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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Inverted 'L' for 160 / 80 / 60 / 40 Metres
Planning to return to the LF Bands after many years absence and a change of QTH.

I'm thinking about putting up a Inverted 'L' Antenna for 160 / 80 / 60 / 40 Metres; I have about 90' of Horizontal available and a mast of of 30'.

I will probably make my own coax traps, although I do have 3.5 MHz & 7.0 MHz (LC) Traps from the set up at my previous QTH.

What I am not sure about is:
a: will the addition of the 60 Metre Band cause any issues?
b: I seem to recall that in the past I used 1/4 wavelength counterpoises for each band ( 1 for 160 and 2 for 80 & 40) which I ran bundled together around the outskirts of the property; is this ok?

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David - G4NVB


Mon Dec 23, 2013 8:31 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
I laid mine with 10m radials. Lots of then.
Your design is to use counterpoises and my understanding of then is that Yes, they can be bundled .

As for 60m.. no idea but I can't think of a problem.

Good luck

David

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Mon Dec 23, 2013 9:35 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
There can be problems with closely spaced bands if the trap L/C ratios are high, because of the inductive loading they add. If you can, keep the L/C ratio low.

If the radials are on or below ground they don't need to be resonant - just get as many down as you can. For a given length of copper, more short ones is a better option than a few long ones.

Steve G3TXQ


Mon Dec 23, 2013 9:35 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
G3TXQ wrote:
If the radials are on or below ground they don't need to be resonant - just get as many down as you can. For a given length of copper, more short ones is a better option than a few long ones.


Would this still be the case for non-resonant lengths if I were to bundle the wires and run them around the perimeter? I could probably get some wires in a radial fashion but not over a very wide arc though.

The wires will be at ground or below ground level.

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David - G4NVB


Mon Dec 23, 2013 10:20 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
G4YVM wrote:
Good luck

Thank you, I am quite looking forward to experimenting with the LF Antennas it's been a long while :)

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David - G4NVB


Mon Dec 23, 2013 10:26 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
If the radials are at or below ground, there's no point in "bundling" ones of different length. Just connect as many as you can and splay them out as evenly as you can. If you're constrained to a particular arc, so be it.

Steve G3TXQ


Mon Dec 23, 2013 11:28 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
G3TXQ wrote:
If the radials are at or below ground, there's no point in "bundling" ones of different length. Just connect as many as you can and splay them out as evenly as you can. If you're constrained to a particular arc, so be it.

Steve G3TXQ


Ok Steve, many thanks.

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David - G4NVB


Mon Dec 23, 2013 11:34 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
Just had another thought; which of the following two options would provide the best performance:-

The above antenna with traps or a SmartTuner feeding a 30' vertical section with a 90' Horizontal?

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David - G4NVB


Mon Dec 23, 2013 1:11 pm
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
G4YVM i told you a while back about K2AV FCP antenna how many DX contacts with the radials have you had just curious to see how it is performing


cheers

steve


Mon Dec 23, 2013 11:00 pm
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
G4NVB wrote:
Just had another thought; which of the following two options would provide the best performance:-

The above antenna with traps or a SmartTuner feeding a 30' vertical section with a 90' Horizontal?


I had an inverted L with a SGC230 smart tuner and about 300ft of radials. It worked absolutely great.

Please please model the antenna before deciding on the final length. I found with mine that changing it by several feet considerably altered the azimuth pattern on 20m which I used to my advantage. It changed from an apple shape to a X shape when I changed the length by several feet due to the ratio of flat top to vertical - see L.E.Cebik's article "straightening the inverted - L" for more information. It was so handy at nulling out the Italians with the additional length, whilst giving a lot of gain NW/SE and NE/SW that I contemplated fitting a relay.

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Tue Dec 24, 2013 10:52 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
Hi Conor,
Thank you for your input much appreciated.

M0GVZ wrote:
I had an inverted L with a SGC230 smart tuner and about 300ft of radials. It worked absolutely great.

Thats encouraging :thumbsup:

M0GVZ wrote:
Please please model the antenna before deciding on the final length.


I'm returning to the LF Bands after a 22 Year break, any previous work was a "suck it and see" so when you say "model" the antenna I may need a little more guidence :confused: Can you recommend any particular website or software to enable me to study further?

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David - G4NVB


Tue Dec 24, 2013 12:57 pm
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
Thinking about where to position the Vertical Mast of the Inverted 'L', one option is just outside The Shack. This would place the base of the Antenna within less than 3 Metres of the Shack Bench; should I be concerned with RF affecting Computers / Radio / electronic equipment? One of the reasons for choosing the location is that there is a tall tree that would hide the mast from view of the neighbours and it's convenient for the Shack.

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Sun Apr 06, 2014 10:48 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
It's very difficult to predict whether any particular set-up will cause RFI problems, but what you're proposing is pretty much a worst-case. If you're still planning a trapped Inverted-L, maximum current (and therefore maximum radiation) is going to be at the lower end of that vertical section!

Steve G3TXQ


Sun Apr 06, 2014 11:17 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
Hi Steve,

Thank you for your reply; I guess it's a case of a: suck it & see or b: choose another Antenna / location. Unfortunately It's not practical / convenient to feed the Inv 'L' from the other end of the garden.

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David - G4NVB


Sun Apr 06, 2014 11:35 am
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 Inverted 'L' for 160 / 80 / 60 / 40 Metres 
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Post Re: Inverted 'L' for 160 / 80 / 60 / 40 Metres
Remote tuner at feed point at the end of gasrden from shack is the way to go.

I run an inverted L approx 30 ft vertical and 45ft horizontal section via a remote tuner.(in my shed)

Counterpoise is around 130ft long. It works pretty well on 40M and is OK on 80, needs to be a bit longer when I get the chance.

I have no RFI issues but from experience having the feedpoint near the shack is a different kettle of fish altogether.

It's worth the lengthy run of coax to the tuner which i conenct to a 12 volt leisure battery inside the shed. Battery and tuner both protected from the elements.

My windom is a better option for 40M but it is somewhat higher and horizontal

Cheers Ian


Mon Apr 07, 2014 3:23 pm
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