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 Inverted l question with 9.1 unun 
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Post Inverted l question with 9.1 unun
I have a 63ft ft inverted l with a good ground system a have put a 9.1 unun and a choke line isolator. What would be the difference in loss with and without the 9.1 unun in line. The tuner tunes both with and without easily. Thanks in advance for reading my post.


Fri Nov 11, 2016 3:40 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
m3xkm wrote:
I have a 63ft ft inverted l with a good ground system a have put a 9.1 unun and a choke line isolator. What would be the difference in loss with and without the 9.1 unun in line. The tuner tunes both with and without easily. Thanks in advance for reading my post.



Probably none.

What is the isolator and where is it?


Fri Nov 11, 2016 3:47 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
I have the isolator just before the feed point of the unun. On 80m with out the unun the swr is very good as it's close to a quarter wave on that band, but with the unun the swr is
With unun
8.1 on 80m
3.1 on 40m
2.1 on 20m
4.1 on 17m
3.1 on 10m

Obviously with out unun swr is high through out the bands but atu will tune them all.

The isolator is 10 turns of coax around a ferrite rod


Fri Nov 11, 2016 3:58 pm
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Post Re: Inverted l question with 9.1 unun
m3xkm wrote:
I have the isolator just before the feed point of the unun. On 80m with out the unun the swr is very good as it's close to a quarter wave on that band, but with the unun the swr is
With unun
8.1 on 80m
3.1 on 40m
2.1 on 20m
4.1 on 17m
3.1 on 10m

Obviously with out unun swr is high through out the bands but atu will tune them all.

The isolator is 10 turns of coax around a ferrite rod


Then it is better to use the unun.

The isolator is dubious


Fri Nov 11, 2016 4:16 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
I seem to pick up a lot of static and spurious noise when I take out the isolator choke. I also use on on my vertical too it does seem to help and also seems to stop rf coming into the shack. I used to use one on my old windom antenna


Fri Nov 11, 2016 4:22 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
It's impossible to answer your question about losses without knowing the length of coax and the type.

The choke will prevent the coax braid becoming part of the antenna system. If you have a decent ground system at the antenna, the choke can prevent noise picked up on the coax braid being injected into the signal path at the feedpoint. It sounds like you already discovered that.

Steve G3TXQ


Fri Nov 11, 2016 7:19 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
a quick question
does anyone on here know how or what antenna configeration to use on the wire output ant 3 on the kenwood at-230. im not aware that there is a built in balun and the ground lug thread is for earthing the tuner ??? in the manual it states for inverted l antenas etc.


Sat Nov 12, 2016 12:09 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
m3xkm wrote:
a quick question
does anyone on here know how or what antenna configeration to use on the wire output ant 3 on the kenwood at-230. im not aware that there is a built in balun and the ground lug thread is for earthing the tuner ??? in the manual it states for inverted l antenas etc.


Ant 3 on mine is for 'single wire' antennas (i.e. straight in with no co-ax). This will only be of use if for example the ATU is on the windowsill, or in a wooden/plastic garden shed etc.

Yes, this includes 'inverted 'L'' antennas, as long as the 'L' is connected directly to the tuner.

In most cases you will need to drive the antenna against earth (either a spike, radials or a counterpoise) which you connect to the ground lug. Forget the Balun/UnUn - just think of the ATU as a gearbox, or in this case as a 'variable UnUn'.

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Sat Nov 12, 2016 12:31 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
ar right so the outer case of the atu would be part of the antena then as the earth, not sure if the tuner would get a good match ill have to try it.


Sat Nov 12, 2016 12:56 pm
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Post Re: Inverted l question with 9.1 unun
m3xkm wrote:
ar right so the outer case of the atu would be part of the antena then as the earth, not sure if the tuner would get a good match ill have to try it.


It should do ... that's what it's for, and your ATU is a grand old piece of 'hefty kit'. :)

Make the length of the wire random - i.e. an 'in-betweeny' length. If it doesn't tune, then add or subtract a few feet to bring it within range of the ATU.

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Sat Nov 12, 2016 1:07 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
could the at-230 tune a loop


Sat Nov 12, 2016 1:19 pm
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Post Re: Inverted l question with 9.1 unun
m3xkm wrote:
could the at-230 tune a loop


Not directly, because - as you say - it hasn't got a balanced output.

But you could tune a loop using coax from the back of the ATU to the loop, and put a 4:1 Balun at the feedpoint (where the coax meets the loop).

Steve's yer man for this kind of stuff. I'm just the monkey, not the organ-grinder :)

I've got an AT200 here which has had an internal Balun retro-fitted, but it doesn't do the WARC bands. Swop if you like.

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Sat Nov 12, 2016 1:26 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
ive not had it that long its a great tuner works perfectly for what i need. i just wondered what the wire output was used for and what type of antennas u could put on to it.


Sat Nov 12, 2016 1:58 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
A much better solution would be to ditch the 9:1 UNUN and put an auto ATU at the base of your inverted "L".

Provided the auto ATU will match the inverted "L" on the required bands, your coax will then see a properly matched load.

A friend of mine uses a LDG RT600 (600W pep) remote ATU and seems to get good results with it. There are many others of course such as the Icom AH3/AH4, SGC230, CG3000 etc; etc; It is much easier if you do not intend to run more than 100W as high power auto ATU's are more expensive.

It is worth decoupling all the leads and coax going to the auto ATU using chokes.

Try to avoid antenna lengths that result in high impedances. Lengths of 50ft and 85ft are good compromises.

It is also beneficial to place the inverted "L" as far away from the house as possible with maybe the vertical section down towards the end of your garden if this is possible. A good earth/radial system is essential for any vertical of course.

I have used an Icom AH3 auto ATU to match the back stay on my son's boat; it gives me near 1:1 swr's on just about any band I care to go on and I know the coax feeding the auto ATU is always operating in a matched condition.

73's Vince G3TKN


Sat Nov 12, 2016 2:04 pm
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 Inverted l question with 9.1 unun 
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Post Re: Inverted l question with 9.1 unun
That's exactly how mine in configured I have around 30 buried radials as the ground system. Used to feed it with an sgc 230 but sold it last year as came out the the hobby for a short while. So now I've brought a new radio and this atu so trying to get the most out of this, without spending anymore money now.


Sat Nov 12, 2016 2:13 pm
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