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