mention the most important
parameter is the input impedance to the antenna.

For an analysis of an inverted-L or vertical antenna, plus tuner L and
C component values, download in a few seconds program ENDFEED from
website below. No unzipping inconveniences. Run immediately. Easy to
use.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Perfecto, Reg!

This is exactly what I was looking for ...but I had forgotten you had
written this little jewel.

I am a bit surprised at the small effect on losses in the number of radials
once one gets above 8 radials of 20m length.

I need to play more with wire size (confounded mm!)

Thanks again for your contribution of this program. 73

....hasan, N0AN
"Reg Edwards" wrote in message
...

For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.
--
73, Cecil http://www.qsl.net/w5dxp

===============================

Cec, it seldom works. You forgot to mention the most important
parameter is the input impedance to the antenna.

For an analysis of an inverted-L or vertical antenna, plus tuner L and
C component values, download in a few seconds program ENDFEED from
website below. No unzipping inconveniences. Run immediately. Easy to
use.
----
.................................................. .........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. .........

Reg Edwards wrote:
For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.

Cec, it seldom works. You forgot to mention the most important
parameter is the input impedance to the antenna.

I didn't forget, Reg. The input impedance was given in the
original posting:

"Frequency = 3.71 MHz Impedance = 29.15 + J 0.308 ohms"

Assuming that is the input impedance, I think my advice was
reasonable. If I had to match 50 ohms to 29 ohms on a single
band, I would just wind an autotransformer.
--
73, Cecil http://www.qsl.net/w5dxp

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Thanks, Cecil, and yes, that would work just fine and I have some B+W coil
stock sitting on a shelf, should work fine. (I used part of it before for a
parallel tuned circuit to tap feed my half-square.)

....hasan, N0AN

"Cecil Moore" wrote in message
...
Reg Edwards wrote:
For single-band operation, an autotransformer comes to mind.
Wind a coil with about 12 microhenries of inductance. Transmitter
output goes to the top of the coil. Ground goes to the bottom.
Tap down from the top on the coil for the antenna feedpoint.
The transformation ratio is roughly equal to the square of the
turns ratio.

Cec, it seldom works. You forgot to mention the most important
parameter is the input impedance to the antenna.

I didn't forget, Reg. The input impedance was given in the
original posting:

"Frequency = 3.71 MHz Impedance = 29.15 + J 0.308 ohms"

Assuming that is the input impedance, I think my advice was
reasonable. If I had to match 50 ohms to 29 ohms on a single
band, I would just wind an autotransformer.
--
73, Cecil http://www.qsl.net/w5dxp

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Assuming that is the input impedance, I think my advice was
reasonable. If I had to match 50 ohms to 29 ohms on a single
band, I would just wind an autotransformer.
--
73, Cecil http://www.qsl.net/w5dxp

==================================
Cec, to prevent the transformer inductance from completely detuning
the antenna, the transformer would have to be wound with a lot of
turns on something like an E and I dust-iron core. It's not worth the
trouble when there are other, more simple ways of doing the job.

The only advantage of a transformer or auto-transformer is that it
will cover several bands or octaves with widely different antenna
impedances.

Nice to bump into each other again.
----
Reg.

Reg Edwards wrote:
Cec, to prevent the transformer inductance from completely detuning
the antenna, the transformer would have to be wound with a lot of
turns on something like an E and I dust-iron core.

Yep, somewhere around here I have a tapped autotransformer
wound on a #2 powdered iron toroid designed for 75m use.
I wound it to be installed at the twinlead/coax junction
on a G5RV to obtain a 1:1 SWR on the coax on 75m. It worked
but I found that a parallel 1000 pf cap works just as well
and is easier to clip on and off.
--
73, Cecil http://www.qsl.net/w5dxp

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"Hasan Schiers" wrote,

I am a bit surprised at the small effect on losses in the number of
radials
once one gets above 8 radials of 20m length.
===========================================

Hasan, why should you be surprised? Have you been reading the
plagiarised old-wives tales in the magazines? ;o)

There's another more accurate program, RADIALS2, which may be of
interest, which deals with shallow-buried radials of any length and
number, in conjunction with a simple vertical antenna of variable
height just to illustrate the practical effects.

Download program RADIALS2 from website below.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

I'm sorta surprised you would need to match it, if it's a
1/4 wave...I think your match in the real world, would
be better than on paper...I've never had to "match" a
1/4 wave here, L or straight.... But.....if I did, I would
just slap the tuner inline...On that band, any mismatch
would have to be large to give a high line loss. That
won't be the case for you just going from one part of
the band to another...Also, you should be able to get
a better match than 1.7:1, just by tweaking the wire
length.
MK