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 Inverted L 
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Post Inverted L
Just a question...I have an inverted L...vertical section is more or less 9 mtrs....and i have about 60ish feet of wire overall....now i have an un-un at the base which i can disconect if i wish..think is it only tunes on a couple of bands..with or without the un-un..i have 2 earth spikes in the ground and a few radials under my lawn..i also have about 60ish feet of wire running around my fence about 10 inches or so off the floor.....i use an ldg 100 pro as a tuner.....i would have thought this would have tuned on 80mtrs...all be it maybe not the best in the world..or even 30 mtrs...but no its doesnt....help anyone...what would i need to do to get it perculating...???

cheers

hughie

m0hms

oh i did have one leg from a w3dzz as the inverted L and that wouldnt tune either.

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Thu Oct 20, 2011 5:58 pm
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 Inverted L 
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Post Re: Inverted L
Hughie,

A couple of questions:

* What's the length of coax between the Inverted-L and the tuner?
* Do you have a choke on that coax run?

Steve G3TXQ


Thu Oct 20, 2011 8:36 pm
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 Inverted L 
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Post Re: Inverted L
coax will be about 55 feet more or less with 35 feet of it under ground....and no there are no chokes Steve.

cheers

hughie

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Thu Oct 20, 2011 8:38 pm
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 Inverted L 
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Post Re: Inverted L
Hughie,

That all sounds very odd. If I model the antenna I don't see any extreme impedances that would trouble the tuner. I wonder if you have an analyser - or could borrow one - to measure the impedance seen at the shack end of the coax?

For the tuner to match it only on a couple of bands, with or without the UnUn, it sounds like there must be a fault somewhere in the system. To eliminate any problem with the autotuner, do you have a manual tuner you could replace it with and check if you can get a match?

Steve G3TXQ


Thu Oct 20, 2011 8:56 pm
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 Inverted L 
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Post Re: Inverted L
Thanks for the info Steve...I have had this set up before and it worked fine..ime wondering if i have a coax problem..but then i think why does it tune on a few bands.....will have to have a look over the weekend when ime off work...will let you know how i get on..again thanks mate,,,,just out of interest should the one leg off the w3dzz have tuned ok on 40...and maybe even 80...??
If its a yes then that would point to a feeder problem i think.

hughie

m0hms

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Thu Oct 20, 2011 10:20 pm
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 Inverted L 
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Post Re: Inverted L
Hughie,

I would have expected one leg of a W3DZZ to be a pretty easy load for the tuner on several bands including 80m and 40m.

Good luck searching for the fault.

Steve G3TXQ

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Thu Oct 20, 2011 10:26 pm
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 Inverted L 
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Post Re: Inverted L
With regards the w3dzz i would have expected the same and that i think points me to a feeder problem

cheers

hughei

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Fri Oct 21, 2011 10:55 am
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 Inverted L 
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Post Re: Inverted L
UPDATE !!!

Replaced the feeder with ur67...replaced the radiator 66ft long.....without the atu it is resonant on 80 mtrs.....also without the unun.....also more or less resonant on 17......with the unun it tunes bottom end of top band...sometimes lol

Running through the atu without the unun it tunes 80 which isnt a suprise...tunes all HF bands.....wont tune on 40...but hey thats life......so ime active on 80 again which is what i wanted to do really......oh doesnt tune 28mhz either.

with the unun it doesnt like to tune LF at all.

cheers

hughie

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Sat Oct 22, 2011 12:56 pm
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 Inverted L 
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Post Re: Inverted L
Buy, beg borrow or steal a SGC 230 Antenna coupler. I use one on my inverted L and it'll tune up anything without the need to resort to an Unun. Also as it is at the antenna end, not the radio end, you have very minimal co-ax losses.

It needs 12v running to it but you can do that through the coax with a Bias T.

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Fri Oct 28, 2011 9:51 pm
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 Inverted L 
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Post Re: Inverted L
Conor, whats the details of your inverted L, height of the vertical section,
lenght of the horizontal section and which bias tees do you use.
Is your L traped or just a plain wire.
Currently mine is based on the GM0ONX inverted L, but it only gives me
80-10 mtrs with the 1 trap fitted.

Phil


Sat Oct 29, 2011 12:32 am
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 Inverted L 
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Post Re: Inverted L
G7BZD wrote:
Conor, whats the details of your inverted L, height of the vertical section,
lenght of the horizontal section and which bias tees do you use.
Is your L traped or just a plain wire.
Currently mine is based on the GM0ONX inverted L, but it only gives me
80-10 mtrs with the 1 trap fitted.

Phil


Mine has a 25ft vertical section and 50ft horizontal which gives me a pattern on 20m with a nice null to Europe which I can change by reducing the overall length to 69ft. As mine is on the 20m to 10m bands, the radiation pattern is in a X and the antenna orientated so the lobes are towards the US, South America, JA land and South Africa. It is not trapped and is just plain 12 AWG copper wire. I run a 12V feed out to it but intend fitting a bias T at some point but will probably homebrew my own.

I strongly suggest reading the article "Straightening out the Inverted L" By L.E.Cebik which you can read for free on his website at http://www.cebik.com. It explains how the antenna works, how changing the vertical to horizontal ratio affects radiation patterns etc.

Just thought I'd mention that the SGC230 is limited to 200W PEP and 80W continuous should you like to run power.

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Sat Oct 29, 2011 7:23 pm
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 Inverted L 
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Post Re: Inverted L
Thanks for that, i run a FT1000MP MKV @ about 150w.
will look into it as i have a SGC230, was going to sell it, not so sure now.
The 25' vertical could be a problem, and the 50' horizontal will be.

Oh for a bigger garden.

Phil


Sat Oct 29, 2011 8:43 pm
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 Inverted L 
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Post Re: Inverted L
i have a 66ft inverted l 10m vertical with 10m horizontal it has an sgc-230 at the base with radials under the garden,, it works fine for me on all bands from 160-10m.


Sun Oct 30, 2011 12:16 pm
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 Inverted L 
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Post Re: Inverted L
G7BZD wrote:
Thanks for that, i run a FT1000MP MKV @ about 150w.
will look into it as i have a SGC230, was going to sell it, not so sure now.
The 25' vertical could be a problem, and the 50' horizontal will be.

Oh for a bigger garden.

Phil


Don't get so worried about it. It'll still work well but the radiation pattern you have would be different to mine - this is where modelling the antenna in EZNEC or which ever software you prefer pays dividends.

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Sun Oct 30, 2011 9:09 pm
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