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 HORIZONTAL LOOP QUESTION? 
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Hi Guyz,

I am currently erecting a Horizontal Loop which will be fed at one corner with 450 ohm ladder feed into a 4:1 balun then a short run of coax from there to an ATU. Due to how things are here at my QTH I am going to be stuck with a size of approx 120 - 130 meters of loop. So as this will be resonant between 160m and 80m I am wondering how well it may perform on 80m compared to an actual resonant 80m loop??? I'm hoping it will perform well due to the fact that there is more wire in the air with a nice capture area.

Regards,
Dom - M0ASR /2E0CIA.


Sat Oct 30, 2010 7:18 pm
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 HORIZONTAL LOOP QUESTION? 
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Love that call Dom, 2e0CIA. Ill bet that gets a few looks on the cluster!


Sat Oct 30, 2010 8:03 pm
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 HORIZONTAL LOOP QUESTION? 
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Post Re: HORIZONTAL LOOP QUESTION?
Hi Dom,

There's very little difference between your larger loop and a smaller resonant 80m loop - no difference at all at high take-off angles and about 1dB difference at low take-off angles. They have almost identical capture areas.

You would do well to feed with a good quality ladderline because the feedpoint impedance on 80m is very high and you will have a VSWR around 24:1.

Is there any reason you are going for a 4:1 balun rather than 1:1?

73,
Steve G3TXQ


Sat Oct 30, 2010 8:04 pm
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 HORIZONTAL LOOP QUESTION? 
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M0TNX wrote:
Steve am I right in thinking it would have to be supported really high up to be a usueful low angle radiator?

I know some 80 metre guys that use full wave vertical loops on 80 quite low to the ground and work good DX with them...

Kev

Kev,

If we are talking horizontal loops, yes an 80m loop will have to be pretty high to generate much low-angle energy - it's no different from a simple dipole. In fact the difference between an 80m full-wave loop at 30ft and a half-wave dipole at 30ft is only 0.7dB to 1.9dB, depending on take-off angle.

A vertical loop would be a different matter, but how do they support a full-wave 80m vertical loop - that's 75ft each side, so presumably you need two 80ft supports to get it clear of the ground!

Steve G3TXQ


Sat Oct 30, 2010 8:24 pm
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 HORIZONTAL LOOP QUESTION? 
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M0TNX wrote:
Dom..

How High is it supported?..

Horizontal loops are great cloudwarmers in my understanding, but saying that, I helped a pal work Indonesia on 20 with a Horizontal loop cut for 80 metress... He was using 10 watts at the time..

Wonder why you've gone for this antenna? If you have no plans to work 160, stick with a resonant antenna everytime...

Best Wishes..

Kev


Hi Kev,

Thanks for your input :)
The height does vary between 25ft - 35ft off ground level.
Well re 'cloudwarmers' going only from what I have read on the internet there seems to be a 50/50 debate regarding this. Some say yay and some say nay! I guess it is a matter of suck it and see :shock:
Well I was originaly thinking of 80m then thought that by feeding it with twin feed I could also use it on 40m. If it would load up on top band then bonus but no major issue if not. What I am hoping for is for this loop to work well inta-G but also do a little DX. I know it is not so easy to have both as it is usualy one or the other but if something inbetween could be achieved this would be my ideal :D

Regards,
Dom.
M0ASR / 2E0CIA


Sun Oct 31, 2010 6:59 pm
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 HORIZONTAL LOOP QUESTION? 
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G0UAZ wrote:
Love that call Dom, 2e0CIA. Ill bet that gets a few looks on the cluster!


.....well the Yanks seem to love it 8) hi!
To be honest I don't use it that often but I am hoping to get some use out of it once I have sorted my antenna system out here.

Regards,
Dom.
M0ASR / 2E0CIA.


Sun Oct 31, 2010 7:02 pm
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 HORIZONTAL LOOP QUESTION? 
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G3TXQ wrote:
Hi Dom,

There's very little difference between your larger loop and a smaller resonant 80m loop - no difference at all at high take-off angles and about 1dB difference at low take-off angles. They have almost identical capture areas.

You would do well to feed with a good quality ladderline because the feedpoint impedance on 80m is very high and you will have a VSWR around 24:1.

Is there any reason you are going for a 4:1 balun rather than 1:1?

73,
Steve G3TXQ


Hi Steve,

Also many thanks for your input :)
Well that's answered my question :D
The ladderline is 450 ohm stuff, the same as the black stuff you get from W&S etc.
Due to this fact I will be going through a 4:1 balun to bring the impedence down to connect a short run of 50 ohm coax :)

Regards,
Dom.
M0ASR / 2E0CIA.


Sun Oct 31, 2010 7:06 pm
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 HORIZONTAL LOOP QUESTION? 
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Post Re: HORIZONTAL LOOP QUESTION?
G3TXQ wrote:
M0TNX wrote:
Steve am I right in thinking it would have to be supported really high up to be a usueful low angle radiator?

I know some 80 metre guys that use full wave vertical loops on 80 quite low to the ground and work good DX with them...

Kev

Kev,

If we are talking horizontal loops, yes an 80m loop will have to be pretty high to generate much low-angle energy - it's no different from a simple dipole. In fact the difference between an 80m full-wave loop at 30ft and a half-wave dipole at 30ft is only 0.7dB to 1.9dB, depending on take-off angle.

A vertical loop would be a different matter, but how do they support a full-wave 80m vertical loop - that's 75ft each side, so presumably you need two 80ft supports to get it clear of the ground!

Steve G3TXQ


Steve,

My loop is between 25ft - 35ft off ground level, so just wondering if this may be adequate for inter-G as well as some DX? As I mentioned in a previous post I am trying to achieve this compromise.

Regards,
Dom.
M0ASR / 2E0CIA.


Sun Oct 31, 2010 7:10 pm
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 HORIZONTAL LOOP QUESTION? 
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Dom,

At that height it will be very poor for DX, better for Inter-G; nearly all the signal is going up vertically.

You made a common mistake when thinking about your balun ratio - it is not directly related to the feedline characteristic impedance. On 80m your loop will have a feedpoint impedance of about 4500+j4900. Depending on the length of your ladderline, the impedance back at the shack end could be anything from 10,000Ω to 17Ω. If it's towards the low end of that range, the last thing you want to be doing is "divide by 4"; if it's towards the top end of the range a 4:1 Voltage balun is going to get very warm :)

You'll have far less trouble matching the loop if you could make it smaller and resonant at 80m.

73,
Steve G3TXQ


Sun Oct 31, 2010 7:26 pm
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 HORIZONTAL LOOP QUESTION? 
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G3TXQ wrote:
Dom,

At that height it will be very poor for DX, better for Inter-G; nearly all the signal is going up vertically.

You made a common mistake when thinking about your balun ratio - it is not directly related to the feedline characteristic impedance. On 80m your loop will have a feedpoint impedance of about 4500+j4900. Depending on the length of your ladderline, the impedance back at the shack end could be anything from 10,000Ω to 17Ω. If it's towards the low end of that range, the last thing you want to be doing is "divide by 4"; if it's towards the top end of the range a 4:1 Voltage balun is going to get very warm :)

You'll have far less trouble matching the loop if you could make it smaller and resonant at 80m.

73,
Steve G3TXQ


Hi Steve,

One again many thanks for your advice :)
Well after some thought I have decided to go for a vertical .....either Delta or Quad Loop.
Re feeding I will feed it with 450 ohm twin feed so that I can use it as a multibander. As the twin feeder run is well over 100ft to the shack will I still require a 4:1 balun???
If I construct it as a Delta Loop then it will have the point towards the ground as I already have the top high end horizontal section up in the trees so it will be just a matter of pulling down the other 2 sides down diagonally. I will then feed this at the bottom pointed end as I have read this will give me a take off angle somewhere between high and low so will be a compromise.
If I decide to construct this as a quad (square) loop instead then I believe that I can feed it either up one side for vertical radiation or in the middle of the bottom section for horizontal radiation.
My questions are how well would the 'Quad' work for DX or inter-G???
Also I may not be able to get all the sides of either a Delta or a Quad loop of equal length, would this matter too much????
BTW the bottom end of either a Delta or Quad loop will be relatively close to the ground but I believe that loops still work well at low levels. However the top horizontal section is approx a good 25ft - 30ft off ground level.

Regards,
Dom.
M0ASR / 2E0CIA.


Sun Oct 31, 2010 8:57 pm
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 HORIZONTAL LOOP QUESTION? 
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Dom,

If you go with the vertical quad loop with the bottom wire at 5ft and the top wire at 30ft, what will the horizontal lengths be?

Steve G3TXQ


Sun Oct 31, 2010 9:12 pm
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 HORIZONTAL LOOP QUESTION? 
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I've been searching back through quite a few posts to see what's been said relative to 80m/160m antennas, resurrected this fairly recent post as it is somewhat applicable.

I am currently using a sort of inverted L although the vertical section is only about 12ft so most of the antenns is horizontal at about 20ft-25ft. I built a coax trap for 80m and then another section of wire to resonate on 160m. The antenna works but is of course not very efficient.

I'd really like to improve on this antenna and want something for 80 and 160. I've considered a horizontal loop as per this original post, I could fit maybe 110m-120m around my garden but how would this compare to the alternatives? I could maybe fit a half wave dipole in if I bent the ends a little, although if fed off center it would be much easier.

Any comparitive thoughts about the options and any other options would be welcome.

Thanks

Richard
M0WBN


Wed Nov 17, 2010 9:38 pm
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 HORIZONTAL LOOP QUESTION? 
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Richard,

A lot depends on what sort of operating you're interested in. Surprisingly, perhaps, the short vertical part of your Inverted-L plays a vital role in lowering the take-off angle compared to a loop or dipole at such a low height; so if DX chasing is your goal, stick with the Inverted-L. On the other hand if what you want is Inter-G contacts the loop or dipole would probably be better.

Of course, how well your Inverted-L works depends on how good your ground system is.

Steve G3TXQ


Wed Nov 17, 2010 10:49 pm
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 HORIZONTAL LOOP QUESTION? 
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Thanks Steve,

I have a few radials running under the grass but they run in the opposite direction of the inverted L because it is partially above the driveway so I'm certain it's not the best ground system. I could just build another leg and trap and convert this to a trap dipole but I'd like to get another antenna up to do a comparison. What are your thoughts around trap dipole vs. a non resonant dipole fed with ladder line and a tuner?

Richard


Thu Nov 18, 2010 11:37 am
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 HORIZONTAL LOOP QUESTION? 
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M0WBN wrote:
What are your thoughts around trap dipole vs. a non resonant dipole fed with ladder line and a tuner?


Very little to choose between them:

Trap losses are nowhere near as bad as some folk claim; on the other hand, a trap dipole can become quite narrow-band, and then you end up having to use a tuner anyway for final "tweaks" and the coax losses begin to rise.

You don't get those problems with a doublet+ladderline, but you do get multi-lobe radiation patterns on the higher frequency bands; that may be a good thing or a bad thing depending on where the lobes and nulls fall.

My personal preference is for the doublet+ladderline - it keeps the stuff that's out in the weather very simple and light :)

Steve G3TXQ


Thu Nov 18, 2010 11:48 am
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