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 resonent Inverted "L" or a long wire for top band. ? 
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Post resonent Inverted "L" or a long wire for top band. ?
What do folk prefer for top band. A resonent inverted L with a 28 ft vertical section or a long wire about 160 ft long also with a
vertical element to it. Both with a dog leg about half way. Also, what sort of coil would I need to fit to make the vertical
section of the inv L , see a 50ft vertical section or could I just form a coil from the antenna wire at the feed point. I wonder what others have
done to get results. after all winter is coming and I have never had anything for top band before.

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73 Ken G0ASI


Sat Oct 18, 2014 8:19 pm
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 resonent Inverted "L" or a long wire for top band. ? 
Silent Key

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Post Re: resonent Inverted "L" or a long wire for top band. ?
Ken,

How much horizontal run do you have? Could you manage 28ft vertical with 150ft horizontal?

Steve G3TXQ


Sat Oct 18, 2014 9:03 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
G3TXQ wrote:
Ken,

How much horizontal run do you have? Could you manage 28ft vertical with 150ft horizontal?

Steve G3TXQ

Hi Steve.
I can do 28ft vertical in one bottom corner of the garden, 30ft accross the bottom of the garden then about 70ft rising from 23ft up to 35ft at the apex of the house, so thats 128ft total , 100ft horizontal. Maybe a bit more if I dangle the free end near the house.

I did try a 180ft long wire zig zagging up and down the garden but it didn't seem to work too well despite being very easy to tune on all bands.
great for listening on but rubbish for TX. It was 180ft as it was a single length I happened to have in stock. I have taken it down as it proved to be
a bit unpopular with the stn manager.

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73 Ken G0ASI


Sun Oct 19, 2014 1:03 am
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 resonent Inverted "L" or a long wire for top band. ? 
Silent Key

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Post Re: resonent Inverted "L" or a long wire for top band. ?
Ken,

There's nothing "magic" about making the Inverted-L resonant. In fact there are some advantages in making it a bit longer than a quarter-wave: it increases the radiation resistance, making the ground losses less important; and it lifts the maximum current point further up the antenna.

If you have the room I'd go for a total length of around 170ft, even if you have to drop a small section at the house end back vertical again. A simple series capacitor at the feedpoint will drop the SWR to the point that you can run coax back to the shack with little loss, and do any final tuning there.

Steve G3TXQ


Sun Oct 19, 2014 8:24 am
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
Thanks Steve.

I was wondering what would happen to the maximum current point if I left it longer.

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73 Ken G0ASI


Sun Oct 19, 2014 12:47 pm
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 resonent Inverted "L" or a long wire for top band. ? 
Silent Key

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Post Re: resonent Inverted "L" or a long wire for top band. ?
You don't want to make it so long that most of the current is in the horizontal section. Aiming to put the maximum current point in the upper half of the vertical section would be a good aiming point.

Steve G3TXQ


Sun Oct 19, 2014 1:13 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
OK on that.
170 ft looks like a "magic" length and I should be able to get it in.
would there be any benefit to spiralling the wire around the vertical section,
or even forming a coil, would it make the vertical section look longer ?.

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73 Ken G0ASI


Sun Oct 19, 2014 5:24 pm
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 resonent Inverted "L" or a long wire for top band. ? 
Silent Key

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Post Re: resonent Inverted "L" or a long wire for top band. ?
Spiralling wire doesn't make an antenna "look longer" as far as it's radiation properties are concerned. For example, a 3-halfwave long centre-fed wire will have 6 major lobes that show some gain over a half-wave centre-fed's "figure of eight" pattern. But you can take that half-wave and stuff as much wire in the legs as you like, you will never generate 6 lobes - it will always behave like a single half-wave simply because of its spatial properties.

You can change the impedance, but you can't change the radiation properties.

Steve G3TXQ


Sun Oct 19, 2014 6:15 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
Never too old to learn something.
End fed antennas are new to me, always used simple dipoles in the past. Top band of course, is a different proposition.

Many thanks Steve

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73 Ken G0ASI


Sun Oct 19, 2014 9:20 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
I use an inverted L on 160m, it is around 116ft long which is a little short but has a shunt inductor at the feed point to cancel any reactance. With 40ft on the vertical section and the rest nearly horizontal it works quite well, and easy to tune with the inductor.

Image

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G0VQO


Mon Oct 20, 2014 2:48 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
Can you provide details of your shunt inductor

Thanks

G0VQO wrote:
I use an inverted L on 160m, it is around 116ft long which is a little short but has a shunt inductor at the feed point to cancel any reactance. With 40ft on the vertical section and the rest nearly horizontal it works quite well, and easy to tune with the inductor.

Image

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Trevor
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Mon Oct 20, 2014 2:57 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
This is the Mk1 version I made, though I have since made a new shunt coil as the original one didn't give me enough inductance.

Image

Ei2GLB Trevor I've sent you an email.

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G0VQO


Mon Oct 20, 2014 3:58 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
The book I have says 15 turns 1 1/4" diameter (3.5 micro farads) for the shunt and 20 turns 1 1/4" diameter on the loading coil (5 micro farads), I ended up with a few more turns on the shunt coil (17 - 18 turns) to get the reading on the analyser for resonance on 1.972 where I usually operate on 160m. The other tapping on the loading coil moves resonance to around 1.850.
The inductors I made were a round 2" diameter made from car brake pipe.

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G0VQO


Mon Oct 20, 2014 4:57 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
Any shunt coils I've made in the past I did using heavy enamelled wire and was able to add or decrease inductance by expanding or compressing the coil and using enamelled meant I could compress it tight if need be.
Well done on the brake pipes, you've managed to keep those coils looking quite neat.

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Mon Oct 20, 2014 5:10 pm
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 resonent Inverted "L" or a long wire for top band. ? 
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Post Re: resonent Inverted "L" or a long wire for top band. ?
Gerry ive made a new shunt coil since that photo as I couldn't compress the coil enough to get the right inductance , now using 2.5 mm wrapped around some 1 1/4" wasee pipe. The original was a little over engineered . :shock:

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G0VQO


Mon Oct 20, 2014 5:20 pm
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